Surface visualisation of tissue interfaces by scanning electron microscopy. Methods for exposure of the basal lamina and associated structures in human amnion

Tissue interfaces such as basal lamina have been traditionally investigated in transmission electron microscopy by sections cut vertical to the lamina, presenting information restricted to a single ultrathin plane. In order to overcome this limitation, a methodology for surface visualisation of the underside cell membranes of the amniotic epithelium, the upper and lower basal lamina surfaces, and their relationship to the stromal collagen has been devised. This involves alkaline, detergent or enzymatic loosening and/or removal of the epithelial monolayer prior to fixation, followed by dry fracture after critical point drying. In this way we have visualised large areas of all interfaces and the inter-relationships between these elements during the process of stromal collagen production by the amniotic epithelial cells.