The superior regenerative potential of muscle-derived stem cells for articular cartilage repair is attributed to high cell survival and chondrogenic potential

Latest Advances in Chondrocyte-Based Cartilage Repair

Chondrocyte-based cell therapy has been used for more than 30 years and is still considered to be a promising method of cartilage repair despite some limitations. This review introduces the latest developments of four generations of autologous chondrocyte implantation and current autologous chondrocyte products. The regeneration of cartilage from adult chondrocytes is limited by culture-induced dedifferentiation and patient age. Cartibeads is an innovative three-step method to produce high-quality hyaline cartilage microtissues, and it is developed from adult dedifferentiated chondrocytes with a high number of cell passages. In addition, allogeneic chondrocyte therapies using the Quantum hollow-fiber bioreactor and several signaling pathways involved in chondrocyte-based cartilage repair are mentioned, such as WNT signaling, the BMP-2/WISP1 pathway, and the FGF19 pathway.

Sex-specific preservation of neuromuscular function and metabolism following systemic transplantation of multipotent adult stem cells in a murine model of progeria

Onset and rates of sarcopenia, a disease characterized by a loss of muscle mass and function with age, vary greatly between sexes. Currently, no clinical interventions successfully arrest age-related muscle impairments since the decline is frequently multifactorial. Previously, we found that systemic transplantation of our unique adult multipotent muscle-derived stem/progenitor cells (MDSPCs) isolated from young mice-but not old-extends the health-span in DNA damage mouse models of progeria, a disease of accelerated aging. Additionally, induced neovascularization in the muscles and brain-where no transplanted cells were detected-strongly suggests a systemic therapeutic mechanism, possibly activated through circulating secreted factors. Herein, we used ZMPSTE24-deficient mice, a lamin A defect progeria model, to investigate the ability of young MDSPCs to preserve neuromuscular tissue structure and function. We show that progeroid ZMPST24-deficient mice faithfully exhibit sarcopenia and age-related metabolic dysfunction. However, systemic transplantation of young MDSPCs into ZMPSTE24-deficient progeroid mice sustained healthy function and histopathology of muscular tissues throughout their 6-month life span in a sex-specific manner. Indeed, female-but not male-mice systemically transplanted with young MDSPCs demonstrated significant preservation of muscle endurance, muscle fiber size, mitochondrial respirometry, and neuromuscular junction morphometrics. These novel findings strongly suggest that young MDSPCs modulate the systemic environment of aged animals by secreted rejuvenating factors to maintain a healthy homeostasis in a sex-specific manner and that the female muscle microenvironment remains responsive to exogenous regenerative cues in older age. This work highlights the age- and sex-related differences in neuromuscular tissue degeneration and the future prospect of preserving health in older adults with systemic regenerative treatments.

Creating and Transferring an Innervated, Vascularized Muscle Flap Made from an Elastic, Cellularized Tissue Construct Developed In Situ

Reanimating facial structures following paralysis and muscle loss is a surgical objective that would benefit from improved options for harvesting appropriately sized muscle flaps. The objective of this study is to apply electrohydrodynamic processing to generate a cellularized, elastic, biocomposite scaffold that could develop and mature as muscle in a prepared donor site in vivo, and then be transferred as a thin muscle flap with a vascular and neural pedicle. First, an effective extracellular matrix (ECM) gel type is selected for the biocomposite scaffold from three types of ECM combined with poly(ester urethane)urea microfibers and evaluated in rat abdominal wall defects. Next, two types of precursor cells (muscle-derived and adipose-derived) are compared in constructs placed in rat hind limb defects for muscle regeneration capacity. Finally, with a construct made from dermal ECM and muscle-derived stem cells, protoflaps are implanted in one hindlimb for development and then microsurgically transferred as a free flap to the contralateral limb where stimulated muscle function is confirmed. This construct generation and in vivo incubation procedure may allow the generation of small-scale muscle flaps appropriate for transfer to the face, offering a new strategy for facial reanimation.

Role and Mechanism of BMP4 in Regenerative Medicine and Tissue Engineering

Bone morphogenetic protein 4 (BMP4) is emerging as a promising cytokine for regenerative medicine and tissue engineering. BMP4 has been shown to promote the regeneration of teeth, periodontal tissue, bone, cartilage, the thymus, hair, neurons, nucleus pulposus, and adipose tissue, as well as the formation of skeletal myotubes and vessels. BMP4 can also contribute to the formation of tissues in the heart, lung, and kidney. However, there are certain deficiencies, including the insufficiency of the mechanism of BMP4 in some fields and an appropriate carrier of BMP4 for clinical use. There has also been a lack of in vivo experiments and orthotopic transplantation studies in some fields. BMP4 has great distance from the clinical application. Therefore, there are many BMP4-related studies waiting to be explored. This review mainly discusses the effects, mechanisms, and applications of BMP4 in regenerative medicine and tissue engineering over the last 10 years in various domains and possible improvements. BMP4 has shown great potential in regenerative medicine and tissue engineering. The research of BMP4 has broad development space and great value.

