Endocrine Abstracts

The sonic hedgehog (shh) pathway is known to be essential for pituitary development but little is known of its role in adult pituitary. Patched1, encoded by the Patched1 (Ptch1) gene, is a receptor for shh expressed in all cell types of the anterior pituitary. Adult onset hypogonadotropic hypogonadism has been reported in a genetically engineered mouse line with deletion of Ptch1 using S100a4 promoter driven CRE recombinase expression which is restricted to folliculostellate cells (Ptch1-cKO). Ptch1-cKO mice exhibit severely reduced circulating gonadotropin levels; reduced levels of mRNA expression for glycoprotein hormones alpha subunit (Cga), follicle stimulating hormone beta (Fshb) and luteinizing hormone beta (Lhb). The aim of the present study was to explore the secretory pathway ultrastructure of anterior pituitary gonadotrophs in Ptch1-cKO compared to control wild-type (WT) mice by electron microscopy, in particular to investigate LH and FSH within the regulated secretory pathway. Ultrastructural features of reduced regulated secretion were predicted. Pituitary glands (5 week old male and female mice) were collected (n=4), fixed and prepared for quantitative electron microscopy. Immunogold labelling of LHβ and FSHβ was performed in order to identify gonadotrophs. In WT and Ptch1-cKO no significant difference in mitochondria number/micron² cell area, secretory granule diameter, secretory granule number/micron² cell area, or rough endoplasmic reticulum amounts were measured. Gonadotroph size in female and male Ptch1-cKO mice, was significantly reduced (P<0.05). No significant difference in immunogold labelling of LH and FSH-positive granules was found. However, folliculostellate cell morphology was altered in Ptch1-cKO pituitary in that long cellular processes that are distinctive in WT were significantly reduced in number and length (P<0.05). Overall, these findings show smaller gonadotrophs and reduced contacts with folliculostellate cells but ultrastructural features of the regulated secretory pathway were not altered.