Morphometric studies on lipid inclusions in Sertoli cells during the spermatogenic cycle in the rat

Abstract

The volume and surface area of lipid inclusions often present in the cytoplasm of rat Sertoli cells was measured directly from semi-thin sections of perfusion-fixed testicular tissues using an image analyser linked to a light microscope. Sertoli cell nuclei were used as a reference for comparing any variations in the measured parameters of lipid inclusions during the rat spermatogenic cycle. Volume density of Sertoli cell lipid inclusions was assessed by morphometric analysis of Sertoli cells photographically reconstructed from electron micrographs. Maximum lipid content in Sertoli cells occurred during stages IX-XIV of the spermatogenic cycle, then declined at stages I-III and remained low from stages IV-VIII. The persistence and increase in number of many large Sertoli cell lipid inclusions beyond the stage where spermatid residual bodies are phagocytosed within the Sertoli cells (stage IX) suggests that the synthesis and lipolysis of Sertoli cell lipid inclusions represents an intrinsic functional cycle of the Sertoli cells. Stage-dependent variations in the lipid content of rat Sertoli cells offers morphological evidence that the metabolic duties of the Sertoli cells are synchronised with the spermatogenic cycle to provide local coordination of the proliferation and maturation of the germ cells.

Localization of hormone‐sensitive lipase to rat Sertoli cells and its expression in developing and degenerating testes

“…Against this background, and the observation that experimental cryptorchidism decreases HSL expression and increases the amount of lipid droplets in Sertoli cells [7,13,29], it appears that this enzyme is involved in the metabolism of lipids like triacylglycerols and cholesterol esters, present in these droplets. The HSL mRNA expression was, however, maximal in the luminal parts of the seminiferous tubules, in contrast to lipid droplets, that in some stages are located principally in the basal compartment of the tubules [28]. The possibility of the expressed protein being directed to the basal parts remains to be investigated by immunohistochemistry.…”

“…The expression of HSL is stage dependent and apparently closely linked to the amount of lipid droplets in the Sertoli cell cytoplasm. The highest amount of lipid and HSL was observed in stages X-XIV and the lowest in stages III-VIII [13,28]. Against this background, and the observation that experimental cryptorchidism decreases HSL expression and increases the amount of lipid droplets in Sertoli cells [7,13,29], it appears that this enzyme is involved in the metabolism of lipids like triacylglycerols and cholesterol esters, present in these droplets.…”

Apoptotic spermatogenic cells can be energy sources for Sertoli cells

“…However, the formation and fate of the lipid droplets have not been extensively studied. The temporal relationship between the phagocytosis of residual bodies and the increased lipid droplets in Sertoli cells suggests that the lipid droplets could result from the breakdown products of phagocytosed residual bodies (Kerr et al 1984, Ueno & Mori 1990, Sasso-Cerri et al 2001. We recently demonstrated in vitro that Sertoli cells can use engulfed apoptotic spermatogenic cells to form the lipid droplets (Wang et al 2006).…”

Intracellular Localization of the Microtubule-Associated Motor Proteins Kinesin and Cytoplasmic Dynein in Rat Sertoli Cells.

“…These findings indicated that intracellular organelle transport directed to the apical end of Sertoli cells may be active throughout the spermatogenic cycle. Various organelles, such as mitochondria [18], the Golgi apparatus [19], lysosomes [20], and lipid droplets [21,22] are bi-directionally transported in Sertoli cells in a stage-dependent manner [23]. In addition, Sertoli cells secrete various growth factors and related molecules.…”