Intra-articular Injections of Platelet-Rich Plasma Releasate Reduce Pain and Synovial Inflammation in a Mouse Model of Osteoarthritis

Platelet-rich plasma alleviates neuropathic pain in osteoarthritis by downregulating microglial activation

BACKGROUND

The development of neuropathic pain (NP) is one of the reasons why the pain is difficult to treat, and microglial activation plays an important role in NP. Recently, platelet-rich plasma (PRP) has emerged as a novel therapeutic method for knee osteoarthritis (KOA). However, it's unclarified whether PRP has analgesic effects on NP induced by KOA and the underlying mechanisms unknown.

PURPOSE

To observe the analgesic effects of PRP on NP induced by KOA and explore the potential mechanisms of PRP in alleviating NP.

METHODS

KOA was induced in male rats with intra-articular injections of monosodium iodoacetate (MIA) on day 0. The rats received PRP or NS (normal saline) treatment at days 15, 17, and 19 after modeling. The Von Frey and Hargreaves tests were applied to assess the pain-related behaviors at different time points. After euthanizing the rats with deep anesthesia at days 28 and 42, the corresponding tissues were taken for subsequent experiments. The expression of activating transcription factor 3 (ATF3) in dorsal root ganglia (DRG) and ionized-calcium-binding adapter molecule-1(Iba-1) in the spinal dorsal horn (SDH) was detected by immunohistochemical staining. In addition, the knee histological assessment was performed by hematoxylin-eosin (HE) staining.

RESULTS

The results indicated that injection of MIA induced mechanical allodynia and thermal hyperalgesia, which could be reversed by PRP treatment. PRP downregulated the expression of ATF3 within the DRG and Iba-1 within the SDH. Furthermore, an inhibitory effect on cartilage degeneration was observed in the MIA + PRP group only on day 28.

CONCLUSION

These results indicate that PRP intra-articular injection therapy may be a potential therapeutic agent for relieving NP induced by KOA. This effect could be attributed to downregulation of microglial activation and reduction in nerve injury.

Emerging Roles of Macrophage Polarization in Osteoarthritis: Mechanisms and Therapeutic Strategies

Osteoarthritis (OA) is the most common chronic degenerative joint disease in middle-aged and elderly people, characterized by joint pain and dysfunction. Macrophages are key players in OA pathology, and their activation state has been studied extensively. Various studies have suggested that macrophages might respond to stimuli in their microenvironment by changing their phenotypes to pro-inflammatory or anti-inflammatory phenotypes, which is called macrophage polarization. Macrophages accumulate and become polarized (M1 or M2) in many tissues, such as synovium, adipose tissue, bone marrow, and bone mesenchymal tissues in joints, while resident macrophages as well as other stromal cells, including fibroblasts, chondrocytes, and osteoblasts, form the joint and function as an integrated unit. In this study, we focus exclusively on synovial macrophages, adipose tissue macrophages, and osteoclasts, to investigate their roles in the development of OA. We review recent key findings related to macrophage polarization and OA, including pathogenesis, molecular pathways, and therapeutics. We summarize several signaling pathways in macrophage reprogramming related to OA, including NF-κB, MAPK, TGF-β, JAK/STAT, PI3K/Akt/mTOR, and NLRP3. Of note, despite the increasing availability of treatments for osteoarthritis, like intra-articular injections, surgery, and cellular therapy, the demand for more effective clinical therapies has remained steady. Therefore, we also describe the current prospective therapeutic methods that deem macrophage polarization to be a therapeutic target, including physical stimulus, chemical compounds, and biological molecules, to enhance cartilage repair and alleviate the progression of OA.

Exploring the potential use of platelet rich plasma (PRP) from adult and umbilical cord blood in murine follicle culture

Ovarian follicle culture is a powerful tool to study follicular physiology and has potential applications in clinical and commercial settings. Despite remarkable progress, recreating folliculogenesis in vitro remains challenging for many mammalian species. This study investigates the impact of platelet-rich plasma (PRP) derived from adult blood (human platelet lysate, hPL) and umbilical cord blood (Umbilical cord plasma, UCP) on murine pre-antral follicle culture and oocyte maturation. Pre-antral follicles were cultured individually for 10 days with fetal bovine serum (FBS) serving as the control and two PRP sources (hPL and UCP) and their activated forms (Ac-hPL and Ac-UCP). The results suggest that neither hPL nor UCP, regardless of activation status, improved follicle culture outcomes compared to FBS. Interestingly, activation did not significantly impact the main functional outcomes such as maturation rates, survival, and growth. Oestradiol secretion and oocyte diameter, often considered hallmarks of follicle quality, did not show significant differences between matured and non-matured oocytes across the treatment groups. However, gene expression analysis revealed a significant upregulation of Gdf-9 and Bmp-15 mRNA levels in oocytes from the Ac-UCP group, regardless of maturation stage, suggesting that the accumulation of the mRNA could be due to potential challenges in translation in the Ac-UCP group. In conclusion, this study challenges the hypothesis that PRP, as a serum source, could improve follicle culture outcomes compared to FBS, the gold standard in murine follicle culture. Further research is needed to understand the species-specific effects of PRP and explore other potential factors affecting follicle culture and oocyte quality.

Impact of autologous platelet-rich plasma therapy vs. hyaluronic acid on synovial fluid biomarkers in knee osteoarthritis: a randomized controlled clinical trial

Objective

Observe the effects of platelet-rich plasma (PRP) therapy on inflammatory cytokines in the synovial fluid of the knee joint of patients with KOA, and explore the effects of PRP intra-articular injection on the inflammation of the knee joint environment and the possible mechanism of action.

Methods

Seventy patients were randomized to undergo three blinded weekly intra-articular injections of PRP or hyaluronic acid (HA). The concentrations of inflammatory cytokines, including interleukin (IL)-6, IL-1β, tumor necrosis factor (TNF)-α, IL-8, IL-17A, IL-17F, IL-4, IL-5, and IL-10, in the synovial fluid were evaluated before the intervention and 1 month after the third injection. The Western Ontario and McMaster University (WOMAC) and visual analog scale (VAS) scores were used to assess pain and functional status of the knee joints in both groups before the intervention, immediately post-intervention, and 1, 3, 6, and 12 months after the intervention.

Results

Baseline characteristics were similar in both groups with no statistical difference. The IL-6, IL-1β, TNF-α, IL-17A, and IL-10 levels in the synovial fluid of the observation group decreased significantly after, vs. before, the intervention (p < 0.05), whereas the IL-8, IL-17F, and IL-4 levels decreased (p > 0.05) and IL-5 levels increased (p > 0.05). There was no statistically significant difference between inflammatory cytokine levels in the synovial fluid of the samples from the control group before and after the intervention (p > 0.05). There were no statistically significant differences between the two groups immediately after intervention (p > 0.05). At 1, 3, 6, and 12 months after intervention, the WOMAC and VAS scores were significantly better in the observation group than in the control group (p < 0.05).

Conclusion

Platelet plasma therapy can reduce the concentrations of inflammatory cytokines IL-6, IL-1β, TNF-α, IL-17A, and IL-10 in the synovial fluid of KOA patients, reduce the expression levels of IL-8, IL-17F, and IL-4, clear the pro-inflammatory factors, improve the inflammatory environment of the affected knee joint, and alleviate pain caused by inflammation. Thus, alleviating pain and improving knee function in patients with KOA.

Inflammatory ultrasound features as prognostic factors of pain and functional outcomes following intra-articular platelet-rich plasma in knee osteoarthritis

AIM

To explore inflammatory ultrasound predictors of improvements in pain and function over 2, 6, and 12 months following administration of intra-articular platelet-rich plasma (PRP) in knee osteoarthritis (OA).

METHOD

Patients with painful mild-moderate radiographic knee OA from a subset of the RESTORE RCT underwent ultrasound assessment according to the standardized OMERACT scanning protocol to detect inflammatory features such as synovitis, synovial hypertrophy, and effusion with power Doppler. The study knee was treated with 3 once-weekly PRP injections obtained after centrifugation at 1500 g for 5 min. Numerical Rating Score (NRS), Intermittent and Constant Osteoarthritis Pain (ICOAP) questionnaire, and the Western Ontario and McMaster Universities Arthritis Index (WOMAC) function sub-score were used to measure pain and functional severity. Separate linear regression models were performed to determine whether baseline ultrasound-detected features of inflammation predicted the improvement in pain and function following PRP injection in both unadjusted and adjusted models for confounders.

RESULTS

Forty-four participants were included, with 25 (56.8%) being female. In an unadjusted model, higher OMERACT scores for inflammatory features such as global synovitis and/or effusion were significantly associated with greater improvement in all outcomes measured at 2 months but not at 6 and 12 months for pain measures. Only global synovitis showed significant association with functional improvement at 2 and 12 months. Similar findings were observed in the adjusted model.

CONCLUSION

Ultrasound indices of knee inflammation predicted short-term improvements in pain severity and both short- and longer-term improvements in function following intra-articular PRP injection.

Efficacy and safety of platelet-rich plasma injections for the treatment of osteoarthritis: a systematic review and meta-analysis of randomized controlled trials

Background

In recent years, platelet-rich plasma (PRP) injections for osteoarthritis (OA) have been widely promoted in clinical practice, but their effectiveness is controversial. Therefore, we conducted a meta-analysis of relevant randomized controlled trials (RCTs) to determine the efficacy and safety of PRP injections for the treatment of OA.

Methods

We searched databases including Embase, Web of Science, Medline, PubMed, and the Cochrane Library for relevant studies. Two researchers (YQX and CG) performed literature screening, baseline data extraction, literature quality assessment, and heterogeneity analysis of RCTs from the retrieved studies. Based on the magnitude of heterogeneity I², random-effects or fixed-effects models were selected for the meta-analysis.

