Isolation and characterization of multipotential mesenchymal cells from the mouse synovium

Early changes in the knee of healer and non-healer mice following non-invasive mechanical injury

In this study, we examined early time-dependent changes in articular cartilage and synovium in response to tibial compression and sought the plausible origin of cells that respond to compression in the healer (LGXSM-6) and non-healer (LGXSM-33) recombinant inbred mouse strains. The right knee of 13-week old male mice was subjected to tibial compression using 9N axial loading. The contralateral left knee served as a control. Knees were harvested at 5, 9, and 14 days post-injury. Histological changes in cartilage and synovium, immunofluorescence pattern of CD44, aggrecan, type-II collagen, cartilage oligomeric matrix protein and the aggrecan neo-epitope NITEGE, and cell apoptosis (by TUNEL) were examined. We used a double nucleoside analog cell-labeling strategy to trace cells responsive to injury. We showed that tibial compression resulted in rupture of anterior cruciate ligament, cartilage matrix loss and chondrocyte apoptosis at the injury site. LGXSM-33 showed higher synovitis and ectopic synovial chondrogenesis than LGXSM-6 with no differences for articular cartilage lesions. With loading, an altered pattern of CD44 and NITEGE was observed: cells in the impacted area underwent apoptosis, cells closely surrounding the injured area expressed CD44, and cells in the intact area expressed NITEGE. Cells responding to injury were found in the synovium, subchondral bone marrow and the Groove of Ranvier. Taken together, we found no strain differences in chondrocytes in the early response to injury. However, the synovial response was greater in LGXSM-33 indicating that, at early time points, there is a genetic difference in synovial cell reaction to injury. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:524-536, 2017.

Adipose, Bone Marrow and Synovial Joint-Derived Mesenchymal Stem Cells for Cartilage Repair

Current cell-based repair strategies have proven unsuccessful for treating cartilage defects and osteoarthritic lesions, consequently advances in innovative therapeutics are required and mesenchymal stem cell-based (MSC) therapies are an expanding area of investigation. MSCs are capable of differentiating into multiple cell lineages and exerting paracrine effects. Due to their easy isolation, expansion, and low immunogenicity, MSCs are an attractive option for regenerative medicine for joint repair. Recent studies have identified several MSC tissue reservoirs including in adipose tissue, bone marrow, cartilage, periosteum, and muscle. MSCs isolated from these discrete tissue niches exhibit distinct biological activities, and have enhanced regenerative potentials for different tissue types. Each MSC type has advantages and disadvantages for cartilage repair and their use in a clinical setting is a balance between expediency and effectiveness. In this review we explore the challenges associated with cartilage repair and regeneration using MSC-based cell therapies and provide an overview of phenotype, biological activities, and functional properties for each MSC population. This paper also specifically explores the therapeutic potential of each type of MSC, particularly focusing on which cells are capable of producing stratified hyaline-like articular cartilage regeneration. Finally we highlight areas for future investigation. Given that patients present with a variety of problems it is unlikely that cartilage regeneration will be a simple "one size fits all," but more likely an array of solutions that need to be applied systematically to achieve regeneration of a biomechanically competent repair tissue.

Interleukin-1β Suppresses the Transporter Genes Ank and Ent1 Expression in Stromal Progenitor Cells Retaining Mineralization

Heterotopic ossification (HO) in various tissues evokes clinical problems. Inflammatory responses of the stromal progenitor cells may be involved in its etiology. Previous report indicated that pro-inflammatory cytokines including IL-1β enhanced the in vitro calcification of human mesenchymal stem cells (MSCs), by suppressing the expression of ectonucleotide pyrophosphatase/phosphodiesterase-1 gene (ENPP1). However, possible contribution of other related factors had not been investigated. Here, we investigated the expression of regulators of extracellular pyrophosphate and nucleosides including Enpp1, Nt5e, Ank, Enptds, and Ent1, examining various connective tissue stromal progenitor cells, including bone marrow stromal cells and synovium derived cells from mouse, or bone marrow MSCs from human. Consistent with previous studies, we observed characteristic suppression of the osteoblastic marker genes by IL-1β during the osteogenic culture for 20 days. In addition, we observed a reduced expression of the important transporter genes, Ank and Ent1, whereas the alteration in Enpp1 and Nt5e levels was not always consistent among the cell types. Our results suggest that IL-1β suppresses not only the osteoblastic but also the negative regulators of soft-tissue calcification, including Ank and Ent1 in stromal progenitor cells, which may contribute to the mechanisms of HO in various disorders.

