Xenogeneic lymphocytic RNA stimulates skeletal muscle regeneration

Objective: to find evidence of the existence of distant lymphocytic RNA control of physiological myogenesis as a way to control the muscle tissue regeneration process.Materials and methods. The study was conducted on male Wistar rats, n=33. In the first part of the experiment, 12 rats were subjected to regular 40-day physical activity (swimming), half of them were intraperitoneally injected 4 times with total RNA isolated from pig spleen lymphocytes at 30 days of age; 6 rats made up the intact control group. In histological preparations of different skeletal muscle groups, the width and cross-sectional area of muscle fibers, the area of nuclei, and the number of myocytes and myosatellite cells were evaluated. In the second part of the experiment, 15 intact rats were injected with the studied xenogeneic RNA and the amounts of ribonucleic acids in peripheral blood lymphocytes, spleen lymphocytes, and skeletal muscles were determined 2 hours and 24 hours after injection.Results. After the 40- day physical activity, the width of the fibers and the area of myocyte nuclei in the skeletal muscles increased; the absolute number of myosatellite cells and the area of their nuclei did not change. After administration of xenogenic RNA in the trained rats, in addition to an increase in the thickness and cross-sectional area of muscle fibers, the absolute number of myosatellite cells in m. biceps femoris, in m. triceps brachii, and in m. pectoralis major increased 1.4-fold, 1.3-fold, and 1.4-fold, respectively; the area of myosatellite nuclei increased on average by 7%. In intact rats, two hours after xenogeneic RNA injection, the amount of RNA in skeletal muscles remained unchanged, it increased by 19% in spleen lymphocytes, and by 16% in peripheral blood lymphocytes. At 24 hours, the RNA amount in the lymphocytes remained significantly higher than the control values, while in the muscle tissue, it didn’t differ from the control.Conclusion. Xenogeneic lymphocytic RNA stimulates physiological myogenesis by activating myosatellite cell proliferation.

Effect of p38 MAPK on oxidative phosphorylation in regeneration of muscle tissue

Цель исследования: определить влияние блокады р38 МАРК на систему окислительного фосфорилирования при репарации мышечной ткани. Материалы и методы: Контрольной группе животных (n = 21) наносили рану длиннейшей мышцы спины, в рану вносили лекарственную плёнку без активного вещества, основной группе (n = 21) пленку с блокатором р38 МАР-киназы SB 203580. Выведение из эксперимента осуществляли на 1, 3, 7, 14 и 30 сутки. При гистологическом исследовании подсчитывали количество миосателлитов и количество образующихся «мышечных почек» в поле зрения в зоне травмы. Иммунофлюоресцентным методом изучали активность экспрессии OxPhos Complex IV. Результаты. Установлено, что блокада р38 МАРК каскада при помощи локального введения активного вещества в составе лекарственной пленки позволила «затормозить» деление миосателлитов в ранние сроки репаративного процесса, обусловила позднее начало образования «мышечных» почек в зоне регенерации - на 7 сутки в сравнение с 3 сутками в контрольной группе, а также привела к резкому усилению окислительного фосфорилирования в зоне регенерации мышечной ткани. The aim of the study was to determine the effect of p38 MAPK inhibition on the oxidative phosphorylation system during repair of muscle tissue. Materials and methods. In the control animal group (n = 21), a wound was inflicted on the longest back muscle; then a medicinal film free of active substance was applied to the wound. In the main group (n = 21), the applied film contained a p38 MAP-kinase inhibitor, SB 203580. The animals were euthanized on days 1, 3, 7, 14, and 30. In the histological study, the number of myosatellite cells per field of view was counted in the trauma zone. The immunofluorescence method was used to study the intensity of OxPhos Complex IV expression. Results. Inhibition of the p38 MAPK cascade by local administration of the active substance formulated into the medicated film allowed «putting the brakes» on division of myosatellite cells during the early reparative process, on day 7 vs. day 3 in the control group, and also resulted in a sharp increase in oxidative phosphorylation in the regeneration zone of muscle tissue.

Myostatin stimulates myosatellite cell differentiation in a novel model system: evidence for gene subfunctionalization

Myosatellite cells play an important role in mammalian muscle regeneration as they differentiate and fuse with mature fibers. In fish, they also contribute to postnatal growth and the formation of new fibers. The relative conservation of fish systems, however, is not well known nor are the underlying mechanisms that control myosatellite cell differentiation. We therefore characterized this process in primary cells from rainbow trout and determined the effects of two known regulators in mammalian systems: IGF-I and myostatin. Unlike mammalian cell lines, subconfluent and proliferating trout myosatellite cells differentiated spontaneously and at a rate proportional to serum concentration. The expression of key myogenic markers (Myf5, MyoD1, myogenin, and MLC) and of the different myostatin paralogs (MSTN-1a/1b/2a) increased with serum-stimulated differentiation, although MSTN-1a expression was consistently higher than that of the other paralogs. In addition, MSTN-2a was only expressed as an unprocessed transcript. In low serum, where differentiation is normally suppressed, recombinant myostatin stimulated myogenic marker expression over time. The opposite was true for IGF-I as it stimulated proliferation, not differentiation, and additionally antagonized myostatin. This includes myostatin's effects on marker expression and on the autoregulation of MSTN-1a and -1b expression. These results conflict with studies using mammalian cell lines and suggest, alternatively, that myostatin is a positive, not negative, regulator of myosatellite cell differentiation. Mammalian myoblasts differentiate when confluent and with serum withdrawal, which differs considerably from how myosatellite cells differentiate in vivo. Thus the primary rainbow trout myosatellite cell culture system appears to be more physiologically relevant.