Results

We included 24 RCTs comprising 1344 patients with OA who met the inclusion criteria, with the main types of morbidity being knee osteoarthritis (KOA), hip osteoarthritis (HOA), ankle osteoarthritis (AOA), and temporomandibular joint osteoarthritis (TMJOA). Our results indicate that PRP injections were effective in improving Visual Analog Scale (VAS) pain scores in patients with KOA, HOA, and AOA compared to controls (AOA, MD = -1.15, CI = 95% [-1.74, -0.56], I² = 40%, P < 0.05; KOA, MD = -1.03, CI = 95% [-1.16, -0.9], I² = 87%, P < 0.05; TMJOA, MD = -1.35, CI = 95% [-1.74, -0.97], I² = 92%, P < 0.05) but showed no significant efficacy in patients with HOA (MD = -0.27, CI = 95% [-0.8, 0.26], I² = 56%, P>0.05). Compared to controls, PRP injections were effective in improving Knee Injury and Osteoarthritis Outcome Score (KOOS), including the patient's pain symptoms, activities of daily living (ADL), and adhesion symptomatology, but not for that of sports function (KOOS-pain, MD = 2.77, CI = 95% [0, 5.53], I² = 0%, P < 0.05; KOOS-symptoms, MD = 3.73, CI = 95% [0.76, 6.71], I² = 0%, P < 0.05; KOOS-ADL, MD = 3.61, CI = 95% [0.79, 6.43], I² = 0%, P < 0.05; KOOS-QOL, MD = 4.66, CI = 95% [0.98, 8.35], I² = 29%, P < 0.05, KOOS-sport, MD = 0.48, CI = 95% [-3.02, 3.98], I² = 0%, P > 0.05). PRP injections were effective in improving Western Ontario and McMaster Universities Arthritis Index (WOMAC) scores, including pain, stiffness, and functional joint motion, in patients with OA compared with the control group (WOMAC-pain, MD = -1.08, CI = 95% [-1.62, -0.53], I² = 87%, P < 0.05; WOMAC-stiffness, MD = -1.17, CI = 88% [-1.72, -0.63], I² = 87%, P < 0.05; WOMAC-function, MD = -1.12, CI = 95% [-1.65, -0.58], I² = 87%, P < 0.05). In addition, subgroup analysis showed that leukocyte-poor (LP) PRP injections were more effective than leukocyte-rich (LR) PRP injections in improving pain symptoms in patients with OA (VAS, LR-PRP, MD = -0.81, CI = 95% [-1.65, -0.03], I² = 83%, P = 0.06 > 0.05; LP-PRP, MD = -1.62, CI = 95% [-2.36, -0.88], I² = 92%, P < 0.05). A subgroup analysis based on injection sites showed that no statistical difference in efficacy between intra-articular (IA) combined with intra-osseous (IO) simultaneous PRP injections. IA PRP injections only improved VAS pain scores in patients with OA (IA+IO PRP injections, MD = -0.74, CI =95% [-1.29, -0.18], I² = 61%, P < 0.05; IA PRP injections, MD = -1.43, CI = 95% [-2.18, -0.68], I² = 87%, P < 0.05, test for subgroup differences, P > 0.05, I² = 52.7%).

Conclusion

PRP injection therapy can safely and effectively improve functional activity in patients with OA and produce positive analgesic effects in patients with KOA, TMJOA, and AOA. However, PRP injection therapy did not significantly reduce pain symptoms in patients with HOA. In addition, the analgesic effect of LP-PRP was greater than that of LR-PRP.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/, identifier: CRD42022362066.

Platelet-Rich Plasma for Knee Osteoarthritis: What Does the Evidence Say?

The utilization of platelet-rich-plasma as a therapeutic intervention for knee osteoarthritis has gained immense attention since 2008. The increase in the number of scientific publications dedicated to this area can be attributed to the majority of favorable results reported in clinical trials and basic science studies. However, despite the growing evidence, the use of platelet-rich plasma in clinical practice still poses controversial aspects. The potential mechanisms of action described for platelet-rich-plasma so far indicate that it could serve as a disease-modifying drug, acting to counteract important aspects of knee osteoarthritis pathophysiology (cartilage breakdown, inflammation, and bone remodeling). Nevertheless, its efficacy in slowing down the progression of knee osteoarthritis remains unproven. While inconsistencies have been noted, the majority of controlled clinical trials and meta-analyses advocate for the utilization of platelet-rich-plasma in treating knee osteoarthritis, as it has demonstrated greater efficacy than hyaluronic acid and placebo, with a follow-up of at least 1 year. Despite advancements made in certain areas, significant diversity persists regarding the formulations used, therapeutic regimen, extended follow-up periods, patient selection, and assessment of clinically relevant outcomes. Consequently, the leading clinical practice guidelines do not recommend its use. In light of the emerging evidence, this narrative review aims to provide an objective evaluation of the recent available scientific literature (last 5 years) focused on randomized clinical trials and meta-analyses to present a current overview of the topic.

The role of WNT and IL-1 signaling in osteoarthritis: therapeutic implications for platelet-rich plasma therapy

Different from inflammatory arthritis, where biologicals and targeted synthetic molecules have revolutionized the disease course, no drug has demonstrated a disease modifying activity in osteoarthritis, which remains one of the most common causes of disability and chronic pain worldwide. The pharmacological therapy of osteoarthritis is mainly directed towards symptom and pain relief, and joint replacement is still the only curative strategy. Elucidating the disease pathophysiology is essential to understand which mechanisms can be targeted by innovative therapies. It has extensively been demonstrated that aberrant WNT and IL-1 signaling pathways are responsible for cartilage degeneration, impaired chondrocyte metabolism and differentiation, increased extracellular matrix degradation, and altered subchondral bone homeostasis. Platelet-rich plasma is an autologous blood derivative containing a concentration of platelets that is much higher than the whole blood counterpart and has shown promising results in the treatment of early knee osteoarthritis. Among the proposed mechanisms, the modulation of WNT and IL-1 pathways is of paramount importance and is herein reviewed in light of the proposed regenerative approaches.

Regenerative methods in osteoarthritis

Osteoarthritis (OA) is the most common type of arthritis that can affect all joint structures. The primary goals of osteoarthritis treatment are to alleviate pain, reduce functional limitations, and improve quality of life. Despite its high prevalence, treatment options for osteoarthritis are limited, with most therapeutic approaches focusing on symptom management. Tissue engineering and regenerative strategies based on biomaterials, cells, and other bioactive molecules have emerged as viable options for osteoarthritis cartilage repair. Platelet-rich plasma (PRP) and mesenchymal stem cells (MSCs) are the most commonly used regenerative therapies today to protect, restore, or increase the function of damaged tissues. Despite promising results, there is conflicting evidence regarding the efficacy of regenerative therapies, and their efficacy remains unknown. The data suggest that more research and standardization are required for the use of these therapies in osteoarthritis. This article provides an overview of the application of MSCs and PRP applications.

The Efficacy of Microfracture Combined with Extracorporeal Shock Wave Therapy for Treating Osteochondral Lesion of the Talus and the Quality of Regenerated Cartilage: A Retrospective Cohort Study and MRI Assessment

BACKGROUND

osteochondral lesion of the talus (OLT) is a common disease in the physically active population, and extracorporeal shock wave therapy (ESWT) is a noninvasive treatment. We hypothesized that microfracture (MF) combined with ESWT may have great potential to become a novel combination treatment of OLT.

METHODS

the OLT patients who received MF + ESWT or MF + platelet-rich plasma (PRP) injection were retrospectively included, with a minimal follow up of 2y. The daily activating VAS, exercising VAS, and American Orthopedic Foot and Ankle Society Ankle-Hindfoot Score (AOFAS) were used to assess the efficacy and functional outcome, and ankle MRI T2 mapping was used to evaluate the quality of regenerated cartilage in the OLT patients.

RESULTS

only transient synovium-stimulated complications were found during the treatment sessions; the complication rate and daily activating VAS did not have differences between groups. MF + ESWT had a higher AOFAS and a lower T2 mapping value than MF + PRP at the 2y follow up.

CONCLUSIONS

the MF + ESWT had superior efficacy for treating OLT, which resulted in better ankle function and more hyaline-like regenerated cartilage, superior to the traditional MF + PRP.

Comparıson of the effect of the autogenıc and xenogenıc use of platelet-rıch plasma on rabbıt chondrocutaneous composıte graft survıval

The platelet-rich plasma (PRP) has become popular in the medical world due to its content of growth factors and numerous studies are experimental. In experimental studies, the preparation and application of PRP are problematic and allogenic PRP transfers have been preffered, because of the difficulties in preparation of autogenic PRP in animal experiments. Xenogenic transfers and their effects have not been studied in this topic. This study aimed to investigate the effect of autogenic and xenogenic use of PRP on composite graft viability.Methods: Two composite grafts are prepared for each ear of nine rabbits. Each ear was randomly divided into three groups. After the procedure, the wound edges and base were injected with 1 cc serum physiologic, autogenic PRP or 1 cc human-derived xenogenic PRP. At 3 weeks, samples were taken, photographic and histopathological evaluations were made.Results: The graft viability was better in autogenic and xenogenic group compared to the control group. In comprasion of autogenic and xenogenic groups, although the macroscopic evaluation revealed better graft viability and less necrosis in the group which had been treated with autogenic PRP, the difference was not statistically significant. The three groups did not significantly differ in terms of inflammation. Vascularization examined histopathologically. CD31 staining, which was used to evaluate angiogenesis, was significantly higher in the autogenic PRP group than the remaining two groups.Conclusion: Although autogenic PRP has better results histopathologically, the xenogenic use of PRP may be an alternative for studies, when macroscopic evaluation is necessary.

Intra-articular injection of platelet-rich plasma in patients with hemophilia and painful knee joint cartilage degeneration

INTRODUCTION

Knee arthropathy causes pain to people with hemophilia (PWH). One of the current controversies is whether injections of intra-articular platelet-rich plasma (PRP) are effective in relieving the knee pain of PWH.

AREAS COVERED

A narrative literature review was conducted on the efficacy of PRP injections in the knees of PWH.

EXPERT OPINION

Intra-articular PRP knee injections are widely used in patients with knee osteoarthritis to relieve pain and delay total knee arthroplasty. Although numerous publications have supported the use of PRP in knee osteoarthritis, there is still major controversy regarding its true usefulness, given that a number of studies with a high degree of evidence have failed to show the efficacy of PRP. With respect to painful hemophilic arthropathy, the use of PRP injections is even more controversial, as there are only four publications on the subject supporting the use of PRP in hemophilia, all of them with a low degree of evidence. A publication with grade 1 evidence recommended against the use of PRP in hemophilic arthropathy because its efficacy has not been demonstrated. My opinion is that intra-articular PRP injections should not be used in hemophilia until there is more evidence of its benefits.

