Muscle-Derived Stem Cell-Enriched Scaffolds Are Capable of Enhanced Healing of a Murine Volumetric Muscle Loss Defect

In vitro myogenesis activation of specific muscle-derived stem cells from patients with Duchenne muscular dystrophy

BACKGROUND

Muscle-derived stem cells (MDSCs) contribute to the repair of injured muscles. However, the myogenicity of MDSCs generated from patients with Duchenne muscular dystrophy (DMD) relative to healthy individuals remains unclear.

METHODS

A human DMD model was established using the stem cells prepared from muscle derived from patients with DMD (DMD-hMDSCs). The expression of myogenic lineage-specific markers in MDSCs was examined with immunofluorescence, real-time polymerase chain reaction, and western blotting.

RESULTS

It was demonstrated that, compared with cells from healthy subjects, DMD-hMDSCs are primed to self-differentiate in growth-inducing medium (GM) and robustly differentiate into myotubes in differentiation-inducing medium(DM). This feature was termed "myogenesis activation," and it was speculated that it contributes to the depletion of myogenic progenitors. Furthermore, MDSCs consistently express pax7, but the time-course of this expression does not correlate with the expression of the myogenic lineage-specific markers.

CONCLUSIONS

The myogenesis activation in DMD-hMDSCs demonstrated in this study may provide novel mechanistic insights into DMD pathogenesis and potential therapies.

Tissue Engineering Applied to Skeletal Muscle: Strategies and Perspectives

Muscle tissue is formed by elongated and contractile cells with specific morphofunctional characteristics. Thus, it is divided into three basic types: smooth muscle tissue, cardiac striated muscle tissue and skeletal striated muscle tissue. The striated skeletal muscle tissue presents high plasticity, regeneration and growth capacity due to the presence of satellite cells, quiescent myoblasts that are activated in case of injury to the tissue and originate new muscle fibers when they differentiate. In more severe deficiencies or injuries there is a loss of their regenerative capacity, thus compromising the body's functionality at different levels. Tissue engineering studies the development of biomaterials capable of stimulating the recovery of cellular activity in injured body tissues, as well as the activity of cells with muscle differentiation potential in injury repair. However, the need for three-dimensional re-assembly in a complex organization makes it difficult to mimic this tissue and fully regenerate it for the sake of precise and effective movements. Thus, this article aims to provide a narrative review of tissue engineering strategies applied to the regeneration of skeletal muscle, in a critical evaluation of research, whether aimed at injury or atrophies such as spinal muscular atrophy.

Recent advances in cell-based and cell-free therapeutic approaches for sarcopenia

Sarcopenia is a progressive loss of muscle mass and function that is connected with increased hospital expenditures, falls, fractures, and mortality. Although muscle loss has been related to aging, injury, hormonal imbalances, and diseases such as malignancies, chronic obstructive pulmonary disease, heart failure, and kidney failure, the underlying pathogenic mechanisms of sarcopenia are unclear. Exercise-based interventions and multimodal strategies are currently being considered as potential therapeutic approaches to prevent or treat these diseases. Although drug therapy research is ongoing, no drug has yet been proven to have a substantial safety and clinical value to be the first drug therapy to be licensed for sarcopenia. To better understand the molecular alterations underlying sarcopenia and effective treatments, we review leading research and available findings from the systemic change to the muscle-specific microenvironment. Furthermore, we explore possible mechanisms of sarcopenia and provide new knowledge for the development of novel cell-free and cell-based therapeutics. This review will assist researchers in developing better therapies to improve muscle health in the elderly.

Amniotic Membrane Scaffolds Support Organized Muscle Regeneration in A Murine Volumetric Muscle Defect Model

Current treatment for volumetric muscle loss is limited to muscle transfer or acellular collagen scaffold (ACS) therapies that are associated with donor site morbidity and nonfunctional fibrosis, respectively. The aim of this study is to assess the utility of amniotic membrane scaffold (AMS) for volumetric muscle loss treatment.

Methods

Murine quadriceps defects were created and randomized to three groups (n = 5/group): untreated controls, ACS, and AMS. In vivo muscle regeneration volume was quantified by MRI and microcomputed tomography. Muscle explants were analyzed using standard histology and whole-mount immunofluorescence at 8 weeks.

