sb203580 preconditioning recharges matrix-expanded human adult stem cells for chondrogenesis in an inflammatory environment - A feasible approach for autologous stem cell based osteoarthritic cartilage repair

MSCs-Derived Decellularised Matrix: Cellular Responses and Regenerative Dentistry

The decellularised extracellular matrix (dECM) of in vitro cell culture is a naturally derived biomaterial formed by the removal of cellular components. The compositions of molecules in the extracellular matrix (ECM) differ depending on various factors, including the culture conditions. Cell-derived ECM provides a 3-dimensional structure that has a complex influence on cell signalling, which in turn affects cell survival and differentiation. This review describes the effects of dECM derived from mesenchymal stem cells (MSCs) on cell responses, including cell migration, cell proliferation, and cell differentiation in vitro. Published articles were searched in the PubMed databases in 2005 to 2022, with assigned keywords (MSCs and decellularisation and cell culture). The 41 articles were reviewed, with the following criteria. (1) ECM was produced exclusively from MSCs; (2) decellularisation processes were performed; and (3) the dECM production was discussed in terms of culture systems and specific supplementations that are suitable for creating the dECM biomaterials. The dECM derived from MSCs supports cell adhesion, enhances cell proliferation, and promotes cell differentiation. Importantly, dECM derived from dental MSCs shows promise in regenerative dentistry applications. Therefore, the literature strongly supports cell-based dECMs as a promising option for innovative tissue engineering approaches for regenerative medicine.

Advances in Stem Cell-Based Therapies in the Treatment of Osteoarthritis

Osteoarthritis (OA) is a chronic, degenerative joint disease presenting a significant global health threat. While current therapeutic approaches primarily target symptom relief, their efficacy in repairing joint damage remains limited. Recent research has highlighted mesenchymal stem cells (MSCs) as potential contributors to cartilage repair, anti-inflammatory modulation, and immune regulation in OA patients. Notably, MSCs from different sources and their derivatives exhibit variations in their effectiveness in treating OA. Moreover, pretreatment and gene editing techniques of MSCs can enhance their therapeutic outcomes in OA. Additionally, the combination of novel biomaterials with MSCs has shown promise in facilitating the repair of damaged cartilage. This review summarizes recent studies on the role of MSCs in the treatment of OA, delving into their advantages and exploring potential directions for development, with the aim of providing fresh insights for future research in this critical field.

Autophagy and apoptosis: regulatory factors of chondrocyte phenotype transition in osteoarthritis

Osteoarthritis (OA) is the main pathogenic factor in diseases that cause joint deformities. As the main manifestation of the progress of OA, cartilage degradation has been closely associated with the degeneration of chondrocytes, which is induced by inflammatory factors and other trauma factors. Autophagy and apoptosis are the main mechanisms for cells to maintain homeostasis and play crucial roles in OA. Under the influence of external environmental factors (such as aging and injury), the metabolism of cells can be altered, which may affect the extent of autophagy and apoptosis. With the progression of OA, these changes can alter the cell phenotypes, and the cells of different phenotypes display distinct differences in morphology and function. In this review, we have summarized the alteration in cell metabolism, autophagy, and the extent of apoptosis during OA progression and its effects on the cell phenotypes to provide new ideas for further research on the mechanisms of phenotypic transition and therapeutic strategies so as to reverse the cell phenotypes.

Recent Advances in Small Molecule Inhibitors for the Treatment of Osteoarthritis

Osteoarthritis refers to a degenerative disease with joint pain as the main symptom, and it is caused by various factors, including fibrosis, chapping, ulcers, and loss of articular cartilage. Traditional treatments can only delay the progression of osteoarthritis, and patients may need joint replacement eventually. As a class of organic compound molecules weighing less than 1000 daltons, small molecule inhibitors can target proteins as the main components of most drugs clinically. Small molecule inhibitors for osteoarthritis are under constant research. In this regard, by reviewing relevant manuscripts, small molecule inhibitors targeting MMPs, ADAMTS, IL-1, TNF, WNT, NF-κB, and other proteins were reviewed. We summarized these small molecule inhibitors with different targets and discussed disease-modifying osteoarthritis drugs based on them. These small molecule inhibitors have good inhibitory effects on osteoarthritis, and this review will provide a reference for the treatment of osteoarthritis.

Functional acellular matrix for tissue repair

In view of their low immunogenicity, biomimetic internal environment, tissue- and organ-like physicochemical properties, and functionalization potential, decellularized extracellular matrix (dECM) materials attract considerable attention and are widely used in tissue engineering. This review describes the composition of extracellular matrices and their role in stem-cell differentiation, discusses the advantages and disadvantages of existing decellularization techniques, and presents methods for the functionalization and characterization of decellularized scaffolds. In addition, we discuss progress in the use of dECMs for cartilage, skin, nerve, and muscle repair and the transplantation or regeneration of different whole organs (e.g., kidneys, liver, uterus, lungs, and heart), summarize the shortcomings of using dECMs for tissue and organ repair after refunctionalization, and examine the corresponding future prospects. Thus, the present review helps to further systematize the application of functionalized dECMs in tissue/organ transplantation and keep researchers up to date on recent progress in dECM usage.