Platelet-rich plasma attenuates the severity of joint capsule fibrosis following post-traumatic joint contracture in rats

Background: Post-traumatic joint contracture (PTJC) mainly manifests as excessive inflammation leading to joint capsule fibrosis. Transforming growth factor (TGF)-β1, a key regulator of inflammation and fibrosis, can promote fibroblast activation, proliferation, migration, and differentiation into myofibroblasts. Platelet-rich plasma (PRP) is considered to have strong potential for improving tissue healing and regeneration, the ability to treat joint capsule fibrosis remains largely unknown. Methods: In this study, we aimed to determine the antifibrotic potential of PRP in vivo or in vitro and its possible molecular mechanisms. The TGF-β1-induced primary joint capsule fibroblast model and rat PTJC model were used to observe several fibrotic markers (TGF-β1, α-SMA, COL-Ⅰ, MMP-9) and signaling transduction pathway (Smad2/3) using histological staining, qRT-PCR and western blot. Results: Fibroblasts transformed to myofibroblasts after TGF-β1 stimulation with an increase of TGF-β1, α-SMA, COL-Ⅰ, MMP-9 and the activation of Smad2/3 in vitro. However, TGF-β1-induced upregulation or activation of these fibrotic markers or signaling could be effectively suppressed by the introduction of PRP. Fibrotic markers' similar changes were observed in the rat PTJC model and PRP effectively reduced inflammatory cell infiltration and collagen fiber deposition in the posterior joint capsule. Interestingly, HE staining showed that articular cartilage was degraded after rat PTJC, and PRP injection also have the potential to protect articular cartilage. Conclusion: PRP can attenuate pathological changes of joint capsule fibrosis during PTJC, which may be implemented by inhibiting TGF-β1/Smad2/3 signaling and downstream fibrotic marker expression in joint capsule fibroblasts.

Platelet-Rich Plasma for Intra-articular Injections: Preclinical and Clinical Evidence

The use of platelet-rich plasma (PRP) has been supported by encouraging data from in vitro and preclinical in vivo studies, both in terms of safety and efficacy. This led to the wide use of PRP injections in the clinical practice, with promising results especially as a minimally invasive treatment for cartilage degeneration and osteoarthritis (OA). While many controversies remain on the best PRP formulation, the overall available clinical studies support the benefits of PRP, with functional improvement and reduction of pain-related symptoms up to 12 months, especially in young patients and early OA stages.

Can platelet-rich plasma enhance the effect of meniscus repair? A meta-analysis of randomized controlled trials Platelet-rich plasma and meniscus repair

BACKGROUND

Studies have shown that platelet-rich plasma (PRP) can enhance the effect of meniscus repair, but some studies have suggested different views on the role of PRP.

PURPOSE

To determine whether PRP can enhance the effect of meniscus repair with respect to pain reduction and improved functionality and cure rate in patients with meniscus injury.

METHODS

By searching PubMed, EMBASE, Cochrane Library databases, clinicaltrials.gov, and the CNKI database from their inception till December 1, 2020, we performed a meta-analysis of RCTs reporting the results of the Pain Visual Analog Scale (VAS), the pain of Knee injury and Osteoarthritis Outcome Score (KOOS), Lysholm score, the International Knee Documentation Committee (IKDC), healing rate, and adverse events. The risk of bias is assessed using Cochrane's collaborative tools. The summary results are expressed with effect size and 95% confidence interval, and sensitivity were performed.

RESULTS

The meta-analysis included 9 RCTs and 345 patients. In general, compared with the control group, used of PRP during meniscus surgery significantly improved the pain (SMD: -0.95, p < 0.00001,95% CI: -1.22 to -0.69, I2 = 42%) and knee joint function (SMD: 1.00, p = 0.01.95% CI: 0.22 to 1.79, I2 = 89%) of patients with meniscus injury at 6 months after treatment. However, both PRP and non-PRP showed improvements in the pain and knee joint function, with no significant difference between the groups at 1 months and beyond 12 months. The PRP enhancement technique showed benefit in improving the cure rate of meniscus repair (RR:1.44; p < 0.0001, 95% CI: 1.20-1.73). No serious adverse events were reported in any study.

CONCLUSION

As an enhancement program for meniscus repair, PRP is worthy of further consideration in improving the function and pain of patients during the mid-term follow-up after surgery, and PRP can further improve the healing rate of meniscus repair. However, the evidence still needs to be interpreted carefully because of the quantity and quality of the included studies.

Biological Targets of Multimolecular Therapies in Middle-Age Osteoarthritis

Knee osteoarthritis (OA) is a common condition, prevalent in middle-agedness, associated with chronic pain and impaired quality of life. Two interrelated biological processes fuel early OA progression: inflammation and structural tissues catabolism. Procatabolic and proinflammatory mediators are interconnected and form part of a self-perpetuating loop. They leverage OA research complexity because of the impossibility to discern certain spatiotemporal tissues' changes from others. Both are shared targets of versatile regenerative multimolecular therapies. In particular, platelet-rich plasma can interfere with inflammation and inflammatory pain. The therapeutic approach is to alter the vicious inflammatory loop by modifying the molecular composition of the synovial fluid, thereby paracrine cellular cross talk. Intra-articular injections of platelet-rich plasma can provide key factors balancing proinflammatory and anti-inflammatory factors, targeting macrophage dysfunction and modulating immune mechanisms within the knee.

Effect of platelet-rich plasma on meniscus repair surgery: A meta-analysis of randomized controlled trials

BACKGROUND

Studies have shown that platelet-rich plasma (PRP) can enhance the effect of meniscus repair, but some studies have suggested different views on the role of PRP. Therefore, a meta-analysis was conducted to determine whether PRP can enhance the effect of meniscus repair with respect to pain reduction and improved functionality and cure rate in patients with meniscus injury.

METHODS

PubMed, EMBASE, Cochrane Library Databases, clinicaltrials.gov, and the CNKI Database were searched from their inception till December 1, 2020. The RCTs reporting the outcomes of the Pain Visual Analog Scale (VAS), Lysholm score, healing rate, and adverse events were included. The risk of bias was assessed using Cochrane collaborative tools. The simulated results were expressed with effect size and 95% confidence interval, and sensitivity and subgroup analysis were performed.

RESULTS

The meta-analysis included 8 RCTs and 431 participants. Compared with the control group, use of PRP during meniscus surgery significantly improved the VAS (SMD: -0.40, P = .002, 95%CI: -0.66 to -0.15) and Lysholm score (MD: 3.06, P < .0001, 95%CI: 1.70-4.42) of meniscus injury, but the PRP showed no benefit in improving the healing rate of meniscus repair (RR: 1.22, P = .06, 95%CI: 0.99-1.51). No serious adverse events were reported in any study.

CONCLUSIONS

PRP is safe and effective in improving the effect of meniscus repair as augment. High quality RCTs with long follow-up and definitive results are needed in the future to confirm the use and efficacy of PRP in meniscus tears.

Comparison of the effects of autologous and allogeneic purified platelet-rich plasma on cartilage damage in a rabbit model of knee osteoarthritis

Background

Purified platelet-rich plasma (P-PRP) is gradually being used in the treatment of osteoarthritis (OA), and its sources are mainly divided into autologous and allogeneic blood. However, it is unclear whether autologous PRP is more effective or allogeneic PRP is superior.

Objective

In this study, autologous and allogeneic P-PRP was injected at early stage of KOA in rabbits, and then the differences in the efficacy of the two P-PRPs against KOA were compared from several perspectives, including pathological histology and immunohistochemistry.

Method

Experimental rabbits were divided into normal group (n = 8), model group (n = 8), autologous P-PRP group (n = 8), and allogeneic P-PRP group (n = 8) using a random number table method. The normal and model groups did not receive any treatment, and the autologous P-PRP and allogeneic P-PRP groups received intra-articular injections of autologous and allogeneic P-PRP, respectively, to observe the changes in the gross specimens of the knee joints of the experimental rabbits in each group. The histopathological changes of chondrocytes were also observed by HE-stained sections of articular cartilage, and the expression of chondrocytes Bone morphogenetic protein-2 (BMP-2) and Sox9 were detected by immunohistochemistry.

Results

Compared with the allogeneic P-PRP group, the differences were statistically significant (P < 0.05) in the gross specimens and pathological histological findings in the autologous PRP group. Immunohistochemical results showed that the expression of BMP-2 and Sox9 was elevated in both the autologous P-PRP group and the allogeneic P-PRP group compared with the model group, and the expression of BMP-2 was higher in the autologous P-PRP group than in the allogeneic P-PRP group, with a statistically significant difference (P < 0.05), while there was no difference in the expression of Sox9 between the two groups (P > 0.05).

Conclusion

Intra-articular injection of autologous P-PRP activated the expression of BMP-2 and Sox9 in chondrocytes and effectively improved KOA cartilage repair and reduced bone redundancy and joint fluid formation, and its efficacy was superior to that of intra-articular injection of allogeneic P-PRP.

Bone Marrow Aspirate Concentrate Is Equivalent to Platelet-Rich Plasma for the Treatment of Knee Osteoarthritis at 2 Years: A Prospective Randomized Trial

BACKGROUND

Autologous platelet-rich plasma (PRP) and bone marrow aspirate concentrate (BMC) are being used clinically as therapeutic agents for the treatment of knee osteoarthritis.

PURPOSE/HYPOTHESIS

The purpose of this study was to compare the efficacy of BMC and PRP on pain and function in patients with knee osteoarthritis up to 24 months after injection. It was hypothesized that patients receiving BMC would have better sustained outcomes than those receiving PRP.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 2.

METHODS

A total of 90 participants aged between 18 and 80 years with symptomatic knee osteoarthritis (Kellgren-Lawrence grades 1-3) were randomized into 2 study groups: PRP and BMC. Both groups completed the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and subjective International Knee Documentation Committee (IKDC) questionnaire before and 1, 3, 6, 9, 12, 18, and 24 months after a single intra-articular injection of leukocyte-rich PRP or BMC. A linear mixed-effects model was performed to quantify the effects over time and the difference between the groups. This model has the random effect for time to assess the extent in which the change over time differs from one person to another.

