Tamoxifen affects chronic pancreatitis-related fibrogenesis in an experimental mouse model: an effect beyond Cre recombination.

Tamoxifen is very successfully used for the induction of Cre -mediated genomic recombination in conditional mouse models. Recent studies, however, indicated that tamoxifen might also affect the fibrotic response in several disease models following administration, both in vitro and in vivo. In order to investigate a possible effect of tamoxifen on pancreatic fibrogenesis and to evaluate an optimal treatment scheme in an experimental pancreatitis mouse model, we administered tamoxifen by oral gavage to both male and female C57BL/6J mice and then waited for different periods of time before inducing chronic pancreatitis by cerulein. We observed a sex-specific and time-dependent effect of tamoxifen on the fibrotic response as measured by collagen deposition and the number of myofibroblasts and macrophages. The findings of in vitro studies, in which cerulein was administrated with or without 4-hydroxytamoxifen to stimulate primary murine female and male pancreatic stellate cells, supported our in vivo observations. Real-time PCR also indicated that this effect may be related to differences in ERα expression between female and male stellate cells. Our data demonstrate that tamoxifen administration has unignorable side effects, which affect the experimental outcome in a cerulein-based model of chronic pancreatitis in mice. We suggest a 2-week waiting period before cerulein administration to reduce side effects to a minimum for the described fibrosis model in female mice.