Matrix from urine stem cells boosts tissue-specific stem cell mediated functional cartilage reconstruction

Articular cartilage has a limited capacity to self-heal once damaged. Tissue-specific stem cells are a solution for cartilage regeneration; however, ex vivo expansion resulting in cell senescence remains a challenge as a large quantity of high-quality tissue-specific stem cells are needed for cartilage regeneration. Our previous report demonstrated that decellularized extracellular matrix (dECM) deposited by human synovium-derived stem cells (SDSCs), adipose-derived stem cells (ADSCs), urine-derived stem cells (UDSCs), or dermal fibroblasts (DFs) provided an ex vivo solution to rejuvenate human SDSCs in proliferation and chondrogenic potential, particularly for dECM deposited by UDSCs. To make the cell-derived dECM (C-dECM) approach applicable clinically, in this study, we evaluated ex vivo rejuvenation of rabbit infrapatellar fat pad-derived stem cells (IPFSCs), an easily accessible alternative for SDSCs, by the abovementioned C-dECMs, in vivo application for functional cartilage repair in a rabbit osteochondral defect model, and potential cellular and molecular mechanisms underlying this rejuvenation. We found that C-dECM rejuvenation promoted rabbit IPFSCs' cartilage engineering and functional regeneration in both ex vivo and in vivo models, particularly for the dECM deposited by UDSCs, which was further confirmed by proteomics data. RNA-Seq analysis indicated that both mesenchymal-epithelial transition (MET) and inflammation-mediated macrophage activation and polarization are potentially involved in the C-dECM-mediated promotion of IPFSCs' chondrogenic capacity, which needs further investigation.

Decellularized extracellular matrix mediates tissue construction and regeneration

Contributing to organ formation and tissue regeneration, extracellular matrix (ECM) constituents provide tissue with three-dimensional (3D) structural integrity and cellular-function regulation. Containing the crucial traits of the cellular microenvironment, ECM substitutes mediate cell–matrix interactions to prompt stem-cell proliferation and differentiation for 3D organoid construction in vitro or tissue regeneration in vivo. However, these ECMs are often applied generically and have yet to be extensively developed for specific cell types in 3D cultures. Cultured cells also produce rich ECM, particularly stromal cells. Cellular ECM improves 3D culture development in vitro and tissue remodeling during wound healing after implantation into the host as well. Gaining better insight into ECM derived from either tissue or cells that regulate 3D tissue reconstruction or organ regeneration helps us to select, produce, and implant the most suitable ECM and thus promote 3D organoid culture and tissue remodeling for in vivo regeneration. Overall, the decellularization methodologies and tissue/cell-derived ECM as scaffolds or cellular-growth supplements used in cell propagation and differentiation for 3D tissue culture in vitro are discussed. Moreover, current preclinical applications by which ECM components modulate the wound-healing process are reviewed.

Stem cells immortalized by hTERT perform differently from those immortalized by SV40LT in proliferation, differentiation, and reconstruction of matrix microenvironment

Although matrix microenvironment has the potential to improve expanded stem cell proliferation and differentiation capacity, decellularized extracellular matrix (dECM) deposited by senescent cells does not contribute to the rejuvenation of adult stem cells, which has become a barrier to personalized stem cell therapy. Genetic modification is an effective strategy to protect cells from senescence but it carries the increased risk of malignant transformation and genetic instability. In this study, lentivirus carrying either human telomerase reverse transcriptase (hTERT) or simian virus 40 large T antigen (SV40LT) was used to transduce human infrapatellar fat pad-derived stem cells (IPFSCs). We found that virus transduction modified the proliferative, chondrogenic, and adipogenic abilities of IPFSCs. Interestingly, dECM deposited by immortalized cells significantly influenced replicative senescent IPFSCs in proliferation and differentiation preference, the effect of which is hinged on the approach of immortalization using either SV40LT or hTERT. Our findings indicate both dECM expansion and immortalization strategies can be used for replicative senescent adult stem cells' proliferation and lineage-specific differentiation, which benefits future stem cell-based tissue regeneration. This approach may also work for adult stem cells with premature senescence in elderly/aged patients, which needs further investigation. STATEMENT OF SIGNIFICANCE: Adult stem cells are a promising solution for autologous cell-based therapy. Unfortunately, cell senescence due to donor age and/or ex vivo expansion prevents clinical application. Recent progress with decellularized extracellular matrix provides a potential for the rejuvenation of senescent stem cells by improving their proliferation and differentiation capacities. Given the fact that the young matrix can provide a healthy and energetic microenvironment, in this study, two approaches using lentivirus transduction of hTERT and SV40LT were compared. The goal was to immortalize donor cells for deposition of decellularized extracellular matrix. The matrix was demonstrated to contribute diverging effects on the chondrogenic and adipogenic differentiation of expanded stem cells and exhibited proliferation benefits as well. These findings provide an invaluable asset for stem cell-based tissue regeneration.

