Expression of both oestrogen receptor alpha and beta in human skeletal muscle tissue

There are two oestrogen receptors (ERs), ERα and ERβ. ERβ protein is expressed in human skeletal muscle in the nuclei of both myofibres and endothelial cells, whether ERα protein is present in this tissue is unknown. We studied the expression of ERα protein in human skeletal muscle biopsies taken from vastus lateralis from four men, four women, two children and two postmenopausal women. Immunohistochemistry was used to determine the proportions of nuclei that were positively stained for ERα, the proportion of ERα-positive nuclei located in the muscle fibres and in capillaries and to test for possible co-expression of ERα and ERβ. Both ERs were expressed in all subjects. Of all nuclei, 63% stained for ERα with no sex difference. ERα was localised both in myofibres and in endothelial cells of the capillaries, 25% of the ERα-positive nuclei were located in the capillaries. ERα and ERβ were generally expressed in the same nuclei. The present study shows for the first time the expression of ERα protein in human skeletal muscle independently of age and sex. These results might improve understanding of the physiological role of oestrogen in human skeletal muscle and raise new questions about activation of ERs in skeletal muscle.