Stem Cells for Temporomandibular Joint Repair and Regeneration

Temporomandibular Disorders (TMD) represent a heterogeneous group of musculoskeletal and neuromuscular conditions involving the temporomandibular joint (TMJ), masticatory muscles and/or associated structures. They are a major cause of non-dental orofacial pain. As a group, they are often multi-factorial in nature and have no common etiology or biological explanations. TMD can be broadly divided into masticatory muscle and TMJ disorders. TMJ disorders are characterized by intra-articular positional and/or structural abnormalities. The most common type of TMJ disorders involves displacement of the TMJ articular disc that precedes progressive degenerative changes of the joint leading to osteoarthritis (OA). In the past decade, progress made in the development of stem cell-based therapies and tissue engineering have provided alternative methods to attenuate the disease symptoms and even replace the diseased tissue in the treatment of TMJ disorders. Resident mesenchymal stem cells (MSCs) have been isolated from the synovia of TMJ, suggesting an important role in the repair and regeneration of TMJ. The seminal discovery of pluripotent stem cells including embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) have provided promising cell sources for drug discovery, transplantation as well as for tissue engineering of TMJ condylar cartilage and disc. This review discusses the most recent advances in development of stem cell-based treatments for TMJ disorders through innovative approaches of cell-based therapeutics, tissue engineering and drug discovery.

Intra-articular injection of synovial mesenchymal stem cells improves cartilage repair in a mouse injury model

Controversy remains whether articular cartilage has an endogenous stem/progenitor cell population, since its poor healing capacity after injury can lead to diseases such as osteoarthritis. In the joint environment there are mesenchymal stem/progenitor cells (MSCs) in the synovial membrane and synovial fluid that can differentiate into cartilage, but it is still under debate if these cells contribute to cartilage repair in vivo. In this study, we isolated a Sca-1 positive, chondrogenesis capable population of mouse synovial MSCs from C57BL6 and MRL/MpJ “super-healer” strains. Intra-articular injection of Sca-1 + GFP + synovial cells from C57BL6 or MRL/MpJ into C57BL6 mice following cartilage injury led to increased cartilage repair by 4 weeks after injury. GFP expression was detected in the injury site at 2 weeks, but not 4 weeks after injury. These results suggest that synovial stem/progenitor cells, regardless of strain background, have beneficial effects when injected into an injured joint. MSCs derived from MRL/MpJ mice did not promote an increased repair capacity compared to MSCs derived from non-healing C57BL6 controls; however, MRL/MpJ MSCs were observed within the defect area at the time points examined, while C57BL6 MSCs were not.

Cartilage regeneration for treatment of osteoarthritis: a paradigm for nonsurgical intervention

Osteoarthritis (OA) is associated with articular cartilage abnormalities and affects people of older age: preventative or therapeutic treatment measures for OA and related articular cartilage disorders remain challenging. In this perspective review, we have integrated multiple biological, morphological, developmental, stem cell and homeostasis concepts of articular cartilage to develop a paradigm for cartilage regeneration. OA is conceptually defined as an injury of cartilage that initiates chondrocyte activation, expression of proteases and growth factor release from the matrix. This regenerative process results in the local activation of inflammatory response genes in cartilage without migration of inflammatory cells or angiogenesis. The end results are catabolic and anabolic responses, and it is the balance between these two outcomes that controls remodelling of the matrix and regeneration. A tantalizing clinical clue for cartilage regrowth in OA joints has been observed in surgically created joint distraction. We hypothesize that cartilage growth in these distracted joints may have a biological connection with the size of organs and regeneration. Therefore we propose a novel, practical and nonsurgical intervention to validate the role of distraction in cartilage regeneration in OA. The approach permits normal wake-up activity while during sleep; the index knee is subjected to distraction with a pull traction device. Comparison of follow-up magnetic resonance imaging (MRI) at 3 and 6 months of therapy to those taken before therapy will provide much-needed objective evidence for the use of this mode of therapy for OA. We suggest that the paradigm presented here merits investigation for treatment of OA in knee joints.

