Objective: To evaluate the potential role of bcl-2 and apoptosis in the histogenesis of segmental renal dysplasia.
Materials and methods: Surgically resected specimens of dysplastic upper poles of duplex kidneys were studied from 19 patients (mean age 3.4 years, range 2 months-9 years). Bcl-2 expression was detected immunohistochemically and apoptosis was investigated using the in situ end-labelling technique (ISEL).
Results: In the histologically normal areas of the specimens, bcl-2 expression was Intense in the proximal and distal convoluted tubules, moderate in Henle's loops and weak or absent in Bowman's capsule. In contrast, in the dysplastic areas there was no or markedly reduced expression of bcl-2 in mesenchyme and tubules. In the normal areas, apoptotic cells were extremely rare (0-1 per 25 high-power fields, HPFs), whereas in the dysplastic areas, some apoptotic cells were identified both in tubules (1-2 per 25 HPF) and in mesenchyme (5-8 per 25 HPF).
Conclusions: As bcl-2 expression is required for normal kidney morphogenesis, finding no or markedly decreased expression of bcl-2 in the dysplastic areas may be related to the persistence of dysplastic fetal-type structures. Finding apoptosis adds further support to the concept that dysplasia represents arrested development at an early stage of morphogenesis before the period when bcl-2 assumes major importance.