Matrix reverses immortalization-mediated stem cell fate determination

Primary cell culture in vitro suffers from cellular senescence. We hypothesized that expansion on decellularized extracellular matrix (dECM) deposited by simian virus 40 large T antigen (SV40LT) transduced autologous infrapatellar fat pad stem cells (IPFSCs) could rejuvenate high-passage IPFSCs in both proliferation and chondrogenic differentiation. In the study, we found that SV40LT transduced IPFSCs exhibited increased proliferation and adipogenic potential but decreased chondrogenic potential. Expansion on dECMs deposited by passage 5 IPFSCs yielded IPFSCs with dramatically increased proliferation and chondrogenic differentiation capacity; however, this enhanced capacity diminished if IPFSCs were grown on dECM deposited by passage 15 IPFSCs. Interestingly, expansion on dECM deposited by SV40LT transduced IPFSCs yielded IPFSCs with enhanced proliferation and chondrogenic capacity but decreased adipogenic potential, particularly for the dECM group derived from SV40LT transduced passage 15 cells. Our immunofluorescence staining and proteomics data identify matrix components such as basement membrane proteins as top candidates for matrix mediated IPFSC rejuvenation. Both cell proliferation and differentiation were endorsed by transcripts measured by RNASeq during the process. This study provides a promising model for in-depth investigation of the matrix protein influence on surrounding stem cell differentiation.

The Emerging Role of Exosomal Non-coding RNAs in Musculoskeletal Diseases

Exosomes are phospholipid bilayer-enclosed membrane vesicles derived and constitutively secreted by various metabolically active cells. They are capable of mediating hetero- and homotypic intercellular communication by transferring multiple cargos from donor cells to recipient cells. Nowadays, non-coding RNAs (ncRNAs) have emerged as novel potential biomarkers or disease-targeting agents in a variety of diseases. However, the lack of effective delivery systems may impair their clinical application. Recently, accumulating evidence demonstrated that ncRNAs could be efficiently delivered to recipient cells using exosomes as a carrier, and therefore can exert a critical role in musculoskeletal diseases including osteoarthritis, rheumatoid arthritis, osteoporosis, muscular dystrophies, osteosarcoma and other diseases. Herein, we present an extensive review of biogenesis, physiological relevance and clinical implication of exosome-derived ncRNAs in musculoskeletal diseases.

Improving Cell Therapy Survival and Anabolism in Harsh Musculoskeletal Disease Environments

Cell therapies are an up and coming technology in orthopedic medicine that has the potential to provide regenerative treatments for musculoskeletal disease. Despite numerous cell therapies showing preclinical success for common musculoskeletal indications of disc degeneration and osteoarthritis, there have been mixed results when testing these therapies in humans during clinical trials. A theory behind the mixed success of these cell therapies is that the harsh microenvironments of the disc and knee they are entering inhibit their anabolism and survival. Therefore, there is much ongoing research looking into how to improve the survival and anabolism of cell therapies within these musculoskeletal disease environments. This includes research into improving cell function under specific microenvironmental conditions known to exist in the intervertebral disc (IVD) and knee environment such as hypoxia, low-nutrient conditions, hyperosmolarity, acidity, and inflammation. This research also includes improving differentiation of cells into desired native cell phenotypes to better enhance their survival and anabolism in the knee and IVD. This review highlights the effects of specific musculoskeletal microenvironmental challenges on cell therapies and what research is being done to overcome these challenges. Impact statement While there has been significant clinical interest in using cell therapies for musculoskeletal pathologies in the knee and intervertebral disc, cell therapy clinical trials have had mixed outcomes. The information presented in this review includes the environmental challenges (i.e., acidic pH, inflammation, hyperosmolarity, hypoxia, and low nutrition) that cell therapies experience in these pathological musculoskeletal environments. This review summarizes studies that describe various approaches to improving the therapeutic capability of cell therapies in these harsh environments. The result is an overview of what approaches can be targeted and/or combined to develop a more consistent cell therapy for musculoskeletal pathologies.

Role of lineage-specific matrix in stem cell chondrogenesis

Cartilage repair in clinics is a challenge owing to the limited regenerative capacities of cartilage. Synovium-derived stem cells (SDSCs) are suggested as tissue-specific stem cells for chondrogenesis. In this study, we hypothesize that decellularized extracellular matrix (dECM) deposited by SDSCs could provide a superior tissue-specific matrix microenvironment for optimal rejuvenation of adult SDSCs for cartilage regeneration. dECMs were deposited by adult stem cells with varying chondrogenic capacities; SDSCs (strong) (SECM), adipose-derived stem cells (weak) (AECM) and dermal fibroblasts (weak) (DECM), and urine-derived stem cells (none) (UECM). Plastic flasks (Plastic) were used as a control substrate. Human SDSCs were expanded on the above substrates for one passage and examined for chondrogenic capacities. We found that each dECM consisted of unique matrix proteins and exhibited varied stiffnesses, which affected cell morphology and elasticity. Human SDSCs grown on dECMs displayed a significant increase in cell proliferation and unique surface phenotypes. Under induction media, dECM expanded cells yielded pellets with a dramatically increased number of chondrogenic markers. Interestingly, SECM expanded cells had less potential for hypertrophy compared to those grown on other dECMs, indicating that a tissue-specific matrix might provide a superior microenvironment for stem cell chondrogenic differentiation.

