Mesenchymal Stromal Cells in Osteoarthritis: Evidence for Structural Benefit and Cartilage Repair

The Interaction Between Microbiota and Stem Cells on Progression of Osteoarthritis and Engineered Stem Cell for Enhancing Osteoarthritis Treatment

Osteoarthritis (OA) is characterized by the degeneration of articular cartilage caused by several factors of which novel most trends include microbiota. Specific microbiota and the role in the development of OA is less clear. The microbiota is presumed to influence OA occurrence and progression mainly via immune modulation. In recent years, bone marrow mesenchymal stem cells (MSCs) have shown great potential for the treatment of OA, however, the therapeutic efficiency has been seriously affected by the harsh microenvironment in the joint cavity. At present, many strategies have been used to enhance the function of MSCs, among them, engineering are a promising method. Therefore, this review mainly focuses on the latest research on how the microbiota affects the development of OA, stem cell repair, and the use of engineered MSCs in the treatment of OA. In addition, engineered MSCs can enhance the therapeutic potential of exosomes as a novel strategy for treating OA. Our review provides a comprehensive perspective on the role of microbiota in OA and the influence of MSCs therapy and engineered MSCs on the treatment of OA.

Bio-3D printing of scaffold-free ADSC-derived cartilage constructs comparable to natural cartilage in vitro

BACKGROUND

In end-stage osteoarthritis (OA), osteochondral defects reach the subchondral bone and cartilage tissue of sufficient thickness is required to compensate for the defects. Adipose-derived mesenchymal stem/stromal cells (ADSCs), which are abundant in the body, have the potential to differentiate into cartilage and may be a useful cell source for cartilage regeneration. If it is possible to fabricate ADSC-derived cartilage constructs that can cover the damaged area, this could lead to the development of a new regenerative therapy for OA that could replace the currently available treatments. We therefore sought to produce cartilage constructs with suitable thickness and biological properties, similar to native cartilage, using the bio-three-dimensional (3D) printer. We also investigated the culture protocol to ensure that the constructs were fully mature even at the internal site.

METHODS

ADSCs were isolated from three rats and expanded to create cartilage spheroids. The spheroids were arranged into patches using a Kenzan bio-3D printer to create scaffold-free, cell-only cartilage constructs. Basic fibroblast growth factor (bFGF) was added during expansion culture and varying concentrations of bone morphogenetic protein2 (BMP2) were supplemented during chondrogenic differentiation. The levels of glycosaminoglycans (GAG) in the spheroids and constructs were measured. The histology of the spheroids and constructs and the compressive strength of the constructs were evaluated.

RESULTS

The amount of GAG in the cartilage spheroids was higher in the bFGF and high-BMP2 concentration groups than in the non-supplemented and low-BMP2 concentration groups. Chondrocytes were abundant in the spheroids and constructs, and the extracellular matrix was homogeneously positive for safranin O staining and type II collagen immunostaining. The strength of cartilage constructs was consistent with that of the native cartilage (compressive strength 4.2 ± 1.5 MPa, n = 12).

CONCLUSION

By optimizing the cell culture conditions, inducing chondrogenic differentiation, and bio-3D printing, we successfully fabricated fully mature cartilage constructs with mechanical and histological properties similar to those of articular cartilage.

Posterior iliac crest vs. proximal tibia: distinct sources of anti-inflammatory and regenerative cells with comparable 6-month clinical outcomes in treatment of osteoarthritis

BACKGROUND

Human bone marrow is a source of mesenchymal stem cells (MSCs), other progenitor cells, and factors with anti-inflammatory and regenerative capacity. Though the fraction of MSCs out of the nucleated cells is very small, bone marrow aspirate (BMA) for osteoarthritis (OA) has noteworthy effects. BMA is usually collected from the posterior or anterior iliac crest, and rarely from the proximal tibia. We investigated the clinically beneficial concentration of ex vivo MSCs, derived from BM harvested from the posterior iliac crest and proximal tibia by Marrow Cellution™ Aspiration System, and their phenotypic differences, in comparison to autologous Platelet-Rich Plasma (PRP) treatment prepared with a manual, closed system.

METHODS

A single-center, parallel, randomized controlled study was designed to investigate the efficacy of BMA from the posterior iliac crest compared to BMA from the proximal tibia, against a control group treated with PRP, in knee OA. Thirty patients with knee OA grade I-IV, according to Kellgren-Lawrence (KL), were distributed into each group. Visual Analog Scale (VAS) and Western Ontario & McMaster Universities Arthritis Index (WOMAC) score were used for clinical outcome evaluation.