Results

The cross-sectional muscle regeneration ratio was 0.64 ± 0.3 for AMS, 0.48 ± 0.07 for ACS, and 0.4 0 ± 0.03 for controls as assessed by MRI (P = 0.09) and 0.61 ± 0.28 for AMS, 0.50 ± 0.06 for ACS, and 0.43 ± 0.04 for controls as assessed by microcomputed tomography (P = 0.2). Histologically, AMS demonstrated significantly higher cellular density (900 ± 2 70 nuclei/high powered field) than ACS (210 ± 36) and control (130 ± 4) groups (P = 0.05). Immunofluorescence for laminin (AMS 623 ± 11 versus ACS 339 ± 3 versus control 115 ± 7; P < 0.01) and myosin heavy chain (AMS 509 ± 7 versus ACS 288 ± 5 versus control 84 ± 5; P = 0.03) indicated greater organized muscle fiber formation with AMS.

Conclusion

AMS mediated muscle healing was characterized by increased cellular infiltration and organized muscle formation when compared with controls and ACS.

Synergistic effects of myogenic cells and fibroblasts on the promotion of engineered tendon regeneration with muscle derived cells

AIMS

Tendon development requires the coordinated interaction of muscles and tendons. Muscle-derived cells (MDCs), a mixed cell population containing both myogenic and fibroblastic cell subsets, have been found to be ideal seed cells for tendon regeneration. However, the necessity of these cell types for tendon regeneration has not yet been tested. In this study, we aim to explore the possible synergistic effects of myogenic cells and fibroblasts in engineered tendon regeneration.

METHODS

MDCs were separated into rapidly adhering cell (RAC; fibroblasts) and slowly adhering cell (SAC; myogenic cells) populations. Myogenic- and tenogenic-related molecules were analyzed by immunofluorescent staining, RT-PCR and real-time PCR. The proliferative abilities of MDCs, RACs and SACs were also evaluated. Cell-scaffold constructs were implanted into nude mice, and subsequently evaluated for their histologic, ultrastructure, gene expression, and biomechanical characteristics.

RESULTS

MDCs have better proliferative activity than RAC and SAC population. RACs could express higher levels of tenogenic-related molecules tenomodulin (TNMD) and scleraxis (SCX) than SACs. Whereas SACs only expressed myogenic-related molecules MyoD. In contrast to the tendons engineered using RACs and SACs, the tendons engineered using MDCs exhibited a relatively more mature and well-organized tissue structure and ultrastructure as well as better mechanical properties.

CONCLUSIONS

Fibroblasts in muscle may be the primary cell population involved in tendon regeneration and that myogenic cells are an important component of the niche and control the fibroblast activity during tendon regeneration. The synergistic effects between fibroblasts and myogenic cells significantly contribute to efficient and effective regeneration of engineered tendons.

A Review of Recent Advances in Natural Polymer-Based Scaffolds for Musculoskeletal Tissue Engineering

The musculoskeletal (MS) system consists of bone, cartilage, tendon, ligament, and skeletal muscle, which forms the basic framework of the human body. This system plays a vital role in appropriate body functions, including movement, the protection of internal organs, support, hematopoiesis, and postural stability. Therefore, it is understandable that the damage or loss of MS tissues significantly reduces the quality of life and limits mobility. Tissue engineering and its applications in the healthcare industry have been rapidly growing over the past few decades. Tissue engineering has made significant contributions toward developing new therapeutic strategies for the treatment of MS defects and relevant disease. Among various biomaterials used for tissue engineering, natural polymers offer superior properties that promote optimal cell interaction and desired biological function. Natural polymers have similarity with the native ECM, including enzymatic degradation, bio-resorb and non-toxic degradation products, ability to conjugate with various agents, and high chemical versatility, biocompatibility, and bioactivity that promote optimal cell interaction and desired biological functions. This review summarizes recent advances in applying natural-based scaffolds for musculoskeletal tissue engineering.

The War after War: Volumetric Muscle Loss Incidence, Implication, Current Therapies and Emerging Reconstructive Strategies, a Comprehensive Review

Volumetric muscle loss (VML) is the massive wasting of skeletal muscle tissue due to traumatic events or surgical ablation. This pathological condition exceeds the physiological healing process carried out by the muscle itself, which owns remarkable capacity to restore damages but only when limited in dimensions. Upon VML occurring, the affected area is severely compromised, heavily influencing the affected a person’s quality of life. Overall, this condition is often associated with chronic disability, which makes the return to duty of highly specialized professional figures (e.g., military personnel or athletes) almost impossible. The actual treatment for VML is based on surgical conservative treatment followed by physical exercise; nevertheless, the results, in terms of either lost mass and/or functionality recovery, are still poor. On the other hand, the efforts of the scientific community are focusing on reconstructive therapy aiming at muscular tissue void volume replenishment by exploiting biomimetic matrix or artificial tissue implantation. Reconstructing strategies represent a valid option to build new muscular tissue not only to recover damaged muscles, but also to better socket prosthesis in terms of anchorage surfaces and reinnervation substrates for reconstructed mass.

