Platelets and plasma stimulate sheep rotator cuff tendon tenocytes when cultured in an extracellular matrix scaffold

Study of bone-tendon interface healing in an animal model using a synthetic scaffold and PRP

PURPOSE

Biological matrices have been used to reinforce large rotator cuff tear repairs. However, rapid resorption and initial immune reactions presented challenges in clinical practice. This study evaluates whether a resorbable synthetic matrix (scaffold), used alone or with platelet-rich plasma (PRP), impacts repair processes at microscopic, ultrasound, and biomechanical levels in a rabbit model of induced tendon-bone interface injury.

METHODS

An experimental study was performed on 24 rabbits. Two experimental groups (n = 12 each) and a control group (n = 24) were defined. In the first group (BioP), the internal gastrocnemius tendon was sectioned and repaired to bone using double-row sutures, reinforced with a PLC (poly-L-lactic-co-ε-caprolactone) and PLA (polylactic acid) scaffold. In the second group (BioP + PRP), autologous PRP was added to the repair. The control group received no scaffold or PRP. Euthanasia was performed at 8 weeks, followed by microscopic, ultrasound, and biomechanical evaluations.

RESULTS

Microscopically, a granulomatous reaction limited to the foreign body was observed in both scaffold groups. The healing process was not altered in any group, showing good biocompatibility of the scaffold. Echographically, a greater sagittal diameter was observed in the group without PRP compared to the other groups. Biomechanically, no significant differences in rupture zones were found across groups, but the scaffold-only group required a higher maximum applied force before rupture.

CONCLUSIONS

At 8 weeks, using a degradable synthetic PLC and PLA scaffold as support at the bone-tendon interface did not significantly alter the normal repair process, showed echographic and biomechanical benefits, and PRP did not show additional benefits in our experimental model.

Exploring the applications of platelet-rich plasma in tissue engineering and regenerative medicine: evidence from goat and sheep experimental research

Platelet-rich plasma (PRP) has emerged as a promising therapeutic approach in regenerative medicine. It contains various growth factors and bioactive molecules that play pivotal roles in tissue repair, regeneration, and inflammation modulation. This comprehensive narrative review delves into the therapeutic potential of PRP in experimental goat and sheep research, exploring recent advancements, challenges, and future prospects in the field. PRP has been explored for its application in musculoskeletal injuries, wound healing, and orthopedic conditions. Studies have demonstrated the ability of PRP to accelerate tissue healing, reduce inflammation, and improve the overall quality of healing. Recent advancements in PRP technology have led to the development of novel formulations and delivery methods to enhance its therapeutic efficacy. PRP has shown promise in tendon and ligament injuries, osteoarthritis, and bone fractures in experimental goat and sheep research. Despite these advancements, several challenges and opportunities exist to harness the full therapeutic potential of PRP in regenerative medicine. Standardizing PRP preparation protocols, including blood collection techniques, centrifugation parameters, and activation methods, is essential to ensure consistency and reproducibility of the findings. Moreover, further research is needed to elucidate the optimal dosing, frequency, and timing of PRP administration for different clinical indications. Research conducted in goat and sheep models provides evidence supporting the translational potential of PRP in tissue engineering and regenerative medicine. By harnessing the regenerative properties of PRP and leveraging insights from preclinical studies, researchers can develop innovative therapeutic strategies to address unmet clinical needs and improve patient outcomes in diverse medical specialties.

Platelet-rich plasma in the pathologic processes of tendinopathy: a review of basic science studies

Tendinopathy is a medical condition that includes a spectrum of inflammatory and degenerative tendon changes caused by traumatic or overuse injuries. The pathological mechanism of tendinopathy has not been well defined, and no ideal treatment is currently available. Platelet-rich plasma (PRP) is an autologous whole blood derivative containing a variety of cytokines and other protein components. Various basic studies have found that PRP has the therapeutic potential to promote cell proliferation and differentiation, regulate angiogenesis, increase extracellular matrix synthesis, and modulate inflammation in degenerative tendons. Therefore, PRP has been widely used as a promising therapeutic agent for tendinopathy. However, controversies exist over the optimal treatment regimen and efficacy of PRP for tendinopathy. This review focuses on the specific molecular and cellular mechanisms by which PRP manipulates tendon healing to better understand how PRP affects tendinopathy and explore the reason for the differences in clinical trial outcomes. This article has also pointed out the future direction of basic research and clinical application of PRP in the treatment of tendinopathy, which will play a guiding role in the design of PRP treatment protocols for tendinopathy.

