Functional Neuronal Differentiation of Injury-Induced Muscle-Derived Stem Cell-Like Cells with Therapeutic Implications

Application of stem cells in regeneration medicine

Regeneration is a complex process affected by many elements independent or combined, including inflammation, proliferation, and tissue remodeling. Stem cells is a class of primitive cells with the potentiality of differentiation, regenerate with self-replication, multidirectional differentiation, and immunomodulatory functions. Stem cells and their cytokines not only inextricably linked to the regeneration of ectodermal and skin tissues, but also can be used for the treatment of a variety of chronic wounds. Stem cells can produce exosomes in a paracrine manner. Stem cell exosomes play an important role in tissue regeneration, repair, and accelerated wound healing, the biological properties of which are similar with stem cells, while stem cell exosomes are safer and more effective. Skin and bone tissues are critical organs in the body, which are essential for sustaining life activities. The weak repairing ability leads a pronounced impact on the quality of life of patients, which could be alleviated by stem cell exosomes treatment. However, there are obstacles that stem cells and stem cells exosomes trough skin for improved bioavailability. This paper summarizes the applications and mechanisms of stem cells and stem cells exosomes for skin and bone healing. We also propose new ways of utilizing stem cells and their exosomes through different nanoformulations, liposomes and nanoliposomes, polymer micelles, microspheres, hydrogels, and scaffold microneedles, to improve their use in tissue healing and regeneration.

Hypoxia-induced reprogrammed myoblasts enhance the formation of neuromuscular junctions: A pioneer study

We previously reported that muscle cells could reprogram into progenitors after traumatic injuries. These injury-induced muscle stem cells (iMuSCs) have increased migration and differentiation capacities, including neuronal differentiation. Recent studies in our laboratory suggest that the hypoxia-induced by tissue injury plays an essential role in the reprogramming process of muscle cells. We hypothesize that muscle cells reprogrammed with hypoxia have increased neuronal differentiation potentials and the neuronal differentiation extends into the formation of neuromuscular junction (NMJ)-like structures. In this study, C2C12 myoblasts were cultured under hypoxic conditions and subsequently in neural differentiation media to generate neurospheres, and then with muscle differentiation media to induce NMJ-like structure formation. Hypoxia-induced muscle cells also produced more robust NMJs compared to controls after intramuscular cell transplantation. Our results suggest hypoxia plays a role in the reprogramming of muscle stem cells, which may have the potential to form neuromuscular junctions and ultimately contribute to functional muscle healing.

The Efficacy of Schwann-Like Differentiated Muscle-Derived Stem Cells in Treating Rodent Upper Extremity Peripheral Nerve Injury

BACKGROUND

There is a pressing need to identify alternative mesenchymal stem cell sources for Schwann cell cellular replacement therapy, to improve peripheral nerve regeneration. This study assessed the efficacy of Schwann cell-like cells (induced muscle-derived stem cells) differentiated from muscle-derived stem cells (MDSCs) in augmenting nerve regeneration and improving muscle function after nerve trauma.

METHODS

The Schwann cell-like nature of induced MDSCs was characterized in vitro using immunofluorescence, flow cytometry, microarray, and reverse-transcription polymerase chain reaction. In vivo, four groups (n = 5 per group) of rats with median nerve injuries were examined: group 1 animals were treated with intraneural phosphate-buffered saline after cold and crush axonotmesis (negative control); group 2 animals were no-injury controls; group 3 animals were treated with intraneural green fluorescent protein-positive MDSCs; and group 4 animals were treated with green fluorescent protein-positive induced MDSCs. All animals underwent weekly upper extremity functional testing. Rats were euthanized 5 weeks after treatment. The median nerve and extrinsic finger flexors were harvested for nerve histomorphometry, myelination, muscle weight, and atrophy analyses.

RESULTS

In vitro, induced MDSCs recapitulated native Schwann cell gene expression patterns and up-regulated pathways involved in neuronal growth/signaling. In vivo, green fluorescent protein-positive induced MDSCs remained stably transformed 5 weeks after injection. Induced MDSC therapy decreased muscle atrophy after median nerve injury (p = 0.0143). Induced MDSC- and MDSC-treated animals demonstrated greater functional muscle recovery when compared to untreated controls (hand grip after induced MDSC treatment: group 1, 0.91 N; group 4, 3.38 N); p < 0.0001) at 5 weeks after treatment. This may demonstrate the potential beneficial effects of MDSC therapy, regardless of differentiation stage.

CONCLUSION

Both MDSCs and induced MDSCs decrease denervation muscle atrophy and improve subsequent functional outcomes after upper extremity nerve trauma in rodents.

Peripheral Nerve Regeneration Using Different Germ Layer-Derived Adult Stem Cells in the Past Decade

Peripheral nerve injuries (PNIs) are some of the most common types of traumatic lesions affecting the nervous system. Although the peripheral nervous system has a higher regenerative ability than the central nervous system, delayed treatment is associated with disturbances in both distal sensory and functional abilities. Over the past decades, adult stem cell-based therapies for peripheral nerve injuries have drawn attention from researchers. This is because various stem cells can promote regeneration after peripheral nerve injuries by differentiating into neural-line cells, secreting various neurotrophic factors, and regulating the activity of in situ Schwann cells (SCs). This article reviewed research from the past 10 years on the role of stem cells in the repair of PNIs. We concluded that adult stem cell-based therapies promote the regeneration of PNI in various ways.