Osteoarthritis: pathogenic signaling pathways and therapeutic targets

Osteoarthritis (OA) is a chronic degenerative joint disorder that leads to disability and affects more than 500 million population worldwide. OA was believed to be caused by the wearing and tearing of articular cartilage, but it is now more commonly referred to as a chronic whole-joint disorder that is initiated with biochemical and cellular alterations in the synovial joint tissues, which leads to the histological and structural changes of the joint and ends up with the whole tissue dysfunction. Currently, there is no cure for OA, partly due to a lack of comprehensive understanding of the pathological mechanism of the initiation and progression of the disease. Therefore, a better understanding of pathological signaling pathways and key molecules involved in OA pathogenesis is crucial for therapeutic target design and drug development. In this review, we first summarize the epidemiology of OA, including its prevalence, incidence and burdens, and OA risk factors. We then focus on the roles and regulation of the pathological signaling pathways, such as Wnt/β-catenin, NF-κB, focal adhesion, HIFs, TGFβ/ΒΜP and FGF signaling pathways, and key regulators AMPK, mTOR, and RUNX2 in the onset and development of OA. In addition, the roles of factors associated with OA, including MMPs, ADAMTS/ADAMs, and PRG4, are discussed in detail. Finally, we provide updates on the current clinical therapies and clinical trials of biological treatments and drugs for OA. Research advances in basic knowledge of articular cartilage biology and OA pathogenesis will have a significant impact and translational value in developing OA therapeutic strategies.

Skeletal Muscle-Derived Cell Implantation for the Treatment of Fecal Incontinence: A Randomized, Placebo-Controlled Study

BACKGROUND AND AIMS

Fecal incontinence (FI) improvement following injection of autologous skeletal muscle-derived cells has been previously suggested. This study aimed to test the efficacy and safety of said cells through a multicenter, placebo-controlled study, to determine an appropriate cell dose, and to delineate the target patient population that can most benefit from cell therapy.

METHODS

Patients experiencing FI for at least 6 months were randomized to receive a cell-free medium or low or high dose of cells. All patients received pelvic floor electrical stimulation before and after treatment. Incontinence episode frequency (IEF), FI quality of life, FI burden assessed on a visual analog scale, Wexner score, and parameters reflecting anorectal physiological function were all assessed for up to 12 months.

RESULTS

Cell therapy improved IEF, FI quality of life, and FI burden, reaching a preset level of statistical significance in IEF change compared with the control treatment. Post hoc exploratory analyses indicated that patients with limited FI duration and high IEF at baseline are most responsive to cells. Effects prevailed or increased in the high cell count group from 6 to 12 months but plateaued or diminished in the low cell count and control groups. Most physiological parameters remained unaltered. No unexpected adverse events were observed.

CONCLUSIONS

Injection of a high dose of autologous skeletal muscle-derived cells followed by electrical stimulation significantly improved FI, particularly in patients with limited FI duration and high IEF at baseline, and could become a valuable tool for treatment of FI, subject to confirmatory phase 3 trial(s). (ClinicalTrialRegister.eu; EudraCT Number: 2010-021463-32).

The role and therapeutic potential of stem cells in skeletal muscle in sarcopenia

Sarcopenia is a common age-related skeletal muscle disorder featuring the loss of muscle mass and function. In regard to tissue repair in the human body, scientists always consider the use of stem cells. In skeletal muscle, satellite cells (SCs) are adult stem cells that maintain tissue homeostasis and repair damaged regions after injury to preserve skeletal muscle integrity. Muscle-derived stem cells (MDSCs) and SCs are the two most commonly studied stem cell populations from skeletal muscle. To date, considerable progress has been achieved in understanding the complex associations between stem cells in muscle and the occurrence and treatment of sarcopenia. In this review, we first give brief introductions to sarcopenia, SCs and MDSCs. Then, we attempt to untangle the differences and connections between these two types of stem cells and further elaborate on the interactions between sarcopenia and stem cells. Finally, our perspectives on the possible application of stem cells for the treatment of sarcopenia in future are presented. Several studies emerging in recent years have shown that changes in the number and function of stem cells can trigger sarcopenia, which in turn leads to adverse influences on stem cells because of the altered internal environment in muscle. A better understanding of the role of stem cells in muscle, especially SCs and MDSCs, in sarcopenia will facilitate the realization of novel therapy approaches based on stem cells to combat sarcopenia.

