Saisho Y, Manesso E, Gurlo T, Huang CJ, Toffolo GM, Cobelli C, Butler PC. Development of factors to convert frequency to rate for -cell replication and apoptosis quantified by time-lapse video microscopy and immunohistochemistry. Am J Physiol Endocrinol Metab 296: E89 -E96, 2009. First published October 21, 2008 doi:10.1152/ajpendo.90697.2008.-An obstacle to development of methods to quantify -cell turnover from pancreas tissue is the lack of conversion factors for the frequency of -cell replication or apoptosis detected by immunohistochemistry to rates of replication or apoptosis. We addressed this obstacle in islets from 1-mo-old rats by quantifying the relationship between the rate of -cell replication observed directly by time-lapse video microscopy (TLVM) and the frequency of -cell replication in the same islets detected by immunohistochemistry using antibodies against Ki67 and insulin in the same islets fixed immediately after TLVM. Similarly, we quantified the rate of -cell apoptosis by TLVM and then the frequency of apoptosis in the same islets using TdT-mediated dUTP nick-end labeling and insulin. Conversion factors were developed by regression analysis. The conversion factor from Ki67 labeling frequency (%) to actual replication rate (%events/h) is 0.025 Ϯ 0.003 h Ϫ1 . The conversion factor from TdT-mediated dUTP nick-end labeling frequency (%) to actual apoptosis rate (%events/h) is 0.41 Ϯ 0.05 h Ϫ1 . These conversion factors will permit development of models to evaluate -cell turnover in fixed pancreas tissue.Ki67; TdT-mediated dUTP nick-end labeling; insulin; conversion factor BOTH TYPE 1 AND TYPE 2 DIABETES are characterized by a deficiency of -cells (5,6,22,30). Pancreas transplantation restores glycemic control in type 1 and type 2 diabetes (10, 26). However, given the insufficient number of pancreases available for transplantation and the risks of prolonged immunosuppression, restoration of -cells by transplantation is not a viable option for most people with diabetes.A potential alternative strategy is restoration of -cells through endogenous regeneration. Induction of diabetes in young rodents by -cell toxins or partial surgical pancreas resection has been followed by regeneration of -cell mass and reversal of diabetes (4, 40). The origin of these -cells has been actively debated: some have proposed duplication of existing -cells, and others have suggested formation of new -cells from a variety of sources (7). Although ongoing lineage studies will provide insights into the origins of -cells in mice (3,11,12,27,37), this approach is not available in humans and does not provide guidance as to the rate of -cell formation that might be anticipated in humans. Thus, although there is indirect evidence that there might be ongoing -cell formation in adult humans with type 1 diabetes (22), there is no information as to rate of -cell turnover in human pancreas. Although methods do exist for detection of -cell replication and -cell apoptosis, these methods cannot yet be used to comp...