Inhibition Of Myogenesis Research Articles

Expression of a developmentally regulated antigen on the surface of skeletal and cardiac muscle cells.

H36 is a species-specific, cell-surface antigen on differentiating newborn rat skeletal myoblasts and myogenic lines. This membrane antigen has been defined by a monoclonal antibody raised by the fusion of SP 2/0-Ag14 myeloma cells with spleen cells from mice immunized with myotubes derived from the myogenic E63 line. H36 antigen, isolated by immunoaffinity chromatography, is comprised of two polypeptides with apparent molecular weights of 98,000 and 117,000. Fluorescence photometry and radioimmunoassays have been used to follow quantitative and topographic changes in the H36 determinant during myogenesis. H36 is present at a basal level on replicating myoblasts; it increases on prefusion myoblasts and persists on myotubes. At or near the time of prefusion, it becomes concentrated between adjacent aligned myoblasts and localized on membrane "blebs". H36 is present on both skeletal and cardiac cells but absent from a variety of cells that include fibroblasts, neuronal cells, and smooth muscle. There are approximately 4 x 10(5) determinants per myoblast, and the Ka of the antibody is 3.8 x 10(8) liters/mol. The distributions of H36 on the top and attached surfaces of myoblasts and myotubes are distinct, which suggests localized specialization of these surfaces. H36 is an integral membrane component and upon cross-linking, it associates with the detergent-insoluble cytoskeletal framework. Inhibition of myogenesis by 5-bromodeoxyuridine or by calcium deprivation prevents the developmentally associated changes in the expression of H36. H36 is also absent or markedly reduced on the fu- and Ama102 developmentally defective mutant myoblast lines. We conclude that H36 is a muscle-specific, developmentally regulated cell-surface antigen that may have a role in myoblast differentiation and that can be used to determine the embryonic lineages of skeletal and cardiac muscle.

Inhibition of myogenesis by trifluoperazine and compound [formula omitted

When trifluoperazine (TFP), a calmodulin antagonist, was given to chick or rat myoblasts in cultures, formation of multinucleated myotubes was inhibited. The inhibition of cell fusion by TFP in rat cultures prevents the normal increase in the amount of acetyl-choline receptors (AChR) and creatine kinase (CK), while the levels of these proteins in chick muscle cultures are hardly affected. Another calmodulin antagonist, compound 48 80 , inhibits fusion at doses that correspond closely to its antagonistic effects on calmodulin. Thus, our results suggest a possible role for calmodulin in the regulation of myoblast fusion, but not on the appearance of muscle proteins.

Culturing chick muscle cells on glycosaminoglycan substrates: Attachment and differentiation

The effects of different glycosaminoglycans (GAGs) on myogenesis were tested by culturing embryonic chick myoblasts on tissue culture dishes to which either hyaluronic acid (HA) or chondroitin sulfate (ChS) was covalently bound. Both in cell number and in apparent cell type distribution, the population of cells bound to GAGs is similar to that on gelatin and significantly different from that observed with uncoated dishes. When plated on ChS, myoblasts proliferate, align, and fuse at a rate similar to cells plated on gelatin. The final fused cells appear as sheets rather than long, thin myotubes. On HA, the cells proliferate but are inhibited from differentiation. The extent of inhibition is dependent on the amount of HA present. The inhibition of myogenesis is maintained through four subcultures on HA, but can be reversed at any time by culturing cells on gelatin. These experiments indicate that different GAGs have different effects on myogenesis and that HA can actively inhibit the process.

Inhibition of muscle cell development in culture by cells from spinal cord due to production of low molecular weight factor

Relatively small numbers of cells cultured from chick embryo spinal cord had the property of inhibiting muscle cell growth and differentiation, as measured by protein synthesis, myoglobin synthesis, and myotube formation, when they had been in culture 4 days before the addition of dispersed muscles cells. Inhibition of pectoral white muscle and thigh red muscle development in culture was similar. Inhibition of this sort was not brought about by similar cocultivation with cells from liver, gizzard, intestine, lung, or skin, although skin cultures were slightly inhibitory. Simultaneous cocultivation of muscle and cord cells failed to result in inhibition of myogenesis. The inhibitory property was present in the medium, and inhibition was reduced by removal of conditioned medium and replenishment with fresh medium before introduction of myoblasts. Medium obtained from other tissues, similarly cultured, did not possess inhibitory properties. The inhibitiory properties of “cord-conditioned” medium were related to a factor or factors able to be concentrated by lyophilization and of relatively low molecular weight, as measured by membrane ultrafiltration and gel filtration chromatography. The nature of the cell type in spinal cord, e.g., neuronal glial, responsible for the production of this factor is not known.

Potential Nitric Oxide Treatment for Alleviating Muscle Atrophy in Hindlimb-Suspended Mice

Muscle atrophy is a debilitating condition that results from muscle disuse and aging. It is often experienced by people who are sedentary or elderly and cannot be effectively treated or prevented. Since nitric oxide (NO) activates muscle stem cells, this study aimed to test the hypothesis that treatment with a NO-donor drug, isosorbide dinitrate, during hindlimb suspension for 18 days, can alleviate muscle atrophy. Muscles in unloaded lower and weight-bearing upper limbs were weighed to study muscle loss. Western blots were used to measure protein levels in experimental (suspended and treated-suspended) and age-matched control groups of young (3 weeks old) and adult (6-8 weeks old) mice. Protein levels of atrogin-1, myostatin, and myosin heavy chain isoforms were analyzed (relative to ß-actin) for changes expected with muscle atrophy. Analysis of variance was used to determine if changes were statistically significant. The weight of unloaded muscles (quadriceps and soleus) in NO-treated-suspended mice tended to increase towards that of the control mice, compared to the atrophy after suspension without treatment. In the same muscles of young and adult suspended mice, NO treatment decreased atrogin-1, a negative regulator of muscle mass (p<0.05 for quadriceps). A precursor protein of myostatin, an inhibitor of myogenesis, showed the same trend. Results suggest that NO treatment has the potential to attenuate muscle-disuse atrophy, with possible significance to preventing atrophy with aging or space travel. This research is supported by the University of Manitoba Research Grant Program (JEA) and NSERC Undergraduate Student Research Award (AZ).