Mesenchymal stem cells in joint disease and repair. Nat Rev Rheumatol. 2013;9:584-594. [PMID: 23881068 DOI: 10.1038/nrrheum.2013.109]

The Functions of BMP3 in Rabbit Articular Cartilage Repair

Bone morphogenetic proteins (BMPs) play important roles in skeletal development and repair. Previously, we found fibroblast growth factor 2 (FGF2) induced up-regulation of BMP2, 3, 4 in the process of rabbit articular cartilage repair, which resulted in satisfactory repair effects. As BMP2/4 show a clearly positive effect for cartilage repair, we investigated the functions of BMP3 in rabbit articular cartilage repair. In this paper, we find that BMP3 inhibits the repair of partial-thickness defect of articular cartilage in rabbit by inducing the degradation of extracellular matrix, interfering with the survival of chondrocytes surrounding the defect, and directly inhibiting the expression of BMP2 and BMP4. Meanwhile BMP3 suppress the repair of full-thickness cartilage defect by destroying the subchondral bone through modulating the proliferation and differentiation of bone marrow stem cells (BMSCs), and directly increasing the expression of BMP4. Although BMP3 has different functions in the repair of partial and full-thickness defects of articular cartilage in rabbit, the regulation of BMP expression is involved in both of them. Together with our previous findings, we suggest the regulation of the BMP signaling pathway by BMP3 is essential in articular cartilage repair.

Therapeutic application of mesenchymal stem cells in osteoarthritis

INTRODUCTION

Osteoarthritis (OA) is a degenerative disease characterized by cartilage degradation and subchondral bone alterations. This disease represents a global public health problem whose prevalence is rapidly growing with the increasing aging of the population. With the discovery of mesenchymal stem cells (MSC) as possible therapeutic agents, their potential for repairing cartilage damage in OA is under investigation.

AREAS COVERED

Characterization of MSCs and their functional properties are mentioned with an insight into their trophic function and secretory profile. We present a special focus on the types of extracellular vesicles (EVs) that are produced by MSCs and their role in the paracrine activity of MSCs. We then discuss the therapeutic approaches that have been evaluated in pre-clinical models of OA and the results coming out from the clinical trials in patients with OA.

EXPERT OPINION

MSC-based therapy seems a promising approach for the treatment of patients with OA. Further research is still needed to demonstrate their efficacy in clinical trials using controlled, prospective studies. However, the emergence of MSC-derived EVs as possible therapeutic agents could be an alternative to cell-based therapy.

Mesenchymal stem cell implantation in knee osteoarthritis: an assessment of the factors influencing clinical outcomes

BACKGROUND

Several clinical studies have reported on cell-based treatment using mesenchymal stem cells (MSCs) for cartilage regeneration in knee osteoarthritis (OA). However, little is known about the factors that influence the clinical outcomes after surgery.

PURPOSE/HYPOTHESIS

This study aimed to investigate the clinical outcomes of MSC implantation in patients with knee OA and assess the factors that are associated with clinical outcomes. The hypothesis was that factors may exist that could influence clinical outcomes.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A total of 49 patients (55 knees) were retrospectively evaluated after MSC implantation for knee OA. The inclusion criteria were patients who had an isolated full-thickness cartilage lesion and Kellgren-Lawrence OA grade 1 or 2. Clinical outcomes were measured with the International Knee Documentation Committee (IKDC) score, Tegner activity score, and patients' overall satisfaction with the surgery. Statistical analyses were performed to determine the effect of different factors on the clinical outcome.

RESULTS

The mean pre- and postoperative IKDC and Tegner activity scores significantly improved from 37.7 ± 6.3 to 67.3 ± 9.5 (IKDC) and from 2.2 ± 0.7 to 3.8 ± 0.7 (Tegner) (P < .001 for both). Twenty-four patients reported their overall satisfaction with the surgery as excellent (43.6%), 17 as good (30.9%), 11 as fair (20.0%), and 3 as poor (5.5%). There were significant differences in clinical outcomes at the final follow-up among the age and lesion size groups (P < .05 for all). Multivariate analyses showed high prognostic significance related to patient age and lesion size, and scatter plots suggested a cutoff age of 60 years and a cutoff lesion size of 6.0 cm(2) for the optimum identification of poor clinical outcomes (P < .05 for both).

CONCLUSION

The clinical outcomes of MSC implantation for knee OA are encouraging. Patient age and lesion size are important factors that affect clinical outcomes; thus, these may serve as a basis for preoperative surgical decisions. Cutoff points exist for the risk of clinical failure in patients older than 60 years and those with a lesion size larger than 6.0 cm(2).

Mesenchymal stem cell therapy for osteoarthritis: current perspectives

Osteoarthritis (OA) is a painful chronic condition with a significant impact on quality of life. The societal burden imposed by OA is increasing in parallel with the aging population; however, no therapies have demonstrated efficacy in preventing the progression of this degenerative joint disease. Current mainstays of therapy include activity modification, conservative pain management strategies, weight loss, and if necessary, replacement of the affected joint. Mesenchymal stem cells (MSCs) are a multipotent endogenous population of progenitors capable of differentiation to musculoskeletal tissues. MSCs have a well-documented immunomodulatory role, managing the inflammatory response primarily through paracrine signaling. Given these properties, MSCs have been proposed as a potential regenerative cell therapy source for patients with OA. Research efforts are focused on determining the ideal source for derivation, as MSCs are native to several tissues. Furthermore, optimizing the mode of delivery remains a challenge both for appropriate localization of MSCs and for directed guidance toward stemming the local inflammatory process and initiating a regenerative response. Scaffolds and matrices with growth factor adjuvants may prove critical in this effort. The purpose of this review is to summarize the current state of MSC-based therapeutics for OA and discuss potential barriers that must be overcome for successful implementation of cell-based therapy as a routine treatment strategy in orthopedics.

Radio-resistant mesenchymal stem cells: mechanisms of resistance and potential implications for the clinic

Mesenchymal stem cells (MSCs) comprise a heterogeneous population of multipotent stromal cells and can be isolated from various tissues and organs. Due to their regenerative potential, they have been subject to intense research efforts, and they may provide an efficient means for treating radiation-induced tissue damage. MSCs are relatively resistant to ionizing radiation and retain their stem cell characteristics even after high radiation doses. The underlying mechanisms for the observed MSC radioresistance have been extensively studied and may involve efficient DNA damage recognition, double strand break repair and evasion of apoptosis. Here, we present a concise review of the published scientific data on the radiobiological features of MSCs. The involvement of different DNA damage recognition and repair pathways in the creation of a radioresistant MSC phenotype is outlined, and the roles of apoptosis, senescence and autophagy regarding the reported radioresistance are summarized. Finally, potential influences of the radioresistant MSCs for the clinic are discussed with respect to the repair and radioprotection of irradiated tissues.

