Proliferating potential and apoptosis in the development of secondary hyperparathyroidism: a study based on Ki-67 immunohistochemical staining and the terminal dUTP nick-end labeling assay.

Secondary hyperparathyroidism (SHPT) is a common complication in hemodialysis (HD) patients. SHPT progresses from initial diffuse hyperplasia (diffuse) to early nodularity (early), then to multinodular hyperplasia (nodular), and finally to a single nodule (single) consisting of uniform parenchymal cells. We analyzed the roles of proliferation and apoptosis in SHPT progression. Seventy-four parathyroid glands from 36 HD patients with SHPT, and 10 parathyroid glands from 10 non-HD patients without SHPT were used for analysis. The former were classified as diffuse (N = 17), early (N = 22), nodular (N = 20), and single (N = 15); the latter were classified as normal (N = 10). To analyze proliferating cells we used Ki-67, and to detect apoptotic cells, we used the terminal deoxynucleotidyl transferase (Tdt)-mediated dUTP nick-end labeling (TUNEL) assay. Concerning the Ki-67 labeling index (LI), the incremental order was single, nodular, early, diffuse, and normal. Oxyphilic cells and around the central portion of each lesion were distinctly stained by Ki-67. Concerning the TUNEL LI, the incremental order was early, diffuse, nodular, single, and normal. Chief cells and around the peripheral portion of each lesion were distinctly stained by TUNEL. In the progression from early to nodular, for oxyphilic cells, the Ki-67 LI increased and the TUNEL LI decreased; for chief cells, the Ki-67 LI decreased and the TUNEL LI showed no significant change. We considered that proliferative activity increases and that the apoptosis rate decreases as SHPT progresses from diffuse to single. Moreover, the specific differences in the rate of proliferation and apoptosis between oxyphilic and chief cells might be associated with SHPT progression.