Extracellular matrix: the critical contributor to skeletal muscle regeneration-a comprehensive review

Mechanical Stress-Oxidative Stress Axis: Biological Basis in the Vaginal Wall and Pelvic Floor Muscles of Rats with Simulated Birth Injury

INTRODUCTION AND HYPOTHESIS

Vaginal delivery and resulting pelvic floor muscle (PFM) dysfunction are significant risk factors for pelvic floor dysfunction (PFD). Despite this, the biological basis underlying PFD after childbirth remain unclear. This study was aimed at assessing the early response of the vaginal wall and PFM to simulated birth injury (SBI) in rats.

METHODS

Forty female Sprague-Dawley rats were divided into four groups: control (sham operation), and 1, 4, and 14 days post-injury. In the SBI groups, a catheter was inserted into the vagina with 130 g of weight attached to the end, and the balloon was inflated to 5 ml for 2 h. Evaluation of vaginal tissues and PFMs included histological, immunohistochemical, Western blot, and uniaxial biomechanical testing.

RESULTS

In the vaginal wall, the SBI group showed significantly lower COL1A1 expression and higher MMP-2 and MMP-9 expression. At 4 and 14 days post-injury, there was a significant decrease in PFM fiber area and increased collagen content. The SBI group also exhibited significant increases in the expression of Nrf2, NQO1, HO-1, and SOD-2, indicating involvement of oxidative stress in both the vaginal wall and PFMs. Protein expression of Pax7 and MyoG, as well as the number of fibers with centralized nuclei, continued to increase significantly after SBI. Additionally, the vaginal wall of the SBI group showed a decreasing trend in tensile strength and elastic modulus, with a greater ultimate strain.

CONCLUSION

Extracellular matrix remodeling, oxidative stress, decreased biomechanical properties, and muscle dysmyogenesis may collectively contribute to increased susceptibility to PFD development.

Towards more realistic cultivated meat by rethinking bioengineering approaches

Cultivated meat (CM) refers to edible lab-grown meat that incorporates cultivated animal cells. It has the potential to address some issues associated with real meat (RM) production, including the ethical and environmental impact of animal farming, and health concerns. Recently, various biomanufacturing methods have been developed to attempt to recreate realistic meat in the laboratory. We therefore overview recent achievements and challenges in the production of CM. We also discuss the issues that need to be addressed and suggest additional recommendations and potential criteria to help to bridge the gap between CM and RM from an engineering standpoint.

Slow-velocity eccentric-only resistance training improves symptoms of type 2 diabetic mellitus patients by regulating plasma MMP-2 and -9

OBJECTIVE

This study investigated the intervention effect of slow-velocity eccentric-only resistance training on type 2 diabetic mellitus (T2DM) patients based on the role of matrix metalloproteinase-2 and -9 (MMP-2 and -9) in regulating extracellular matrix homeostasis.

METHODS

50 T2DM patients were randomly divided into the slow-velocity eccentric-only resistance training group (E) and control group (C). The E group performed eccentric-only resistance training 3 times a week, every other day for 10 weeks, while the C group did not. Blood samples were collected before and after training, and subjects were tested for changes in clinical parameters, insulin resistance indices [fasting insulin, homeostatic model assessment insulin resistance (HOMA-IR)], MMP-2 and -9, and hydroxyproline, and muscle strength (12-RM), respectively.

RESULTS

After 10 weeks of training, the E group showed significant decreases in fasting glucose (P < .05), insulin (P < .05), insulin resistance indices (P < .05), hemoglobin A1c (HbA1c) (P < .01), triglycerides (P = .06) and MMP-2 (P < .05), while total cholesterol (P < .05), MMP-9 (P < .05), hydroxyproline (P < .01), Creatine Kinase (CK) (P < .05), and muscle strength (P < .001) significantly increased. There were no significant changes in the count of neutrophil, lymphocyte and platelet, neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), high-density lipoprotein cholesterol (HDL-c), and low-density lipoprotein cholesterol (LDL-c). Compared with the C group, the E group showed a trend of a significant decrease in triglyceride (P < .05), lymphocyte count (P < .05), fasting glucose (P = .07), and plasma MMP-2 (P < .05), while MMP-9 (P < .05), hydroxyproline (P < .001), and muscle strength (P < .01) significantly increased. However, no significant changes were observed in insulin and insulin resistance indices, HbA1c, total cholesterol, HDL-c, LDL-c, CK, and other inflammatory indicators.

