Effects Of One-time Exhaustive Exercise And Contusion On Skeletal Muscle Satellite Cells And Hepatocyte Growth Factor In Rat

Objective:The purpose of this paper was to investigated effects of one-time exhaustive exercise and contusion on skeletal muscle satellite cells and hepatocyte growth factor(HGF) in rat.Methods:24male wistar rats of6-week-old were randomly divided into4groups:control group(C), and immediately after exhaustive exercise group (Exhaustiive, EO),24h group (E24),48h group (E48).The one-time exhaustive exercise group performed an exhaustive downhill running to exhaustion state.The exhaustive exercise group and the control group were anesthetized with20%urethane by an intraperitoneal injection at different time points after the last exhaustive exercise and in a quiet state.5ml bloods sample was taken from the abdominal aorta to make serum, and the serum was used to measure the hepatocyte growth factor contents. A side of the rectus femoris muscle sample was fixed with2.5%glutaraldehyde for producing ultrathin sections used to observe the ultrastructural changes by transmission electron microscope. The other side was reserved in liquid nitrogen to measure the hepatocyte growth factor contents.Another4adult rats was divided into4groups:control group, Immediately after contusion group (Contusion, D0),24h group (D24),48h group (D48). At different time points after contusion, a side of the rectus femoris muscle samples were fixed with2.5%glutaraldehyde for producing ultrathin sections used to observe the ultrastructural changes by transmission electron microscope. The other side of the vastus lateralis muscle for culture of satellite cells.Another neonatal rat’s vastus lateralis also used for culture of muscle satellite cells.Results:1)After one-time exhaustive exercise, exhaustive exercise group’s(E0, E24, E48) skeletal muscle ultrastructural structure was siginificiantly changed:①The myofibril became thinner and more incompact.H band and I band took ill-defined.M lines and Z lines blurred.Z lines were flowed distorted and disappeared;②uscle gap widened with an interstitial edema;③Endoplasmic reticulum slightly deformed, or even twisted;④Some matrix become shallow, and mitochondrials were obviously deformed, distorted and even swollen.With time extending,the damage of the exhaustive exercise group’s muscle cell was more and more heavy.2)The contusion group’s (DO, D24,D48) skeletal muscle structure was also siginificiantly damaged.①The myofibril disordered;②Muscle cell membrane was protrusions or incomplete;③Some matrix became shallow, and the size of mitochondrials were obviously inequality,swelling or shrinkage.Mitochondrials were maldistributed and blurred;④The muscle were into vacuolation, granular degeneration and hyaline degeneration. With time extending, The damage of the contusion group’s muscle cell was more and more heavy.3)ELISA results showed that the HGF content in skeletal muscle increased significiantly after an one-time exhaustive exercise.the HGF contents in the exhaustive exercise groups (E0, E24, E48) increased significiantly(P<0.01) compared with the control group.On the other hand, the HGF content in serum in the exhaustive exercise groups (E0, E24, E48) also increased significiantly(P<0.01) compared with the control group.4) By oberserving the cultivation of satellite cells in vitro during contusion and recovery,the number of satellite cells in contusion group (D0, D24, D48) was more than control group. And with the elapse of time after contusion,the number of satellite cells showed a trend of increase. Then the cells showed stronger proliferation capacity in the process of cultivation. On the other hand,the absolute content of skeletal muscle satellite cells in neonatal rat’s muscle tissue was less than the adult rat’s, but neonatal rats have higher satellite cells content in each unit of skeletal muscle than adult rat. The skeletal muscle atellite cells in neonatal rat’s tissue showed stronger proliferation capacity. Contusion can activate the dormant skeletal muscle satellite cells (SCConclusions:1)The results by electron microscopy showed as follow:one-time exhaustive exercise can cause significant changes in the ultrastructure of skeletal muscle. The myofibril disorder.Endoplasmic reticulum with slight deformed, or even twisted. Mitochondrials were obviously deformed, distorted and even swollen. With time extending,the damage degree of the exhaustive exercise group’s skeletal muscle cell was more and more heavy.On the other hand, contusion can caused significant changes in the ultrastructure of skeletal muscle, With time extending, the damage degree of the contusion group’s skeletal muscle cell was also more and more heavy.2) The contents of hepatocyte growth factor(HGF) in rat’s serum and in skeletal muscle were significiantly increased in exhaustive exercise groups (E0、E24、E48).It indicated that hepatocyte growth factor(HGF) may accelerate the soft tissue, vascular repair and activate dormant skeletal muscle satellite cells (SC). 3) The number of satellite cells in contusion group (D0, D24, D48) was more than control group. And with the elapse of time after contusion,the number of satellite cells showed a trend of increase. Then the cells showed stronger proliferation capacity in the process of cultivation.Contusion can activate the dormant skeletal muscle satellite cells(SC).In addtition,the content of skeletal muscle satellite cells in neonatal rat’s muscle tissue was bigger than the adult rat’s in each unit,and showed stronger proliferation capacity.