Hypoxia in Cell Reprogramming and the Epigenetic Regulations

Cellular reprogramming is a fundamental topic in the research of stem cells and molecular biology. It is widely investigated and its understanding is crucial for learning about different aspects of development such as cell proliferation, determination of cell fate and stem cell renewal. Other factors involved during development include hypoxia and epigenetics, which play major roles in the development of tissues and organs. This review will discuss the involvement of hypoxia and epigenetics in the regulation of cellular reprogramming and how interplay between each factor can contribute to different cellular functions as well as tissue regeneration.

Grafted muscle-derived stem cells promote the therapeutic efficiency of epimysium conduits in mice with peripheral nerve gap injury

Our research aimed to build allogeneic artificial conduits with epimysium and muscle-derived stem cells (MDSCs) from the skeletal muscle of mice. We applied the conduit to repair peripheral nerve defects and estimated the effectiveness of the repair process. In the research, we prepared epimysium conduits with lumens to bridge repair a 5-mm-long sciatic nerve defect from C57 wild-type mice and then transplanted green fluorescent protein (GFP)-MDSCs and Matrigel suspensions into the conduit. Histological and functional assessments were performed 4 and 8 weeks after surgery. The tissue-engineered conduit from muscle effectively repaired the nerve defect, while the group with GFP-MDSCs showed improved histological examinations and functional assessments, and the newborn nerves highly expressed GFP. As the results suggested, autologous epimysium conduits represent a reliable method to repair peripheral nerve defects, and the addition of MDSCs promote the effectiveness of differentiating into multiple lineages. Our research simultaneously demonstrated the myogenic, neurogenic, and angiogenic potential of MDSCs in vivo for the first time.

A modified preplate technique for efficient isolation and proliferation of mice muscle-derived stem cells

We modified an existing protocol to develop a more efficient method to acquire and culture muscle-derived stem cells (MDSCs) and compared the characteristics of cells obtained from the two methods. This method is based on currently used multistep enzymatic digestion and preplate technique. During the replating process, we replaced the traditional medium with isolation medium to promote fibroblast-like cell adherence at initial replating step, which shortened the purifying duration by up to 4 days. Moreover, we modified the culture container to provide a stable microenvironment that promotes MDSC adherence. We compared the cell morphology, growth curve and the expression of specific markers (Sca-1, CD34, PAX7 and Desmin) between the two cell groups separately obtained from the two methods. Afterwards, we compared the neural differentiation capacity of MDSCs with other muscle-derived cell lineages. The protocol developed here is a fast and effective method to harvest and purify MDSCs from mice limb skeletal muscle.

Cytogenetic and Transcriptomic Analysis of Human Endometrial MSC Retaining Proliferative Activity after Sublethal Heat Shock

Temperature is an important exogenous factor capable of leading to irreversible processes in the vital activity of cells. However, the long-term effects of heat shock (HS) on mesenchymal stromal cells (MSC) remain unstudied. We investigated the karyotype and DNA repair drivers and pathways in the human endometrium MSC (eMSC) survived progeny at passage 6 after sublethal heat stress (sublethal heat stress survived progeny (SHS-SP)). G-banding revealed an outbreak of random karyotype instability caused by chromosome breakages and aneuploidy. Molecular karyotyping confirmed the random nature of this instability. Transcriptome analysis found homologous recombination (HR) deficiency that most likely originated from the low thermostability of the AT-rich HR driving genes. SHS-SP protection from transformation is provided presumably by low oncogene expression maintained by tight co-regulation between thermosensitive HR drivers BRCA, ATM, ATR, and RAD51 (decreasing expression after SHS), and oncogenes mTOR, MDM2, KRAS, and EGFR. The cancer-related transcriptomic features previously identified in hTERT transformed MSC in culture were not found in SHS-SP, suggesting no traits of malignancy in them. The entrance of SHS-SP into replicative senescence after 25 passages confirms their mortality and absence of transformation features. Overall, our data indicate that SHS may trigger non-tumorigenic karyotypic instability due to HR deficiency and decrease of oncogene expression in progeny of SHS-survived MSC. These data can be helpful for the development of new therapeutic approaches in personalized medicine.

Anterior cruciate ligament reconstruction in a patient who has received systemic steroids for autoimmune disease

Background

An anterior cruciate ligament (ACL) reconstruction has become more common and the surgical morbidity has decreased, it has been performed not only in younger people to play sports but also middle-aged people, with satisfactory results. Therefore, some patients might have comorbidities for which they take medicines. Especially the medicines, such as systemic steroids, might influence the reconstructed ligament strength and durability.

Case report

A 49-year-old woman who was taking oral steroids for autoimmune hepatitis suffered a spontaneous ACL injury. She complained of unstable symptoms in the knee despite initial conservative treatment. Then, she was treated operatively with autologous hamstring tendon grafts. Three years postoperatively, her knee remained stable with 1.8 mm side-to-side difference on a Kneelax arthrometer and with 1.6 mm on anterior stress radiographs. There was no rerupture or instability.

Conclusion

The patient who had received systemic steroids for a long time recovered satisfactorily after the operation, with achievement of knee stability and possibility to prevent degenerative change in the knee joint. ACL reconstruction should be considered even in patients with such medication.