RESULTS

Data from an intermediate analysis of 6-months follow-up, involving 15 patients in each arm, showed that the posterior iliac crest was significantly more densely populated with mononuclear cells, than the proximal tibia (p = 0.005). Flow cytometric analysis on ex vivo BMA showed a significantly greater number of MSCs in the BM-derived from the posterior iliac crest when compared with the proximal tibia (p < 0.001), together with a significantly higher number of platelets (PLTs) (p < 0.001). Surprisingly, despite these differences in cells number, the improvement in early pain and function scores, after each treatment, were statistically significant within each of the three arms. BM from the proximal tibia showed the highest ΔWOMAC, while BM from the posterior iliac crest showed the highest ΔVAS; however, these differences were not statistically significant across the three arms (p > 0.05). A better outcome, in terms of ΔVAS, was observed in patients classified as KL I-II, when treated with BMA from crest (p < 0.001) and PRP (p = 0.004). Moreover, the effect of BMA treatment on ΔVAS depends on MSCs % only in the Tibia Arm (r = -0.59, p = 0.021), where we also found a correlation between ΔWOMAC and monocytes (r = 0.75, p = 0.016).

CONCLUSION

The results indicate that the iliac crest yields a higher concentration of MSCs compared to the proximal tibia, however both BM, independently of the MSCs concentration, show a beneficial clinical outcome in the treatment of knee OA. Furthermore, BMA is not superior to PRP treatment.

Safety and efficacy of placental mesenchymal stromal cells-derived extracellular vesicles in knee osteoarthritis: a randomized, triple-blind, placebo-controlled clinical trial

BACKGROUND

Knee osteoarthritis causes pain and disability in many people worldwide, for which no definitive treatment has yet been proposed. In this study, we investigated the safety and efficacy of placental mesenchymal stromal cells-derived extracellular vesicles in patients with knee osteoarthritis.

METHODS

This triple-blind, randomized clinical trial included patients suffering from bilateral knee osteoarthritis with grade 2 or 3. The knees of each patient were randomized to intervention and control. For the intervention knee, 5 cc of placental mesenchymal stromal cells-derived extracellular vesicles were injected, and for the control knee, 5 cc of normal saline was injected. The patients' symptoms were evaluated before the intervention and 2 and 6 months after the intervention using VAS, WOMAC questionnaire, and Lequesne index. MRI was performed before the intervention and 6 months after the intervention to evaluate retropatellar and tibiofemoral cartilage volume, medial and lateral meniscal disintegrity, ACL injury, and effusion-synovitis.

RESULTS

62 knees (31 patients) were enrolled in this study. There were 31 knees as intervention and 31 knees as control. Finally, the data of 58 knees (29 patients) were analyzed, including 28 women and 1 man. The mean age of the patients was 55.38 ± 6.07 years. No statistically significant difference was detected between the two groups in clinical outcomes (including VAS, WOMAC, and Lequesne scores) before treatment and 2 and 6 months after treatment. Also, no statistically significant difference was detected between the two groups in MRI findings before treatment and 6 months after treatment. No systemic complications or severe local reactions occurred in the patients.

CONCLUSION

A single intra-articular injection of placental mesenchymal stromal cells-derived extracellular vesicles (5 cc, 7 × 109 particles/cc) is safe, but does not improve clinical symptoms or MRI findings in knee osteoarthritis beyond placebo. The protocol of this study was approved on 11 May 2022 with registration number IRCT20210423051054N1.

Safety and efficacy of an allogeneic adipose-derived mesenchymal stem cell preparation in the treatment of knee osteoarthritis: A Phase I/IIa randomised controlled trial

Objectives

To assess the safety and efficacy of an allogeneic adipose-derived mesenchymal stem cell preparation (MAG200) in the treatment of knee osteoarthritis over 12 months.

Design

A single-centre, double-blind, ascending dose, randomised controlled trial. 40 participants with moderate knee osteoarthritis were randomised to receive a single intra-articular injection of MAG200 (dose cohorts:10, 20, 50, 100 ​× ​106 ​cells) or placebo. Primary objectives were safety and efficacy according to a compound responder analysis of minimal clinically important difference in pain (numerical pain rating scale [NPRS]) and function (Knee Injury and Osteoarthritis Outcome Score - Function in Daily Living subscale [KOOSADL]) at month 12. Secondary efficacy outcomes included changes from baseline in patient reported outcome measures and evaluation of disease-modification using quantitative MRI.