Cell-based articular cartilage repair: the link between development and regeneration

Clinical efforts to repair damaged articular cartilage (AC) currently face major obstacles due to limited intrinsic repair capacity of the tissue and unsuccessful biological interventions. This highlights a need for better therapeutic strategies. This review summarizes the recent advances in the field of cell-based AC repair. In both animals and humans, AC defects that penetrate into the subchondral bone marrow are mainly filled with fibrocartilaginous tissue through the differentiation of bone marrow mesenchymal stem cells (MSCs), followed by degeneration of repaired cartilage and osteoarthritis (OA). Cell therapy and tissue engineering techniques using culture-expanded chondrocytes, bone marrow MSCs, or pluripotent stem cells with chondroinductive growth factors may generate cartilaginous tissue in AC defects but do not form hyaline cartilage-based articular surface because repair cells often lose chondrogenic activity or result in chondrocyte hypertrophy. The new evidence that AC and synovium develop from the same pool of precursors with similar gene profiles and that synovium-derived chondrocytes have stable chondrogenic activity has promoted use of synovium as a new cell source for AC repair. The recent finding that NFAT1 and NFAT2 transcription factors (TFs) inhibit chondrocyte hypertrophy and maintain metabolic balance in AC is a significant advance in the field of AC repair. The use of synovial MSCs and discovery of upstream transcriptional regulators that help maintain the AC phenotype have opened new avenues to improve the outcome of AC regeneration.

WNT-inflammasome signaling mediates NOD2-induced development of acute arthritis in mice

In addition to its role in innate immunity, the intracellular pathogen sensor nucleotide-binding oligomerization domain 2 (NOD2) has been implicated in various inflammatory disorders, including the development of acute arthritis. However, the molecular mechanisms involved in the development of NOD2-responsive acute arthritis are not clear. In this study, we demonstrate that NOD2 signals to a cellular protein, Ly6/PLAUR domain-containing protein 6, in a receptor-interacting protein kinase 2-TGF-β-activated kinase 1-independent manner to activate the WNT signaling cascade. Gain- or loss-of-function of the WNT signaling pathway in an in vivo experimental mouse arthritis model or in vitro systems established the role for WNT-responsive X-linked inhibitor of apoptosis during the development of acute arthritis. Importantly, WNT-stimulated X-linked inhibitor of apoptosis mediates the activation of inflammasomes. The subsequent caspase-1 activation and IL-1β secretion together contribute to the phenotypic character of the inflammatory condition of acute arthritis. Thus, identification of a role for WNT-mediated inflammasome activation during NOD2 stimulation serves as a paradigm to understand NOD2-associated inflammatory disorders and develop novel therapeutics.

Mouse synovial mesenchymal stem cells increase in yield with knee inflammation

Even though mouse studies have various advantages, harvesting an adequate number of synovial mesenchymal stem cells (MSCs) is difficult in mice. We investigated whether the total yield of MSCs increased in synovium with inflammation in mice. Infrapatellar fat pads (IFPs) were harvested from 10 knees of 5 mice 3, 7, and 14 days after intraarticular injection of carrageenan. Ten IFPs were also harvested from untreated knees as a control. Seven days after initial plating, the total yield of cells was compared among the 4 groups (n = 4-6). The harvested cells were analyzed for multipotentiality and surface epitopes. Furthermore, knee synovitis was compared among the 4 groups in histology. The number of cells in the 3 and 7 days treated group was significantly higher than the other groups. The harvested cells had characteristics of MSCs. Synovitis in the 3 and 7 days treated groups was significantly severer than the other groups. There seemed to be a relationship between the synovitis score and the total yield of cells derived from IFPs. In mice, it became possible to increase the yield 50-fold by inducing inflammation. This method makes it possible to analyze the molecular mechanisms of cartilage regeneration of synovial MSCs in mice models.