Emerging drugs for the treatment of knee osteoarthritis

INTRODUCTION

Osteoarthritis (OA) is the most prevailing form of joint disease, with symptoms affecting 10 - 12% of the adult population with a projection of a 50% increase in prevalence in the next two decades. The disease characteristics are defined by articular cartilage damage, low-grade synovial inflammation and hypertrophic bone changes, leading to pain and functional deterioration. To date, available pain treatments are limited in their efficacy and have associated toxicities. No structural disease modification agents have been approved by regulatory agencies for this indication.

AREAS COVERED

We reviewed drugs in Phase II - III for OA pain and joint structure modification. Different aspects of structure modification are divided into targets of inflammatory pathway, cartilage catabolism and anabolism, and subchondral bone remodeling.

EXPERT OPINION

Further insight into the pathophysiology of the disease will allow for development of novel target classes focusing on the link between symptomatology and structural changes. Given the complexity of OA, one single therapy is unlikely to be universally and uniformly effective. Promising therapies are under development, but there are obstacles in the translation of treatment from preclinical models and trial designs need to be cognizant of the complex reasons for previous trial failures.

Therapeutic Potential of Differentiated Mesenchymal Stem Cells for Treatment of Osteoarthritis

Osteoarthritis (OA) is a chronic, progressive, and irreversible degenerative joint disease. Conventional OA treatments often result in complications such as pain and limited activity. However, transplantation of mesenchymal stem cells (MSCs) has several beneficial effects such as paracrine effects, anti-inflammatory activity, and immunomodulatory capacity. In addition, MSCs can be differentiated into several cell types, including chondrocytes, osteocytes, endothelia, and adipocytes. Thus, transplantation of MSCs is a suggested therapeutic tool for treatment of OA. However, transplanted naïve MSCs can cause problems such as heterogeneous populations including differentiated MSCs and undifferentiated cells. To overcome this problem, new strategies for inducing differentiation of MSCs are needed. One possibility is the application of microRNA (miRNA) and small molecules, which regulate multiple molecular pathways and cellular processes such as differentiation. Here, we provide insight into possible strategies for cartilage regeneration by transplantation of differentiated MSCs to treat OA patients.

Allogeneic Bone Marrow Transplant from MRL/MpJ Super-Healer Mice Does Not Improve Articular Cartilage Repair in the C57Bl/6 Strain

Background

Articular cartilage has been the focus of multiple strategies to improve its regenerative/ repair capacity. The Murphy Roths Large (MRL/MpJ) “super-healer” mouse demonstrates an unusual enhanced regenerative capacity in many tissues and provides an opportunity to further study endogenous cartilage repair. The objective of this study was to test whether the super-healer phenotype could be transferred from MRL/MpJ to non-healer C57Bl/6 mice by allogeneic bone marrow transplant.

Methodology

The healing of 2mm ear punches and full thickness cartilage defects was measured 4 and 8 weeks after injury in control C57Bl/6 and MRL/MpJ “super-healer” mice, and in radiation chimeras reconstituted with bone marrow from the other mouse strain. Healing was assessed using ear hole diameter measurement, a 14 point histological scoring scale for the cartilage defect and an adapted version of the Osteoarthritis Research Society International scale for assessment of osteoarthritis in mouse knee joints.

Principal Findings

Normal and chimeric MRL mice showed significantly better healing of articular cartilage and ear wounds along with less severe signs of osteoarthritis after cartilage injury than the control strain. Contrary to our hypothesis, however, bone marrow transplant from MRL mice did not confer improved healing on the C57Bl/6 chimeras, either in regards to ear wound healing or cartilage repair.

Conclusion and Significance

The elusive cellular basis for the MRL regenerative phenotype still requires additional study and may possibly be dependent on additional cell types external to the bone marrow.

CXC chemokine ligand 12a enhances chondrocyte proliferation and maturation during endochondral bone formation

OBJECTIVE

We investigated the roles of CXC chemokine ligand 12a (CXCL12a), also known as stromal cell-derived factor-1α (SDF-1α), in endochondral bone growth, which can give us important clues to understand the role of CXCL12a in osteoarthritis (OA).

METHODS

Primary chondrocytes and tibial explants from embryonic 15.5 day-old mice were cultured with recombinant mouse CXCL12a. To assess the role of CXCL12a in chondrogenic differentiation, we conducted mesenchymal cell micromass culture.

RESULTS

In tibia organ cultures, CXCL12a increased total bone length in a dose-dependent manner through proportional effects on cartilage and bone. In accordance with increased length, CXCL12a increased the protein level of proliferation markers, such as cyclin D1 and proliferating cell nuclear antigen (PCNA), in primary chondrocytes as well as in tibia organ culture. In addition, CXCL12a increased the expression of Runx2, Col10 and MMP13 in primary chondrocytes and tibia organ culture system, implying a role of CXCL12a in chondrocyte maturation. Micromass cultures of limb-bud mesenchymal progenitor cells (MPCs) revealed that CXCL12a has a limited effect on early chondrogenesis, but significantly promoted maturation of chondrocytes. CXCL12a induced the phosphorylation of p38 and Erk1/2 MAP kinases and IκB. The increased expression of cyclin D1 by CXCL12a was significantly attenuated by inhibitors of MEK1 and NF-κB. On the other hand, p38 and Erk1/2 MAP kinase and NF-κB signaling were associated with CXCL12a-induced expression of Runx2 and MMP13, the marker of chondrocyte maturation.

CONCLUSION

CXCL12a promoted the proliferation and maturation of chondrocytes, which strongly suggest that CXCL12a may have a negative effect on articular cartilage and contribute to OA progression.

Mesenchymal stem cell therapy for knee osteoarthritis: 5 years follow-up of three patients

AIM

Osteoarthritis is a degenerative joint disease characterized by the destruction of joint cartilage. Mesenchymal stem cells (MSCs) are found in low numbers in normal cartilage, mainly in the superficial layer, acting as repairing agents. In OA, MSCs are seen in larger numbers, but act chaotic and are unable to repair the cartilage. The synovial membrane becomes inflamed and interacts with the cartilage. Transplanted MSC have the ability to normalize them, redirecting them to their normal function. In a preliminary study, we showed that MSC could improve knee OA in four patients at 6 months. This report shows their long-term follow-up at 5 years.

METHODS

One patient was lost to follow-up at 2 years and three were followed for 5 years. They were aged 55, 57, 65 and 54 years, and had moderate to severe knee osteoarthritis. The worse knee of each patient was injected with 8-9 × 10(6) MSC.