Results

Treatment was well tolerated with no treatment-related serious adverse events. MAG200 cohorts reported a greater proportion of responders than placebo and demonstrated clinical and statistically significant improvement in pain and clinically relevant improvement in all KOOS subscales. MAG200 demonstrated a reproducible treatment effect over placebo, which was clinically relevant for pain in the 10 ​× ​106 dose cohort (mean difference NPRS:-2.25[95%CI:-4.47,-0.03, p ​= ​0.0468]) and for function in the 20 ​× ​106 and 100 ​× ​106 dose cohorts (mean difference KOOSADL:10.12[95%CI:-1.51,21.76, p ​= ​0.0863] and 10.81[95%CI:-1.42,23.04, p ​= ​0.0810] respectively). A trend in disease-modification was observed with improvement in total knee cartilage volume in MAG200 10, 20, and 100 ​× ​106 dose cohorts, with progression of osteoarthritis in placebo, though this was not statistically significant. No clear dose response was observed.

Conclusion

This early-phase study provides supportive safety and efficacy evidence to progress MAG200 to later-stage trial development.

Trial registration

ACTRN12617001095358/ACTRN12621000622808.

Effect of mesenchymal stromal cells transplantation on the outcomes of patients with knee osteoarthritis: A systematic review and meta-analysis

Cell therapy has been explored as a new regenerative treatment for osteoarthritis in the field of regenerative medicine. However, the efficacy of stem cell transplantation from different sources for the treatment of knee osteoarthritis (KOA) remains controversial. This study integrates and evaluates the previously published data of stem cell transplantation for KOA to explore the curative effect of different stem cells. We conducted a meta-analysis of randomized controlled trials on stem cell therapy for KOA. Measures of efficacy included Visual Analog Scale (VAS), Lequesne index, Lysholm Knee Scoring Scale (LKSS), and Western Ontario and McMaster University Osteoarthritis Index (WOMAC). Joint injury was evaluated through the Whole-Organ Magnetic Resonance Imaging Score (WORMS) system. We analyzed 16 studies involving 875 KOA patients. The stem cell treatment showed significant VAS reduction from the third month onwards. Subgroup analysis suggested the most significant pain relief at different postoperative months came from adipose-derived and umbilical cord-derived stem cells. Autologous adipose tissue resulted in better pain alleviation compared with allogenic. However, autologous bone marrow stem cells did not show increased pain relief over allogeneic ones. Combination therapy (HA and/or PRP) showed no effect. Autologous adipose-derived stem cells demonstrate the most effective recovery of knee joint function. In WORMS assessment, there was no significant difference between the stem cell group and control. Stem cell transplantation proved safe and effective for KOA treatment. Different sources stem cells have a good effect on alleviating knee joint pain, restoring knee joint function, and minimizing patient trauma.

Comparison studies identify mesenchymal stromal cells with potent regenerative activity in osteoarthritis treatment

Osteoarthritis affects 15% of people over 65 years of age. It is characterized by articular cartilage degradation and inflammation, leading to joint pain and disability. Osteoarthritis is incurable and the patients may eventually need joint replacement. An emerging treatment is mesenchymal stromal cells (MSCs), with over two hundred clinical trials being registered. However, the outcomes of these trials have fallen short of the expectation, due to heterogeneity of MSCs and uncertain mechanisms of action. It is generally believed that MSCs exert their function mainly by secreting immunomodulatory and trophic factors. Here we used knee osteoarthritis mouse model to assess the therapeutic effects of MSCs isolated from the white adipose or dermal adipose tissue of Prrx1-Cre; R26tdTomato mice and Dermo1-Cre; R26tdTomato mice. We found that the Prrx1-lineage MSCs from the white adipose tissues showed the greatest in vitro differentiation potentials among the four MSC groups and single cell profiling showed that the Prrx1-lineage MSCs contained more stem cells than the Dermo1 counterpart. Only the Prrx1-lineage cells isolated from white adipose tissues showed long-term therapeutic effectiveness on early-stage osteoarthritis models. Mechanistically, Prrx1-lineage MSCs differentiated into Col2+ chondrocytes and replaced the damage cartilage, activated Col1 expressing in resident chondrocytes, and inhibited synovial inflammation. Transcriptome analysis showed that the articular chondrocytes derived from injected MSCs expressed immunomodulatory cytokines, trophic factors, and chondrocyte-specific genes. Our study identified a MSC population genetically marked by Prrx1 that has great multipotentiality and can differentiate into chondrocytes to replace the damaged cartilage.