Strategies to improve homing of mesenchymal stem cells for greater efficacy in stem cell therapy

Stem/progenitor cell-based therapeutic approach in clinical practice has been an elusive dream in medical sciences, and improvement of stem cell homing is one of major challenges in cell therapy programs. Stem/progenitor cells have a homing response to injured tissues/organs, mediated by interactions of chemokine receptors expressed on the cells and chemokines secreted by the injured tissue. For improvement of directed homing of the cells, many techniques have been developed either to engineer stem/progenitor cells with higher amount of chemokine receptors (stem cell-based strategies) or to modulate the target tissues to release higher level of the corresponding chemokines (target tissue-based strategies). This review discusses both of these strategies involved in the improvement of stem cell homing focusing on mesenchymal stem cells as most frequent studied model in cellular therapies.

Transplantation of stem cells from human exfoliated deciduous teeth for bone regeneration in the dog mandibular defect

AIM: To investigate the effect of stem cells from human exfoliated deciduous teeth (SHED) transplanted for bone regeneration in the dog mandibular defect.

METHODS: In this prospective comparative study, SHEDs had been isolated 5 years ago from human exfoliated deciduous teeth. The undifferentiated stem cells were seeded into mandibular bone through-and-through defects of 4 dogs. Similar defects in control group were filled with cell-free collagen scaffold. After 12 wk, biopsies were taken and morphometric analysis was performed. The percentage of new bone formation and foreign body reaction were measured in each case. The data were subject to statistical analysis using the Mann-Whitney U and Kruskalwalis statistical tests. Differences at P < 0.05 was considered as significant level.

RESULTS: There were no significant differences between control and SHED-seeded groups in connective tissue (P = 0.248), woven bone (P = 0.248) and compact bone (P = 0.082). There were not any side effects in transplanted SHED group such as teratoma or malignancy and abnormalities in this period.

CONCLUSION: SHEDs which had been isolated and characterized 5 years ago and stored with cryopreservation banking were capable of proliferation and osteogenesis after 5 years, and no immune response was observed after three months of seeded SHEDs.

Resident mesenchymal progenitors of articular cartilage

Articular cartilage has poor capacity of self-renewal and repair. Insufficient number and activity of resident mesenchymal (connective tissue) progenitors is likely one of the underlying reasons. Chondroprogenitors reside not only in the superficial zone of articular cartilage but also in other zones of articular cartilage and in the neighboring tissues, including perichondrium (groove of Ranvier), synovium and fat pad. These cells may respond to injury and contribute to articular cartilage healing. In addition, marrow stromal cells can migrate through subchondral bone when articular cartilage is damaged. We should develop drugs and methods that correctly stimulate resident progenitors for improvement of repair and inhibition of degenerative changes in articular cartilage.

Toward regeneration of articular cartilage

Articular cartilage is classified as permanent hyaline cartilage and has significant differences in structure, extracelluar matrix components, gene expression profile, and mechanical property from transient hyaline cartilage found in the epiphyseal growth plate. In the process of synovial joint development, articular cartilage originates from the interzone, developing at the edge of the cartilaginous anlagen, and establishes zonal structure over time and supports smooth movement of the synovial joint through life. The cascade actions of key regulators, such as Wnts, GDF5, Erg, and PTHLH, coordinate sequential steps of articular cartilage formation. Articular chondrocytes are restrictedly controlled not to differentiate into a hypertrophic stage by autocrine and paracrine factors and extracellular matrix microenvironment, but retain potential to undergo hypertrophy. The basal calcified zone of articular cartilage is connected with subchondral bone, but not invaded by blood vessels nor replaced by bone, which is highly contrasted with the growth plate. Articular cartilage has limited regenerative capacity, but likely possesses and potentially uses intrinsic stem cell source in the superficial layer, Ranvier's groove, the intra-articular tissues such as synovium and fat pad, and marrow below the subchondral bone. Considering the biological views on articular cartilage, several important points are raised for regeneration of articular cartilage. We should evaluate the nature of regenerated cartilage as permanent hyaline cartilage and not just hyaline cartilage. We should study how a hypertrophic phenotype of transplanted cells can be lastingly suppressed in regenerating tissue. Furthermore, we should develop the methods and reagents to activate recruitment of intrinsic stem/progenitor cells into the damaged site.

