Ageing of human epidermis: the role of apoptosis, Fas and telomerase.

BACKGROUND: Aged human epidermis is characterized by morphological changes including flattening of the dermal-epidermal junction and a decrease in thickness. OBJECTIVES: To determine the roles of proliferation, apoptosis, Fas (CD95), Fas ligand (FasL) and telomerase in changes of human epidermis during ageing. METHODS: Human epidermis from aged subjects (n = 14; mean age 70.7 years) and young subjects (n = 14; mean age 23.4 years) was studied by histology, immunohistochemistry, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labelling assay for apoptotic cells and reverse transcription-polymerase chain reaction to determine epidermal thickness, proliferation (Ki-67), apoptosis, expression of Fas and FasL, and telomerase activity. RESULTS: Aged skin was associated with thinning of the epidermis, decreased proliferation, and increased apoptosis below the granular layer. This was associated with increased epidermal expression of Fas and FasL. Telomerase activity was similar in aged and young epidermis. CONCLUSIONS: Fas/FasL-mediated apoptosis, along with decreased proliferation, may have a role in changes of human epidermis during ageing. Telomerase activity did not appear to be limiting in young vs. old human epidermis.

Melanocyte-associated T cell epitopes can function as autoantigens for transfer of alopecia areata to human scalp explants on Prkdc(scid) mice.

Alopecia areata is a tissue restricted autoimmune condition affecting the hair follicle, resulting in hair loss. The goal of this study was to test the hypothesis that the autoantigen of alopecia areata is melanocyte associated. Potential autoantigens were tested in the human scalp explant/Prkd(scid) CB-17 mouse transfer system. Scalp T cells from lesional (bald) alopecia areata scalp were cultured with antigen-presenting cells, and antigen, along with interleukin-2. The T cells were then injected into autologous lesional scalp grafts on SCID mice, and hair regrowth was measured. Hair follicle homogenate was used as an autoantigen control. T cells cultured with melanoma homogenate induced statistically significant reduction in hair growth (p <0.01 by ANOVA). HLA-A2-restricted melanocyte peptide epitopes were then tested with lesional scalp T cells from HLA-A2-positive alopecia areata patients. Melanocyte-peptide-activated T cells significantly reduced the number of hairs regrowing in two experiments with six patients (p <0.001 by ANOVA). Injected scalp grafts showed histologic and immunochemical changes of alopecia areata. The most consistent peptide autoantigens were the Gp100-derived G9-209 and G9-280 peptides, as well as MART-1 (27-35). Melanocyte peptide epitopes can function as autoantigens for alopecia areata. Multiple peptides were recognized, suggesting epitope spreading.

Alopecia areata is a T-lymphocyte mediated autoimmune disease: lesional human T-lymphocytes transfer alopecia areata to human skin grafts on SCID mice.

Much evidence suggests that alopecia areata is a tissue restricted autoimmune disease. Alopecia areata responds to immunosuppressive agents, and is associated with other tissue restricted autoimmune diseases, including autoimmune thyroiditis and vitiligo. Furthermore, hair regrows when involved scalp is transplanted to nude mice. This study was undertaken to determine whether alopecia areata is mediated by T lymphocytes. Involved scalp from alopecia areata patients was grafted onto SCID mice. Additional biopsies from lesional scalp of the same patients were used to isolate T lymphocytes. These T lymphocytes were cultured with hair follicle homogenate, as well as autologous antigen presenting cells. The T lymphocytes were then injected into autologous scalp grafts on the SCID mice, which had regrown hair. Injection of scalp T lymphocytes resulted in hair loss. Hair loss was associated with the histologic and immunochemical changes of alopecia areata, including perifollicular infiltrates of T cells, along with HLA-DR and ICAM-1 expression by the follicular epithelium. Scalp T lymphocytes that had not been cultured with hair follicle homogenate did not have this effect. Preliminary data suggests hair loss requires a collaboration between CD8+ and CD4+T cells. These studies have demonstrated that alopecia areata can be induced by the transfer of T cells that recognize a hair follicle autoantigen.