Housekeeping Gene Stability in Adipose Mesenchymal Stromal Cells Cultivated in Serum/Xeno-Free Media for Osteoarthritis

Among the available therapeutics for the conservative treatment of osteoarthritis (OA), mesenchymal stromal cells (MSCs)-based products appear to be the most promising. Alongside minimally manipulated cell-based orthobiologics, where MSCs are the engine of the bioactive properties, cell expansion under good manufacturing practice (GMP) settings is actively studied to obtain clinical-grade pure populations able to concentrate the biological activity. One of the main characteristics of GMP protocols is the use of clinical-grade reagents, including the recently released serum-free/xeno-free (SFM/XFM) synthetic media, which differ significantly from the traditional reagents like those based on fetal bovine serum (FBS). As SFM/XFM are still poorly characterized, a main lack is the notion of reliable housekeeping genes (HKGs) for molecular studies, either standalone or in combination with standard conditions. Indeed, the aim of this work was to test the stability of five commonly used HKGs (ACTB, EF1A, GAPDH, RPLP0, and TBP) in adipose-derived MSCs (ASCs) cultivated in two commercially available SFM/XFM and to compare outcomes with those obtained in FBS. Four different applets widely recognized by the scientific community (NormFinder, geNorm, comparative ΔCt method, and BestKeeper) were used and data were merged to obtain a final stability order. The analysis showed that cells cultured in both synthetic media had a similar ranking for HKGs stability (GAPDH being best), albeit divergent from FBS expanded products (EF1A at top). Moreover, it was possible to identify specific HKGs for side by side studies, with EF1A/TBP being the most reliable normalizers for single SFM/XFM vs. FBS cultured cells and TBP the best one for a comprehensive analysis of all samples. In addition, stability of HKGs was donor-dependent. The normalization effect on selected genes coding for factors known to be involved in OA pathology, and whose amount should be carefully considered for the selection of the most appropriate MSC-based treatment, showed how HKGs choice might affect the perceived amount for the different media or donor. Overall, this work confirms the impact of SFM/XFM conditions on HKGs stability performance, which resulted similarly for both synthetic media analyzed in the study.

Pro-Inflammatory Cytokine Priming and Purification Method Modulate the Impact of Exosomes Derived from Equine Bone Marrow Mesenchymal Stromal Cells on Equine Articular Chondrocytes

Osteoarthritis (OA) is a widespread osteoarticular pathology characterized by progressive hyaline cartilage degradation, exposing horses to impaired well-being, premature career termination, alongside substantial financial losses for horse owners. Among the new therapeutic strategies for OA, using mesenchymal stromal cell (MSC)-derived exosomes (MSC-exos) appears to be a promising option for conveying MSC therapeutic potential, yet avoiding the limitations inherent to cell therapy. Here, we first purified and characterized exosomes from MSCs by membrane affinity capture (MAC) and size-exclusion chromatography (SEC). We showed that intact MSC-exos are indeed internalized by equine articular chondrocytes (eACs), and then evaluated their functionality on cartilaginous organoids. Compared to SEC, mRNA and protein expression profiles revealed that MAC-exos induced a greater improvement of eAC-neosynthesized hyaline-like matrix by modulating collagen levels, increasing PCNA, and decreasing Htra1 synthesis. However, because the MAC elution buffer induced unexpected effects on eACs, an ultrafiltration step was included to the isolation protocol. Finally, exosomes from MSCs primed with equine pro-inflammatory cytokines (IL-1β, TNF-α, or IFN-γ) further improved the eAC hyaline-like phenotype, particularly IL-1β and TNF-α. Altogether, these findings indicate the importance of the exosome purification method and further demonstrate the potential of pro-inflammatory priming in the enhancement of the therapeutic value of MSC-exos for equine OA treatment.

