Immunohistological Localization of Peroxisome Proliferator-Activated Receptor α and γ in Human Sebaceous Glands.

The immunohistological localization of peroxisome proliferator-activated receptor a (PPARa) and PPAR g was examined in 28 pilosebaceous units in 10 paraffin-embedded normal human skin specimens. Rabbit polyclonal antibody against human PPARa and monoclonal antibody against human PPARg were used as specific primary antibodies. The nuclear and cytoplasmic expression of PPARa was detected in basal to differentiated sebocytes. In contrast, the expression of PPARg was confined to nuclei of suprabasal to early-differentiated sebocytes. The nuclear PPARg expression was present only occasionally in the basal sebocytes. These results suggest that PPARa and PPARg are integral parts of sebocyte differentiation in human sebaceous glands.

Overexpression of p16(INK4a) in Mastocytosis (Urticarial Pigmentosa).

The expression of p16(INK4a) has been reported to induce cell-cycle arrest and cellular senescence. The p16(INK4a) expression has never been examined in human mast cells and mastocytosis. We immunohistologically examined the expression of p16(INK4a) and tryptase in 5 normal human skin and 4 mastocytosis. In normal mast cells, only 5.9 ± 3.4 (mean ± standard deviation) % of tryptase-positive mast cells coexpressed p16(INK4a). However, significantly higher percentage (86.0 ± 14.1%) of tryptase-positive tumor cells was immunoreactive to p16(INK4a) in all of 4 mastocytosis. The p16(INK4a) overexpression may induce the senescence of neoplastic mast cells to undergo spontaneous regression of mastocytosis.