title: Effect of cell shape and packing density on granulosa cell proliferation and formation of multiple layers during early follicle development in the ovary.
abstract: The postnatal mouse ovary is rich in quiescent and early-growing oocytes, each one surrounded by a layer of somatic granulosa cells (GCs) on a basal lamina. As oocytes start to grow the GCs change shape from flattened to cuboidal, increase their proliferation and form multiple layers, providing a unique model for studying the relationship between cell shape, proliferation and multilayering within the context of two different intercommunicating cell types: somatic and germ cells. Proliferation of GCs was quantified using immunohistochemistry for Ki67 and demonstrated that, unusually, cuboidal cells divided more than flat cells. As a second layer of GCs started to appear, cells on the basal lamina reached maximum packing density and the axes of their mitoses became perpendicular to the basal lamina, resulting in cells dividing inwards to form second and subsequent layers. Proliferation of basal GCs was less than that of inner cells. Ultrastructurally, collagen fibrils outside the basal lamina became more numerous as follicles developed. We propose that the basement membrane and/or theca cells that surround the follicle provide an important confinement for rapidly dividing columnar cells so that they attain maximum packing density, which restricts lateral mitosis and promotes inwardly oriented cell divisions and subsequent multilayering.
authors.affiliation: Institute of Reproductive and Developmental Biology, Imperial College London, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK.
authors.forename: Patricia
authors.initials: P
authors.lastname: Da Silva-Buttkus
authors.forename: Gayani S
authors.initials: GS
authors.lastname: Jayasooriya
authors.forename: Jocelyn M
authors.initials: JM
authors.lastname: Mora
authors.forename: Margaret
authors.initials: M
authors.lastname: Mobberley
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Ryder
authors.forename: Marianne
authors.initials: M
authors.lastname: Baithun
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Stark
authors.forename: Stephen
authors.initials: S
authors.lastname: Franks
authors.forename: Kate
authors.initials: K
authors.lastname: Hardy
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D048430:Cell Shape; D005260:Female; D006107:Granulosa Cells / Q000166:cytology* / Q000648:ultrastructure; D007150:Immunohistochemistry; D019394:Ki-67 Antigen / Q000378:metabolism; D051379:Mice; D046529:Microscopy, Electron, Transmission; D008938:Mitosis; D009865:Oocytes / Q000254:growth & development; D006080:Ovarian Follicle / Q000254:growth & development* / Q000648:ultrastructure; D010053:Ovary / Q000378:metabolism / Q000648:ultrastructure; D013799:Theca Cells / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D019394:Ki-67 Antigen