RESULTS

An overall 84 patients completed questionnaires from baseline to 12 months; however, 17 patients (n = 9; PRP group) were lost to follow-up at 18 months and 25 (n = 13; PRP group) at 24 months. There were no statistically significant differences in IKDC (P = .909; 95% CI, -6.26 to 7.03) or WOMAC (P = .789; 95% CI, -6.26 to 4.77) scores over time between the groups. Both groups had significantly improved IKDC (P < .001; 95% CI, 0.275-0.596) and WOMAC (P = .001; 95% CI, -0.41 to -0.13) scores from baseline to 24 months after the injection. These improvements plateaued at 3 months and were sustained for 24 months after the injection, with no difference between PRP and BMC at any time point.

CONCLUSIONS

For the treatment of osteoarthritis, PRP and BMC performed similarly out to 24 months. BMC was not superior to PRP.

REGISTRATION

NCT03289416 (ClincalTrials.gov identifier).

Intra-Articular Platelet-Rich Plasma Injections in Knee Osteoarthritis: A Review of Their Current Molecular Mechanisms of Action and Their Degree of Efficacy

Knee osteoarthritis (OA) is estimated to affect more than 10% of the population, with a lifetime risk of 45%. Contemporary guidelines advise control of body weight, therapeutic physical exercise, drug treatment (oral non-steroidal anti-inflammatory drugs, paracetamol, opioids), and mechanical aids (walking aids, braces, orthoses). Nevertheless, these treatments typically have only short-term benefits. Intra-articular corticosteroids are typically advised, but only for short-term pain alleviation, given that their benefits last only a few weeks. The efficacy of hyaluronic acid is controversial. When the aforesaid options fail, total knee arthroplasty is generally recommended as an efficacious treatment. However, it is costly and can involve medical and postoperative complications. Therefore, determining alternate safe and effective treatments for knee OA is paramount. Platelet-rich plasma (PRP) has lately been investigated for the treatment of knee OA. This article reviews recent knowledge concerning PRP’s molecular mechanisms of action. The effectiveness of intra-articular PRP injections in the knee joint remains controversial, although most recent publications show pain alleviation in the short term. Orthopedic surgeons treating people with knee OA are becoming increasingly interested in PRP, despite indecisive clinical data and basic science information. Further studies comparing PRP with placebo are required.

Chondroprotective effects of multiple PRP injections in osteoarthritis by apoptosis regulation and increased aggrecan synthesis- Immunohistochemistry based Guinea pig study

OBJECTIVE

Use of Immunohistochemistry as a tool to assess anti-apoptotic effects and cartilage regeneration effects of PRP in guinea pig model of spontaneous OA.

STUDY DESIGN

Controlled Laboratory Study involving Dunkin-Hartley guinea pigs.

METHODS

12 Dunkin-Hartley guinea pigs (weighing ∼600-800 g) were chosen for this study. One knee of each animal received 3 injections of allogenic PRP at weekly intervals (Group A = 12 Knees). The other knee received normal saline and acted as the control group (Group B = 12 Knees). Half of the animals from each group (subgroups A3 & B3 = 6 Knees each) were sacrificed at 3 months, and the remaining half (subgroups A6 & B6 = 6 Knees each) were sacrificed at 6 months after intervention. Immunohistochemistry (IHC) staining and evaluation were done for Collagen-II, Caspase-3 and Aggrecan.

RESULTS

The mean IHC score for Caspase-3 were significantly low in PRP knees compared to placebo Knees at 3 months (P = 0.031) and 6 months (P = 0.012) suggesting its down-regulation and inhibition of apoptosis. The mean IHC score for content of collagen- II and aggrecan at 3 months were higher in PRP Knees (A3) compared to placebo (B3) (Not significant). At 6 months, the Mean IHC Score decreased in both PRP (A6) and Control Knees (B6) for Collagen, but increased for aggrecan compared to its value at 3 months; and this was better in PRP group than in the control (P = 0.024).

CONCLUSION

Multiple injections of PRP has a chondroprotective role by its anti-apoptotic effect and by increasing the aggrecan content in ECM.

Remnants-preserving ACL reconstruction using direct tendinous graft fixation: a new rat model

BACKGROUND

Anterior cruciate ligament (ACL) repair techniques are new emerging strategies prevailing, in selected cases, over standard reconstruction of the ACL with excision of its remnants. Mid-substance ACL tears represent a challenge for ACL repair techniques, and remnants-preserving ACL reconstruction (rp-ACLR) using an autograft remains the recommended treatment in this situation. However, morbidity associated with the autograft harvesting prompts the need for alternative surgical strategies based on the use of synthetic scaffolds. Relevant small animal models of mid-substance tears with ACL remnants preservation and reconstruction are necessary to establish the preliminary proof of concept of these new strategies.

METHODS

A rat model of rp-ACLR using a tendinous autograft after complete mid-substance ACL transection was established. Twelve weeks following surgery, clinical outcomes and knee joints were assessed through visual gait analysis, Lachman tests, thigh perimeter measurements, magnetic resonance imaging, micro-computed tomography, and histology, to evaluate the morbidity of the procedure, accuracy of bone tunnel positioning, ACL remnants fate, osteoarthritis, and autograft bony integration. Results were compared with those obtained with isolated ACL transection without reconstruction and to right non-operated knees.

RESULTS AND DISCUSSION

Most operated animals were weight-bearing the day following surgery, and no adverse inflammatory reaction has been observed for the whole duration of the study. Autograft fixation with cortical screws provided effective graft anchorage until sacrifice. Healing of the transected ACL was not observed in the animals in which no graft reconstruction was performed. rp-ACLR was associated with a reduced degeneration of the ACL remnants (p = 0.004) and cartilages (p = 0.0437). Joint effusion and synovitis were significantly lower in the reconstructed group compared to the transected ACL group (p = 0.004). Most of the bone tunnel apertures were anatomically positioned in the coronal and/or sagittal plane. The most deviated bone tunnel apertures were the tibial ones, located in median less than 1 mm posteriorly to anatomical ACL footprint center.

CONCLUSION

This study presents a cost-effective, new relevant and objective rat model associated with low morbidity for the preliminary study of bio-implantable materials designed for remnants-preserving ACL surgery after mid-substance ACL tear.

Platelet-rich plasma improves lipopolysaccharide-induced inflammatory response by upgrading autophagy

Objectives

Platelet-rich plasma (PRP) plays an important role at all stages of wound healing, including the inflammatory stage. Macrophage autophagy has been found to influence the inflammatory response process. However, it is unclear whether PRP can affect inflammatory responses via macrophage autophagy. In the present study, we explored the effect of PRP on inflammatory responses and researched the underlying mechanism.

Methods

RAW 264.7 macrophages were treated with PRP and/or lipopolysaccharide (LPS). The effects of PRP on the expression of inflammatory factors were determined by ELISA and qRT-PCR. Macrophage autophagosomes were also assessed by TEM and immunofluorescence. Autophagy and NLRP3-related proteins were investigated using Western blot analysis.

Results

PRP reduced the levels of inflammatory factors and increased autophagy in RAW 264.7 cells. Pretreatment with 3-MA, which is an autophagy inhibitor, abolished the impact of PRP on the inflammatory response. Moreover, PRP induced macrophage autophagy by activating the NLRP3 inflammasome.

Conclusions

These results show that PRP can attenuate LPS-induced inflammatory responses by enhancing autophagy via NLRP3. These study also provides a new perspective on the molecular mechanism of PRP therapy in wound healing.

Intra-articular injection of triamcinolone acetonide sustains macrophage levels and aggravates osteophytosis during degenerative joint disease in mice

BACKGROUND AND PURPOSE

Corticosteroids such as triamcinolone acetonide (TAA) are potent drugs administered intra-articularly as an anti-inflammatory therapy to relieve pain associated with osteoarthritis (OA). However, the ability of early TAA intervention to mitigate OA progression and modulate immune cell subsets remains unclear. Here we sought to understand the effect of early intra-articular injection of TAA towards OA progression, local macrophages and peripheral blood monocytes.

EXPERIMENTAL APPROACH

Degenerative joint disease was induced by intra-articular injection of collagenase into the knee joint of C57BL/6 mice. After one week, TAA or saline was injected intra-articularly. Blood was taken throughout the study to analyse monocyte subsets. Mice were euthanised at day 14 and 56 post-induction of collagenase-induced OA (CiOA) to examine synovial macrophages and structural OA features.

KEY RESULTS

The percentage of macrophages relative to total live cells present within knee joints was increased in collagenase- compared to saline-injected knees at day 14 and was not altered by TAA treatment. However, at day 56 post-induction of CiOA TAA-treated knees had increased levels of macrophages compared with the knees of untreated CiOA-mice. The distribution of monocyte subsets present in peripheral blood was not altered by TAA treatment during the development of CiOA. Osteophyte maturation was increased in TAA-injected knees at day 56.

CONCLUSION AND IMPLICATIONS

Intra-articular injection of TAA increases long-term synovial macrophage numbers and osteophytosis. Our findings suggest that TAA accentuates the progression of osteoarthritis-associated features when applied to an acutely inflamed knee.

PRP Injections for the Treatment of Knee Osteoarthritis: A Meta-Analysis of Randomized Controlled Trials

OBJECTIVE

To evaluate effectiveness, in terms of patient-reported outcome measures, of platelet-rich plasma (PRP) injections for knee osteoarthritis compared to placebo and other intraarticular treatments.

DESIGN

PubMed, Cochrane Library, Scopus, Embase, Web of Science, as well as the gray literature were searched on January 17, 2020. Randomized controlled trials (RCTs) comparing PRP injections with placebo or other injectable treatments, in any language, on humans, were included. Risk of bias was assessed following the Cochrane guidelines; quality of evidence was graded using the GRADE guidelines.

RESULTS

Thirty-four RCTs, including 1403 knees in PRP groups and 1426 in control groups, were selected. WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index) score favored PRP, with a statistically and clinically significant difference versus placebo at 12-month follow-up (P = 0.02) and versus HA (hyaluronic acid) at 6-month (P < 0.001) and 12-month (P < 0.001) follow-ups. A clinically significant difference favoring PRP versus steroids was documented for VAS (Visual Analogue Scale) pain (P < 0.001), KOOS (Knee Injury and Osteoarthritis Outcome Score) pain (P < 0.001), function in daily activities (P = 0.001), and quality of life (P < 0.001) at 6-month follow-up. However, superiority of PRP did not reach the minimal clinically important difference for all outcomes, and quality of evidence was low.