Influential Studies in Orthopaedic Platelet-Rich Plasma Research Are Recent and Consist of High Levels of Evidence: A Review of the Top 50 Most Cited Publications

Platelet-rich plasma (PRP) has garnered widespread and increasing attention in recent years. We aimed to characterize the most influential articles in PRP research while clarifying controversies surrounding its use and clinical efficacy and identifying important areas on which to focus future research efforts. The Science Citation Index Expanded subsection of the Web of Science Core Collection was systematically searched to identify the top 50 cited publications on orthopedic PRP research. Publication and study characteristics were extracted, and Spearman's correlations were calculated to assess the relationship between citation data and level of evidence. The top 50 articles were published between the years 2005 and 2016, with 68% published in the year 2010 or later. Of the 33 studies for which level of evidence was assessed, the majority were of level I or II (18, 54.5%). Seventeen articles (34%) were classified as basic science. All clinical studies were prospective, and most (12 studies, 60%) included a high number of metrics related to the PRP preparation protocol and composition. Knee osteoarthritis was the most common topic among clinical studies in the top 50 cited articles (11 studies, 34%). More recent articles were associated with higher citation rates (ρ = 0.46, p < 0.001). The most influential articles on orthopaedic PRP research are recent and consist of high-level of evidence studies mostly. Randomized controlled trials were the most common study type, while basic science articles were relatively less common. The most influential clinical studies reported a high number of metrics related to their PRP preparation protocol and the final PRP composition. These results suggest a rapidly evolving field with the potential to better explain inconsistent clinical results with improved understanding and documentation of basic science concepts such as PRP composition, preparation, and combination techniques.

Effect of suprascapular nerve injury on rotator cuff enthesis

BACKGROUND

Numerous reports have shown that retracted rotator cuff tears may cause suprascapular nerve injury, and nerve injury causes atrophy and fat accumulation in the rotator cuff muscles. However, the effect of suprascapular nerve injury on rotator cuff enthesis has not been directly defined. This study aimed to investigate the effect of suprascapular nerve injury on rotator cuff enthesis.

METHODS

Twenty-four Wistar albino rats underwent bilateral transection of the suprascapular nerve. Additional 6 rats were used as the sham group. Bilateral supraspinatus and infraspinatus entheses were examined after 1, 4, 8, and 12 weeks of nerve transection. Histomorphometric analyses were performed for each zone of enthesis.

RESULTS

Compared with normal enthesis, significant and consistent decrease in cellularity were observed in the tendon and bone at all time points (P < .001). Collagen bundle diameter in the tendon also decreased in a similar manner (P < .001). Apart from the tendon and bone zones, fibrocartilage and calcified fibrocartilage zones showed similar response, and significant decrease in cellularity was observed 8 weeks after nerve transection (P < .001).

CONCLUSION

This study identifies suprascapular nerve injury as an underlying mechanism leading to compromise of the rotator cuff enthesis structure. Suprascapular nerve injury may be considered as an etiologic factor for the impaired healing after repair of a massive tear.

The Effects of Platelet-Rich Plasma to Decrease the Risk of Seroma Formation After Mastectomy and Axillary Dissection

BACKGROUND

Seroma, which is the most common complication after mastectomy and axillary dissection, is the leakage of the lymphovascular fluid into the dead space. It can cause local complications varying from delayed wound healing to infection and skin flap necrosis. The aim of this study was to evaluate whether platelet-rich plasma (PRP) reduces the risk of seroma formation.

MATERIALS AND METHODS

A total of 24 Wistar albino rats were randomly divided into three groups of eight rats in each. For the rats in group 1, no additional procedures were carried out. The rats in groups 2 and 3 were applied with 0.25 and 0.5 mL/cm² PRP, respectively, to the operation site. The groups were compared in respect of adhesion scores, histopathologic examination, and tissue seroma volume.

RESULTS

The mean seroma volume was 2.19 ± 0.78 mL in group 1, 1.43 ± 0.35 mL in group 2, and 0.96 ± 0.24 mL in group 3. The seroma volumes of groups 3 and 2 were significantly lower than those in group 1. In the macroscopic assessment the mean general adhesion score was 6 ± 0.75 in group 3. The other general adhesion scores were 5.25 ± 0.70 and 2.12 ± 0.64 in groups 2 and 1, respectively. The adhesion scores of groups 3 and 2 were significantly higher than those of group 1. The mean inflammatory cell score was 0.87 ± 0.83 in group 3, 2.0 ± 0.92 in group 2, and 3.0 ± 0.53 in group 1. There were significantly lower levels of inflammatory cells in group 3 than in the other groups and the group 2 inflammatory cell count was lower than that of group 1. Fibroblast density score was significantly higher in group 3 (2.50 ± 1.06) compared with the other groups. Neovascularization was significantly higher in groups 3 and 2 compared with group 1. The mean neovascularization score was 2.25 ± 1.16 and 2.12 ± 1.12 in groups 2 and 3, respectively. There were no statistically significant differences between the groups in respect of collagen levels.