CONCLUSIONS

Slow-velocity eccentric-only resistance training was beneficial for T2DM, but the potential role of MMP-2 and -9 in regulating extracellular matrix homeostasis is very different in T2DM patients.

Mechanisms of regeneration: to what extent do they recapitulate development?

One of the enduring debates in regeneration biology is the degree to which regeneration mirrors development. Recent technical advances, such as single-cell transcriptomics and the broad applicability of CRISPR systems, coupled with new model organisms in research, have led to the exploration of this longstanding concept from a broader perspective. In this Review, I outline the historical parallels between development and regeneration before focusing on recent research that highlights how dissecting the divergence between these processes can uncover previously unreported biological mechanisms. Finally, I discuss how these advances position regeneration as a more dynamic and variable process with expanded possibilities for morphogenesis compared with development. Collectively, these insights into mechanisms that orchestrate morphogenesis may reshape our understanding of the evolution of regeneration, reveal hidden biology activated by injury, and offer non-developmental strategies for restoring lost or damaged organs and tissues.

miR-27b-3p reduces muscle fibrosis during chronic skeletal muscle injury by targeting TGF-βR1/Smad pathway

BACKGROUND

Fibrosis is a significant pathological feature of chronic skeletal muscle injury, profoundly affecting muscle regeneration. Fibro-adipogenic progenitors (FAPs) have the ability to differentiate into myofibroblasts, acting as a primary source of extracellular matrix (ECM). the process by which FAPs differentiate into myofibroblasts during chronic skeletal muscle injury remains inadequately explored.

METHOD

mouse model with sciatic nerve denervated was constructed and miRNA expression profiles between the mouse model and uninjured mouse were analyzed. qRT/PCR and immunofluorescence elucidated the effect of miR-27b-3p on fibrosis in vivo and in vitro. Dual-luciferase reporter identified the target gene of miR-27b-3p, and finally knocked down or overexpressed the target gene and phosphorylation inhibition of Smad verified the influence of downstream molecules on the abundance of miR-27b-3p and fibrogenic differentiation of FAPs.

RESULT

FAPs derived from a mouse model with sciatic nerves denervated exhibited a progressively worsening fibrotic phenotype over time. Introducing agomiR-27b-3p effectively suppressed fibrosis both in vitro and in vivo. MiR-27b-3p targeted Transforming Growth Factor Beta Receptor 1 (TGF-βR1) and the abundance of miR-27b-3p was negatively regulated by TGF-βR1/Smad.

CONCLUSION

miR-27b-3p targeting the TGF-βR1/Smad pathway is a novel mechanism for regulating fibrogenic differentiation of FAPs. Increasing abundance of miR-27b-3p, suppressing expression of TGF-βR1 and inhibiting phosphorylation of smad3 presented potential strategies for treating fibrosis in chronic skeletal muscle injury.

Low-intensity pulsed ultrasound (LIPUS) promotes skeletal muscle regeneration by regulating PGC-1α/AMPK/GLUT4 pathways in satellite cells/myoblasts

Low-Intensity Pulsed Ultrasound (LIPUS) holds therapeutic potential in promoting skeletal muscle regeneration, a biological process mediated by satellite cells and myoblasts. Despite their central roles in regeneration, the detailed mechanistic of LIPUS influence on satellite cells and myoblasts are not fully underexplored. In the current investigation, we administrated LIPUS treatment to injured skeletal muscles and C2C12 myoblasts over five consecutive days. Muscle samples were collected on days 6 and 30 post-injury for an in-depth histological and molecular assessment, both in vivo and in vitro with immunofluorescence analysis. During the acute injury phase, LIPUS treatment significantly augmented the satellite cell population, concurrently enhancing the number and size of newly formed myofibers whilst reducing fibrosis levels. At 30 days post-injury, the LIPUS-treated group demonstrated a more robust satellite cell pool and a higher myofiber count, suggesting that early LIPUS intervention facilitates satellite cell proliferation and differentiation, thereby promoting long-term recovery. Additionally, LIPUS markedly accelerated C2C12 myoblast differentiation, with observed increases in AMPK phosphorylation in myoblasts, leading to elevated expression of Glut4 and PGC-1α, and subsequent glucose uptake and mitochondrial biogenesis. These findings imply that LIPUS-induced modulation of myoblasts may culminate in enhanced cellular energy availability, laying a theoretical groundwork for employing LIPUS in ameliorating skeletal muscle regeneration post-injury. NEW & NOTEWORTHY: Utilizing the cardiotoxin (CTX) muscle injury model, we investigated the influence of LIPUS on satellite cell homeostasis and skeletal muscle regeneration. Our findings indicate that LIPUS promotes satellite cell proliferation and differentiation, thereby facilitating skeletal muscle repair. Additionally, in vitro investigations lend credence to the hypothesis that the regulatory effect of LIPUS on satellite cells may be attributed to its capability to enhance cellular energy metabolism.

