The process of myogenesis gradually deteriorates as the skeletal muscle ages, contributing to muscle mass loss. The aim of this study is to investigate the effect of senescence/aging on skeletal myogenesis, in vitro. A model of multiple cell divisions of C2C12 myoblasts was used to replicate cell senescence. Control and aged myoblasts were investigated during myogenesis, i.e., at days 0, 2, and 6of differentiation. SA-β-gal activity and comet assay were used as markers of aging and DNA damage. Flow cytometry was performed to characterize potential differences in cell cycle between control and aged cells. Alterations in the mRNA and/or protein expression of myogenic regulatory factors (MRFs), IGF-1 isoforms, apoptotic, atrophy, inflammatory, metabolic and aging-related factors were evaluated. Compared with the control cells, aged myoblasts exhibited G0/G1 cell cycle arrest, DNA damage, increased SA-β-gal activity, and increased expression of aging-related factors p16 and p21 during differentiation. Moreover, aged myoblasts showed a reduction in the expression of MRFs and metabolic/anabolic factors, along with an increased expression of apoptotic, atrophy and inflammatory factors. A diminished differentiation capacity characterized the aged myoblasts which, in combination with the induction of apoptotic and atrophy factors, indicated a disrupted myogenic lineage in the senescent muscle cells.

Background/Objectives: There is a growing interest in the research of wound healing mechanisms worldwide. Particular attention has been paid to the expression of tissue remodeling- and inflammation-related factors. Herein, we investigate the expression patterns of TGF-β1, IL-6, TNF-a, uPA, uPA receptors, MMP-2, and MMP-9 through the four phases of the normal wound-healing process in humans. Methods: Twenty-two individuals presenting with a first episode of pilonidal sinus underwent surgical excision and the wound was left to heal by secondary intention. Sequential biopsies were collected on day 0 (operation), day 2 (inflammatory phase), day 9 (proliferative phase), and day 14 (tissue remodeling phase). The expression levels of the proteins were evaluated using reverse transcription–quantitative PCR. Statistical analyses were performed using GraphPad Prism software. One-way analysis of variance (ANOVA) with Dunn’s Multiple Comparison post hoc test was used. Results: The results showed statistically significant differences in the expressions of the factors during wound healing (p < 0.05). TGF-b1 increased on days 2 and 9. TNF-a increased on day 2 and then decreased on day 9. Il-6 was increased on day 2 and decreased on days 9 and 14. uPa mRNA increased up to day 9 but its receptor exhibited high expression throughout the observation time. Finally, MMP-2 mRNA expression increased on day 2 and declined on days 9 and 14, while MMP-9 was highly expressed until the 14th postoperative day. Conclusions: Each factor investigated in this study has an important and distinct role in the normal wound repair procedure. Further investigation is required to evaluate the tissue-specific regulation of these factors and their potential use as therapeutic targets or prognostic biomarkers in wound healing.

Background: During aging, muscle cell apoptosis increases and myogenesis gradually declines. The impaired myogenic and survival potential of the aged skeletal muscle can be ameliorated by its mechanical loading. However, the molecular responses of aged muscle cells to mechanical loading remain unclear. This study examined the effect of mechanical loading of aged, proliferating, and differentiated myoblasts on the gene expression and signaling responses associated with their myogenic lineage progression and survival. Methods: Control and aged C2C12 cells were cultured on elastic membranes and underwent passive stretching for 12 h at a low frequency (0.25 Hz) and different elongations, varying the strain on days 0 and 10 of myoblast differentiation. Activation of ERK1/2 and Akt, and the expression of focal adhesion kinase (FAK) and key myogenic regulatory factors (MRFs), MyoD and Myogenin, were determined by immunoblotting of the cell lysates derived from stretched and non-stretched myoblasts. Changes in the expression levels of the MRFs, muscle growth, atrophy, and pro-apoptotic factors in response to mechanical loading of the aged and control cells were quantified by real-time qRT-PCR. Results: Mechanical stretching applied on myoblasts resulted in the upregulation of FAK both in proliferating (day 0) and differentiated (day 10) cells, as well as in increased phosphorylation of ERK1/2 in both control and aged cells. Moreover, Akt activation and the expression of early differentiation factor MyoD increased significantly after stretching only in the control myoblasts, while the late differentiation factor Myogenin was upregulated in both the control and aged myoblasts. At the transcriptional level, mechanical loading of the proliferating myoblasts led to an increased expression of IGF-1 isoforms and MRFs, and to downregulation of muscle atrophy factors mainly in control cells, as well as in the upregulation of pro-apoptotic factors both in control and aged cells. In differentiated cells, mechanical loading resulted in an increased expression of the IGF-1Ea isoform and Myogenin, and in the downregulation of atrophy and pro-apoptotic factors in both the control and aged cells. Conclusions: This study revealed a diminished beneficial effect of mechanical loading on the myogenic and survival ability of the senescent muscle cells compared with the controls, with a low strain (2%) loading being most effective in upregulating myogenic/anabolic factors and downregulating atrophy and pro-apoptotic genes mainly in the aged myotubes.

