Morpho-functional aspects of human placental vessels.

: This study reports some morphological characteristics of human placenta that play an important physiological role in normal pregnancies. The structures were the spiral arteries, the extracellular matrix and the MHC-antigens bearing cells. We studied these important tissue compartments in 80 placentas from normal and abnormal pregnancies (affected by in utero growth-retardation), where we could hypothesize an altered pattern of the same structures. Placental specimens were evaluated using histochemistry and immunohistochemical methods, like echo-doppler and echography. Our data show uterine and spiral arteries as markedly changing during pregnancy in normal women, but surely involved in some different morphological alterations in the pathological groups. The extracellular matrix compartment is strictly related with the vascular one, both under a physiological point of view (artery resistance and sometimes blood flow inversion) and under a non-cellular component pattern. Normal specimens are rich in sialomucins, solfomucins and glycoproteins. Collagen bundles are mainly of fetal type III, by also adult type I is present at the physiological end of pregnancy. In placentas with blood supply alteration, morphological studies suggest an early aging of the extracellular matrix (with prevalence of adult type I collagen in perivascular muffs). These changes could make more difficult all the exchanges from the blood to the tissues. The immunocompetent cell population is normally well represented in placental tissue: these cells are dentritic-shaped and lie in the perivascular spaces and in the placental and villous stroma. In the altered placentas examined, we were able to identify HLA-DR+ cells that exhibit Langerhans cell markers and are strongly suggestive of an alteration of the normal immunitary relationship between fetal antigens and mother T-cell populations.