CONCLUSIONS

The effect of platelet concentrates goes beyond its mere placebo effect, and PRP injections provide better results than other injectable options. This benefit increases over time, being not significant at earlier follow-ups but becoming clinically significant after 6 to 12 months. However, although substantial, the improvement remains partial and supported by low level of evidence. This finding urges further research to confirm benefits and identify the best formulation and indications for PRP injections in knee OA.

Platelet-rich plasma injections induce disease-modifying effects in the treatment of osteoarthritis in animal models

PURPOSE

The mechanisms of action and disease-modifying potential of platelet-rich plasma (PRP) injection for osteoarthritis (OA) treatment are still not fully established. The aim of this systematic review of preclinical evidence was to determine if PRP injections can induce disease-modifying effects in OA joints.

METHODS

A systematic review was performed on animal studies evaluating intra-articular PRP injections as treatment for OA joints. A synthesis of the results was performed investigating the disease-modifying effects of PRP by evaluating studies that compared PRP with OA controls or other injectable products, different PRP formulations or injection intervals, and the combination of PRP with other products. The risk of bias was assessed according to the SYRCLE's tool.

RESULTS

Forty-four articles were included, for a total of 1251 animals. The publication trend remarkably increased over time. PRP injections showed clinical effects in 80% and disease-modifying effects in 68% of the studies, attenuating cartilage damage progression and reducing synovial inflammation, coupled with changes in biomarker levels. Evidence is limited on the best PRP formulation, injection intervals, and synergistic effect with other injectables. The risk of bias was low in 40%, unclear in 56%, and high in 4% of items.

CONCLUSION

Intra-articular PRP injections showed disease-modifying effects in most studies, both at the cartilage and synovial level. These findings in animal OA models can play a crucial role in understanding mechanism of action and structural effects of this biological approach. Nevertheless, the overall low quality of the published studies warrants further preclinical studies to confirm the positive findings, as well as high-level human trials to demonstrate if these results translate into disease-modifying effects when PRP is used in the clinical practice to treat OA.

LEVEL OF EVIDENCE

Level II.

Platelet-rich plasma treatment alleviates osteoarthritis-related pain, inflammation, and apoptosis by upregulating the expression levels of microRNA-375 and microRNA-337

OBJECTIVE

The present study was designed to determine the molecular mechanism by which platelet-rich plasma (PRP) acts on Osteoarthritis (OA) -related pain, inflammation, and apoptosis in vivo and in vitro.

MATERIALS AND METHODS

An in vivo OA model was established in rats using anterior cruciate ligament transection, and an in vitro OA model was created by treating chondrocytes with IL-1β. Then, the induced rats and chondrocytes were treated with PRP. Real-time PCR were used to examine the expression of micorRNAs (miRs) and mRNAs of inflammatory cytokines. WB were performed to detect the expression of apoptotic factors and Wnt/β-catenin signals. Structural damage of the cartilage and pain in OA rats were analyzed and represented by Mankin Score, OARSIS score, Tender threshold, and Thermal pain threshold. CCK-8 assay and flow cytometry were used to determine cell viability and apoptosis.

RESULTS

The expression levels of miR-337 and miR-375 were downregulated in the in vivo and vitro OA models; however, PRP treatment elevated their levels. miR-337 and miR-375 inhibition reversed the effects of PRP of reducing tenderness and thermal pain thresholds in OA rats. Moreover, PRP decreased the mRNA expression levels of MMP-13, Bax, and inflammatory factors, such as IL-1β, IL-18, and TNF-α, as well as increased the expression levels of collagen II and antiapoptotic Bcl-2. The decrease in inflammation and apoptosis was reversed by miR-337 and miR-375 inhibition, respectively.

DISCUSSION AND CONCLUSIONS

In conclusion, miR-337 and miR-375 are involved in PRP-delayed OA progression by affecting inflammation and apoptosis.

Intra-articular injection of loaded sPL sustained-release microspheres inhibits osteoarthritis and promotes cartilaginous repairs

BACKGROUND

Osteoarthritis is a chronic inflammatory disease of the joints associated with significant morbidity and lower quality of life. Current treatment strategies focus on reducing cartilage degeneration but fail to restore their proliferative ability. Super-activated platelet lysate (sPL) is an enhanced form of platelet-rich plasma that can be easily inactivated. The purpose of this study is to evaluate whether sPL-loaded PLGA/chitosan/gelatin microspheres can prevent and treat osteoarthritis.

METHODS

Features of biological microspheres were detected by SEM and ELISA. Osteoarthritis chondrocytes were co-cultured with hydrogel loaded with sPL. The effect of biological microspheres on chondrocyte proliferation was evaluated using a CCK-8 cell proliferation test. Cell morphology and cell necrosis were measured with a microscope. The gene expression levels of cartilage-related markers type 2 collagen, aggrecan (ACAN), and SRY type high mobility group box-9 (SOX9) were determined by real-time quantitative polymerase chain reaction (Rt-PCR). A rat osteoarthritis model was established. Micro-CT was used to characterize cartilaginous changes after the injection of biological microspheres. Histopathological HE staining, Safranin-O Fast Green staining and staining scores, type II collagen staining, and proteoglycan staining were used to evaluate the degree of cartilaginous repair.

RESULTS

Biological microspheres were able to continuously release biological factors. Exposure to loading sPL microspheres significantly increased chondrocyte proliferation, reduced cell necrosis, and increased the expression of cartilage markers type 2 collagen, ACAN, and SOX9 in osteoarthritic chondrocytes. In vivo experiments found that biological microspheres also smoothen cartilage surfaces, promote the expression of proteoglycan and type 2 collagen while also increasing cartilaginous integrity as evaluated using Safranin-O Fast Green staining.

CONCLUSIONS

PLGA/chitosan/gelatin hydrogel loaded with sPL is a promising tool for effective and non-invasive articular cartilage repair in osteoarthritis. Biological microspheres loaded with sPL release various biological factors to promote chondrocyte proliferation and upregulate chondrocyte functionalization genes (SOX9, CoX II, ACAN), leading to an overall enhanced cartilaginous matrix.

A 3D-printed PRP-GelMA hydrogel promotes osteochondral regeneration through M2 macrophage polarization in a rabbit model

Osteochondral regeneration is an orchestrated process of inflammatory immunity, host cell response, and implant degradation in tissue engineering. Here, the effects of a platelet-rich plasma (PRP)-gelatin methacryloyl (GelMA) hydrogel scaffold fabricated using the digital micro-mirror device (DMD) technique for osteochondral repair were investigated in a rabbit model. GelMA hydrogels with different PRP concentrations were fabricated, and their roles in bone marrow mesenchymal stem cells (BMSCs) and macrophage polarization in vitro were investigated. The incorporation of 20% PRP into the hydrogel showed optimal effects on the proliferation, migration, and osteogenic and chondrogenic differentiation of BMSCs. The 20% PRP-GelMA (v/v) hydrogel also promoted M2 polarization with high expression of Arg1 and CD206. Compared to the 20% PRP group, the 50% PRP group showed similar biological roles in BMSCs but less extent of osteogenesis. In the vivo study, the 20% PRP-GelMA composite was used for osteochondral reconstruction and showed more cartilage and subchondral bone regeneration than that observed using the pure GelMA hydrogel. The PRP-GelMA group exhibited more M2 macrophage infiltration and less M1 macrophage presentation at three time points as compared to the nontreatment group. The expression of Arg1 in the PRP-GelMA group increased significantly at 6 weeks but decreased to a lower level at 12 weeks, while CD163 showed sustained high expression until 18 weeks. Our findings demonstrated that the 3D-printed PRP-GelMA composite could promote osteochondral repair through immune regulation by M2 polarization and could be a potential candidate for osteochondral tissue engineering. STATEMENT OF SIGNIFICANCE: PRP-GelMA hydrogels promoted the migration and osteogenic and chondrogenic differentiation of BMSCs. PRP-GelMA hydrogels participated in immune regulation and M1-to-M2 transition of macrophages. PRP-GelMA hydrogels coordinated and promoted several overlapping osteochondral repair events, including dynamic immune regulation, chemotaxis of MSCs, and osteochondral differentiation. PRP-GelMA hydrogels showed superior cartilage and subchondral bone repair properties.

The Effect of Platelet-Rich Plasma on the Intra-Articular Microenvironment in Knee Osteoarthritis

Knee osteoarthritis (KOA) represents a clinical challenge due to poor potential for spontaneous healing of cartilage lesions. Several treatment options are available for KOA, including oral nonsteroidal anti-inflammatory drugs, physical therapy, braces, activity modification, and finally operative treatment. Intra-articular (IA) injections are usually used when the non-operative treatment is not effective, and when the surgery is not yet indicated. More and more studies suggesting that IA injections are as or even more efficient and safe than NSAIDs. Recently, research to improve intra-articular homeostasis has focused on biologic adjuncts, such as platelet-rich plasma (PRP). The catabolic and inflammatory intra-articular processes that exists in knee osteoarthritis (KOA) may be influenced by the administration of PRP and its derivatives. PRP can induce a regenerative response and lead to the improvement of metabolic functions of damaged structures. However, the positive effect on chondrogenesis and proliferation of mesenchymal stem cells (MSC) is still highly controversial. Recommendations from in vitro and animal research often lead to different clinical outcomes because it is difficult to translate non-clinical study outcomes and methodology recommendations to human clinical treatment protocols. In recent years, significant progress has been made in understanding the mechanism of PRP action. In this review, we will discuss mechanisms related to inflammation and chondrogenesis in cartilage repair and regenerative processes after PRP administration in in vitro and animal studies. Furthermore, we review clinical trials of PRP efficiency in changing the OA biomarkers in knee joint.

Fargesin ameliorates osteoarthritis via macrophage reprogramming by downregulating MAPK and NF-κB pathways

Background

To investigate the role and regulatory mechanisms of fargesin, one of the main components of Magnolia fargesii, in macrophage reprogramming and crosstalk across cartilage and synovium during osteoarthritis (OA) development.