CONCLUSIONS

Local application of PRP in rats after experimental mastectomy and axillary dissection was observed to decrease seroma formation and to increase neovascularization and fibroblast density.

Effect of light-emitting diodes, platelet-rich plasma, and their combination on the activity of sheep tenocytes

Healthy tendons play an important role in joint movements and subjected to a group of pathologies called tendinopathy due to multiple factors. Tendons have a slowly repairing process due to the low vascularity and cellularity. Treatment options aimed at potentiating the healing response and relieving symptoms. Phototherapy and platelet-rich plasma were novel treatment modalities in tendons based on photobiomodulation and growth factors during healing, and the results were encouraging suggesting calibrating treatment parameters. This study utilizes cell culture to explore the potential effect of light-emitting diode and/or growth factors in the form of platelet-rich plasma (PRP) on the activity of tenocytes isolated from sheep Achilles tendons by measuring the cell metabolism and cell mobility using cell viability and migration assays to proof safety and confirm activity. Results showed that sheep tenocyte-cultured groups treated with 5% platelet-rich plasma alone or combined with 4 J/cm² light-emitting diode have increased viability significantly when compared to control group after a 48 h, while light-emitting diode treatment has not decreased cell migration significantly when compared with control. Result suggests that using platelet-rich plasma alone or combined with light-emitting diode might have potential to enhance healing response at the conditions applied. PRP could enhance proliferation while LED could enhance migration and proliferation. Further research is needed at longer durations.

Completion repair exhibits increased healing characteristics compared with in situ repair of partial thickness bursal rotator cuff tears

PURPOSE

Little information is available regarding the healing capacity of in situ and completion repair for the treatment of partial thickness rotator cuff tears. The purpose of the study was to analyze the healing characteristics of both techniques.

METHODS

Twenty-four adult Sprague-Dawley rats were operated. Partial thickness bursal side tears were created bilaterally at the supraspinatus tendons. Additional 6 rats were used as the sham group. The right shoulders were repaired in situ, and the left shoulders were repaired using the tear completion technique on the 10th day after detachment surgery. Rats were sacrificed on the 10th and 30th days after repair surgery. Type I collagen, the TNF-α concentrations, the number and diameter of fibroblasts, and neovascularization were examined at two different time points.

RESULTS

The collagen concentration (ng/mg total protein) was significantly increased in both groups at T1 and decreased in the in situ group, whereas completion repair continued to increase at T2 (P < 0.05). The mean fibroblast diameter in the completion repair group continued to increase at both time points (P < 0.05). Neovascularization was significantly increased with tear completion compared with in situ repair (P < 0.05) at T1. No significant (n.s.) differences regarding the TNF-α concentration (pg/mg total protein) were noted for both surgical techniques at T2 (P > 0.05).

CONCLUSION

Despite the concerns of detaching the intact tendon, the completion repair technique exhibited increased healing characteristics compared with the in situ technique. The reason for this finding might be the refreshing effect of debridement at the chronic degenerated tendon that could improve the healing response.

The Efficacy of Platelet-Rich Plasma on Tendon and Ligament Healing: A Systematic Review and Meta-analysis With Bias Assessment

BACKGROUND

There has been a surge in high-level studies investigating platelet-rich plasma (PRP) for tendon and ligament injuries. A number of meta-analyses have been published, but few studies have focused exclusively on tendon and ligament injuries.

PURPOSE

To perform a meta-analysis assessing the ability of PRP to reduce pain in patients with tendon and ligament injuries.

STUDY DESIGN

Systematic review and meta-analysis.

METHODS

This study followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. A comprehensive search of the literature was carried out in April 2017 using electronic databases PubMed, MEDLINE, and the Cochrane Library. Only level 1 studies were included. Platelet and leukocyte count, injection volume, kit used, participant age/sex, comparator, and activating agent used were recorded. The short-term and long-term efficacy of PRP was assessed using the visual analog scale (VAS) to measure pain intensity. Injury subgroups (rotator cuff, tendinopathy, anterior cruciate ligament, and lateral epicondylitis) were evaluated. Funnel plots and the Egger test were used to screen for publication bias, and sensitivity analysis was performed to evaluate the effect of potential outliers by removing studies one at a time.