CXCR4/TGF-β1 mediated self-differentiation of human mesenchymal stem cells to carcinoma-associated fibroblasts and promoted colorectal carcinoma development

Background: Tumor microenvironment (TME) is a crucial part of tumor hallmarks. Mesenchymal stem cells (MSCs), important components of TME, are the main source of Carcinoma-associated fibroblasts (CAFs), but the mechanism of transformation regulation is still unclear. Transforming growth factor-β1 (TGF-β1), chemokine Stromal cell-derived factor-1 (SDF-1) and its endogenous receptor CXCR4 may play important roles during this process.Methods: Co-culture technique was used to explore the effects of MSCs on the proliferation, migration and invasion of colorectal carcinoma (CRC) cells and how they induced MSCs to differentiate into CAFs. The expression of α-SMA, Vimentin, S100A4 and FAP were detected as CAFs markers. Inhibitors AMD3100 and cyclophosphamide (Cy) were pre-treated in MSCs to verify the functions of CXCR4/TGF-β1. Finally, the xenograft models in nude mice were generated to further verify this process in vivo.Results: MSCs promoted the CRCs proliferation, invasion and migration, and induced SDF-1 expression and secretion, which dramatically up-regulated CXCR4 and TGF-β1 expression in MSCs. The levels of CAFs markers elevated in MSCs, indicating CAFs differentiation occurred in MSCs. AMD3100 and Cy treatment significantly blocked this differentiation process of MSCs by suppressing CXCR4 expression and TGF-β1 secretion. In vivo xenograft experiments also demonstrated that MSCs promoted differentiation into CAFs through CXCR4/TGF-β1 signaling in either primary tumor tissues or hepatic metastatic tissues of CRC.Conclusion: Our studies have revealed the essential role of CXCR4/TGF-β1 axis playing in the transformation of tumor microenvironment by mediating MSCs differentiation into CAFs, promoting CRCs growth and metastasis.

Impact of Fibronectin Knockout on Proliferation and Differentiation of Human Infrapatellar Fat Pad-Derived Stem Cells

Fibronectin plays an essential role in tissue development and regeneration. However, the effects of fibronectin knockout (FN1-KO) on stem cells' proliferation and differentiation remain unknown. In this study, CRISPR/Cas9 generated FN1-KO in human infrapatellar fat pad-derived stem cells (IPFSCs) was evaluated for proliferation ability including cell cycle and surface markers as well as stemness gene expression and for differentiation capacity including chondrogenic and adipogenic differentiation. High passage IPFSCs were also evaluated for proliferation and differentiation capacity after expansion on decellularized ECM (dECM) deposited by FN1-KO cells. Successful FN1-KO in IPFSCs was confirmed by Sanger sequencing and Inference of CRISPR Edits analysis (ICE) as well as immunostaining for fibronectin expression. Compared to the GFP control, FN1-KO cells showed an increase in cell growth, percentage of cells in the S and G2 phases, and CD105 and CD146 expression but a decrease in expression of stemness markers CD73, CD90, SSEA4, and mesenchymal condensation marker CDH2 gene. FN1-KO decreased both chondrogenic and adipogenic differentiation capacity. Interestingly, IPFSCs grown on dECMs deposited by FN1-KO cells exhibited a decrease in cell proliferation along with a decline in CDH2 expression. After induction, IPFSCs plated on dECMs deposited by FN1-KO cells also displayed decreased expression of both chondrogenic and adipogenic capacity. We concluded that FN1-KO increased human IPFSCs' proliferation capacity; however, this capacity was reversed after expansion on dECM deposited by FN1-KO cells. Significance of fibronectin in chondrogenic and adipogenic differentiation was demonstrated in both FN1-KO IPFSCs and FN(-) matrix microenvironment.