Culture-expanded mesenchymal stromal cell therapy: does it work in knee osteoarthritis? A pathway to clinical success

Osteoarthritis (OA) is a degenerative multifactorial disease with concomitant structural, inflammatory, and metabolic changes that fluctuate in a temporal and patient-specific manner. This complexity has contributed to refractory responses to various treatments. MSCs have shown promise as multimodal therapeutics in mitigating OA symptoms and disease progression. Here, we evaluated 15 randomized controlled clinical trials (RCTs) and 11 nonrandomized RCTs using culture-expanded MSCs in the treatment of knee OA, and we found net positive effects of MSCs on mitigating pain and symptoms (improving function in 12/15 RCTs relative to baseline and in 11/15 RCTs relative to control groups at study endpoints) and on cartilage protection and/or repair (18/21 clinical studies). We examined MSC dose, tissue of origin, and autologous vs. allogeneic origins as well as patient clinical phenotype, endotype, age, sex and level of OA severity as key parameters in parsing MSC clinical effectiveness. The relatively small sample size of 610 patients limited the drawing of definitive conclusions. Nonetheless, we noted trends toward moderate to higher doses of MSCs in select OA patient clinical phenotypes mitigating pain and leading to structural improvements or cartilage preservation. Evidence from preclinical studies is supportive of MSC anti-inflammatory and immunomodulatory effects, but additional investigations on immunomodulatory, chondroprotective and other clinical mechanisms of action are needed. We hypothesize that MSC basal immunomodulatory "fitness" correlates with OA treatment efficacy, but this hypothesis needs to be validated in future studies. We conclude with a roadmap articulating the need to match an OA patient subset defined by molecular endotype and clinical phenotype with basally immunomodulatory "fit" or engineered-to-be-fit-for-OA MSCs in well-designed, data-intensive clinical trials to advance the field.

Equine osteoarthritis: Strategies to enhance mesenchymal stromal cell-based acellular therapies

Osteoarthritis (OA) is a degenerative disease that eventually leads to the complete degradation of articular cartilage. Articular cartilage has limited intrinsic capacity for self-repair and, to date, there is no curative treatment for OA. Humans and horses have a similar articular cartilage and OA etiology. Thus, in the context of a One Health approach, progress in the treatment of equine OA can help improve horse health and can also constitute preclinical studies for human medicine. Furthermore, equine OA affects horse welfare and leads to significant financial losses in the equine industry. In the last few years, the immunomodulatory and cartilage regenerative potentials of mesenchymal stromal cells (MSCs) have been demonstrated, but have also raised several concerns. However, most of MSC therapeutic properties are contained in their secretome, particularly in their extracellular vesicles (EVs), a promising avenue for acellular therapy. From tissue origin to in vitro culture methods, various aspects must be taken into consideration to optimize MSC secretome potential for OA treatment. Immunomodulatory and regenerative properties of MSCs can also be enhanced by recreating a pro-inflammatory environment to mimic an in vivo pathological setting, but more unusual methods also deserve to be investigated. Altogether, these strategies hold substantial potential for the development of MSC secretome-based therapies suitable for OA management. The aim of this mini review is to survey the most recent advances on MSC secretome research with regard to equine OA.

Implication of Cellular Senescence in Osteoarthritis: A Study on Equine Synovial Fluid Mesenchymal Stromal Cells

Osteoarthritis (OA) is described as a chronic degenerative disease characterized by the loss of articular cartilage. Senescence is a natural cellular response to stressors. Beneficial in certain conditions, the accumulation of senescent cells has been implicated in the pathophysiology of many diseases associated with aging. Recently, it has been demonstrated that mesenchymal stem/stromal cells isolated from OA patients contain many senescent cells that inhibit cartilage regeneration. However, the link between cellular senescence in MSCs and OA progression is still debated. In this study, we aim to characterize and compare synovial fluid MSCs (sf-MSCs), isolated from OA joints, with healthy sf-MSCs, investigating the senescence hallmarks and how this state could affect cartilage repair. Sf-MSCs were isolated from tibiotarsal joints of healthy and diseased horses with an established diagnosis of OA with an age ranging from 8 to 14 years. Cells were cultured in vitro and characterized for cell proliferation assay, cell cycle analysis, ROS detection assay, ultrastructure analysis, and the expression of senescent markers. To evaluate the influence of senescence on chondrogenic differentiation, OA sf-MSCs were stimulated in vitro for up to 21 days with chondrogenic factors, and the expression of chondrogenic markers was compared with healthy sf-MSCs. Our findings demonstrated the presence of senescent sf-MSCs in OA joints with impaired chondrogenic differentiation abilities, which could have a potential influence on OA progression.