RESULTS

As previously reported, all parameters improved in transplant knees at 6 months (walking time, stair climbing, gelling pain, patella crepitus, flection contracture and the visual analogue score on pain). Then, they started gradually to deteriorate, but at 5 years they were still better than at baseline. PGA (Patient Global Assessment) improved from baseline to 5 years. The better knee at baseline (no MSC), continued its progression toward aggravation and at 5 years became the worse knee.

CONCLUSION

Transplant knees were all in a rather advanced stage of OA. Earlier transplantation may give better results in long-term follow-up. This is what future studies have to demonstrate.

Are mesenchymal stem cells in rheumatoid arthritis the good or bad guys?

The advancements in our understanding of the inflammatory and immune mechanisms in rheumatoid arthritis (RA) have fuelled the development of targeted therapies that block cytokine networks and pathogenic immune cells, leading to a considerable improvement in the management of RA patients. Nonetheless, no therapy is curative and clinical remission does not necessarily correspond to non-progression of joint damage. Hence, the biomedical community has redirected scientific efforts and resources towards the investigation of other biological aspects of the disease, including the mechanisms driving tissue remodelling and repair. In this regard, stem cell research has attracted extraordinary attention, with the ultimate goal to develop interventions for the biological repair of damaged tissues in joint disorders, including RA. The recent evidence that mesenchymal stem cells (MSCs) with the ability to differentiate into cartilage are present in joint tissues raises an opportunity for therapeutic interventions via targeting intrinsic repair mechanisms. Under physiological conditions, MSCs in the joint are believed to contribute to the maintenance and repair of joint tissues. In RA, however, the repair function of MSCs appears to be repressed by the inflammatory milieu. In addition to being passive targets, MSCs could interact with the immune system and play an active role in the perpetuation of arthritis and progression of joint damage. Like MSCs, fibroblast-like synoviocytes (FLSs) are part of the stroma of the synovial membrane. During RA, FLSs undergo proliferation and contribute to the formation of the deleterious pannus, which mediates damage to articular cartilage and bone. Both FLSs and MSCs are contained within the mononuclear cell fraction in vitro, from which they can be culture expanded as plastic-adherent fibroblast-like cells. An important question to address relates to the relationship between MSCs and FLSs. MSCs and FLSs could be the same cell type with functional specialisation or represent different functional stages of the same stromal lineage. This review will discuss the roles of MSCs in RA and will address current knowledge of the relative identity between MSCs and FLSs. It will also examine the immunomodulatory properties of the MSCs and the potential to harness such properties for the treatment of RA.

Mesenchymal Stem Cells Facilitate In Vitro Development of Human Preantral Follicle

Biological folliculogenesis is a lengthy and complicated process, and follicle growth microenvironment is poorly understood. Mesenchymal stem cells (MSCs) have been shown to establish a supportive microenvironment for wound repair, autoimmune diseases amelioration, and tumor development. Therefore, this study is aimed to investigate whether MSCs could help to reconstruct a microenvironment to facilitate the in vitro follicle development. Here we show human MSCs significantly promote the survival rates, increase the growth velocity, and improve the viability of preantral follicles in a dose-dependent manner. Further analyses reveal that growth differentiation factor 9 and bone morphogenetic protein 15 in oocytes and inhibin βA and transforming growth factor β1 in granulose cells within the follicles cocultured with MSCs express notably higher than those in the follicles cultured without MSCs. In summary, our findings demonstrate a previously unrecognized function of MSCs in promoting preantral follicle development and provide a useful strategy to optimize fertility preservation and restoration by facilitating in vitro follicle growth.

Comparative Characterization of Human and Equine Mesenchymal Stromal Cells: A Basis for Translational Studies in the Equine Model

Multipotent mesenchymal stromal cells (MSCs) have gained tremendous attention as potential therapeutic agents for the treatment of orthopedic diseases. Promising results have been obtained after application of MSCs for treatment of tendon and joint disease in the equine model, making it appear favorable to use these results as a basis for the translational process of the therapy. However, while the horse is considered a highly suitable model for orthopedic diseases, knowledge is lacking regarding the level of analogy of equine MSCs and their human counterparts. Therefore, the aim of this study was to assess the properties of human and equine adipose- and tendon-derived MSCs in a direct comparison. Basic properties of human and equine MSCs from both tissues were similar. The cells expressed CD29, CD44, CD90, and CD105 and lacked expression of CD73, CD14, CD34, CD45, CD79α, and MCHII/HLA-DR. No significant differences were found between proliferation potential of human and equine MSCs in early passages, but recovery of nucleated cells after tissue digestion as well as proliferation in later passages was higher in equine samples (p < 0.01). All samples showed a good migration capacity and multilineage differentiation potential. However, while osteogenic differentiation was achieved in all equine samples, it was only evident in five out of nine human tendon-derived samples. Human MSCs further showed a higher expression of collagen IIIA1 and tenascin-C, but lower expression of decorin and scleraxis (p < 0.01). Although revealing some potentially relevant differences, the study demonstrates a high level of analogy between human and equine MSCs, providing a basis for translational research in the equine model according to the guidelines issued by the authorities.

Mechano growth factor (MGF) and transforming growth factor (TGF)-β3 functionalized silk scaffolds enhance articular hyaline cartilage regeneration in rabbit model

Damaged cartilage has poor self-healing ability and usually progresses to scar or fibrocartilaginous tissue, and finally degenerates to osteoarthritis (OA). Here we demonstrated that one of alternative isoforms of IGF-1, mechano growth factor (MGF) acted synergistically with transforming growth factor β3 (TGF-β3) embedded in silk fibroin scaffolds to induce chemotactic homing and chondrogenic differentiation of mesenchymal stem cells (MSCs). Combination of MGF and TGF-β3 significantly increased cell recruitment up to 1.8 times and 2 times higher than TGF-β3 did in vitro and in vivo. Moreover, MGF increased Collagen II and aggrecan secretion of TGF-β3 induced hMSCs chondrogenesis, but decreased Collagen I in vitro. Silk fibroin (SF) scaffolds have been widely used for tissue engineering, and we showed that methanol treated pured SF scaffolds were porous, similar to compressive module of native cartilage, slow degradation rate and excellent drug released curves. At 7 days after subcutaneous implantation, TGF-β3 and MGF functionalized silk fibroin scaffolds (STM) recruited more CD29+/CD44+cells (P<0.05). Similarly, more cartilage-like extracellular matrix and less fibrillar collagen were detected in STM scaffolds than that in TGF-β3 modified scaffolds (ST) at 2 months after subcutaneous implantation. When implanted into articular joints in a rabbit osteochondral defect model, STM scaffolds showed the best integration into host tissues, similar architecture and collagen organization to native hyaline cartilage, as evidenced by immunostaining of aggrecan, collagen II and collagen I, as well as Safranin O and Masson's trichrome staining, and histological evalution based on the modified O'Driscoll histological scoring system (P<0.05), indicating that MGF and TGF-β3 might be a better candidate for cartilage regeneration. This study demonstrated that TGF-β3 and MGF functionalized silk fibroin scaffolds enhanced endogenous stem cell recruitment and facilitated in situ articular cartilage regeneration, thus providing a novel strategy for cartilage repair.