DNA Methylation-Based Regulation of Human Bone Marrow-Derived Mesenchymal Stem/Progenitor Cell Chondrogenic Differentiation

Stem cells have essential applications in in vitro tissue engineering or regenerative medicine. However, there is still a need to understand more deeply the mechanisms of stem cell differentiation and to optimize the methods to control stem cell function. In this study, we first investigated the activity of DNA methyltransferases (DNMTs) during chondrogenic differentiation of human bone marrow-derived mesenchymal stem/progenitor cells (hBMSCs) and found that DNMT3A and DNMT3B were markedly upregulated during hBMSC chondrogenic differentiation. In an attempt to understand the effect of DNMT3A and DNMT3B on the chondrogenic differentiation of hBMSCs, we transiently transfected the cells with expression vectors for the two enzymes. Interestingly, DNMT3A overexpression strongly enhanced the chondrogenesis of hBMSCs, by increasing the gene expression of the mature chondrocyte marker, collagen type II, more than 200-fold. Analysis of the methylation condition in the cells revealed that DNMT3A and DNMT3B methylated the promoter sequence of early stem cell markers, NANOG and POU5F1(OCT-4). Conversely, the suppression of chondrogenic differentiation and the increase in stem cell markers of hBMSCs were obtained by chemical stimulation with the demethylating agent, 5-azacitidine. Loss-of-function assays with siRNAs targeting DNMT3A also significantly suppressed the chondrogenic differentiation of hBMSCs. Together, these results not only show the critical roles of DNMTs in regulating the chondrogenic differentiation of hBMSCs, but also suggest that manipulation of DNMT activity can be important tools to enhance the differentiation of hBMSCs towards chondrogenesis for potential application in cartilage tissue engineering or cartilage regeneration.

[Mechanical stress promotes cartilage repair in inflammatory environment]

OBJECTIVE

To investigate the effect and mechanism of mechanical stress on cartilage repair in inflammatory environment.

METHODS

The chondrogenic progenitor cells (CPCs) were isolated from the knee joint cartilage of patients with osteoarthritis (OA) undergoing total knee arthroplasty. The CPCs were cultured and expanded in a 3-D scaffold constructed with alginate. Intermittent hydrostatic pressure (IHP) was applied in a inflammatory environment induced by IL-1β, and Western blot was used to detect the expression of MAPK signaling pathway proteins. Cell proliferation was detected by CCK-8 method, and the expression of related genes like matrix metallo-proteinases 13 (MMP-13) and a disintegrins and metalloproteinase with thrombospondin motif 5 (ADAMTS-5) was detected by real-time RT-PCR. The anterior cruciate ligament of the rats was cut to construct the knee joint OA model, and the appropriate mechanical stress was constructed with external fixation to distract the knee joint in order to observe the repair of the cartilage and to explore its mechanism.

RESULTS

Adding 0.01 ng/ml IL-1β in cell culture inhibited the proliferation of CPCs. After IHP application, the expression of MAPK pathway protein was decreased, the mRNA expression of MMP-13 and ADAMTS-5 was reduced. The inhibition of IL-1β on CPCs was counteracted by IHP. Four weeks after the anterior cruciate ligament resected, the articular cartilage degeneration was observed in rats. The Mankin score in the OA treatment (joint distraction) group was lower, and the cartilage repair was better than that of the control group (P<0.01). Animal experiments found that the suitable mechanical stress reduced the expression of P-p38, MMP-13 and COLL-X, inhibited cartilage cells apoptosis and promoted the repair of OA cartilage.

CONCLUSIONS

Mechanical stress can promote the proliferation of CPCs, reduce the expression of matrix degrading enzymes, and promote the repair of OA cartilage by inhibiting MAPK signaling pathway.

A prospect of cell immortalization combined with matrix microenvironmental optimization strategy for tissue engineering and regeneration

Cellular senescence is a major hurdle for primary cell-based tissue engineering and regenerative medicine. Telomere erosion, oxidative stress, the expression of oncogenes and the loss of tumor suppressor genes all may account for the cellular senescence process with the involvement of various signaling pathways. To establish immortalized cell lines for research and clinical use, strategies have been applied including internal genomic or external matrix microenvironment modification. Considering the potential risks of malignant transformation and tumorigenesis of genetic manipulation, environmental modification methods, especially the decellularized cell-deposited extracellular matrix (dECM)-based preconditioning strategy, appear to be promising for tissue engineering-aimed cell immortalization. Due to few review articles focusing on this topic, this review provides a summary of cell senescence and immortalization and discusses advantages and limitations of tissue engineering and regeneration with the use of immortalized cells as well as a potential rejuvenation strategy through combination with the dECM approach.

Extracellular matrix deposited by Wharton's jelly mesenchymal stem cells enhances cell expansion and tissue specific lineage potential

