Lost in translation: The search for an in vitro screen for spermatogenic toxicity.

The last two decades have seen an increasing search for in vitro models that can replace the use of animals for safety testing. We adapted the methods from a recent nonquantitative report of spermatogenesis occurring in ex vivo mouse testis explants and tried to develop them into a screening assay. The model consisted of small pieces of neonatal mouse testis (testis "chunks"), explanted and placed on pillars of agarose or chamber inserts, and cultured at the air-liquid interface.

In vitro differentiation of rat spermatogonia into round spermatids in tissue culture.

Study Question: Do the organ culture conditions, previously defined for in vitro murine male germ cell differentiation, also result in differentiation of rat spermatogonia into post-meiotic germ cells exhibiting specific markers for haploid germ cells?

Summary Answer: We demonstrated the differentiation of rat spermatogonia into post-meiotic cells in vitro, with emphasis on exhibiting, protein markers described for round spermatids.

What Is Known Already: Full spermatogenesis in vitro from immature germ cells using an organ culture technique in mice was first reported 5 years ago. However, no studies reporting the differentiation of rat spermatogonia into post-meiotic germ cells exhibiting the characteristic protein expression profile or into functional sperm have been reported.

Primary cell cultures for understanding rat epididymal inflammation.

Treatment-induced epididymal inflammation and granuloma formation is only an occasional problem in preclinical drug development, but it can effectively terminate the development of that candidate molecule. Screening for backup molecules without that toxicity must be performed in animals (generally rats) that requires at least 2 to 3 weeks of in vivo exposure, a great deal of specially synthesized candidate compound, and histologic examination of the target tissues. We instead hypothesized that these treatments induced proinflammatory gene expression, and so used mixed-cell cultures from the rat epididymal tubule to monitor the induction of proinflammatory cytokines.

Comparative assessment of the timing of sexual maturation in male Wistar Han and Sprague-Dawley rats.

Given the increasing use of Wistar Han (WH) rats in regulatory toxicology studies, these studies were performed to characterize the onset of sexual maturation in maturing WH rats as compared to Sprague-Dawley (SD) rats. Beginning on postnatal day (PND) 38 through PND 91 groups (n=8) of untreated WH rats were evaluated for maturation of the male reproductive system. Testicular spermatid head counts increased beginning on PND 42 until PND 70.

Isoflurane reduces motile sperm counts in the Sprague-Dawley rat.

Animal and care use practices are constantly evolving. These can have unexpected consequences on the data collected from such procedures. One example is the recent change in our animal facility, based on recommendations from the Newcastle Consensus Meeting on Carbon Dioxide Euthanasia of Laboratory Animals, from CO(2) to isoflurane for anesthesia.