Current understanding of pathogenesis and treatment of TMJ osteoarthritis

Osteoarthritis is a common disease that can cause severe pain and dysfunction in any joint, including the temporomandibular joint (TMJ). TMJ osteoarthritis (TMJOA) is an important subtype in the classification of temporomandibular disorders. TMJOA pathology is characterized by progressive cartilage degradation, subchondral bone remodeling, and chronic inflammation in the synovial tissue. However, the exact pathogenesis and process of TMJOA remain to be understood. An increasing number of studies have recently focused on inflammation and remodeling of subchondral bone during the early stage of TMJOA, which may elucidate the possible mechanism of initiation and progression of TMJOA. The treatment strategy for TMJOA aims at relieving pain, preventing the progression of cartilage and subchondral bone destruction, and restoring joint function. Conservative therapy with nonsteroidal anti-inflammatory drugs, splint, and physical therapy, such as low-energy laser and arthrocentesis, are the most common treatments for TMJOA. These therapies are effective in most cases in relieving the signs and symptoms, but their long-term therapeutic effect on the pathologic articular structure is unsatisfactory. A treatment that can reverse the damage of TMJOA remains unavailable to date. Treatments that prevent the progression of cartilage degradation and subchondral bone damage should be explored, and regeneration for the TMJ may provide the ideal long-term solution. This review summarizes the current understanding of mechanisms underlying the pathogenesis and treatment of TMJOA.

Platelet-derived growth factor-BB enhances MSC-mediated cardioprotection via suppression of miR-320 expression

Delivery of bone marrow-derived mesenchymal stem cells (MSCs) to myocardium protects ischemic tissue through the paracrine release of beneficial angiogenic and cytoprotective factors. Platelet-derived growth factor (PDGF)-BB, a potent mitogen of MSCs, is involved in the pathophysiology of ischemic heart disease. However, the role(s) of PDGF in MSC-mediated cardioprotection remains unknown. Here, we found that PDGF treatment of MSCs resulted in rapid activation of both Akt and ERK (central intracellular signal mediators), upregulated VEGF, and induced phosphorylation of the activator protein-1 (AP-1) transcription factor c-Jun. Examination of several microRNA genes having predicted promoter c-Jun-binding sites showed that PDGF treatment resulted in upregulation of miR-16-2 and downregulation of miRs-23b, -27b, and -320b. To examine possible PDGF augmentation of therapeutic potential, we evaluated the effects of PDGF using an ex vivo isolated mouse heart ischemia-reperfusion model. Human MSCs, with or without PDGF preconditioning, were infused into the coronary circulation of isolated mouse hearts. The hearts that received PDGF-treated MSCs exhibited a greater functional recovery compared with naïve MSC-infused hearts, following ischemia-reperfusion injury. This enhanced functional recovery was abolished by overexpression of miR-320, a microRNA we found downregulated by PDGF-activated c-Jun. Overexpression of miR-320 also resulted in upregulation of insulin-like growth factor binding protein (IGFBP) family members, suggesting PDGF "cross talk" with the mitogenic IGF signaling pathway. Collectively, we conclude that PDGF enhances MSC-mediated cardioprotection via a c-Jun/miR-320 signaling mechanism and PDGF MSC preconditioning may be an effective therapeutic strategy for cardiac ischemia.

Mesenchymal stromal cells and rheumatic diseases: new tools from pathogenesis to regenerative therapies

In recent years, mesenchymal stromal cells (MSCs) have been largely investigated and tested as a new therapeutic tool for several clinical applications, including the treatment of different rheumatic diseases. MSCs are responsible for the normal turnover and maintenance of adult mesenchymal tissues as the result of their multipotent differentiation abilities and their secretion of a variety of cytokines and growth factors. Although initially derived from bone marrow, MSCs are present in many different tissues such as many peri-articular tissues. MSCs may exert immune-modulatory properties, modulating different immune cells in both in vitro and in vivo models, and they are considered immune-privileged cells. At present, these capacities are considered the most intriguing aspect of their biology, introducing the possibility that these cells may be used as effective therapy in autoimmune diseases. Therefore, stem cell therapies may represent an innovative approach for the treatment of rheumatic diseases, especially for the forms that are not responsive to standard treatments or alternatively still lacking a definite therapy. At present, although the data from scientific literature appear to suggest that such treatments might be more effective whether administered as soon as possible, the use of MSCs in clinical practice is likely to be restricted to patients with a long history of a severe refractory disease. Further results from larger clinical trials are needed to corroborate preclinical findings and human non-controlled studies, and advancement in the knowledge of MSCs might provide information about the therapeutic role of these cells in the treatment of many rheumatic diseases.

Stem cells for the treatment of musculoskeletal pain

Musculoskeletal-related pain is one of the most disabling health conditions affecting more than one third of the adult population worldwide. Pain from various mechanisms and origins is currently underdiagnosed and undertreated. The complexity of molecular mechanisms correlating pain and the progression of musculoskeletal diseases is not yet fully understood. Molecular biomarkers for objective evaluation and treatment follow-up are needed as a step towards targeted treatment of pain as a symptom or as a disease. Stem cell therapy is already under investigation for the treatment of different types of musculoskeletal-related pain. Mesenchymal stem cell-based therapies are already being tested in various clinical trials that use musculoskeletal system-related pain as the primary or secondary endpoint. Genetically engineered stem cells, as well as induced pluripotent stem cells, offer promising novel perspectives for pain treatment. It is possible that a more focused approach and reassessment of therapeutic goals will contribute to the overall efficacy, as well as to the clinical acceptance of regenerative medicine therapies. This article briefly describes the principal types of musculoskeletal-related pain and reviews the stem cell-based therapies that have been specifically designed for its treatment.

Intra-articular administration of xenogeneic neonatal Mesenchymal Stromal Cells early after meniscal injury down-regulates metalloproteinase gene expression in synovium and prevents cartilage degradation in a rabbit model of osteoarthritis

OBJECTIVE

The anti-inflammatory and anti-catabolic effects of neonatal Mesenchymal Stromal Cell (MSC) were investigated in a xenogeneic model of mild osteoarthritis (OA). The paracrine properties of MSC on synoviocytes were further investigated in vitro.