This article aims to explore whether Wharton's jelly (WJ) derived mesenchymal stem cells (MSCs) (WJ-MSCs) decellularized extracellular matrix (dECM) can rejuvenate MSCs during in vitro expansion. Passage 10 synovium-derived mesenchymal stem cells (SDSCs) and WJ-MSCs were expanded on plastic flasks (PL) or dECMs derived from SDSCs and WJ-MSCs. Flow cytometry was applied to evaluate surface phenotypes and proliferation capacity. Early (7 days) and late (21 days) chondrogenic potentials were assessed using histology, immunohistochemistry, and real-time polymerase chain reaction (PCR). Western blot analysis was applied to evaluate the potential involvement of MAPK and Wnts signals during the proliferation and chondrogenic processes. Cells were further evaluated for their osteogenic potential using alkaline phosphatase staining and RT-PCR and adipogenic potential using oil red O staining and RT-PCR. Compared to PL expanded cells, dECMs yielded expanded cells with better proliferation capacity as well as decreased percentage of HLA-DR positive SDSCs. Meanwhile, a decrease in CD105 median fluorescence intensity of WJ-MSCs groups were observed compared to the corresponding SDSCs groups. Moreover, both SDSCs and WJ-MSCs acquired better chondrogenic potential after dECM treatment, as evidenced by increased pellet sizes and increased expression of chondrogenic marker genes. WJ-MSCs dECM was inferior to SDSCs dECM in enhancing early stage chondrogenic differentiation, which was compensated during late stage chondrogenesis, despite causing an increased type X collagen accumulation. p-JNK and p-38 were implicated in the expansion and late chondrogenic differentiation stages, respectively. However, dECM preconditioning did not enhance either osteogenic or adipogenic potential of SDSCs and WJ-MSCs. WJ-MSCs dECM is superior to SDSCs dECM on enhancing proliferation, lowering immunogenicity and promoting late stage chondrogenesis.

Functionality of decellularized matrix in cartilage regeneration: A comparison of tissue versus cell sources

Increasing evidence indicates that decellularized extracellular matrices (dECMs) derived from cartilage tissues (T-dECMs) or chondrocytes/stem cells (C-dECMs) can support proliferation and chondrogenic differentiation of cartilage-forming cells. However, few review papers compare the differences between these dECMs when they serve as substrates for cartilage regeneration. In this review, after an introduction of cartilage immunogenicity and decellularization methods to prepare T-dECMs and C-dECMs, a comprehensive comparison focuses on the effects of T-dECMs and C-dECMs on proliferation and chondrogenic differentiation of chondrocytes/stem cells in vitro and in vivo. Key factors within dECMs, consisting of microarchitecture characteristics and micromechanical properties as well as retained insoluble and soluble matrix components, are discussed in-depth for potential mechanisms underlying the functionality of these dECMs in regulating chondrogenesis. With this information, we hope to benefit dECM based cartilage engineering and tissue regeneration for future clinical application.

STATEMENT OF SIGNIFICANCE

The use of decellularized extracellular matrix (dECM) is becoming a promising approach for tissue engineering and regeneration. Compared to dECM derived from cartilage tissue, recently reported dECM from cell sources exhibits a distinct role in cell based cartilage regeneration. In this review paper, for the first time, tissue and cell based dECMs are comprehensively compared for their functionality in cartilage regeneration. This information is expected to provide an update for dECM based cartilage regeneration.

Downregulation of HS6ST2 by miR-23b-3p enhances matrix degradation through p38 MAPK pathway in osteoarthritis

Osteoarthritis (OA) is the most common form of arthritis involving major structural changes of peripheral joints and local or systemic inflammation and in lack of therapeutic approaches because of complexity of underlying molecular basis. Our previous work showed that HS6ST2, an enzyme involved in the transfer of sulfate, is downregulated in cartilage tissues of OA patients compared with normal donors, but little is known about its regulatory mechanism. In this study, we demonstrated that the expression of HS6ST2 was lower in OA-damaged cartilage than smooth cartilage from the same patient. In chondrocytes, HS6ST2 could be targeted by miR-23b-3p, which was higher expressed in OA-damaged cartilage. Under TNF-α stimulation, the expression of HS6ST2 was found inversely correlated with the expression of miR-23b-3p. Downregulation of HS6ST2 regulated by overexpression of miR-23b-3p and siRNAs against HS6ST2 could enhance the protein level of MMP13 and aggravate the matrix degradation in chondrocytes. Increased expression of MMP13 depended on activity of p38 MAPK rather than total p38 MAPK level and was abrogated by HS6ST2 overexpression. Together, the results indicated that downregulated HS6ST2 targeted by miR-23b-3p promotes matrix degradation by activating p38 MAPK in chondrocytes and OA cartilage.

N-acetyl-L-cysteine improves mesenchymal stem cell function in prolonged isolated thrombocytopenia post-allotransplant

Prolonged isolated thrombocytopenia (PT) is a serious complication of allogeneic haematopoietic stem cell transplantation (allo-HSCT). Murine studies and in vitro experiments suggest that mesenchymal stem cells (MSCs) can, not only to support haematopoiesis, but also preferentially support megakaryocytopoiesis in bone marrow (BM). However, little is known about the quantity and function of BM MSCs in PT patients. In a case-control study, we found that BM MSCs from PT patients exhibited significantly reduced proliferative capacities, increased reactive oxygen species and senescence. Antioxidant (N-acetyl-L-cysteine, NAC) treatment in vitro not only quantitatively and functionally improved BM MSCs derived from PT patients through down-regulation of the p38 (also termed MAPK14) and p53 (also termed TP53) pathways but also partially rescued the impaired ability of BM MSCs to support megakaryocytopoiesis. Subsequently, a pilot study showed that the overall response of NAC treatment was obtained in 7 of the enrolled PT patients (N = 10) without significant side effects. Taken together, the results indicated that dysfunctional BM MSCs played a role in the pathogenesis of PT and the impaired BM MSCs could be improved by NAC in vitro. Although requiring further validation, our data indicate that NAC might be a potential therapeutic approach for PT patients after allo-HSCT.

