Simultaneous accumulation of hyaluronan binding protein 1 (HABP1/p32/gC1qR) and apoptotic induction of germ cells in cryptorchid testis.

In the experimentally cryptorchid rat, spermatogenic arrest is associated with the formation of multinuclear giant cells, leading to large-scale apoptosis and elimination of germ cells from the seminiferous epithelium. Using this model, the role of Hyaluronan Binding Protein 1 (HABP1), which expresses a stage specifically in post-meiotic cells during spermatogenesis, was examined. Cryptorchidism induced complete arrest of spermatogenesis by 2 days, and by 3-5 days many large and small multinucleated giant cells populated the affected tubules. Ultrastructure of the giant cells revealed both single and multiple chromatin aggregation, with some less compact and distorted, and others broken down into tiny fragments. These cells along with other germ cells were stained terminal deoxynucleotidyl transferase dUTP nick-end labeling positive, demonstrating strong expression of Bax and Heat Shock Protein 70. Simultaneously, there was an up-regulation of the proprotein form of HABP1 in these cells and a decrease in the mature form of protein. The above findings indicate a possible role for HABP1 proprotein in apoptosis induction of germ cells in the cryptorchid testes.