RESULTS

Thirty-seven articles were included in this review, 21 (1031 participants) of which could be included in the quantitative analysis. The majority of studies published investigated rotator cuff injuries (38.1%) or lateral epicondylitis (38.1%). Seventeen studies (844 participants) reported short-term VAS data, and 14 studies (771 participants) reported long-term VAS data. Overall, long-term follow-up results showed significantly less pain in the PRP group compared with the control group (weighted mean difference [WMD], -0.84; 95% CI, -1.23 to -0.44; P < .01). Patients treated with PRP for rotator cuff injuries (WMD, -0.53; 95% CI, -0.98 to -0.09; P = .02) and lateral epicondylitis (WMD, -1.39; 95% CI, -2.49 to -0.29; P = .01) reported significantly less pain in the long term. Substantial heterogeneity was reported at baseline ( I² = 72.0%; P < .01), short-term follow-up ( I² = 72.5%; P < .01), long-term follow-up ( I² = 76.1%; P < .01), and overall ( I² = 75.8%; P < .01). The funnel plot appeared to be asymmetric, with some missingness at the lower right portion of the plot suggesting possible publication bias.

CONCLUSION

This review shows that PRP may reduce pain associated with lateral epicondylitis and rotator cuff injuries.

Regenerative Engineering of the Rotator Cuff of the Shoulder

Rotator cuff tears often heal poorly, leading to re-tears after repair. This is in part attributed to the low proliferative ability of the resident cells (tendon fibroblasts and tendon-stem cells) upon injury to the rotator cuff tissue and the low vascularity of the tendon insertion. In addition, surgical outcomes of current techniques used in clinical settings are often suboptimal, leading to the formation of neo-tissue with poor biomechanics and structural characteristics, which results in re-tears. This has prompted interest in a new approach, which we term as "Regenerative Engineering", for regenerating rotator cuff tendons. In the Regenerative Engineering paradigm, roles played by stem cells, scaffolds, growth factors/small molecules, the use of local physical forces, and morphogenesis interplayed with clinical surgery techniques may synchronously act, leading to synergistic effects and resulting in successful tissue regeneration. In this regard, various cell sources such as tendon fibroblasts and adult tissue-derived stem cells have been isolated, characterized, and investigated for regenerating rotator cuff tendons. Likewise, numerous scaffolds with varying architecture, geometry, and mechanical characteristics of biologic and synthetic origin have been developed. Furthermore, these scaffolds have been also fabricated with biochemical cues (growth factors and small molecules), facilitating tissue regeneration. In this Review, various strategies to regenerate rotator cuff tendons using stem cells, advanced materials, and factors in the setting of physical forces under the Regenerative Engineering paradigm are described.

New insights into tenocyte-immune cell interplay in an in vitro model of inflammation

Inflammation plays an important role in the development and resolution of tendon diseases, but underlying mechanisms are poorly understood. We therefore aimed to analyze the response of human tenocytes to inflammatory stimuli and to uncover their interplay with macrophages in vitro. Tenocytes from human ruptured supraspinatus tendons (n = 10) were treated for three days with a stimulation mixture derived from activated mononuclear cells isolated from healthy human peripheral blood. Significantly increased expression levels of selected adhesion- and human leukocyte antigen (HLA)-molecules, and enhanced interleukin (IL)-6 release were detected by flow cytometry. Tenocyte stimulation with the pro-inflammatory cytokines interferon gamma, tumor necrosis factor alpha and IL-1ß triggered similar changes in surface markers and enhanced the release of IL-6, IL-8 and monocyte chemoattractant protein 1 (MCP-1). In co-cultures of macrophages with pre-stimulated tenocytes, macrophages significantly increased CD80 expression, but simultaneously decreased HLA-DR-expression, which are both typical pro-inflammatory polarization markers. Co-cultures also released more IL-6, IL-8, MCP-1 than tenocyte-cultures alone. We demonstrate that tenocytes respond to inflammatory environments in vitro with altered surface marker and cytokine profiles and influence macrophage polarization. Importantly, all changes detected in direct co-cultures were also present in a transwell setting, implicating that communication between the cells involves soluble factors.

PRP Treatment Efficacy for Tendinopathy: A Review of Basic Science Studies

Platelet-Rich Plasma (PRP) has been widely used in orthopaedic surgery and sport medicine to treat tendon injuries. However, the efficacy of PRP treatment for tendinopathy is controversial. This paper focuses on reviewing the basic science studies on PRP performed under well-controlled conditions. Both in vitro and in vivo studies describe PRP's anabolic and anti-inflammatory effects on tendons. While some clinical trials support these findings, others refute them. In this review, we discuss the effectiveness of PRP to treat tendon injuries with evidence presented in basic science studies and the potential reasons for the controversial results in clinical trials. Finally, we comment on the approaches that may be required to improve the efficacy of PRP treatment for tendinopathy.