SIRT1-dependent anti-senescence effects of cell-deposited matrix on human umbilical cord mesenchymal stem cells

Human umbilical cord-derived mesenchymal stem cells (UC-MSCs) are considered an attractive cell source for tissue regeneration. However, environmental oxidative stress can trigger premature senescence in MSCs and thus compromises their regenerative potential. Extracellular matrix (ECM) derived from MSCs has been shown to facilitate cell proliferation and multi-lineage differentiation. This investigation evaluated the effect of cell-deposited decellularized ECM (DECM) on oxidative stress-induced premature senescence in UC-MSCs. Sublethal dosages of H₂ O₂ , ranging from 50 μm to 200 μm, were used to induce senescence in MSCs. We found that DECM protected UC-MSCs from oxidative stress-induced premature senescence. When treated with H₂ O₂ at the same concentration, cell proliferation of DECM-cultured UC-MSCs was twofold higher than those on standard tissue culture polystyrene (TCPS). After exposure to 100 μm H₂ O₂ , fewer senescence-associated β-galactosidase-positive cells were observed on DECM than those on TCPS (17.6  ±  4.0% vs. 60.4  ±  6.2%). UC-MSCs cultured on DECM also showed significantly lower levels of senescence-related regulators, such as p16^INK4α and p21. Most importantly, DECM preserved the osteogenic differentiation potential of UC-MSCs with premature senescence. The underlying molecular mechanisms involved the silent information regulator type 1 (SIRT1)-dependent signalling pathway, confirmed by the fact that the SIRT1 inhibitor nicotinamide counteracted the DECM-mediated anti-senescent effect. Collagen type I, rather than fibronectin, partially contributed to the protective effect of decellularized matrix. These findings provide a new strategy of using stem cell-deposited matrix to overcome the challenge of cellular senescence and to facilitate the clinical application of MSCs in regenerative medicine. Copyright © 2017 John Wiley & Sons, Ltd.

Fibroblast Growth Factor Ligand Dependent Proliferation and Chondrogenic Differentiation of Synovium-Derived Stem Cells and Concomitant Adaptation of Wnt/Mitogen-Activated Protein Kinase Signals

Cell expansion techniques commonly utilize exogenous factors to increase cell proliferation and create a larger cell population for use in cell-based therapies. One strategy for cartilage regenerative therapies is autologous stem cell expansion and fibroblast growth factor (FGF) supplementation during cell expansion, particularly FGF-2. However, it is unknown whether FGF-10, another FGF implicated in limb and skeletal development, can elicit the same rejuvenation responses in terms of proliferation and differentiation of human synovium-derived stem cells (SDSCs). In this study, we expanded SDSCs in either FGF-2 or FGF-10 for 7 days; a control group had no treatment. FGF-2 and FGF-10 supplementation was also exclusively tested during the differentiation phase. Expanded SDSCs were evaluated for their ability to successfully engage in chondrogenic and osteogenic differentiation. We found that FGF-2 supplementation during proliferation, but not differentiation, was able to increase glycosaminoglycan deposition, pellet size, and chondrogenic gene expression following chondrogenic induction, as well as increased calcium deposition, alkaline phosphatase activity, and expression of vital osteogenic differentiation genes following osteogenic induction. FGF-10 did not elicit a similar preconditioning effect. We also observed changes of both Wnt signals and mitogen-activated protein kinase expression during SDSC chondrogenesis, which occurred in a manner dependent upon the supplementation phase of FGF-2 administration. These results indicated that FGF-2, but not FGF-10, may be supplemented during stem cell expansion to prime cells for successful chondrogenesis and osteogenesis.

The role of laminins in cartilaginous tissues: from development to regeneration

As a key molecule of the extracellular matrix, laminin provides a delicate microenvironment for cell functions. Recent findings suggest that laminins expressed by cartilage-forming cells (chondrocytes, progenitor cells and stem cells) could promote chondrogenesis. However, few papers outline the effect of laminins on providing a favorable matrix microenvironment for cartilage regeneration. In this review, we delineated the expression of laminins in hyaline cartilage, fibrocartilage and cartilage-like tissue (nucleus pulposus) throughout several developmental stages. We also examined the effect of laminins on the biological activities of chondrocytes, including adhesion, migration and survival. Furthermore, we scrutinized the potential influence of various laminin isoforms on cartilage-forming cells' proliferation and chondrogenic differentiation. With this information, we hope to facilitate the understanding of the spatial and temporal interactions between cartilage-forming cells and laminin microenvironment to eventually advance cell-based cartilage engineering and regeneration.

