Histologic characteristics of lichen planus transplanted onto nude mice and cultured in vitro

[Development of precancerous lesions of oral mucous membrane diseases and oral cancer animal models]

Precancerous lesions of oral mucous membrane diseases and oral cancer are common diseases in developing countries, especially in South Asia. However, the cancerous mechanism remains unclear, and no efficient treatment and prognosis measure are currently available. Thus, precancerous lesions of the oral mucosa and oral cancer animal models must be identified to further understand their function. In this paper, we systematically review the development of oral mucosal precancerous lesions and oral cancer animal models by referring to related research.

Delayed type hypersensitivity is abnormal in patients with lichen planus

Lichen planus is characterized by the histological features of a cell-mediated attack on the epidermis. To see whether there is any defect in cutaneous immunity in non-lesional skin, we measured the response to a contact sensitizer in 17 patients with lichen planus and 27 control subjects. Sensitization was induced with 30 micrograms dinitrochlorobenzene applied to the thigh. The subjects were challenged 4 weeks later with three doses of dinitrochlorobenzene (8.8, 12.5 and 17.7 micrograms), and responses were quantified with calipers as the change in skinfold thickness at 48 h. Patients with lichen planus were significantly less responsive with smaller reactions at all challenge doses. These abnormalities suggest that the skin is abnormal in areas unaffected by the rash, and raise the possibility that there may be a primary defect in the cutaneous immune system in lichen planus.

Aged versus young skin before and after transplantation onto nude mice

The behaviour of aged skin transplanted onto nude mice was investigated to determine whether the skin maintains its histological features. Split-thickness skin grafts obtained from the unexposed skin on the thighs of healthy aged and young volunteers were grafted onto nude mice. A significant difference between the mean thickness of young versus aged epidermis was noted before transplantation (P less than 0.001). The epidermis of aged and young skin showed an increase in thickness following engraftment with a mean increase in epidermal thickness of 18.8% in the young (P less than 0.01) and 142.5% in aged skin (P less than 0.001). The number of blood vessels in the aged skin was significantly lower than in the young skin, but a remarkable increase was found post-transplantation. These findings indicate that part of the typical histological changes of unexposed aged skin are reversible.

Immunopathogenesis of oral lichen planus

Oral lichen planus (LP) is a common mucosal disorder in which cell mediated immunity is thought to play a major role. In this paper, a unifying hypothesis which attempts to integrate cellular and molecular signals in the local immune response in oral LP is presented. In this model, modified keratinocyte surface antigens are the target for the cytotoxic cell response which characterizes oral LP, whereas mast cells and antigen presenting Langerhans cells are key cellular elements in the evolving lesion. It has been established that mast cell degranulation induces adhesion molecule expression on endothelium which facilitates lymphocyte homing to the tissues. These adhesive interactions between lymphocytes and keratinocytes are postulated to be important determinants in the effector phase of the lesion. Cytokines produced by both lymphocytes and keratinocytes which influence the local immune response could promote chronicity. Accordingly, modulation of immunologic events is a potential therapeutic approach for oral LP.

Cyclosporin A inhibits directly in vivo keratinocyte proliferation of living human skin

A direct in vivo antiproliferative effect of cyclosporin A (CsA) on human epidermal keratinocytes (EK) grafted onto nude mice was evaluated. Using pulse-labeling of 5-bromo-2'-deoxyuridine (BrdU), a thymidine analogue incorporated into the nuclei of DNA-synthesizing (S-phase) cells, the antiproliferative effect of CsA was revealed as a decrease in the number of BrdU-positive human EK grafted onto nude mice receiving a daily subcutaneous injection of 50 mg/kg of CsA. The blood level of CsA in the treated mice, evaluated by a radioimmunologic assay, was 679 +/- 501 ng/ml (n = 3). Using an antibody to leukocyte common antigen, it was shown that no human lymphocytes were present in the grafted skin. Therefore, this antiproliferative effect of CsA on human EK seems to be due to a direct effect on EK rather than to lymphocyte regulation.

Mast cell density in psoriatic skin. The effect of PUVA and corticosteroid therapy

Numbers and volume fractions of mast cells in nonlesional and chronic lesional skin of psoriatic patients were compared with those of normal control skin. Mast cell densities were similar in psoriatic nonlesional and normal control skin. The superficial dermis of lesional psoriatic skin contained more mast cells than either normal or nonlesional psoriatic skin. Neither PUVA nor corticosteroid treatment for 3-4 weeks significantly reduced mast cell numbers or volume fractions in lesional skin, although both treatments clinically and histologically markedly improved the lesions. The results indicate that the initiation of the healing process in psoriatic plaques is not correlated with the mast cell density. The remaining high mast cell density may be normalized later, or after a longer therapy.