The dermoepidermal junction in psoriatic skin as revealed by scanning electron microscopy

Our previous ultrastructural and immunohistochemical studies, in vivo and i n vitro, have shown important modifications of the basement membrane of pso riatic skin, which could play a key role in the alterations of keratinocyte adhesion, migration, proliferation and differentiation. In order to comple te the morphological examination of all the structures in the dermoepiderma l junction of psoriatic skin, we carried out a scanning electron microscopi c study using biopsies taken from eight psoriatic patients, The biopsies we re fixed in a mixture of 0.2% paraformaldehyde and 0.25% glutaraldehyde in 0.1 M cacodylate buffer at pH 7.4. The specimens were then frozen in liquid nitrogen and fractured following the natural cleavage planes and observed under a Jeol JSM-6301F field emission scanning electron microscope operatin g at 1.8-2.0 kV. The basal keratinocytes observed showed pore-like depressi ons on the lateral plasmalemma and villous like projections in very dilated intercellular spaces. Moreover the basal cell plasma membrane was seen to rest on the papillary dermis without interposition of the lamina densa, The detachment of some keratinocytes enabled the examination of the lamina den sa, which appeared slightly granular with numerous focal interruptions thro ugh which it was possible to observe the underlying collagen fibres, These findings, together with previously reported findings, support the hypothesi s that in psoriasis molecular and structural alterations of the dermoepider mal junction are present, that could fundamentally alter the regulation of the cytomorphological processes and the normal functions of the basement me mbrane.