A comparison of BMP2 delivery by coacervate and gene therapy for promoting human muscle-derived stem cell-mediated articular cartilage repair

Background

Osteoarthritis and cartilage injury treatment is an unmet clinical need. Therefore, development of new approaches to treat these diseases is critically needed. Previous work in our laboratory has shown that murine muscle-derived stem cells (MDSCs) can efficiently repair articular cartilage in an osteochondral and osteoarthritis model. However, the cartilage repair capacity of human muscle-derived stem cells has not been studied which prompt this study.

Method

In this study, we tested the in vitro chondrogenesis ability of six populations of human muscle-derived stem cells (hMDSCs), before and after lenti-BMP2/GFP transduction using pellet culture and evaluated chondrogenic differentiation of via histology and Raman spectroscopy. We further compared the in vivo articular cartilage repair of hMDSCs stimulated with BMP2 delivered through coacervate sustain release technology and lenti-viral gene therapy-mediated gene delivery in a monoiodoacetate (MIA)-induced osteoarthritis (OA) model. We used microCT and histology to evaluate the cartilage repair.

Results

We observed that all hMDSCs were able to undergo chondrogenic differentiation in vitro. As expected, lenti-BMP2/GFP transduction further enhanced the chondrogenic differentiation capacities of hMDSCs, as confirmed by Alcian blue and Col2A1staining as well as Raman spectroscopy analysis. We observed through micro-CT scanning, Col2A1 staining, and histological analyses that delivery of BMP2 with coacervate could achieve a similar articular cartilage repair to that mediated by hMDSC-LBMP2/GFP. We also found that the addition of soluble fms-like tyrosine kinase-1 (sFLT-1) protein further improved the regenerative potential of hMDSCs/BMP2 delivered through the coacervate sustain release technology. Donor cells did not primarily contribute to the repaired articular cartilage since most of the repair cells are host derived as indicated by GFP staining.

Conclusions

We conclude that the delivery of hMDSCs and BMP2 with the coacervate technology can achieve a similar cartilage repair relative to lenti-BMP2/GFP-mediated gene therapy. The use of coacervate technology to deliver BMP2/sFLT1 with hMDSCs for cartilage repair holds promise for possible clinical translation into an effective treatment modality for osteoarthritis and traumatic cartilage injury.

Cell therapy to improve regeneration of skeletal muscle injuries

Diseases that jeopardize the musculoskeletal system and cause chronic impairment are prevalent throughout the Western world. In Germany alone, ~1.8 million patients suffer from these diseases annually, and medical expenses have been reported to reach 34.2bn Euros. Although musculoskeletal disorders are seldom fatal, they compromise quality of life and diminish functional capacity. For example, musculoskeletal disorders incur an annual loss of over 0.8 million workforce years to the German economy. Among these diseases, traumatic skeletal muscle injuries are especially problematic because they can occur owing to a variety of causes and are very challenging to treat. In contrast to chronic muscle diseases such as dystrophy, sarcopenia, or cachexia, traumatic muscle injuries inflict damage to localized muscle groups. Although minor muscle trauma heals without severe consequences, no reliable clinical strategy exists to prevent excessive fibrosis or fatty degeneration, both of which occur after severe traumatic injury and contribute to muscle degeneration and dysfunction. Of the many proposed strategies, cell-based approaches have shown the most promising results in numerous pre-clinical studies and have demonstrated success in the handful of clinical trials performed so far. A number of myogenic and non-myogenic cell types benefit muscle healing, either by directly participating in new tissue formation or by stimulating the endogenous processes of muscle repair. These cell types operate via distinct modes of action, and they demonstrate varying levels of feasibility for muscle regeneration depending, to an extent, on the muscle injury model used. While in some models the injury naturally resolves over time, other models have been developed to recapitulate the peculiarities of real-life injuries and therefore mimic the structural and functional impairment observed in humans. Existing limitations of cell therapy approaches include issues related to autologous harvesting, expansion and sorting protocols, optimal dosage, and viability after transplantation. Several clinical trials have been performed to treat skeletal muscle injuries using myogenic progenitor cells or multipotent stromal cells, with promising outcomes. Recent improvements in our understanding of cell behaviour and the mechanistic basis for their modes of action have led to a new paradigm in cell therapies where physical, chemical, and signalling cues presented through biomaterials can instruct cells and enhance their regenerative capacity. Altogether, these studies and experiences provide a positive outlook on future opportunities towards innovative cell-based solutions for treating traumatic muscle injuries-a so far unmet clinical need.