Endometriosis is a benign, estrogen-dependent gynecological condition with an uncertain exact pathogenetic mechanism. The aim of this study was to evaluate the potential differential expression of Insulin Growth Factor 1 (IGF-1) isoforms in deeply infiltrating endometriotic (DIE) lesions, in ovarian endometriomas, and in the eutopic endometrium of the same endometriosis patients and to compare their expression with that in the eutopic endometrium of women without endometriosis. A total of 39 patients were included: 28 with endometriosis, of whom 15 had endometriomas only, 7 had DIE nodules only, and 6 had both DIE and endometriomas, and 11 without endometriosis served as controls. We noticed a similar pattern of expression between IGF-1Ea and IGF-1Ec, which differed from that of the IGF-1Eb isoform, possibly implying differential biological actions of different isoforms in DIE subtypes. We observed a tendency of lower expression of IGF-1Ea and IGF-1Ec in endometriomas without DIE compared to endometriomas with concurrent DIE or in DIE nodules. In conclusion, differential expression of IGF-1 isoforms may indicate that DIE with its associated ovarian lesions and simple ovarian endometriosis should be considered as two forms of the disease developing under different molecular pathways.

Cardiomyocytes possess the ability to respond to mechanical stimuli by adapting their biological functions. This study investigated cellular and molecular events in cardiomyocyte-like H9C2 cells during differentiation as well as the signalling and gene expression responses of the differentiated cells under various mechanical stretching protocols in vitro. Immunofluorescence was used to monitor MyHC expression and structural changes during cardiomyoblast differentiation. Moreover, alterations in the expression of cardiac-specific markers, cell cycle regulatory factors, MRFs, hypertrophic, apoptotic, atrophy and inflammatory factors, as well as the activation of major intracellular signalling pathways were evaluated during differentiation and under mechanical stretching of the differentiated H9C2 cells. Compared to undifferentiated cells, advanced-differentiation cardiomyoblasts exhibited increased expression of cardiac-specific markers, MyHC, MRFs, and IGF-1 isoforms. Moreover, differentiated cells that underwent a low strain/frequency mechanical loading protocol of intermediate duration showed enhanced expression of MRFs and hypertrophic factors, along with a decreased expression of apoptotic, atrophy, and inflammatory factors compared to both high-strain/frequency loading protocols and to unloaded cells. These findings suggest that altering the strain and frequency of mechanical loading applied on differentiated H9C2 cardiomyoblasts can regulate their anabolic/survival program, with a low-strain/frequency stretching being, overall, most effective at inducing beneficial responses.

Purpose: High-intensity interval training (HIIT) has emerged as a time-efficient alternative to traditional endurance training. This study investigated the molecular, systemic, and physiological adaptations induced by an 8-week HIIT program in national-level flatwater kayak athletes. Methods: Six trained male kayakers completed an 8-week HIIT intervention. Skeletal muscle biopsies and venous blood samples were collected before and after training to assess markers related to endocrine function, growth and remodeling, angiogenesis, and inflammation. Physiological and performance measures were evaluated using a maximal oxygen uptake (VO₂max) test and kayak ergometer trials. Results: HIIT elicited significant improvements across molecular, systemic, and performance parameters. Post-training analyses showed increased expression of IGF-1R, MMP-4, MMP-9, and TNF-α (p < 0.05), along with elevated serum testosterone concentrations (p < 0.05). Notable performance gains were observed in paddling speed at the second ventilatory threshold (PSVT2; p < 0.05) and in 1000 m (p < 0.01) and 200 m (p < 0.001) time-trial performances. Conclusions: An 8-week HIIT program effectively enhanced molecular signaling, systemic adaptation, and sport-specific performance in elite flatwater kayak athletes. The concurrent upregulation of anabolic, remodeling, and inflammatory pathways suggests that HIIT facilitates coordinated muscular and systemic adaptations beneficial for kayak performance.