Characterization of Skeletal Muscle Endocrine Control in an In Vitro Model of Myogenesis

Abstract

Skeletal muscle has remarkable regenerative abilities regulated by a highly orchestrated process involving the activation of cellular and molecular responses, which are dependent on satellite cells. These cells maintain the stem cell population and provide numerous myogenic cells that proliferate, differentiate, fuse and lead to new myofiber formation for a functional contractile tissue. We have isolated and characterized satellite cells obtained from human biopsies and established an in vitro model of myogenesis, evaluating muscle regeneration, monitoring the dynamic increases of the specific myogenic regulatory factors and the final formation of multinucleated myofibers. As the skeletal muscle is an endocrine tissue able of producing many substances that can act on distant organs, and it can be physiologically modulated by a variety of hormones, we embarked in a project of characterization of muscle cell endocrinology machinery. The expression of a large array of hormone receptors was quantified during the process of myogenesis. The results obtained showed a significant and generalized increase of all the tested hormone receptors along the process of differentiation of human cultured cells from myoblasts to myocytes. Interestingly, also the production of the myokine irisin increased in a parallel manner. These findings point to the human cultured myoblasts as an ideal model to characterize the skeletal muscle endocrine machinery and its hormonal regulation.

Muscle Microbiopsy to Delineate Stem Cell Involvement in Young Patients: A Novel Approach for Children With Cerebral Palsy

“…However, SC-derived progenitors, when amplified in vitro , have been reported to lose the expression of PAX7. Indeed, recent data report that SC-levels of PAX7, detectable at 24 h after extraction, dramatically decrease at passage 4 in vitro ( Romagnoli et al, 2020 ). Therefore, to confirm the identity of SC-derived population, we showed the expression of CD56 marker together with MYOD, the master-gene for muscle development.…”

Links Between Testosterone, Oestrogen, and the Growth Hormone/Insulin-Like Growth Factor Axis and Resistance Exercise Muscle Adaptations

“…Skeletal muscle accounts for ~40–45% of total body mass (Romagnoli et al, 2020 ). Following a rapid post-natal growth phase, skeletal muscle mass is typically maintained at a steady state in adulthood through a controlled balance between muscle protein synthesis (MPS) and breakdown (MPB)—unless in the presence of physiological (exercise) or pathological (age or disease) stimuli.…”

“…Even today after significant efforts to develop pharmaceutical strategies to mitigate muscle wasting (Sepulveda et al, 2015 ), contractile activity in the form of resistance exercise (RE) remains the most efficacious intervention. RE training (RET) leads to muscle hypertrophy through a sustained elevation of MPS (Hooper et al, 2017 )—responses which are driven by a combination of mechanical overload, and an associated release of hormones; e.g., androgens and insulin-like growth factor-1 (IGF-1) (Romagnoli et al, 2020 ) and by muscle mechano-sensitive signals.…”

Study of the Expression and Function of Calcium-Sensing Receptor in Human Skeletal Muscle

“…Real-time qPCR detected very low CaSR expression levels in hSMts and in the established hSC lines, but since the quantity was extremely small in all of the assayed samples, it was not possible to sequence the amplicons to confirm the detected mRNA products (Figure 3E). Subsequently, since during in vitro myogenesis satellite cells mature and gradually express receptors [14], we analyzed CaSR gene expression by RT-PCR at T 0 and after 9 days of myogenic differentiation, using all three different pairs of primers previously utilized. The analyses showed no CaSR gene expression at these experimental time points, demonstrating the absence of CaSR gene during the in vitro myogenesis of the three primary hSC lines.…”

“…In the last decade, it has become possible to isolate and culture a population of SCs [ 11 , 12 , 13 , 14 ]. While the use of primary cultures of SCs also has some inherent drawbacks, mainly relating to the fact that they are generally slow growing and can undergo a limited number of divisions [ 15 ], SCs represent an important in vitro model to understand skeletal muscle physiology and pathology.…”