[Role of apoptosis in the progression of secondary hyperparathyroidism]

In many tissues, cell proliferation is counterbalanced by apoptosis. Hyperparathyroidism is one of the most important complications in long term dialysis patients and is characterized by remarkable cell proliferation of parathyroid cells. Therefore, alteration in the regulation and clearance of excess cells by apoptosis may occur in hyperparathyroidism. In the present study, we evaluated the expression of Ki-67 (proliferative cell associated protein) and Bcl-2(apoptosis-preventing molecules), and the number of apoptotic cells in the nodular lesion of parathyroid glands with secondary hyperparathyroidism(2 degrees HPT), as compared with primary hyperparathyroidism(1 degree HPT) for clarification of the role of apoptosis in the development of 2 degrees HPT. The number of Ki-67+ cells was remarkably increased in 2 degrees HPT(12.02 +/- 10.87, mean +/- SD) compared to in 1 degree HPT(0.81 +/- 0.53) (p < 0.01). However, the number of apoptotic cells was significantly decreased in 2 degrees HPT(0.10 +/- 0.06) compared to in 1 degree HPT(0.31 +/- 0.19) (p < 0.05). To the contrary, Bcl-2+ cells were increased in 2 degrees HPT(0.35 +/- 0.23) compared to in 1 degree HPT(0.10 +/- 0.13) (p < 0.05). These results suggest that the mechanisms of parathyroid cell proliferation are different in each nodular lesion of 1 degree HPT and 2 degrees HPT. Furthermore, the remarkable proliferation of parathyroid glands may have been due to the reduction of the apoptotic process via Bcl-2 expression in 2 degrees HPT.