Ultrastructural cytochemical characterization of collagen-associated proteoglycans in the endometrium of mice

The decidual reaction in mice is characterized by the transformation of a s pecific population of endometrial fibroblasts into epithelioid cells, known as decidual cells. An important feature of decidualization in mice is a re markable modification of the endometrial extracellular matrix. The present work is an ultrastructural cytochemical study of matrix with the purpose of analyzing the arrangement of collagen-associated proteoglycans (PGs) at va rious regions of nulliparous endometrium and of the antimesometrial decidua of mice using the cationic dye cuprolinic blue associated with enzymatic t reatments with chondroitinase ABC, chondroitinase AC, and hyaluronidase. Th e staining with cuprolinic blue showed PGs as rods and granules of several sizes. Rods measuring 40-60 nm in length (named F2-rods) were apposed to th in collagen fibrils whereas granules were associated with thick collagen fi brils, particularly in the region occupied by mature decidual cells on the 7th day of pregnancy. The amount of granules was higher than that of F2-rod s. Both F2-rods and granules were affected by chondroitinase ABC or AC trea tment, indicating that they were PGs containing chondroitin sulfate and der matan sulfate chains. However, the granules associated with thick collagen fibrils were more resistant to chondroitinase AC treatment than F2-rods, in dicating the presence of dermatan sulfate chains that contain both L-iduron ic and D-glucuronic acid sugar residues. We suggest that the differences of the nature and amount of PGs may be associated with the changes of the thi ckness of collagen fibrils observed during decidualization of the endometri um in the mouse. Anat Rec 259:413-423, 2000. (C) 2000 Wiley-Liss, Inc.