Internal organization of plasma membranes during the acantholytic process. A freeze-fracture study

Internalization of gap junctions in benign familial pemphigus (Hailey-Hailey disease) and keratosis follicularis (Darier's disease)

Hereditary skin disorders involving acantholysis, such as Hailey-Hailey disease and Darier's disease, have been genetically linked to distinct chromosomal parts which do not code for known structural proteins. Such evidence suggests that the genomic abnormalities underlying these dermatoses may concern functional/regulatory mechanisms of keratinocyte cohesion. Epidermal communication junctions (gap junctions) are responsible for direct coupling of cells and, thus, co-ordinate the behaviour of keratinocytes within the tissue. Consequently, they remain one of the potential, and poorly studied, elements in the pathogenesis of hereditary acantholytic diseases. We have investigated the distribution and fate of gap junctions during non-immune acantholysis, using fine immunolocalization methods at the light and electron microscopic levels. Our results demonstrate normal expression of epidermal gap junction proteins, connexins 26 and 43, in non-lesional skin of Hailey-Hailey and Darier's diseases. The gap junctions were not primarily dismantled during acantholysis, typical of both of the studied dermatoses, but underwent internalization and subsequent cytoplasmic dispersion in the portions of cells which were no longer attached to the rest of the tissue. In Darier's disease, perifollicular acantholysis did not specifically concern epithelium of appendages coexpressing connexin 26 in addition to connexin 43, further indicating that the observed changes in gap junction localization were secondary to the loss of cell-cell contact. We demonstrated that the sequence of changes was identical in both diseases and that the previously described putative differences were apparently related to the degree of acantholysis present in the studied biopsies. The fate of the junctional structures and proteins, documented in the present study, is most probably a form of recycling process also used by normal keratinocytes during organogenesis and tissue differentiation.

Carbon dioxide laserabrasion: a new approach to management of familial benign chronic pemphigus (Hailey-Hailey disease)

Familial benign chronic pemphigus (FBCP), or Hailey-Hailey disease, can be a debilitating condition. Treatment is palliative and only excision of lesional skin followed by split-thickness grafting may be curative. The success of surgery is attributed to the removal of adnexal structures and a decrease in sweating and maceration. This is the first report of successful carbon dioxide (CO2) laserabrasion of a patient with FBCP. The procedure spared the underlying adnexae which contributed to the reepithelialization of the epidermis. The selective destructive property of the CO2 laser may contribute to understanding the pathophysiology of FBCP.

Freeze-fracture replication technique of human skin

The freeze-fracture replication technique represents one of the most advanced methods for studying the ultrastructure of biological tissues and has given a new dimension to the ultrastructure research. This technique makes it possible to obtain a cast of a fracture surface of frozen preparations. Apart from allowing samples to be examined without being dehydrated, i.e. under conditions very close to those of living state, it has proved especially useful for the analysis of many tissue functions concerned with membrane activity and exchanges between cells and their disturbance in specific disease conditions. Even through good quality replicas had already been obtained back in 1961 (Moor et al. 1961), only after 1970, mainly thanks to the contribution made by Breathnach and his collaborators (Breathnach et al. 1972, Breathnach 1973, Breathnach et al. 1973) was the freeze-fracture replication technique successfully used in the study of the skin, since this tissue had proved especially difficult to process. In this review paper, technical principles will be summarized and the most important findings so far obtained in the study of normal and pathologic skin will be illustrated.

Freeze-fracturing of oral epithelial cells in pemphigus

Biopsies from the oral mucosa of three patients (two with pemphigus vulgaris and one with pemphigus erythematosus) were taken for both freeze-fracturing and thin-sectioning studies. Oral mucosa from a clinically healthy volunteer was used as control. The samples collected from both the involved and uninvolved oral mucosa of pemphigus patients showed widened intercellular spaces and fewer than normal desmosomes. Thin sections showed a random distribution of tonofilaments. However, in freeze-fracture replicas tonofilaments were arranged in thick bundles with a slightly coiled orientation. In freeze-fracture replicas of samples from a pemphigus patient in remission no difference was found in the number of particles on both fracture faces.