Temporal expression of regulatory and structural muscle proteins during myogenesis of satellite cells on isolated adult rat fibers

Abstract

Myogenic precursors in adult skeletal muscle (satellite cells) are mitotically quiescent but can proliferate in response to a variety of stresses including muscle injury. To gain further understanding of adult myoblasts, we analyzed myogenesis of satellite cells on intact fibers isolated from adult rat muscle. In this culture model, satellite cells are maintained in their in situ position underneath the fiber basement membrane. In the present study patterns of satellite cell proliferation, expression of myogenic regulatory factor proteins, and expression of differentiationspecific, cytoskeletal proteins were determined, via immunohistochemistry of cultured fibers. The temporal appearance and the numbers of cells positive for proliferating cell nuclear antigen (PCNA) or for MyoD were similar, suggesting that MyoD is present in detectable amounts in proliferating but not quiescent satellite cells. Satellite cells positive for myogenin, α-smooth muscle actin (αSMactin), or developmental sarcomeric myosin (DEVmyosin) appeared following the decline in PCNA and MyoD expression. However, expression of myogenin and αSMactin was transient, while DEVmyosin expression was continuously maintained. Moreover, the number of DEVmyosin+ cells was only half of the number of myogenin+ or αSMactin+ cells-indicating, perhaps, that only 50% of the satellite cell descendants entered the phase of terminal differentiation. We further determined that the number of proliferating satellite cells can be modulated by basic FGF but the overall schedule of cell cycle entry, proliferation, differentiation, and temporal expression of regulatory and structural proteins was unaffected. We thus conclude that satellite cells conform to a highly coordinated program when undergoing myogenesis at their native position along the muscle fiber.

Muscle-derived stem cells

“…Their progeny, myoblasts, fuse to form new multinucleated myofibers. [7][8][9][10] Cell surface markers associated with the satellite cell phenotype, either in the quiescent or activated state, have attempted to be elucidated and include: M-cadherin, c-met, and CD34. [10][11][12][13][14] Figure 1 presents a proposed mechanism of…”

Formoterol May Activate Rat Muscle Regeneration During Cancer Cachexia

“…In adult skeletal muscle, Pax7 is expressed in the majority of quiescent satellite cells. These cells, when activated, coexpress Pax7 and MyoD 28,34,35 . When they proliferate, the levels of Pax7 decrease and other molecules involved in differentiation (such as myogenin) increase their expression.…”

Time-based gene expression programme following diaphragm injury in a rat model

“…The proto-oncogene cFos promotes muscle cell repair and hypertrophy in immediate response to both injury [29] and mechanical stress [30,31], while myogenin is a potent regulator of terminal muscle differentiation during myogenesis and regeneration [32][33][34]. Unexpectedly, myogenin rose as early as 12 h PI, whereas cFos increased later than expected at 72 h PI.…”