Spermiation in the Mouse: Contribution of the Invading Sertoli Cell Process to Adluminal Displacement of the...

At the maturation phase of spermiogenesis in mice, the spermatid heads that are embedded deeply in the epithelium of the seminiferous tubules dislocate toward the luminal surface. In the present study, to clarify the manner in which the spermatid head is displaced toward the lumen, morphological changes in spermatids and Sertoli cells were examined on ultrathin and thick sections stained with adenosine triphosphatase cytochemistry. During adluminal displacement, the spermatid head is surrounded by an invading process of Sertoli cell which invaginates into the spermatid cytoplasm to form complicated passages called the canal complex. At the site of the spermatid head, the wall of an invading Sertoli cell process folds to form a sheath in which the spermatid head is located. The sheath correspond to a structure known as ectoplasmic specialization. The invading Sertoli cell process also shows branching and swelling at the site where spermatid heads are present. The present results suggest that the canal complex is directly involved in the adluminal displacement of the spermatid head. Dynamic changes of invading Sertoli cell processes may produce the motive force for adluminal displacment of the spermatid head. Also, ectoplasmic specialization may contribute to the adluminal displacement of the spermatid possibly by mediating cell to cell interaction between the spermatid nucleus and the invading Sertoli cell process.