Surface modification on polycaprolactone electrospun mesh and human decalcified bone scaffold with synovium-derived mesenchymal stem cells-affinity peptide for tissue engineering

Synovium-derived mesenchymal stem cells (SMSC) have been studied for over a decade since first being successfully isolated in 2001. These cells demonstrate the most promising therapeutic efficacy for musculoskeletal regeneration of the MSC family, particularly for cartilage regeneration. However, the mobilization and transfer of MSCs to defective or damaged tissues and organs in vivo with high accuracy and efficiency has been a major problem in tissue engineering (TE). In the present study, we identified a seven amino acid peptide sequence [SMSCs-affinity peptide (LTHPRWP; L7)] through phage display technology that has a high specific affinity to SMSCs. Our analysis suggested that L7 efficiently and specifically interacted with SMSCs without any species specificity. Thereafter, L7 was covalently conjugated onto both polycaprolactone (PCL) electrospun meshes and human decalcified bone scaffolds (hDBSc) to investigate its TE applications. After 24 h coculture with human SMSCs (hSMSCs), L7-conjugated PCL electrospun meshes had significantly more adherent hSMSCs than the control group, and the cells expanded well. Similar results were obtained using hDBSs. These results suggest that the novel L7 peptide sequence has a high specific affinity to SMSCs. Covalently conjugating this peptide to either artificial polymer material (PCL mesh) or natural material (hDBS) significantly enhances the adhesion of SMSCs. This method is applicable to a wide range of potential SMSC-based TE applications, particularly to cartilage regeneration, via surface modification on various type of materials.

Arthritic periosteal tissue from joint replacement surgery: a novel, autologous source of stem cells

The overarching aim of this study is to assess the feasibility of using periosteal tissue from the femoral neck of arthritic hip joints, usually discarded in the normal course of hip replacement surgery, as an autologous source of stem cells. In addition, the study aims to characterize intrinsic differences between periosteum-derived cell (PDC) populations, isolated via either enzymatic digestion or a migration assay, including their proliferative capacity, surface marker expression, and multipotency, relative to commercially available human bone marrow-derived stromal cells (BMSCs) cultured under identical conditions. Commercial BMSCs and PDCs were characterized in vitro, using a growth assay, flow cytometry, as well as assay of Oil Red O, alizarin red, and Safranin O/Fast Green staining after respective culture in adipo-, osteo-, and chondrogenic media. Based on these outcome measures, PDCs exhibited proliferation rate, morphology, surface receptor expression, and multipotency similar to those of BMSCs. No significant correlation was observed between outcome measures and donor age or diagnosis (osteoarthritis [OA] and rheumatoid arthritis [RA], respectively), a profound finding given recent rheumatological studies indicating that OA and RA share not only common biomarkers and molecular mechanisms but also common pathophysiology, ultimately resulting in the need for joint replacement. Furthermore, PDCs isolated via enzymatic digestion and migration assay showed subtle differences in surface marker expression but otherwise no significant differences in proliferation or multipotency; the observed differences in surface marker expression may indicate potential effects of isolation method on the population of cells isolated and/or the behavior of the respective isolated cell populations. This study demonstrates, for the first time to our knowledge, the feasibility of using arthritic tissue resected during hip replacement as a source of autologous stem cells. In sum, periosteum tissue that is resected with the femoral neck in replacing the hip represents an unprecedented and, to date, unstudied source of stem cells from OA and RA patients. Follow-up studies will determine the degree to which this new, autologous source of stem cells can be banked for future use.

