Histologic localization of surgically transplanted syngeneic seminiferous tubule segments into testis with Fast Blue as tracer.

Spermatogenesis is a complex differentiative process influenced by the testicular extratubular and intratubular tissue environments. One method of determining the relative importance of intratubular versus extratubular factors in cases of deficient spermatogenesis has been syngeneic seminiferous tubule transplantation. Generally in such a scheme, tubule segments from a testis deficient in spermatogenesis are transplanted into an intact recipient testis, and the progression of spermatogenesis in transplanted tubules is examined histologically. However, this experimental approach has been complicated by the tedious histologic serial sectioning required to locate these transplanted tubules and the need to distinguish them from recipient testis solely by structural differences. A method is described for the surgical transplantation of seminiferous tubule segments into rat testes that uses prelabeling donor tubules in vitro with the fluorescent tracer Fast Blue to facilitate their localization. The technique was evaluated by transplanting cut segments of Fast Blue-labeled seminiferous tubules from 15-day-old rat testis into normal adult rat testis (recipient), then localizing and histologically examining the progression of spermatogenesis in the transplanted tubules for up to 28 days. Transplanted tubules were easily identified in sections of recipient testis by fluorescent microscopy; intense Fast Blue staining with low background was seen up to 28 days after transplantation. Histologically, transplanted tubules had limited germ cell differentiation in recipient testis for the Fischer rat strain. At 10 days after transplantation, tubules had characteristics qualitatively similar to tubules from 25-day-old rat testis, with increased tubular diameter and abundant germ cells at the pachytene spermatocyte stage.(ABSTRACT TRUNCATED AT 250 WORDS)