Preparation of Stretchable Nanofibrous Sheets with Sacrificial Coaxial Electrospinning for Treatment of Traumatic Muscle Injury

Traumatic muscle injury with massive loss of muscle volume requires intramuscular implantation of proper scaffolds for fast and successful recovery. Although many artificial scaffolds effectively accelerate formation and maturation of myotubes, limited studies are showing the therapeutic effect of artificial scaffolds in animal models with massive muscle injury. In this study, improved myotube differentiation is approved on stepwise stretched gelatin nanofibers and applied to damaged muscle recovery in an animal model. The gelatin nanofibers are fabricated by a two-step process composed of co-axial electrospinning of poly(ɛ-caprolactone) and gelatin and subsequent removal of the outer shells. When stepwise stretching is applied to the myoblasts on gelatin nanofibers for five days, enhanced myotube formation and polarized elongation are observed. Animal models with volumetric loss at quadriceps femoris muscles (>50%) are transplanted with the myotubes cultivated on thin and flexible gelatin nanofiber. Treated animals more efficiently recover exercising functions of the leg when myotubes and the gelatin nanofiber are co-implanted at the injury sites. This result suggests that mechanically stimulated myotubes on gelatin nanofiber is therapeutically feasible for the robust recovery of volumetric muscle loss.

Effects of SW033291 on the myogenesis of muscle-derived stem cells and muscle regeneration

Background

The unmet medical needs in repairing large muscle defects promote the development of tissue regeneration strategy. The use of bioactive molecules in combination with biomaterial scaffold has become an area of great interest. SW033291, a small-molecule inhibitor targeting 15-hydroxyprostaglandin dehydrogenase (15-PDGH) and subsequently elevating the production of prostaglandin E2 (PGE2), has been proved to accelerate the recovery and potentiate the regeneration of multiple tissues including the bone, liver, and colon. The limited understanding of the potential therapeutic effects on myogenesis motivated us to investigate the role of SW033291 in regulating muscle-derived stem cell (MDSC) myogenic differentiation and MDSC-mediated muscle regeneration.

Methods

The characteristics of rat MDSCs, including cell-specific markers and myogenic differentiation potential, were determined. MDSCs were incubated with SW033291 to evaluate PGE2 production and cytotoxicity. The effects of SW033291 on MDSC myogenic differentiation were assessed by quantitative real-time polymerase chain reaction (qPCR), western blot, and immunocytochemistry. The fibrin gel containing MDSCs and SW033291 was used for muscle regeneration in a tibialis anterior muscle defect model.

Results

Our data demonstrated that MDSCs were well-tolerated to SW033291 and treatment with SW033291 significantly promoted the production of PGE2 by MDSCs. In vitro analysis showed that SW033291 enhanced the myogenic differentiation and myotube formation by upregulating a series of myogenic markers. Additionally, the activation of PI3K/Akt pathway was involved in the mechanism underlying these promotive effects. Then, in situ casting of fibrin gel containing MDSCs and SW033291 was used to repair the tibialis anterior muscle defect; the addition of SW033291 significantly promoted myofiber formation within the defect region with mild immune response, less fibrosis, and sufficient vascularization.

Conclusion

SW033291 acted as a positive regulator of MDSC myogenic differentiation, and incorporating the compound with MDSCs in fibrin gel could serve as an effective method to repair large skeletal muscle defects.

Muscle stem cells: what's new in orthopedics?

BACKGROUND AND AIM OF THE WORK

Adult stem cells were studied as a source of potentially useful development for tissue engineering and repair techniques. The aim of this review is to clarify the actual and possible uses of muscle stem cells in orthopedics.

METHODS

A selection of studies was made to obtain a homogeneous and up to date overview on the muscle stem cells applications.

RESULTS

In recent years muscle was studied as a good source of adult stem cells that can differentiate into different cell lineages. Muscle stem cells are a heterogeneous population of cells, which demonstrated in vitro a great potential for the regeneration and repair of muscle, bone and cartilage tissue. Among muscle stem cells, satellite stem cells are the most known progenitor cells: they can differentiate in osteoblasts, adipocytes, chondrocytes and myocytes.

CONCLUSIONS

Although muscle stem cells are a promising field of research, more pre-clinical studies in animal models are still needed to determine the safety and efficiency of the transplant procedures in humans.