IMMUNOHISTOCHEMICAL CHARACTERIZATION OF HUMAN ENDOMETRIAL MICROVASCULAR BASEMENT-MEMBRANE COMPONENTS DURING THE NORMAL MENSTRUAL-CYCLE

The expression of three basement membrane components [collagen IV (CIV ), laminin and heparan sulphate proteoglycan (HSPG)] and platelet endo thelial cell adhesion molecule (PECAM) were examined by immunohistoche mistry in cryostat sections of normal human endometrium. Alkaline phos phatase (ALP) was detected using enzyme histochemistry, Endometrial bi opsies from the menstrual (n = 4), mid-late proliferative (n = 5), ear ly-mid secretory (n = 5) and late secretory (n = 5) stages were collec ted from women with a normal menstrual cycle, At all four stages of th e menstrual cycle, CIV, laminin and HSPG were expressed on basement me mbranes of both vessels and glands whilst PECAM expression was localiz ed specifically to endothelial cells. A similar number of vessels/mm(2 ) stained for CIV and laminin, as well as for PECAM at each stage of t he menstrual cycle, demonstrating that all vessels in endometrium stai n for these two basement membrane components. By contrast, the number of vessels/ mm(2) that stained positively for HSPG and ALP was signifi cantly lower, averaging similar to 55% of the total that stained posit ively for PECAM, CIV and laminin. During the menstrual stage, HSPG sta ining intensity remained strong in glandular basement membranes but de creased dramatically in vascular basement membranes. ALP activity was variable in both the vessels and glands throughout the four stages of the menstrual cycle studied. This study demonstrates heterogeneity in basement membrane components within the endometrial microvasculature. It is postulated that the disappearance of HSPG from vascular basement membranes may play a role in the process of vascular remodelling duri ng the menstrual stage of the cycle.