STUDY DESIGN

OA was induced by medial meniscal release (MMR) in 30 rabbit knees. A single early (day 3) or delayed (day 15) intra-articular (IA) injection of MSC isolated from equine Umbilical Cord Wharton's jelly (UC-MSC) was performed. Rabbits were euthanized on days 15 or 56. OA grading was performed and gene expression of inflammatory cytokines and metalloproteinases was measured in synovial tissue. Paracrine effects of UC-MSC were investigated using UC-conditioned vs control medium on rabbit primary synoviocytes stimulated with interleukin 1 beta in vitro.

RESULTS

No adverse local or systemic responses were observed clinically after xenogeneic UC-MSC injection. At study end point, cartilage fibrillation was lower in early treatment than in delayed treatment group. Cellular infiltrate was observed in the synovium of both UC-MSC groups. OA synovium exhibited a reduced expression of metalloproteinases-1, -3, -13 in the early cell-treated group at d56. In vitro, UC-conditioned medium exerted anti-inflammatory and anti-catabolic effects on synoviocytes exposed to pro-inflammatory stimulus.

CONCLUSIONS

Early IA injection of equine UC-MSC was effective in preventing OA signs in rabbit knees following MMR. UC-MSC target the synovium and modulate the gene expression pattern of synoviocytes to promote an anti-catabolic environment. This confirms the synovium is a major target and mediator of MSC therapy, modulating the expression of matrix-degrading enzymes.

Biological differences between native and cultured mesenchymal stem cells: implications for therapies

We describe the current knowledge of the surface marker phenotype of native bone marrow mesenchymal stem/stromal cells (MSCs) in humans and in mouse models, highlighting similarities in the MSC marker "signature" between the two species. The chapter proceeds to discuss the published literature pertaining to native MSC topography and their interactions with hematopoietic stem cells and their progeny, as well as with blood vessels and nerve endings. Additionally, the chapter describes phenotypic and functional "drifts" that occur in MSC preparations as they are taken out of their native bone marrow microenvironment and induced to proliferate in vitro (in the presence of animal or human serum). We propose that the understanding of the biology of MSCs in their native niches in the bone marrow could lead to future developments in the treatment of hematological diseases such as multiple myeloma. Additionally, this knowledge would assist in the development of more "natural" MSC culture conditions, best preserving MSC functionality including their homing potential in order to optimize MSC transplantation in the context of graft-versus-host and other diseases.

Mesenchymal stem cell implantation in osteoarthritic knees: is fibrin glue effective as a scaffold?

BACKGROUND

The cell-based tissue engineering approach that uses mesenchymal stem cells (MSCs) has addressed the issue of articular cartilage repair in osteoarthritic (OA) knees. However, to improve outcomes, an advanced surgical procedure with tissue-engineered scaffolds may be needed to treat patients with large cartilage lesions.

PURPOSE

To investigate the clinical and second-look arthroscopic outcomes of the implantation of MSCs loaded in fibrin glue as a scaffold in patients with OA knees and to compare these outcomes with those of MSC implantation without a scaffold.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

This study retrospectively evaluated 54 patients (56 knees) who were examined with second-look arthroscopy after MSC implantation for cartilage lesions in their OA knees. Patients were divided into 2 groups: 37 patients (39 knees) were treated with MSC implantation without a scaffold (group 1), and 17 patients (17 knees) underwent implantation of MSCs loaded in fibrin glue as a scaffold (group 2). Clinical outcomes were evaluated according to the International Knee Documentation Committee (IKDC) score and the Tegner activity scale, and cartilage repair was assessed with the International Cartilage Repair Society (ICRS) grade. Statistical analyses were performed to identify various prognostic factors associated with the clinical and second-look arthroscopic outcomes.

RESULTS

At final follow-up (mean, 28.6 months; range, 24-34 months), the mean IKDC score and Tegner activity scale in each group significantly improved: group 1, from 38.1±7.7 to 62.0±11.7 (IKDC) and from 2.5±0.9 to 3.5±0.8 (Tegner); group 2, from 36.1±6.2 to 64.4±11.5 (IKDC) and from 2.2±0.8 to 3.8±0.8 (Tegner) (P<.001 for all). According to the overall ICRS cartilage repair grades, 9 of the 39 lesions (23%) in group 1 and 12 of the 17 lesions (58%) in group 2 achieved a grade of I or II. There was a significant difference in ICRS grades between the groups (P=.028). Overweight (body mass index≥27.5 kg/m2) and large lesion size (≥5.7 cm2) were significant predictors of poor clinical and arthroscopic outcomes in group 1 (P<.05 for both). There was a similar trend in group 2, but the differences were not significant, possibly owing to the smaller sample size.

CONCLUSION

Clinical and arthroscopic outcomes of MSC implantation were encouraging for OA knees in both groups, although there were no significant differences in outcome scores between groups. However, at second-look arthroscopy, there were better ICRS grades in group 2.

Pluripotency maintenance of amniotic fluid-derived stem cells cultured on biomaterials

Human amniotic fluid-derived stem cells can maintain their pluripotency when cultured on soft hydrogels.

Current concepts: the role of mesenchymal stem cells in the management of knee osteoarthritis

Context:

The number of adults with osteoarthritis in the United States is expected to nearly double from 21.4 million in 2005 to 41.1 million by 2030. As a result, medical costs and associated comorbidity will exponentially increase in the coming decades. In the past decade, mesenchymal stem cells (MSCs) have emerged as a novel treatment for degenerative joint disease.

Evidence Acquisition:

PubMed (from 1990 to 2013) was searched to identify relevant studies. Reference lists of included studies were also reviewed.

Study Design:

Clinical review.

Level of Evidence:

Level 3.

Results:

We identified 9 animal and 7 human studies investigating the use of MSCs in the treatment of osteoarthritis, with varying levels of support for this therapy.

Conclusion:

While MSCs have shown potential for improving function and decreasing inflammation in animal studies, translation to patients is still in question. There is a great deal of heterogeneity in treatment methods. Standardizing the manufacturing and characterization of MSCs will allow for better comparisons.

