HEAT-SHOCK PROTEINS IN HUMAN ENDOMETRIUM THROUGHOUT THE MENSTRUAL-CYCLE

Human endometrium is a steroid-sensitive tissue and there is evidence that supports the viewpoint that heat shock proteins (HSP) are implica ted in the regulation of steroid function. Therefore, in this study we examined the expression of various members of the heat shock family o f proteins in the steroid-responsive human endometrium, Western blot a nalysis revealed that the expression of HSP90 showed minimal changes t hroughout the menstrual cycle, When normalized to the amount of HSP90, the expression of HSP27, HSP60 and the constitutive form of heat shoc k protein 70 (HSC70) increased progressively during the late prolifera tive and early secretory phases, and diminished in the mid- to late se cretory and menstrual phases, In contrast, the inducible form of heat shock protein 70 (HSP70) did not undergo these changes. The cellular a nd subcellular localizations of these proteins were examined in human endometria by immunohistochemical staining, With the exception of HSP7 0, which was found primarily in the epithelial cells, the immunoreacti vity for other heat shock proteins was found in both the stroma and th e epithelium. Immunoreactivity for HSP27 was found in the lymphoid agg regates within endometrial stroma, and both HSP27 and HSP90 were found in endothelial cells, The immunoreactive heat shock proteins were fou nd in the nuclei and/or cytoplasm of cells. However, no consistent nuc lear versus cytoplasmic staining emerged, and such localization was ir respective of the site, the cell type or the phase of the menstrual cy cle, Our findings show that endometrium has a full complement of heat shock proteins, The menstrual cycle-dependent changes in the amounts o f heat shock protein suggest regulation by steroid hormones.