Stromal cell-derived factor-1α and transforming growth factor-β1 synergistically facilitate migration and chondrogenesis of synovium-derived stem cells through MAPK pathways

The clinical translation of tissue engineering methods is confined by the limited external cell sources, which is hopefully to be addressed by the cell guidance approach as cytokine-induced homing and differentiation of the patients' autologous cells. Synovium-derived stem cells (SDSCs) are a potent cell source for cartilage restoration due to its intrinsic proximity and tissue-specific chondrogenic capacity. In this study, stromal cell-derived factor-1α (SDF-1α) in combination with transforming growth factor β₁ (TGF-β₁) were used to induce SDSCs migration and chondrogenesis in vitro. The migration capacity was evaluated by transwell assay and for chondrogenic evaluation, the expression of Sox9, ACAN and COL2A1 were assessed by quantitative RT-PCR while the expression of sulfated GAG and collagen II were evaluated by Alcian Blue stain and immunohistochemistry respectively. Our data showed that SDF-1α/CXC chemokine receptor 4 (CXCR4) was involved in SDSCs migration through phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway. Exogenous TGF-β₁ enhanced SDF-1α-induced SDSCs migration in a concentration and time-dependent manner through CXCR4, evidenced as complete blockage by AMD3100, the CXCR4 antagonist and this effect was mediated by extracellular regulated protein kinases (ERK) activation. Moreover, the addition of SDF-1α augmented the TGF-β₁-induced SDSCs chondrogenesis, evidenced by the increased pellet sizes and the expressions of COL 2A1, ACAN and Sox9. This effect was related to c-Jun N-terminal kinase (JNK) activation. Collectively, these results suggest that SDF-1α and TGF-β₁ interacts with each other and synergistically enhance the SDSCs migration and chondrogenesis through MAPK pathways.

Environmental preconditioning rejuvenates adult stem cells' proliferation and chondrogenic potential

Adult stem cells are a promising cell source for cartilage regeneration. Unfortunately, due to donor age and ex vivo expansion, stem cell senescence becomes a huge hurdle for these cells to be used clinically. Increasing evidence indicates that environmental preconditioning is a powerful approach in promoting stem cells' ability to resist a harsh environment post-engraftment, such as hypoxia and inflammation. However, few reports organize and evaluate the literature regarding the rejuvenation effect of environmental preconditioning on stem cell proliferation and chondrogenic differentiation capacity, which are important variables for stem cell based tissue regeneration. This report aims to identify several critical environmental factors such as oxygen concentration, growth factors, and extracellular matrix and to discuss their preconditioning influence on stem cells' rejuvenation including proliferation and chondrogenic potential as well as underlying molecular mechanisms. We believe that environmental preconditioning based rejuvenation is a simpler and safer strategy to program pre-engraftment stem cells for better survival and enhanced proliferation and differentiation capacity without the undesired effects of some treatments, such as genetic manipulation.

Ascorbate-dependent impact on cell-derived matrix in modulation of stiffness and rejuvenation of infrapatellar fat derived stem cells toward chondrogenesis

Developing an in vitro microenvironment using cell-derived decellularized extracellular matrix (dECM) is a promising approach to efficiently expand adult stem cells for cartilage engineering and regeneration. Ascorbic acid serves as a critical stimulus for cells to synthesize collagens, which constitute the major component of dECM. In this study, we hypothesized that optimization of ascorbate treatment would maximize the rejuvenation effect of dECM on expanded stem cells from human infrapatellar fat pad in both proliferation and chondrogenic differentiation. In the duration regimen study, we found that dECM without L-ascorbic acid phosphate (AA) treatment, exhibiting lower stiffness measured by atomic force microscopy, yielded expanded cells with higher proliferation capacity but lower chondrogenic potential when compared to those with varied durations of AA treatment. dECM with 250 µM of AA treatment for 10 d had better rejuvenation in chondrogenic capacity if the deposited cells were from passage 2 rather than passage 5, despite no significant difference in matrix stiffness. In the dose regimen study, we found that dECMs deposited by varied concentrations of AA yielded expanded cells with higher proliferation capacity despite lower expression levels of stem cell related surface markers. Compared to cells expanded on tissue culture polystyrene, those on dECM exhibited greater chondrogenic potential, particularly for the dECMs with 50 µM and 250 µM of AA treatment. With the supplementation of ethyl-3,4-dihydroxybenzoate (EDHB), an inhibitor targeting procollagen synthesis, the dECM with 50 µM of AA treatment exhibited a dramatic decrease in the rejuvenation effect of expanded cell chondrogenic potential at both mRNA and protein levels despite no significant difference in matrix stiffness. Defined AA treatments during matrix preparation will benefit dECM-mediated stem cell engineering and future treatments for cartilage defects.