Hypoxia-inducible factor 1α (HIF-1α) is a major determinant in the enhanced function of muscle-derived progenitors from MRL/MpJ mice

Although the mouse strain Murphy Roths Large (MRL/MpJ) possesses high regenerative potential, the mechanism of tissue regeneration, including skeletal muscle, in MRL/MpJ mice after injury is still unclear. Our previous studies have shown that muscle-derived stem/progenitor cell (MDSPC) function is significantly enhanced in MRL/MpJ mice when compared with MDSPCs isolated from age-matched wild-type (WT) mice. Using mass spectrometry-based proteomic analysis, we identified increased expression of hypoxia-inducible factor (HIF) 1α target genes (expression of glycolytic factors and antioxidants) in sera from MRL/MpJ mice compared with WT mice. Therefore, we hypothesized that HIF-1α promotes the high muscle healing capacity of MRL/MpJ mice by increasing the potency of MDSPCs. We demonstrated that treating MRL/MpJ MDSPCs with dimethyloxalylglycine and CoCl₂ increased the expression of HIF-1α and target genes, including angiogenic and cell survival genes. We also observed that HIF-1α activated the expression of paired box (Pax)7 through direct interaction with the Pax7 promoter. Furthermore, we also observed a higher myogenic potential of MDSPCs derived from prolyl hydroxylase (Phd) 3-knockout (Phd3^-/-) mice, which displayed higher stability of HIF-1α. Taken together, our findings suggest that HIF-1α is a major determinant in the increased MDSPC function of MRL/MpJ mice through enhancement of cell survival, proliferation, and myogenic differentiation.-Sinha, K. M., Tseng, C., Guo, P., Lu, A., Pan, H., Gao, X., Andrews, R., Eltzschig, H., Huard, J. Hypoxia-inducible factor 1α (HIF-1α) is a major determinant in the enhanced function of muscle-derived progenitors from MRL/MpJ mice.

Bone morphogenetic proteins for articular cartilage regeneration

Degeneration of articular cartilage (AC) tissue is the most common cause of osteoarthritis (OA) and rheumatoid arthritis. Bone morphogenetic proteins (BMPs) play important roles in bone and cartilage formation. This article reviews the experimental and clinical applications of BMPs in cartilage regeneration. Experimental evidence indicates that BMPs play an important role in protection against cartilage damage caused by inflammation or trauma, by binding to different receptor combinations and, consequently, activating different intracellular signaling pathways. Loss of function of BMP-related receptors contributes to the decreased intrinsic repair capacity of damaged cartilage and, thus, the multifunctional effects of BMPs make them attractive tools for the treatment of cartilage damage in patients with degenerative diseases. However, the development of BMP therapy as a treatment modality for cartilage regeneration has been hampered by certain factors, such as the eligibility of participants in clinical trials, financial support, drug delivery carrier safety, availabilities of effective scaffolds, appropriate selection of optimal dose and timing of administration, and side effects. Further research is needed to overcome these issues for future routine clinical applications. Research and development leading to the successful application of BMPs can initiate a new era in the treatment of cartilage degenerative diseases like OA.

Gene therapy for chondral and osteochondral regeneration: is the future now?

Gene therapy might represent a promising strategy for chondral and osteochondral defects repair by balancing the management of temporary joint mechanical incompetence with altered metabolic and inflammatory homeostasis. This review analysed preclinical and clinical studies on gene therapy for the repair of articular cartilage defects performed over the last 10 years, focussing on expression vectors (non-viral and viral), type of genes delivered and gene therapy procedures (direct or indirect). Plasmids (non-viral expression vectors) and adenovirus (viral vectors) were the most employed vectors in preclinical studies. Genes delivered encoded mainly for growth factors, followed by transcription factors, anti-inflammatory cytokines and, less frequently, by cell signalling proteins, matrix proteins and receptors. Direct injection of the expression vector was used less than indirect injection of cells, with or without scaffolds, transduced with genes of interest and then implanted into the lesion site. Clinical trials (phases I, II or III) on safety, biological activity, efficacy, toxicity or bio-distribution employed adenovirus viral vectors to deliver growth factors or anti-inflammatory cytokines, for the treatment of osteoarthritis or degenerative arthritis, and tumour necrosis factor receptor or interferon for the treatment of inflammatory arthritis.