Methods

Ten-week-old male C57BL/6 mice were randomized and assigned to vehicle, collagenase-induced OA (CIOA), or CIOA with intra-articular fargesin treatment groups. Articular cartilage degeneration was evaluated using the Osteoarthritis Research Society International (OARSI) score. Immunostaining and western blot analyses were conducted to detect relative protein. Raw264.7 cells were treated with LPS or IL-4 to investigate the role of polarized macrophages. ADTC5 cells were treated with IL-1β and conditioned medium was collected to investigate the crosstalk between chondrocytes and macrophages.

Results

Fargesin attenuated articular cartilage degeneration and synovitis, resulting in substantially lower Osteoarthritis Research Society International (OARSI) and synovitis scores. In particular, significantly increased M2 polarization and decreased M1 polarization in synovial macrophages were found in fargesin-treated CIOA mice compared to controls. This was accompanied by downregulation of IL-6 and IL-1β and upregulation of IL-10 in serum. Conditioned medium (CM) from M1 macrophages treated with fargesin reduced the expression of matrix metalloproteinase-13, RUNX2, and type X collagen and increased Col2a1 and SOX9 in OA chondrocytes, but fargesin alone did not affect chondrocyte catabolic processes. Moreover, fargesin exerted protective effects by suppressing p38/ERK MAPK and p65/NF-κB signaling.

Conclusions

This study showed that fargesin switched the polarized phenotypes of macrophages from M1 to M2 subtypes and prevented cartilage degeneration partially by downregulating p38/ERK MAPK and p65/NF-κB signaling. Targeting macrophage reprogramming or blocking the crosstalk between macrophages and chondrocytes in early OA may be an effective preventive strategy.

Effect of Freshly Isolated Bone Marrow Mononuclear Cells and Cultured Bone Marrow Stromal Cells in Graft Cell Repopulation and Tendon-Bone Healing after Allograft Anterior Cruciate Ligament Reconstruction

Graft cell repopulation and tendon-bone tunnel healing are important after allograft anterior cruciate ligament reconstruction (ACLR). Freshly isolated bone marrow mononuclear cells (BMMNCs) have the advantage of short isolation time during surgery and may enhance tissue regeneration. Thus, we hypothesized that the effect of intra-articular BMMNCs in post-allograft ACLR treatment is comparable to that of cultured bone marrow stromal cells (BMSCs). A rabbit model of hamstring allograft ACLR was used in this study. Animals were randomly assigned to the BMMNC, BMSC, and control groups. Fresh BMMNCs isolated from the iliac crest during surgery and cultured BMSCs at passage four were used in this study. A total of 1 × 10⁷ BMMNCs or BMSCs in 100 µL phosphate-buffered saline were injected into the knee joint immediately after ACLR. The control group was not injected with cells. At two and six weeks post operation, we assessed graft cell repopulation with histological and cell tracking staining (PKH26), and tendon-bone healing with histological micro-computed tomography and immunohistochemical analyses for collagen I and monocyte chemoattractant protein-1 (MCP1). At two weeks post operation, there was no significant difference in the total cell population within the allograft among the three groups. However, the control group showed significantly higher cell population within the allograft than that of BM cell groups at six weeks. Histological examination of proximal tibia revealed that the intra-articular delivered cells infiltrated into the tendon-bone interface. Compared to the control group, the BM cell groups showed broader gaps with interfacial fibrocartilage healing, similar collagen I level, and higher MCP1 expression in the early stage. Micro-CT did not reveal any significant difference among the three groups. BMMNCs and BMSCs had comparable effects on cell repopulation and interfacial allograft-bone healing. Intra-articular BM cells delivery had limited benefits on graft cell repopulation and caused higher inflammation than that in the control group in the early stage, with fibrocartilage formation in the tendon-bone interface after allograft ACLR.

Intra-articular injections of platelet-rich plasma in symptomatic knee osteoarthritis: a consensus statement from French-speaking experts

PURPOSE

There has been much debate regarding the use of intra-articular injections of platelet-rich plasma (PRP) as symptomatic treatment for knee osteoarthritis. The objective of this consensus was to develop guidelines for PRP injections in knee osteoarthritis according to the French National Authority for Health recommendations.

METHODS

Fifteen physicians from different French-speaking countries (10 rheumatologists, 4 specialists in rehabilitation and sports medicine and 1 radiologist) were selected for their expertise in the areas of PRP and osteoarthritis. A comprehensive literature review was conducted on Medline including all published therapeutic trials, open studies, meta-analysis and systematic reviews focusing on the effects of PRP in knee OA, as well as fundamental studies concerning the characteristics of the various types of PRP and their mechanisms, indexed before April 2019. Using the method recommended by the French National Authority for Health inspired by the Delphi consensus process, 25 recommendations were finally retained and evaluated. The recommendations were classified as appropriate or not appropriate, with strong or relative agreement, or uncertain if a consensus was not achieved.

RESULTS

Among the 25 recommendations selected, the main ones are the following: (1) Intra-articular injections of PRP are an effective symptomatic treatment for early to moderate knee osteoarthritis. This recommendation was considered appropriate with a relative agreement (Median = 8; rank = 6-9). Level of evidence 1A. (2) A PRP treatment sequence in knee osteoarthritis may include 1-3 injections. This recommendation was considered appropriate with a strong agreement (Median = 9; rank = 7-9). Level of evidence 1A. (3) Leucocytes-poor PRP should be preferred in knee osteoarthritis. This recommendation was considered appropriate with a relative agreement (Median = 8; rank = 5-9). Level of evidence 5. (4) Intra-articular PRP knee injections should be performed under ultrasound or fluoroscopic guidance. This recommendation was considered uncertain with no consensus (Median = 8; rank = 3-9). Level of evidence 5. (5) PRP should not be mixed with an anesthetic or intra-articular corticosteroid. This recommendation was considered appropriate with a relative agreement (Median = 9; rank = 6-9). Level of evidence 5 CONCLUSION: Those 25 recommendations should standardize and facilitate the use of IA PRP injections, which are considered by experts as an effective treatment especially in early or moderate knee OA. Although a strong or relative agreement from the experts was obtained for most of the recommendations, many of them had a very low level of evidence (Level 5) and were principally based on the clinical experience of the experts.

Platelet-Rich Plasma Therapy in the Treatment of Diseases Associated with Orthopedic Injuries

Platelet-rich plasma (PRP) is an autologous platelet concentrate prepared from the whole blood that is activated to release growth factors (GFs) and cytokines and has been shown to have the potential capacity to reduce inflammation and improve tissue anabolism for regeneration. The use of PRP provides a potential for repair due to its abundant GFs and cytokines, which are key in initiating and modulating regenerative microenvironments for soft and hard tissues. Among outpatients, orthopedic injuries are common and include bone defects, ligament injury, enthesopathy, musculoskeletal injury, peripheral nerve injury, chronic nonhealing wounds, articular cartilage lesions, and osteoarthritis, which are caused by trauma, sport-related or other types of trauma, or tumor resection. Surgical intervention is often required to treat these injuries. However, for numerous reasons regarding limited regeneration capacity and insufficient blood supply of the defect region, these treatments commonly result in unsatisfactory outcomes, and follow-up treatment is challenging. The aim of the present review is to explore future research in the field of PRP therapy in the treatment of diseases associated with orthopedic injuries. Impact statement In recent years, platelet-rich plasma (PRP) has become widely used in the treatment of diseases associated with orthopedic injuries, and the results of numerous studies are encouraging. Due to diseases associated with orthopedic injuries being common in clinics, as a conservative treatment, more and more doctors and patients are more likely to accept PRP. Importantly, PRP is a biological product of autologous blood that is obtained by a centrifugation procedure to enrich platelets from whole blood, resulting in few complications, such as negligible immunogenicity from an autologous source, and it is also simple to produce through an efficient and cost-effective method in a sterile environment. However, the applicability, advantages, and disadvantages of PRP therapy have not yet been fully elucidated. The aim of the present review is to explore future research in the field of PRP therapy in the treatment of diseases associated with orthopedic injuries, as well as to provide references for clinics.

Leukocyte-dependent effects of platelet-rich plasma on cartilage loss and thermal hyperalgesia in a mouse model of post-traumatic osteoarthritis

OBJECTIVE

Platelet-rich plasma (PRP) is an emerging therapeutic strategy for treatment of osteoarthritis (OA); however, there is a lack of preclinical and clinical evidence for its efficacy and its mechanism of action is unclear. In the current study, we utilized leukocyte poor-PRP (LP-PRP) and leukocyte rich-PRP (LR-PRP) to mimic clinical point of care formulations and assessed their potential to alter disease progression in a mouse model of post-traumatic OA.

METHOD

Three-month-old wild-type male FVB/N mice received destabilization of the medial meniscus (DMM) surgery to induce OA. To assess the efficacy of LP-PRP and LR-PRP, mice were given intraarticular injections at 2-, 7- and 28-days post-surgery. Mice were then assessed at 5-, 9-, and 13-weeks post-surgery for changes in chronic pain using the hot plate nociceptive assay. At 14-weeks, OA pathogenesis was evaluated using histology and phase-contrast μCT.

RESULTS

Treatment with LP-PRP and to a lesser extent LR-PRP preserved cartilage volume and surface area compared to phosphate-buffered saline (PBS) as measured by phase-contrast μCT. However, both treatments had higher Osteoarthritis Research Society International (OARSI) and synovitis scores compared to sham, and neither substantially improved scores compared to PBS controls. With respect to thermal hyperalgesia, PBS-treated mice displayed reduced latency to response compared to sham, and LR-PRP but not LP-PRP improved latency to response at 5-, 9- and 13-weeks post-surgery compared to PBS.

CONCLUSION

The results of this study suggest that effects of PRP therapy on OA progression and disease-induced hyperalgesia may be leukocyte-dependent. And while LP-PRP and to a lesser extent LR-PRP protect from volume and surface loss, significant pathology is still seen within OA joints. Future work is needed to understand how the different components of PRP effect OA pathogenesis and pain, and how these could be modified to achieve greater therapeutic efficacy.

Platelet-Rich Plasma Combined with Alendronate Reduces Pain and Inflammation in Induced Osteoarthritis in Rats by Inhibiting the Nuclear Factor-Kappa B Signaling Pathway

Purpose

Osteoarthritis (OA) is one of the common degenerative diseases of the joint in the world. This study was designed to explore the effect of platelet-rich plasma (PRP) combined with alendronate (ALN) on OA.