Intra-articular injection of mesenchymal stem cells for the treatment of osteoarthritis of the knee: a proof-of-concept clinical trial

Mesenchymal stem cells (MSCs) are known to have a potential for articular cartilage regeneration. However, most studies focused on focal cartilage defect through surgical implantation. For the treatment of generalized cartilage loss in osteoarthritis, an alternative delivery strategy would be more appropriate. The purpose of this study was to assess the safety and efficacy of intra-articular injection of autologous adipose tissue derived MSCs (AD-MSCs) for knee osteoarthritis. We enrolled 18 patients with osteoarthritis of the knee and injected AD MSCs into the knee. The phase I study consists of three dose-escalation cohorts; the low-dose (1.0 × 10(7) cells), mid-dose (5.0 × 10(7)), and high-dose (1.0 × 10(8)) group with three patients each. The phase II included nine patients receiving the high-dose. The primary outcomes were the safety and the Western Ontario and McMaster Universities Osteoarthritis index (WOMAC) at 6 months. Secondary outcomes included clinical, radiological, arthroscopic, and histological evaluations. There was no treatment-related adverse event. The WOMAC score improved at 6 months after injection in the high-dose group. The size of cartilage defect decreased while the volume of cartilage increased in the medial femoral and tibial condyles of the high-dose group. Arthroscopy showed that the size of cartilage defect decreased in the medial femoral and medial tibial condyles of the high-dose group. Histology demonstrated thick, hyaline-like cartilage regeneration. These results showed that intra-articular injection of 1.0 × 10(8) AD MSCs into the osteoarthritic knee improved function and pain of the knee joint without causing adverse events, and reduced cartilage defects by regeneration of hyaline-like articular cartilage.

Current perspectives in mesenchymal stem cell therapies for osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease most commonly occurring in the ageing population. It is a slow progressive condition resulting in the destruction of hyaline cartilage followed by pain and reduced activity. Conventional treatments have little effects on the progression of the condition often leaving surgery as the last option. In the last 10 years tissue engineering utilising mesenchymal stem cells has been emerging as an alternative method for treating OA. Mesenchymal stem cells (MSCs) are multipotent progenitor cells found in various tissues, most commonly bone marrow and adipose tissue. MSCs are capable of differentiating into osteocytes, adipocytes, and chondrocytes. Autologous MSCs can be easily harvested and applied in treatment, but allogenic cells can also be employed. The early uses of MSCs focused on the implantations of cell rich matrixes during open surgeries, resulting in the formation of hyaline-like durable cartilage. More recently, the focus has completely shifted towards direct intra-articular injections where a great number of cells are suspended and injected into affected joints. In this review the history and early uses of MSCs in cartilage regeneration are reviewed and different approaches in current trends are explained and evaluated.

Acquiring chondrocyte phenotype from human mesenchymal stem cells under inflammatory conditions

An inflammatory milieu breaks down the cartilage matrix and induces chondrocyte apoptosis, resulting in cartilage destruction in patients with cartilage degenerative diseases, such as rheumatoid arthritis or osteoarthritis. Because of the limited regenerative ability of chondrocytes, defects in cartilage are irreversible and difficult to repair. Mesenchymal stem cells (MSCs) are expected to be a new tool for cartilage repair because they are present in the cartilage and are able to differentiate into multiple lineages of cells, including chondrocytes. Although clinical trials using MSCs for patients with cartilage defects have already begun, its efficacy and repair mechanisms remain unknown. A PubMed search conducted in October 2014 using the following medical subject headings (MeSH) terms: mesenchymal stromal cells, chondrogenesis, and cytokines resulted in 204 articles. The titles and abstracts were screened and nine articles relevant to “inflammatory” cytokines and “human” MSCs were identified. Herein, we review the cell biology and mechanisms of chondrocyte phenotype acquisition from human MSCs in an inflammatory milieu and discuss the clinical potential of MSCs for cartilage repair.

Tracking of mesenchymal stem cells labeled with gadolinium diethylenetriamine pentaacetic acid by 7T magnetic resonance imaging in a model of cerebral ischemia

Progress in the development of stem cell and gene therapy requires repeatable and non-invasive techniques to monitor the survival and integration of stem cells in vivo with a high temporal and spatial resolution. The purpose of the present study was to examine the feasibility of using the standard contrast agent gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) to label rat mesenchymal stem cells (MSCs) for stem cell tracking. MSCs, obtained from the bilateral femora of rats, were cultured and propagated. The non-liposomal lipid transfection reagent effectene was then used to induce the intracellular uptake of Gd-DTPA. Electron microscopy was used to detect the distribution of Gd-DTPA particles in the MSCs. The labeling efficiency of the Gd-DTPA particles in the MSCs was determined using spectrophotometry, and MTT and trypan blue exclusion assays were used to evaluate the viability and proliferation of the labeled MSCs. T1-weighted magnetic resonance imaging (MRI) was used to observe the labeled cells in vitro and in the rat brain. Gd-DTPA particles were detected inside the MSCs using transmission electron microscopy and a high labeling efficiency was observed. No difference was observed in cell viability or proliferation between the labeled and unlabeled MSCs (P>0.05). In the in vitro T1-weighted MRI and in the rat brain, a high signal intensity was observed in the labeled MSCs. The T1-weighted imaging of the labeled cells revealed a significantly higher signal intensity compared with that of the unlabeled cells (P<0.05) and the T1 values were significantly lower. The function of the labeled MSCs demonstrated no change following Gd-DTPA labeling, with no evident adverse effect on cell viability or proliferation. Therefore, a change in MR signal intensity was detected in vitro and in vivo, suggesting Gd-DTPA can be used to label MSCs for MRI tracking.

Mesenchymal Stem Cells Enhance Angiogenesis and Follicle Survival in Human Cryopreserved Ovarian Cortex Transplantation

Transplantation of cryopreserved ovarian tissue is a novel technique to restore endocrine function and fertility especially for cancer patients. However, the main obstacle of the technique is massive follicle loss as a result of ischemia in the process of transplantation. Mesenchymal stem cells (MSCs) have been acknowledged to play an important role in supporting angiogenesis and stabilizing long-lasting blood vessel networks through release of angiogenic factors and differentiation into pericytes and endothelial cells. This study is aimed to investigate whether MSCs could be applied to overcome the above obstacle to support the ovarian tissue survival in the transplantation. Here we show that human MSCs could enhance the expression level of VEGF, FGF2, and especially the level of angiogenin, significantly stimulate neovascularization, and increase blood perfusion of the grafts in the cryopreserved ovarian tissue transplantation. Further studies reveal that MSCs could notably reduce the apoptotic rates of primordial follicles and decrease follicle loss in the grafted ovarian tissues. In summary, our findings demonstrate a previously unrecognized function of MSCs in improving human ovarian tissue transplantation and provide a useful strategy to optimize fertility preservation and restoration.

