Vh. Lee et al., LOCALIZATION OF LAMININ PROTEINS DURING EARLY FOLLICULAR DEVELOPMENT IN PIG AND RABBIT OVARIES, Journal of Reproduction and Fertility, 108(1), 1996, pp. 115-122
Laminin, a major component of the basal lamina, is known to be importa
nt in the differentiation of epithelial cells. The outer granulosa cel
l layer of ovarian follicles is attached to a basal lamina surrounding
the follicle and it has been demonstrated that proteins of the basal
lamina can alter the steroidogenic capacity and cytoskeletal compositi
on of mature granulosa cells. The present studies were carried out to
evaluate the developmental expression of laminin proteins in the basal
lamina of ovarian follicles during early stages of granulosa cell dif
ferentiation. Ovaries from sexually immature pigs (0-20 weeks of age)
and rabbits (0-12 weeks of age) were used for this study because forma
tion of primordial follicles and initiation of follicular growth occur
partially or completely postnatally. Specific antibodies were made ag
ainst laminin beta 1/gamma 1 chains using protein purified by high res
olution two-dimensional polyacrylamide gel electrophoresis. These anti
bodies were used in immunohistochemical localization studies to demons
trate that laminin is associated with the basal lamina surrounding egg
clusters and their connections to the ovarian surface epithelium and
ovarian rete during early ovarian development. In addition, laminin wa
s observed to associate with a continuous matrix that surrounds formin
g primordial follicles as they are isolated from the egg clusters. Lam
inin is localized in the basal lamina of primordial, primary, secondar
y, and tertiary follicles of both pig and rabbit ovaries. Laminin prot
eins are not only expressed throughout early follicular development in
pigs and rabbits, but are also found surrounding the germ cell compar
tments prior to initiation of meiosis and formation of primordial foll
icles. These results demonstrate that laminin proteins are deposited i
n the basal lamina well before granulosa cells undergo morphological d
ifferentiation. This pattern of expression suggests that laminin prote
ins alone do not control changes in granulosa cell morphology during e
arly development but may be required to maintain cell lineage commitme
nt.