Methods

We induced OA model by anterior cruciate ligament transection (ACLT) method in rats and treating chondrocytes by IL-1β in vitro. PRP and/or ALN were used to treat induced rats and chondrocytes. Hematoxylin and eosin (H&E) and Safranin O staining were used to observe the structures of cartilage. The mRNA expression of Collagen II, MMP-13, and inflammatory factors (IL-18, IL-1β, and TNF-α) in the cartilage and chondrocytes of rats was determined by qRT-PCR. The expression of NF-κB pathway-related proteins (p-p65, p65, IκBα, and p-IκBα) in the cartilage and chondrocytes of rats was determined by Western blot. The proliferation of chondrocytes was detected by MTT assay.

Results

Treatment with PRP, ALN, or PRP combined with ALN decreased the degree of cartilage destruction, the mRNA expression of MMP-13 and inflammatory factors (IL-18, IL-1β, and TNF-α), and the protein expression of p-IκBα/IκBα and p-p65/p65, increased Collagen II expression, and the threshold of tender and thermal pain in OA rats. Meanwhile, ALN, PRP, or ALN combined with PRP reversed the inhibiting effect of phorbol myristate acetate (PMA, an NF-κB agonist) on cell proliferation and cartilage matrix metabolism. Among them, the effects of ALN combined with PRP were most obvious.

Conclusion

PRP combined with ALN delayed OA progression by inhibiting the NF-κB signaling pathway.

Platelet-rich plasma for the treatment of knee osteoarthritis: an expert opinion and proposal for a novel classification and coding system

INTRODUCTION

Platelet-rich plasma (PRP) is able to modulate the joint environment by reducing the inflammatory distress and promoting tissue anabolism. Therefore, it has gained increasing popularity among clinicians in the treatment of osteoarthritis (OA), and it is currently proposed beside consolidated options such as viscosupplementation.

AREAS COVERED

A systematic review of all available meta-analyses evaluating intra-articular PRP injections in patients affected by knee OA was performed, to understand how this biologic treatment approach compares to the traditional injective therapies available in clinical practice. Moreover, a novel coding system and 'minimum reporting requirements' are proposed to improve future research in this field and promote a better understanding of the mechanisms of action and indications.

EXPERT OPINION

The main limitation in the current literature is the extreme variability of PRP products used, with often paucity or even lack of data on the biologic features of PRP, which should not be considered as a simple substance, but rather a 'procedure' requiring accurate reporting of the characteristics of the product but also all preparation and application modalities. This approach will aid in matching the optimal PRP product to specific patient factors, leading to improved outcomes and the elucidation of the cost-effectiveness of this treatment.

Autologous Protein Solution Injections for the Treatment of Knee Osteoarthritis: 3-Year Results

BACKGROUND

Blood derivative injections have been recently proposed to address osteoarthritis (OA) with overall positive results, although long-term data on their efficacy are lacking. A novel blood derivative has been developed to concentrate growth factors and antagonists of inflammatory cytokines and shown promising early findings.

PURPOSE

To investigate if the positive effects of a single intra-articular injection of autologous protein solution (APS) in patients affected by knee OA-previously documented at 1 year in a multicenter double-blind randomized saline-controlled trial-last up to 3 years.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A total of 46 patients with Kellgren-Lawrence 2 or 3 knee OA were randomized into 2 groups: 1 ultrasound-guided APS injection (n = 31) or 1 saline injection (n = 15). At 1 year, the saline group was allowed to cross over. Patients were re-evaluated at 24 and 36 months through the visual analog scale for pain (VAS), Western Ontario and McMaster Universities Osteoarthritis Index Likert 3.1 (WOMAC LK 3.1), Knee injury and Osteoarthritis Outcome Score (KOOS), 36-Item Short Form Health Survey (SF-36), and Outcome Measures in Rheumatology-Osteoarthritis Research Society International (OMERACT-OARSI) responder rate. Magnetic resonance imaging evaluation was performed with the MRI Osteoarthritis Knee Score (MOAKS) before and at 24 months after treatment, and radiographs were assessed per Kellgren-Lawrence before and annually after treatment.

RESULTS

In the APS cohort, WOMAC pain improved from 11.5 ± 2.4 (mean ± SD) to 4.3 ± 4.0 at 1 year and to 5.7 ± 5.0 at 3 years (P < .0001 vs baseline). The APS cohort also showed a statistically significant improvement in its KOOS pain score from 39.4 ± 13.1 to 70.6 ± 21.5 at 1 year and to 64.1 ± 24.6 at 3 years (P < .0001 vs baseline) and VAS pain scores from 5.5 ± 2.2 to 2.6 ± 2.5 at 1 year and to 3.4 ± 2.9 at 3 years (P = .0184 vs baseline). VAS pain score significantly worsened from 12 to 36 months (P = .0411). All patients in the saline group decided to cross over to APS, and their final scores were better than baseline, although not significantly better than at the crossover point. Overall, 7 of 26 (26.9%) APS cases and 4 of 14 (28.6%) crossover cases were considered failures as patients underwent further injective treatments or surgical procedures between the 12- and 36-month follow-up. MOAKS findings showed no statistically significant differences. Patients with better cartilage had greater WOMAC pain improvement when their baseline scores were worse, whereas the trend was reversed for patients with cartilage loss at baseline.

CONCLUSION

Intra-articular use of APS for mild to moderate knee OA was safe, and significant pain improvement was documented 3 years after a single injection. Patients with better cartilage status seem to respond better than patients with more cartilage loss, with more clinical improvement even when starting from more painful conditions.

REGISTRATION

NCT02138890 (ClinicalTrials.gov identifier).

Intra-articular Injection of Pure Platelet-Rich Plasma Is the Most Effective Treatment for Joint Pain by Modulating Synovial Inflammation and Calcitonin Gene-Related Peptide Expression in a Rat Arthritis Model

BACKGROUND

Platelet-rich plasma (PRP) has emerged as a treatment for osteoarthritis (OA). However, the effect that leukocyte concentrations in PRP have on OA remains unclear.

PURPOSE

To clarify the optimal PRP formulation for OA treatment by comparing pure PRP, leukocyte-poor PRP (LP-PRP), and leukocyte-rich PRP (LR-PRP) in a rat arthritis model.

STUDY DESIGN

Controlled laboratory study.

METHODS

Knee arthritis was induced bilaterally in male Wistar rats with intra-articular injections of monosodium iodoacetate (MIA) on day 0. Rats were randomly assigned to 1 of 3 treatment groups (pure PRP, LP-PRP, and LR-PRP). On day 1, allogenic PRP was injected into the right knee of rats and phosphate-buffered saline was injected into the left knee as a control. Weight distribution on the hindlimbs was measured for 14 days to assess pain behavior. Rats were euthanized at day 5 or 14 for histological assessment of synovial tissue and cartilage. Immunohistochemical staining of calcitonin gene-related peptide (CGRP) and α-smooth muscle actin was performed to determine the mechanism of pain relief induced by the PRP preparations.

RESULTS

In all groups, PRP increased the load-sharing ratio on PRP-injected knees, with pure PRP eliciting the largest effect among the 3 kinds of PRP (P < .05). Structural changes in the synovial tissue were significantly inhibited in the pure-PRP group compared with the control group after both 5 and 14 days (P < .001 and P = .025, respectively), whereas no significant difference was found between the control, LP-PRP, and LR-PRP groups. An inhibitory effect on cartilage degeneration was observed only in the pure-PRP group on day 14. Pure PRP also significantly inhibited expression of CGRP-positive nerve fibers in the infrapatellar fat pad compared with the other groups (P < .05).

CONCLUSION

In an MIA-induced arthritis model, pure PRP injection was the most effective treatment for reduction of pain-related behavior and inhibition of synovial inflammation and pain sensitization.

CLINICAL RELEVANCE

PRP formulations should be optimized for each specific disease. This study shows the superiority of pure PRP for treatment of arthritis and joint pain.

Dose-Dependent Effects of Platelet-Rich Plasma Powder on Chondrocytes In Vitro

BACKGROUND

Platelet-rich plasma (PRP) is widely used in sports medicine. However, neither preparation nor parameters for clinical application, such as concentration, timing, and number of applications, are standardized, making research and clinical utilization challenging.

PURPOSE

To investigate the effect of varying doses of PRP powder in terms of different concentrations, timing, and number of applications on human chondrocytes in a reproducible cell culture model.

STUDY DESIGN

Controlled laboratory study.

METHODS

A standardized lyophilized platelet growth factor preparation (PRP powder) was used to stimulate human chondrocytes. Chondrocytes were cultivated for 2 weeks with different stimulation frequencies (2×, 3×, 6×) and different concentrations of PRP powders (0.5%, 1%, 5%). Cell proliferation and metabolic cell activity were analyzed on days 7 and 14. Phenotypic changes were visualized through live-dead staining. Chondrogenic differentiation was quantified with enzyme-linked immunosorbent assay to assess the synthesis of procollagen types 1 and 2. Furthermore, sulfated proteoglycans and glycosaminoglycans were analyzed.

RESULTS

Human chondrocytes exhibited a significant dose- and time-dependent increase after 14 days in cell number (1% and 5% PRP powder vs unstimulated control: 7.95- and 15.45-fold increase, respectively; 2× vs 6× stimulation with 5% PRP powder: 4.00-fold increase) and metabolic cell activity (1% and 5% PRP powder vs unstimulated control: 3.27-fold and 3.58-fold change, respectively). Furthermore, cells revealed a significant increase in the amount of bone-specific procollagen type 1 (14 days, 1.94-fold) and sulfated glycosaminoglycans (14 days, 2.69-fold); however, no significant change was observed in the amount of cartilage-specific collagen type 2.

CONCLUSION

We showed that chondrocytes exhibit a significant dose- and time-dependent increase in cell number and metabolic cell activity. The standardized use of growth factor concentrates in cell culture models can contribute to clinical knowledge in terms of dosage and timing of PRP applications.

CLINICAL RELEVANCE

Problems with PRP, such as the absence of standardization, lack of consistency among studies, and unknown dosage, could be solved by using characterized PRP powder made by pooling and lyophilizing multiple platelet concentrates. The innovative PRP powder generates new possibilities for PRP research, as well as for the treatment of patients.