Synovial fluid and synovial membrane mesenchymal stem cells: latest discoveries and therapeutic perspectives

Mesenchymal stem cells (MSCs) have the ability to differentiate into osteoblasts, chondroblasts, adipocytes, and even myoblasts. Most studies have focused on finding MSCs in different parts of the body for medical treatment. Every joint structure, including bone, joint fat, articular cartilage, and synovium, potentially contains resident MSCs. Recently, a progenitor cell population has been found in synovial fluid and showed similarities with both bone marrow and synovial membrane MSCs. Synovial fluid MSCs have been studied in healthy persons and osteoarthritic patients in order to explore its potential for treatment of some orthopedic disorders. Here, we briefly review the current knowledge on synovial fluid MSCs, their origin, relation to some orthopedic diseases, and future applications.

Biomechanical and cellular segmental characterization of human meniscus: building the basis for Tissue Engineering therapies

OBJECTIVE

To overcome current limitations of Tissue Engineering (TE) strategies, deeper comprehension on meniscus biology is required. This study aims to combine biomechanical segmental analysis of fresh human meniscus tissues and its correlation with architectural and cellular characterization.

METHOD

Morphologically intact menisci, from 44 live donors were studied after division into three radial segments. Dynamic mechanical analysis (DMA) was performed at physiological-like conditions. Micro-computed tomography (CT) analysis of freeze-dried samples assessed micro-structure. Flow cytometry, histology and histomorphometry were used for cellular study and quantification.

RESULTS

Anterior segments present significantly higher damping properties. Mid body fresh medial meniscus presents higher values of E' compared to lateral. Cyclic loads influence the viscoelastic behavior of menisci. By increasing the frequency leads to an increase in stiffness. Conversely, with increasing frequencies, the capacity to dissipate energy and damping properties initially decrease and then rise again. Age and gender directly correlate with higher E' and tan δ. Micro-CT analysis revealed that mean porosity was 55.5 (21.2-89.8)% and 64.7 (47.7-81.8)% for freeze-dried lateral and medial meniscus, respectively. Predominant cells are positive for CD44, CD73, CD90 and CD105, and lack CD31, CD34 and CD45 (present in smaller populations). Histomorphometry revealed that cellularity decreases from vascular zone 1 to zone 3. Anterior segments of lateral and medial meniscus have inferior cellularity as compared to mid body and posterior ones.

CONCLUSION

Menisci are not uniform structures. Anterior segments have lower cellularity and higher damping. Cyclic loads influence viscoelastic characteristics. Future TE therapies should consider segmental architecture, cellularity and biomechanics of fresh tissue.

Single cell sorting identifies progenitor cell population from full thickness bovine articular cartilage

OBJECTIVE

To date, no approved clinical intervention successfully prevents the progressive degradation of injured articular cartilage that leads to osteoarthritis (OA). Stem/progenitor cell populations within tissues of diarthrodial joint have shown their therapeutic potential in treating OA. However, this potential has not been fully realized due in part to the heterogeneity of these subpopulations. Characterization of clonal populations derived from a single cell may help identify more homogenous stem/progenitor populations within articular cartilage. Moreover, chondrogenic potential of clonal populations from different zones could be further examined to elucidate their differential roles in maintaining articular cartilage homeostasis.

METHOD

We combined Fluorescence-activated cell sorting (FACS) and clonogenicity screening to identify stem/progenitor cells cloned from single cells. High-efficiency colony-forming cells (HCCs) were isolated, and evaluated for stem/progenitor cell characteristics. HCCs were also isolated from different zones of articular cartilage. Their function was compared by lineage-specific gene expression, and differentiation potential.

RESULTS

A difference in colony-forming efficiency was observed in terms of colony sizes. HCCs were highly clonogenic and multipotent, and overexpressed stem/progenitor cell markers. Also, proliferation and migration associated genes were over-expressed in HCCs. HCCs showed zonal differences with deep HCCs more chondrogenic and osteogenic than superficial HCCs.

CONCLUSION

Our approach is a simple yet practical way to identify homogeneous stem/progenitor cell populations with clonal origin. The discovery of progenitor cells demonstrates the intrinsic self-repairing potential of articular cartilage. Differences in differentiation potential may represent the distinct roles of superficial and deep zone stem/progenitor cells in the maintenance of articular cartilage homeostasis.

Differential regulation of osteogenic differentiation of stem cells on surface roughness gradients

Tissue engineering using scaffold-cell constructs holds the potential to develop functional strategies to regenerate bone. The interface of orthopedic implants with the host tissues is of great importance for its later performance. Thus, the optimization of the implant surface in a way that could stimulate osteogenic differentiation of mesenchymal stem cells (MSCs) is of significant therapeutic interest. The effect of surface roughness of polycaprolactone (PCL) on the osteogenic differentiation of human bone-marrow MSCs was investigated. We prepared surface roughness gradients of average roughness (Ra) varying from the sub-micron to the micrometer range (∼0.5-4.7 μm), and mean distance between peaks (RSm) gradually varying from ∼214 μm to 33 μm. We analyzed the degree of cytoskeleton spreading, expression of alkaline phosphatase, collagen type 1 and mineralization. The response of cells to roughness divided the gradient into three groups of elicited stem cell behavior: 1) faster osteogenic commitment and strongest osteogenic expression; 2) slower osteogenic commitment but strong osteogenic expression, and 3) similar or inferior osteogenic potential in comparison to the control material. The stem-cell modulation by specific PCL roughness surfaces highlights the potential for creating effective solutions for orthopedic applications featuring a clinically relevant biodegradable material.

Mesenchymal stem cells, autoimmunity and rheumatoid arthritis

The vast majority of literature pertaining to mesenchymal stem cells (MSC) immunomodulation has focussed on bone marrow-derived MSC that are systemically infused to alleviate inflammatory conditions. Rheumatoid arthritis (RA) is the commonest autoimmune joint disease that has witnessed significant therapeutic advances in the past decade, but remains stubbornly difficult to treat in a subset of cases. Pre-clinical research has demonstrated that bone marrow, adipose, synovial and umbilical cord-derived MSC all suppress the functions of different immune cells thus raising the possibility of new therapies for autoimmune diseases including RA. Indeed, preliminary evidence for MSC efficacy has been reported in some cases of RA and systemic lupus erythromatosis. The potential use of bone marrow-MSC (BM-MSC) for RA therapy is emerging but the use of synovial MSC (S-MSC) to suppress the exaggerated immune response within the inflamed joints remains rudimentary. Synovial fibroblasts that are likely derived from S-MSCs, also give rise to a cell-cultured progeny termed fibroblast-like synoviocytes (FLS), which are key players in the perpetuation of joint inflammation and destruction. A better understanding of the link between these cells and their biology could be a key to developing novel MSC-based strategies for therapy. The review briefly focuses on BM-MSC and gives particular attention to joint niche synovial MSC and FLS with respect to immunoregulatory potential therapy roles.

