Sarcopenia is an age-related degenerative skeletal muscle disorder characterized by the loss of skeletal muscle mass and function during aging.Sarcopenia can impair the elderly's ability to perform daily activities and is associated with high risks of falls,fractures,and hospitalization.It seriously affects the quality of life of the elderly and becomes one of the major health problems in the aging society.Skeletal muscle stem cells,also known as muscle satellite cells,play a key role in supporting muscle regeneration and homeostasis maintenance.Studies have suggested that muscle satellite cell functions are tightly regulated by microenvironment signals in the skeletal muscle.Of note,skeletal muscle fibers,serving as an immediate niche of muscle satellite cells,regulate their activation,proliferation,and self-renewal.This article reviews the research progress in the regulatory roles of skeletal muscle stem cells and their microenvironment in sarcopenia during aging,providing theoretical support for potential treatment of sarcopenia via modifying skeletal muscle microenvironment and regulating muscle satellite cell functions.
Sarcopenia/physiopathology* ; Humans ; Satellite Cells, Skeletal Muscle/physiology* ; Muscle, Skeletal/physiopathology* ; Aging/physiology* ; Animals ; Stem Cells

OBJECTIVETo study the effects of skeletal muscle satellite cells implanted into infarcted myocardium on the volume of remnant myocytes.

METHODSThirty-six adult mongrel canines were divided randomly into implantation group and control group. In the implantation group, skeletal muscle satellite cells taken from the gluteus maximus muscles of the dogs were cultured, proliferated and labeled with 4',6-diamidino-2-phenylindone (DAPI) in vitro. In both groups, a model of acute myocardial infarction was established in every dog. In the implantation group, each dog was injected with M199 solution containing autologous skeletal muscle satellite cells. The dogs in the control group received M199 solution without skeletal muscle satellite cells. The dogs of both groups were killed 2, 4 and 8 weeks after implantation (six dogs in a separate group each time). Both infarcted myocardium and normal myocytes distal from the infracted regions isolated were observed under optical and fluorescent microscope. Their volumes were determined using a confocal microscopy image analysis system and analyzed using SAS. A P < 0.05 was considered significant.

RESULTSA portion of the implanted cells differentiated into muscle fiber with striations and were connected with intercalated discs. Cross-sectional area and cell volume were increased in normal myocardium. Hypertrophy of remnant myocytes in the infarcted site after skeletal muscle cell implantation was much more evident than in the control group. Cross-sectional area, cell area and cell volume differed significantly from those of the control group (P < 0.05). Hypertrophy of the cells occurred predominantly in terms of width and thickness, whereas cell length remained unchanged.

CONCLUSIONSkeletal muscle satellite cells implanted into infarct myocardium, could induce the hypertrophy of remnant myocyte cells in the infarcted site and could also aid in the recovery of the contractile force of the infarcted myocardium.

Animals ; Cell Size ; Dogs ; Myocardial Infarction ; pathology ; Myocardium ; pathology ; Myocytes, Cardiac ; cytology ; Random Allocation ; Satellite Cells, Skeletal Muscle ; cytology ; physiology

OBJECTIVETo study the effect of different access routes on autologous satellite cell implantation to stimulate myocardial regeneration.

METHODSSatellite cells were procured from skeletal muscle (gluteus max) of adult mongrel canine, cultured, proliferated and labeled with 4', 6-diamidino-2-phenylindone (DAPI) in vitro. The cells were autologously implanted into the site of acute myocardial infarction by local injection or perfusion through the ligated distal left anterior descending coronary artery. Specimens were harvested 2, 4 and 8 weeks later for histological study.

RESULTSThe labeling efficiency of satellite cells with DAPI was close to 100%. Fluorescent cells were found at the infarcted zone, papillary muscle and local injection site. Some of these cells had progressively differentiated into striated muscle fibers connected to intercalated discs. The infant cells appeared different from the mature myocardium under an electron microscope. Satellite cells implanted by perfusion through the coronary artery were arranged in order of consistency with host myocardial fibers. The satellite cells, implanted by local injection, were found growing in a disordered way.

CONCLUSIONSatellite cells, implanted by coronary artery perfusion, can progressively differentiate into striated muscle fibers, arranging in order and disseminating over the infarcted zone. This approach seems more favorable for the recovery of myocardial contractile function than that of local injection.

Animals ; Cell Differentiation ; physiology ; Dogs ; Myocardial Infarction ; pathology ; therapy ; Myocardium ; cytology ; Regeneration ; Satellite Cells, Skeletal Muscle ; cytology ; transplantation ; Transplantation, Autologous