miRNA let-7e targeting MMP9 is involved in adipose-derived stem cell differentiation toward epithelia

miRNA let-7e is involved in stem cell differentiation, and metalloproteinases are among its potential target genes. We hypothesized that the inhibitory action of let-7e on regulation of MMP9 expression could represent a crucial mechanism during differentiation of adipose-derived stem cells (ASCs). ASCs were differentiated with all-trans retinoic acid (ATRA) to promote differentiation, and the effect of let-7 silencing during differentiation was tested. Results indicate that ASCs cultured with ATRA differentiated into cells of the epithelial lineage. We found that ASCs cultured with ATRA or transfected with miRNA let-7e expressed epithelial markers such as cytokeratin-18 and early renal organogenesis markers such as Pax2, Wt1, Wnt4 and megalin. Conversely, the specific knockdown of miRNA let-7e in ASCs significantly decreased the expression of these genes, indicating its vital role during the differentiation process. Using luciferase reporter assays, we also showed that MMP9 is a direct target of miRNA let-7e. Thus, our results suggest that miRNA let-7e acts as a matrix metalloproteinase-9 (MMP9) inhibitor and differentiation inducer in ASCs.

In vitro synthesis of tensioned synoviocyte bioscaffolds for meniscal fibrocartilage tissue engineering

Background

Meniscal injury is a common cause of lameness in the dog. Tissue engineered bioscaffolds may be a treatment option for meniscal incompetency, and ideally would possess meniscus- like extracellular matrix (ECM) and withstand meniscal tensile hoop strains. Synovium may be a useful cell source for meniscal tissue engineering because of its natural role in meniscal deficiency and its in vitro chondrogenic potential. The objective of this study is to compare meniscal -like extracellular matrix content of hyperconfluent synoviocyte cell sheets (“HCS”) and hyperconfluent synoviocyte sheets which have been tensioned over wire hoops (tensioned synoviocyte bioscaffolds, “TSB”) and cultured for 1 month.

Results

Long term culture with tension resulted in higher GAG concentration, higher chondrogenic index, higher collagen concentration, and type II collagen immunoreactivity in TSB versus HCS. Both HCS and TSB were immunoreactive for type I collagen, however, HCS had mild, patchy intracellular immunoreactivity while TSB had diffuse moderate immunoreactivity over the entire bisocaffold. The tissue architecture was markedly different between TSB and HCS, with TSB containing collagen organized in bands and sheets. Both HCS and TSB expressed alpha smooth muscle actin and displayed active contractile behavior. Double stranded DNA content was not different between TSB and HCS, while cell viability decreased in TSB.

Conclusions

Long term culture of synoviocytes with tension improved meniscal- like extra cellular matrix components, specifically, the total collagen content, including type I and II collagen, and increased GAG content relative to HCS. Future research is warranted to investigate the potential of TSB for meniscal tissue engineering.

Synovial perlecan is required for osteophyte formation in knee osteoarthritis

The osteophyte associated with osteoarthritis (OA) is a bony outgrowth formed at the margins of the affected joint through endochondral ossification-like processes. However, the mechanism of osteophyte formation and its pathogenesis are unclear. Perlecan (Hspg2), a heparan sulfate proteoglycan, is expressed in many extracellular tissues and plays critical roles in skeletal development and diseases. The aim of the present study is to identify the role of synovial perlecan in osteophyte formation using perinatal lethality rescued perlecan-knockout mice (Hspg2(-/-)-Tg) wherein perlecan expression is lacking in the synovial and other tissues, except for cartilage. We analyzed the development of osteophytes in joints of Hspg2(-/-)-Tg mice in two different animal models: the surgical OA model, in which the medial collateral ligament was transected and the medial meniscus was resected, and the TGF-β-induced osteophyte formation model. In the surgical OA model, the osteophyte size and maturation were significantly reduced in the OA joints of Hspg2(-/-)-Tg mice compared with control mice, while OA developed on the medial side of the knee joints with no differences in the cartilage degradation score or synovitis score between control and Hspg2(-/-)-Tg mice. The reduced osteophyte formation in Hspg2(-/-)-Tg mice was associated with reduced cell proliferation and chondrogenesis. In the TGF-β model, the osteophyte size and maturation were also significantly reduced in Hspg2(-/-)-Tg mice compared with control mice. Our findings suggest that synovial perlecan plays an important role in osteophyte development in OA, and they provide insights that may facilitate the development of OA therapy.