Intrinsic multipotential mesenchymal stromal cell activity in gelatinous Heberden's nodes in osteoarthritis at clinical presentation

INTRODUCTION

Gelatinous Heberden's nodes (HNs), also termed synovial cysts, are a common form of generalized osteoarthritis (OA). We sought to determine whether HN cases at clinical presentation contained multipotential stromal cells (MSCs) and to explore whether such cells were more closely related to bone marrow (BM) or synovial fluid (SF) MSCs by transcriptional analysis.

METHODS

At clinical presentation, gelatinous material was extracted/extruded from the distal phalangeal joint of OA patients with HNs. From this, plastic adherent cells were culture-expanded for phenotypic and functional characterization and comparison with BM- and SF-MSCs. Mesenchymal related gene expression was studied by using a custom-designed TaqMan Low Density Array to determine transcriptional similarities between different MSC groups and skin fibroblasts.

RESULTS

In all cases, HN material produced MSC-like colonies. Adherent cultures displayed an MSC phenotype (CD29(+), CD44(+), CD73(+), CD81(+), and CD90(+) and CD14(-) CD19(-), CD31(-), CD34(-), CD45(-), and HLADR(-)) and exhibited osteogenic, chondrogenic lineage differentiation but weak adipogenesis. Gene cluster analysis showed that HN-MSCs were more closely related to SF- than normal or OA BM-MSCs with significantly higher expression of synovium-related gene markers such as bone morphogenic protein 4 (BMP4), bone morphogenetic protein receptor type 1A (BMPR1A), protein/leucine-rich end leucine-rich repeat protein (PRELP), secreted frizzled-related protein 4 (SFRP4), and tumor necrosis factor alpha-induced protein 6 (TNFAIP6) (P <0.05).

CONCLUSIONS

Gelatinous HNs derived from hand OA at clinical presentation contain a population of MSCs that share transcriptional similarities with SF-derived MSCs. Their aberrant entrapment within the synovial cysts may impact on their normal role in joint homeostasis.

Melatonin regulates mesenchymal stem cell differentiation: a review

Among the numerous functions of melatonin, the control of survival and differentiation of mesenchymal stem cells (MSCs) has been recently proposed. MSCs are a heterogeneous population of multipotent elements resident in tissues such as bone marrow, muscle, and adipose tissue, which are primarily involved in developmental and regeneration processes, gaining thus increasing interest for tissue repair and restoration therapeutic protocols. Receptor-dependent and receptor-independent responses to melatonin are suggested to occur in these cells. These involve antioxidant or redox-dependent functions of this indolamine as well as secondary effects resulting from autocrine and paracrine responses. Inflammatory cytokines and adipokines, proangiogenic/mitogenic stimuli, and other mediators that influence the differentiation processes may affect the survival and functional integrity of these mesenchymal precursor cells. In this scenario, melatonin seems to regulate signaling pathways that drive commitment and differentiation of MSC into osteogenic, chondrogenic, adipogenic, or myogenic lineages. Common pathways suggested to be involved as master regulators of these processes are the Wnt/β-catenin pathway, the MAPKs and the, TGF-β signaling. In this respect melatonin emerges a novel and potential modulator of MSC lineage commitment and adipogenic differentiation. These and other aspects of the physiological and pharmacological effects of melatonin as regulator of MSC are discussed in this review.

Future directions for the management of pain in osteoarthritis

Osteoarthritis (OA) is the predominant form of arthritis worldwide, resulting in a high degree of functional impairment and reduced quality of life owing to chronic pain. To date, there are no treatments that are known to modify disease progression of OA in the long term. Current treatments are largely based on the modulation of pain, including NSAIDs, opiates and, more recently, centrally acting pharmacotherapies to avert pain. This review will focus on the rationale for new avenues in pain modulation, including inhibition with anti-NGF antibodies and centrally acting analgesics. The authors also consider the potential for structure modification in cartilage/bone using growth factors and stem cell therapies. The possible mismatch between structural change and pain perception will also be discussed, introducing recent techniques that may assist in improved patient phenotyping of pain subsets in OA. Such developments could help further stratify subgroups and treatments for people with OA in future.

Tracking gene and cell fate for therapeutic gain

Parallel advances in molecular imaging modalities and in gene- and cell-based therapeutics have significantly advanced their respective fields. Here we discuss how the collaborative, preclinical intersection of these technologies will facilitate more informed and effective clinical translation of relevant therapies.

Progress in intra-articular therapy

Diarthrodial joints are well suited to intra-articular injection, and the local delivery of therapeutics in this fashion brings several potential advantages to the treatment of a wide range of arthropathies. Possible benefits over systemic delivery include increased bioavailability, reduced systemic exposure, fewer adverse events, and lower total drug costs. Nevertheless, intra-articular therapy is challenging because of the rapid egress of injected materials from the joint space; this elimination is true of both small molecules, which exit via synovial capillaries, and of macromolecules, which are cleared by the lymphatic system. In general, soluble materials have an intra-articular dwell time measured only in hours. Corticosteroids and hyaluronate preparations constitute the mainstay of FDA-approved intra-articular therapeutics. Recombinant proteins, autologous blood products and analgesics have also found clinical use via intra-articular delivery. Several alternative approaches, such as local delivery of cell and gene therapy, as well as the use of microparticles, liposomes, and modified drugs, are in various stages of preclinical development.

Biocompatibility and enhanced osteogenic differentiation of human mesenchymal stem cells in response to surface engineered poly(D,L-lactic-co-glycolic acid) microparticles

Tissue engineering strategies can be applied to enhancing osseous integration of soft tissue grafts during ligament reconstruction. Ligament rupture results in a hemarthrosis, an acute intra-articular bleed rich in osteogenic human mesenchymal stem cells (hMSCs). With the aim of identifying an appropriate biomaterial with which to combine hemarthrosis fluid-derived hMSCs (HF-hMSCs) for therapeutic application, this work has investigated the biocompatibility of microparticles manufactured from two forms of poly(D,L-lactic-co-glycolic acid) (PLGA), one synthesized with equal monomeric ratios of lactic acid to glycolic acid (PLGA 50:50) and the other with a higher proportion of lactic acid (PLGA 85:15) which confers a longer biodegradation time. The surfaces of both types of microparticles were functionalized by plasma polymerization with allylamine to increase hydrophilicity and promote cell attachment. HF-hMSCs attached to and spread along the surface of both forms of PLGA microparticle. The osteogenic response of HF-hMSCs was enhanced when cultured with PLGA compared with control cultures differentiated on tissue culture plastic and this was independent of the type of polymer used. We have demonstrated that surface engineered PLGA microparticles are an appropriate biomaterial for combining with HF-hMSCs and the selection of PLGA is relevant only when considering the biodegradation time for each biomedical application.