Leptin Immunohistochemical Expression in situ during the Differenciation of Orbital Adipose Tissue in Human Fetuses

Abstract

Abstract: : Purpose: to study with histochemical and immunohistochemical techniques the developmental topography of orbital structures and regarding this topography, to follow the expression of differenciation markers in orbital adipose tissue in human fetuses. Methods: The study was performed with fetuses obtained in legal pregnancy termination. Twenty five orbits were excised from fetuses (range 10 to 37 weeks) fixated in formolin and then frozen in liquid nitrogen. Semi-serial frozen sections were realised for Oil Red O coloration and classical histological staining techniques. Then we selected sections with preadipose cells containing lipid droplets and we performed in the following sections immunohistological methods using specific leptin antibodies. Results: In our early fetuses the muscular cone disposition was present with no preadipose cells differenciation. We only observed in 17 weeks fetuses, lipoblasts with small fat vacuoles. At 23 weeks, the Oil Red O staining maturing lipoblasts. We observed also immunostaining for leptin in older fetuses in the cytoplasm of adipose cells.Adipose structures started around vascular buds with concomitant apparition in intra and extra conic areas. We compared this orbital fat pad development to other adipose tissues development of the body (abdominal subcutaneous adipose tissue and plantar fat pad). In the oldest fetuses (30 to 37 weeks) we defined the orbital topography and structure of the adipose tissue comparing with orbital structures as muscular cone, lacrimal gland, optic nerve and vessels. Conclusions: This developmental orbital analysis can be useful in oculoplastic surgical applications with orbital fat removal. The interest of a 3D cartography of the orbit and of the differenciation of orbital adipose tissue can help in a better understanding of orbital decompression surgery and in medical approach of Graves' disease

Keywords: microscopy: light/fluorescence/immunohistochem • anatomy • orbit