Structural changes of the villous core in diabetic placenta

Introduction: Maternal diabetes mellitus represents a serious complication of pregnancy associated with increased maternal and fetal risks. Metabolic disturbances of diabetic mother have also an impact on the placental structure. Structural changes are characterized as delayed villous maturation, which includes among other great variability of villous vascularity. It is manifested by focal occurrence of either large and strikingly hypovascular villi or large hypervascular villi.

In our previous papers we demonstrated the following. First, the villous capillary bed of term placenta is commonly branched. Second, that signs of both the longitudinal and sprouting capillary growth are present till the end of pregnancy. Third, that the villous capillary bed is more complicated due to enhanced capillary branching in placentas from pregnancies complicated by gestational as well as type 1 maternal diabetes mellitus.

Aim: In this work, normal placental terminal villi and pathological villi of diabetic placentas were compared concerning the spatial arrangement of villous capillary bed and some structural parameters of villous stroma.

Material and methods: Formalin fixed and paraffin embedded specimens of normal term placentas and term placentas from pregnancies complicated by type 1 maternal diabetes were used for picrosirius staining, vimentin and desmin immunohistochemistry and confocal microscopy. 3D models of villi and villous capillaries were constructed from stacks of confocal optical sections.

Results: Pathological villi of diabetic placenta displayed changed stromal architecture. The mantle of collagen fibrils surrounding capillaries was thinner and stromal collagen network was markedly rare. Desmin filaments were decreased or even absent in bodies and projections of stromal cells, whereas the detection of vimentin showed that it is confined to cells constituting the capillary wall and to stromal cells and their projections in normal as well as pathologically changed villi. In hypovascular villi, capillaries had a smaller diameter and displayed a markedly wavy course, in hypervascular villi, numerous capillaries of large diameter occurred in highly reduced stroma.

Conclusions: Maternal diabetes mellitus influences the placental structure in a complex manner. The stromal architecture of pathological terminal villi shows changed configuration, which is favourable for development of altered capillary arrangement, i.e. more waved course or enlarged diameter, both supporting enlargement of the total area of capillary wall.

Project is supported by the Research Programme of Charles University.