Synovial Fluid Derived from Human Knee Osteoarthritis Increases the Viability of Human Adipose-Derived Stem Cells through Upregulation of FOSL1

Knee osteoarthritis (Knee OA) is an irreversible condition that causes bone deformity and degeneration of the articular cartilage that comprises the joints, resulting in chronic pain and movement disorders. The administration of cultured adipose-derived stem cells (ADSCs) into the knee joint cavity improves the clinical symptoms of Knee OA; however, the effect of synovial fluid (SF) filling the joint cavity on the injected ADSCs remains unclear. In this study, we investigated the effect of adding SF from Knee OA patients to cultured ADSCs prepared for therapeutic use in an environment that mimics the joint cavity. An increase in the viability of ADSCs was observed following the addition of SF. Gene expression profiling of SF-treated ADSCs using DNA microarrays revealed changes in several genes involved in cell survival. Of these genes, we focused on FOSL1, which is involved in the therapeutic effect of ADSCs and the survival and proliferation of cancer stem cells. We confirmed the upregulation of FOSL1 mRNA and protein expression using RT-PCR and western blot analysis, respectively. Next, we knocked down FOSL1 in ADSCs using siRNA and observed a decrease in cell viability, indicating the involvement of FOSL1 in the survival of ADSCs. Interestingly, in the knockdown cells, ADSC viability was also decreased by SF exposure. These results suggest that SF enhances cell viability by upregulating FOSL1 expression in ADSCs. For therapy using cultured ADSCs, the therapeutic effect of ADSCs may be further enhanced if an environment more conducive to the upregulation of FOSL1 expression in ADSCs can be established.

Extracellular vesicles in osteoarthritis of peripheral joint and temporomandibular joint

Osteoarthritis (OA) is a disabling disease with significant morbidity worldwide. OA attacks the large synovial joint, including the peripheral joints and temporomandibular joint (TMJ). As a representative of peripheral joint OA, knee OA shares similar symptoms with TMJ OA. However, these two joints also display differences based on their distinct development, anatomy, and physiology. Extracellular vesicles (EVs) are phospholipid bilayer nanoparticles, including exosomes, microvesicles, and apoptotic bodies. EVs contain proteins, lipids, DNA, micro-RNA, and mRNA that regulate tissue homeostasis and cell-to-cell communication, which play an essential role in the progression and treatment of OA. They are likely to partake in mechanical response, extracellular matrix degradation, and inflammatory regulation during OA. More evidence has shown that synovial fluid and synovium-derived EVs may serve as OA biomarkers. More importantly, mesenchymal stem cell-derived EV shows a therapeutic effect on OA. However, the different function of EVs in these two joints is largely unknown based on their distinct biological characteristic. Here, we reviewed the effects of EVs in OA progression and compared the difference between the knee joint and TMJ, and summarized their potential therapeutic role in the treatment of OA.

Strategy insight: Mechanical properties of biomaterials' influence on hydrogel-mesenchymal stromal cell combination for osteoarthritis therapy

Osteoarthritis (OA) is a kind of degenerative joint disease usually found in older adults and those who have received meniscal surgery, bringing great suffering to a number of patients worldwide. One of the major pathological features of OA is retrograde changes in the articular cartilage. Mesenchymal stromal cells (MSCs) can differentiate into chondrocytes and promote cartilage regeneration, thus having great potential for the treatment of osteoarthritis. However, improving the therapeutic effect of MSCs in the joint cavity is still an open problem. Hydrogel made of different biomaterials has been recognized as an ideal carrier for MSCs in recent years. This review focuses on the influence of the mechanical properties of hydrogels on the efficacy of MSCs in OA treatment and compares artificial materials with articular cartilage, hoping to provide a reference for further development of modified hydrogels to improve the therapeutic effect of MSCs.

Human Adipose- and Amnion-Derived Mesenchymal Stromal Cells Similarly Mitigate Osteoarthritis Progression in the Dunkin Hartley Guinea Pig

BACKGROUND

Clinical trials are currently underway to investigate the efficacy of intra-articular administration of mesenchymal stromal cells (MSCs) to mitigate osteoarthritis (OA) progression in the knee. Although multiple MSC sources exist, studies have yet to determine whether differences in therapeutic efficacy exist between them.