Therapeutic applications of biological macromolecules and scaffolds for skeletal muscle regeneration: A review

Skeletal muscle (SM) mass and strength maintenance are important requirements for human well-being. SM regeneration to repair minor injuries depends upon the myogenic activities of muscle satellite (stem) cells. However, losses of regenerative properties following volumetric muscle loss or severe trauma or due to congenital muscular abnormalities are not self-restorable, and thus, these conditions have major healthcare implications and pose clinical challenges. In this context, tissue engineering based on different types of biomaterials and scaffolds provides an encouraging means of structural and functional SM reconstruction. In particular, biomimetic (able to transmit biological signals) and several porous scaffolds are rapidly evolving. Several biological macromolecules/biomaterials (collagen, gelatin, alginate, chitosan, and fibrin etc.) are being widely used for SM regeneration. However, available alternatives for SM regeneration must be redesigned to make them more user-friendly and economically feasible with longer shelf lives. This review aimed to explore the biological aspects of SM regeneration and the roles played by several biological macromolecules and scaffolds in SM regeneration in cases of volumetric muscle loss.

Vitamin a potentiates sheep myoblasts myogenic differentiation through BHLHE40-modulated ID3 expression

BACKGROUND

Vitamin A and retinoic acid (RA, a metabolite of vitamin A), are inextricably involved to the development of skeletal muscle in animals. However, the mechanisms regulating skeletal muscle development by vitamin A remain poorly reported. The current study designed to investigate the underlying mechanism of vitamin A affecting myogenic differentiation of lamb myoblasts through transcriptome sequencing (RNA-Seq) and gene function validation experiments. It provides a theoretical basis for elucidating the regulation of vitamin A on skeletal muscle development as well as for improving the economic benefits of the mutton sheep industry.

RESULTS

Newborn lambs were injected with 7,500 IU vitamin A, and longissimus dorsi (LD) muscle tissue was surgically sampled for RNA-Seq analysis and primary myoblasts isolation at 3 weeks of age. The results showed that a total of 14 down-regulated and 3 up-regulated genes, were identified between control and vitamin A groups. Among them, BHLHE40 expression was upregulated in vitamin A group lambs. Furthermore, BHLHE40 expression is significantly increased after initiation of differentiation in myoblasts, and RA addition during differentiation greatly promoted BHLHE40 mRNA expression. In vitro, RA inhibited myoblasts proliferation and promoted myoblasts myogenic differentiation through BHLHE40. Moreover, BHLHE40 was proved to inhibit the expression of the DNA binding inhibitor 3 (ID3), and meanwhile, ID3 could effectively promote myoblasts proliferation and inhibit myoblasts myogenic differentiation.

CONCLUSIONS

Taken together, our results suggested that vitamin A inhibited myoblasts proliferation and promoted myoblasts myogenic differentiation by inhibiting ID3 expression through BHLHE40.

Therapeutic Applications of Ginseng Natural Compounds for Health Management

Ginseng is usually consumed as a daily food supplement to improve health and has been shown to benefit skeletal muscle, improve glucose metabolism, and ameliorate muscle-wasting conditions, cardiovascular diseases, stroke, and the effects of aging and cancers. Ginseng has also been reported to help maintain bone strength and liver (digestion, metabolism, detoxification, and protein synthesis) and kidney functions. In addition, ginseng is often used to treat age-associated neurodegenerative disorders, and ginseng and ginseng-derived natural products are popular natural remedies for diseases such as diabetes, obesity, oxidative stress, and inflammation, as well as fungal, bacterial, and viral infections. Ginseng is a well-known herbal medication, known to alleviate the actions of several cytokines. The article concludes with future directions and significant application of ginseng compounds for researchers in understanding the promising role of ginseng in the treatment of several diseases. Overall, this study was undertaken to highlight the broad-spectrum therapeutic applications of ginseng compounds for health management.