Intra-articular injection of culture-expanded mesenchymal stem cells with or without addition of platelet-rich plasma is effective in decreasing pain and symptoms in knee osteoarthritis: a controlled, double-blind clinical trial

PURPOSE

To compare the clinical and laboratory outcomes of intra-articular injections of culture-expanded bone-derived mesenchymal stem cells (MSCs) with or without platelet-rich plasma (PRP) to intra-articular corticosteroid injections for the treatment of knee osteoarthritis (OA).

METHODS

Forty-seven patients with radiographic and symptomatic knee OA were randomized into three groups for intra-articular injections: autologous bone marrow-derived culture-expanded MSCs (n = 16); autologous bone marrow-derived culture-expanded MSCs + PRP (n = 14); and corticosteroid (n = 17). The outcomes were assessed by the Knee Injury and Osteoarthritis Outcome Score (KOOS) and range of motion (ROM) at baseline, 1, 2, 3, 6, 9 and 12 months and intra-articular cytokines analysis at baseline, 6 and 12 months postoperatively.

RESULTS

The three groups showed significant improvement in most KOOS domains and global score at 1st month and all domains and global score at 12-month follow-up (p < 0.05). At the 1st month, only the MSCs group showed significant differences in KOOS symptoms domain (p = 0.003). The MSCs and MSCs + PRP groups showed the highest percentage of improvement in most KOOS domains and global score compared to the corticosteroid group. All three groups showed a significant reduction in intra-articular levels of human interleukin-10 cytokine, from baseline to 12 months (p < 0.05).

CONCLUSION

An intra-articular injection of bone marrow-derived culture-expanded MSCs with or without the addiction of PRP is effective in improving the function and decreasing symptoms caused by knee OA at 12-month follow-up.

LEVEL OF EVIDENCE

II.

MSC encapsulation in alginate microcapsules prolongs survival after intra-articular injection, a longitudinal in vivo cell and bead integrity tracking study

Mesenchymal stem cells (MSC) are promising candidates for use as a biological therapeutic. Since locally injected MSC disappear within a few weeks, we hypothesize that efficacy of MSC can be enhanced by prolonging their presence. Previously, encapsulation in alginate was suggested as a suitable approach for this purpose. We found no differences between the two alginate types, alginate high in mannuronic acid (High M) and alginate high in guluronic acid (High G), regarding MSC viability, MSC immunomodulatory capability, or retention of capsule integrity after subcutaneous implantation in immune competent rats. High G proved to be more suitable for production of injectable beads. Firefly luciferase-expressing rat MSC were used to track MSC viability. Encapsulation in high G alginate prolonged the presence of metabolically active allogenic MSC in immune competent rats with monoiodoacetate-induced osteoarthritis for at least 8 weeks. Encapsulation of human MSC for local treatment by intra-articular injection did not significantly influence the effect on pain, synovial inflammation, or cartilage damage in this disease model. MSC encapsulation in alginate allows for an injectable approach which prolongs the presence of viable cells subcutaneously or in an osteoarthritic joint. Further fine tuning of alginate formulation and effective dosage for might be required in order to improve therapeutic efficacy depending on the target disease.

Platelet-Rich Plasma Augmentation to Microfracture Provides a Limited Benefit for the Treatment of Cartilage Lesions: A Meta-analysis

Background:

Microfracture is the most common first-line option for the treatment of small chondral lesions, although increasing evidence shows that the clinical benefit of microfracture decreases over time. Platelet-rich plasma (PRP) has been suggested as an effective biological augmentation to improve clinical outcomes after microfracture.

Purpose:

To evaluate the clinical evidence regarding the application of PRP, documenting safety and efficacy of this augmentation technique to improve microfracture for the treatment of cartilage lesions.

Study Design:

Systematic review; Level of evidence, 3.

Methods:

A systematic review was performed in PubMed, EBSCOhost database, and the Cochrane Library to identify comparative studies evaluating the clinical efficacy of PRP augmentation to microfracture. A meta-analysis was performed on articles that reported results for visual analog scale (VAS) for pain, International Knee Documentation Committee (IKDC), and American Orthopaedic Foot and Ankle Society (AOFAS) scores. Risk of bias was documented through use of the Cochrane Collaboration Risk of Bias 2.0 and Risk of Bias in Non-randomized Studies of Interventions assessment tools. The quality assessment was performed according to the Grading of Recommendations Assessment, Development and Evaluation guidelines.

Results:

A total of 7 studies met the inclusion criteria and were included in the meta-analysis: 4 randomized controlled trials, 2 prospective comparative studies, and 1 retrospective comparative study, for a total of 234 patients. Of the 7 studies included, 4 studies evaluated the effects of PRP treatment in the knee, and 3 studies evaluated effects in the ankle. The analysis of all scores showed a difference favoring PRP treatment in knees (VAS, P = .002 and P < .001 at 12 and 24 months, respectively; IKDC, P < .001 at both follow-up points) and ankles (both VAS and AOFAS, P < .001 at 12 months). The improvement offered by PRP did not reach the minimal clinically important difference (MCID).

Conclusion:

PRP provided an improvement to microfracture in knees and ankles at short-term follow-up. However, this improvement did not reach the MCID, and thus it was not clinically perceivable by the patients. Moreover, the overall low evidence and the paucity of high-level studies indicate further research is needed to confirm the potential of PRP augmentation to microfracture for the treatment of cartilage lesions.

Bone Marrow Aspirate Concentrate Is Equivalent to Platelet-Rich Plasma for the Treatment of Knee Osteoarthritis at 1 Year: A Prospective, Randomized Trial

Background:

Approximately 47 million people in the United States have been diagnosed with arthritis. Autologous platelet-rich plasma (PRP) injections have been documented to alleviate symptoms related to knee osteoarthritis (OA) in randomized controlled trials, systematic reviews, and meta-analyses. Autologous bone marrow aspirate concentrate (BMC) injections have also emerged as a treatment option for knee OA, with a limited clinical evidence base.

Purpose:

To compare the efficacy of BMC to PRP for the treatment of knee OA regarding pain and function at multiple time points up to 12 months after an injection. We hypothesized that BMC will be more effective in improving outcomes in patients with knee OA.

Study Design:

Randomized controlled trial; Level of evidence, 2

Methods:

A total of 90 participants aged between 18 and 80 years with symptomatic knee OA (Kellgren-Lawrence grades 1-3) were randomized into 2 study groups: PRP and BMC. Both groups completed the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and subjective International Knee Documentation Committee (IKDC) questionnaires before and 1, 3, 6, 9, and 12 months after a single intra-articular injection of leukocyte-rich PRP or BMC.

Results:

There were no statistically significant differences in baseline IKDC or WOMAC scores between the 2 groups. All IKDC and WOMAC scores for both the PRP and BMC groups significantly improved from baseline to 1 month after the injection (P < .001). These improvements were sustained for 12 months after the injection, with no difference between PRP and BMC at any time point.

Conclusion:

Both PRP and BMC were effective in improving patient-reported outcomes in patients with mild to moderate knee OA for at least 12 months; neither treatment provided a superior clinical benefit. Autologous PRP and BMC showed promising clinical potential as therapeutic agents for the treatment of OA, and while PRP has strong clinical evidence to support its efficacy, BMC has limited support. This study did not prove BMC to be superior to PRP, providing guidance to clinicians treating OA. It is possible that the results were affected by patients knowing that there was no control group.

Registration:

NCT03289416 (ClinicalTrials.gov identifier).

Platelet-rich Plasma-induced Inhibition of Chondrocyte Apoptosis Directly Affects Cartilage Thickness in Osteoarthritis

Abstract

The search for minimally invasive treatment of osteoarthritis has led to the development of biological options such as platelet-rich plasma (PRP), mesenchymal stem cells (MSCs), and bone marrow aspirate concentrates. This research was conducted to study the outcomes of PRP administration in the chemical-induced model of osteoarthritis in rat knee.

Methods and results

Two milligrams of monoiodoacetate (MIA) was used for the induction of arthritis in the right knee of 16 rats. Autologous PRP was prepared by double centrifugation, which was then administered in the arthritic knee of eight rats. This group was labeled as the treated group (A) while the rest were counted as the non-treated group (B). Chondrocyte count and uncalcified cartilage thickness were morphometrically assessed on hematoxylin and eosin (H&E) stained slides, and it was noted that treated group A had a higher chondrocyte count and more cartilage height as compared to non-treated group B. Intergroup comparison was done between the treated group (A) and non-treated group (B) using the independent t-test. P-values were found to be statistically significant for these parameters.

Conclusion

This study thus concluded that PRP had induced an inhibitory effect on the apoptosis of chondrocytes, which, in turn, prevented the loss of cartilage height by inhibiting matrix loss.

Local controlled release of corticosteroids extends surgically induced joint instability by inhibiting tissue healing

Background and Purpose

Corticosteroids are intra‐articularly injected to relieve pain in joints with osteoarthritis (OA) or acute tissue damage such as ligament or tendon tears, despite its unverified contraindication in unstable joints. Biomaterial‐based sustained delivery may prolong reduction of inflammatory pain, while avoiding harmful peak drug concentrations.

Experimental Approach

The applicability of prolonged corticosteroid exposure was examined in a rat model of anterior cruciate ligament and medial meniscus transection (ACLT + pMMx) with ensuing degenerative changes.

Key Results

Intra‐articular injection of a bolus of the corticosteroid triamcinolone acetonide (TAA) resulted in enhanced joint instability in 50% of the joints, but neither instability‐induced OA cartilage degeneration, synovitis, nor the OA‐related bone phenotype was affected. However, biomaterial microsphere‐based extended TAA release enhanced instability in 94% of the animals and induced dystrophic calcification and exacerbation of cartilage degeneration. In healthy joints, injection with TAA releasing microspheres had no effect at all. In vitro, TAA inhibited cell migration out of joint tissue explants, suggesting inhibited tissue healing in vivo as mechanisms for enhanced instability and subsequent cartilage degeneration.

Conclusions and Implications

We conclude that short‐term TAA exposure has minor effects on surgically induced unstable joints, but its extended presence is detrimental by extending instability and associated joint degeneration through compromised healing. This supports a contraindication of prolonged corticosteroid exposure in tissue damage‐associated joint instability, but not of brief exposure.