PURPOSE

To compare the ability of intra-articularly injected adipose-derived MSCs (AD-MSCs) and amnion-derived MSCs (AM-MSCs) to mitigate the progression of knee OA in a small animal model of spontaneous OA, as well as to compare the therapeutic potential of MSCs in hyaluronic acid (HA) and in HA only with saline (OA) controls.

STUDY DESIGN

Controlled laboratory study.

METHODS

Injections of AD-MSCs or AM-MSCs suspended in HA or HA only were performed in the rear stifle joints of 3-month-old Dunkin Hartley guinea pigs (DHGPs). Repeat injections occurred at 2 and 4 months after the initial injection in each animal. Contralateral limbs received saline injections and served as untreated controls. Subsequently, joints were analyzed for osteoarthritic changes of the cartilage and subchondral bone via histologic and biochemical analyses. To evaluate MSC retention time in the joint space, DHGPs received a single intra-articular injection of fluorescently labeled AD-MSCs or AM-MSCs, and the fluorescence intensity was longitudinally tracked via an in vivo imaging system.

RESULTS

No statistically significant differences in outcomes were found when comparing the ability of AD-MSCs and AM-MSCs to mitigate OA. However, the injection of AD-MSCs, AM-MSCs, and HA-only treatments more effectively mitigated cartilage damage compared with that of saline controls by demonstrating higher amounts of cartilage glycosaminoglycan content and improved histological proteoglycan scoring while reducing the percentage of osteophytes present.

CONCLUSION

Intra-articular injection of AD-MSCs, AM-MSCs, or HA only was able to similarly mitigate the progression of cartilage damage and reduce the percentage of osteophytes compared with that of saline controls in the DHGP. However, this study was unable to establish the superiority of AD-MSCs versus AM-MSCs as a treatment to mitigate spontaneous OA.

CLINICAL RELEVANCE

MSCs demonstrate the ability to mitigate the progression of knee OA and thus may be used in a prophylactic approach to delay the need for end-stage treatment strategies.

Within or Without You? A Perspective Comparing In Situ and Ex Situ Tissue Engineering Strategies for Articular Cartilage Repair

Human articular cartilage has a poor ability to self-repair, meaning small injuries often lead to osteoarthritis, a painful and debilitating condition which is a major contributor to the global burden of disease. Existing clinical strategies generally do not regenerate hyaline type cartilage, motivating research toward tissue engineering solutions. Prospective cartilage tissue engineering therapies can be placed into two broad categories: i) Ex situ strategies, where cartilage tissue constructs are engineered in the lab prior to implantation and ii) in situ strategies, where cells and/or a bioscaffold are delivered to the defect site to stimulate chondral repair directly. While commonalities exist between these two approaches, the core point of distinction-whether chondrogenesis primarily occurs "within" or "without" (outside) the body-can dictate many aspects of the treatment. This difference influences decisions around cell selection, the biomaterials formulation and the surgical implantation procedure, the processes of tissue integration and maturation, as well as, the prospects for regulatory clearance and clinical translation. Here, ex situ and in situ cartilage engineering strategies are compared: Highlighting their respective challenges, opportunities, and prospects on their translational pathways toward long term human cartilage repair.

Secreted Factors and Extracellular Vesicles Account for the Immunomodulatory and Tissue Regenerative Properties of Bone-Marrow-Derived Mesenchymal Stromal Cells for Osteoarthritis

Bone-marrow-derived mesenchymal stromal cells (BMSCs) showed therapeutic potential in the treatment of musculoskeletal diseases, including osteoarthritis (OA). Their soluble mediators and extracellular vesicles (EVs), which make up the secretome, suppress immune response, attenuate inflammation and promote cartilage repair. EVs, as well as the whole secretome, have been investigated as cell free approaches for OA although, to date, a disease-tailored molecular fingerprint is missing. In this study, soluble mediators and miRNAs were sifted in the BMSCs' secretome and EVs, respectively, and analyzed in the frame of cell types and factors involved in OA. The majority of identified molecules repress the activation of immune cells and the production of OA-related inflammatory mediators, as well as promote cartilage protection by acting on both chondrocytes homeostasis and extracellular matrix-degrading enzymes. These data provide the molecular ground for the therapeutic potential of BMSCs for regenerative applications for OA and support the use of secretome or EVs as cell-free applications in joint diseases.