DIFFERENTIAL-EFFECTS OF INSULIN-LIKE GROWTH-FACTOR-I AND FOLLICLE-STIMULATING-HORMONE ON PROLIFERATION AND DIFFERENTIATION OF BOVINE CUMULUS CELLS AND GRANULOSA-CELLS
Dt. Armstrong et al., DIFFERENTIAL-EFFECTS OF INSULIN-LIKE GROWTH-FACTOR-I AND FOLLICLE-STIMULATING-HORMONE ON PROLIFERATION AND DIFFERENTIATION OF BOVINE CUMULUS CELLS AND GRANULOSA-CELLS, Biology of reproduction, 54(2), 1996, pp. 331-338
Effects of gonadotropins and peptide growth factors on H-3-thymidine i
ncorporation, as an indicator of proliferation of granulosa cells and
cumulus cells from bovine ovarian follicles during in vitro culture, w
ere determined. Incorporation of H-3-thymidine in cumulus cells during
24-h culture in protein-free medium was about 100-fold greater than i
n granulosa cells from small follicles. Small but significant (p < 0.0
5) increases in incorporation of H-3-thymidine in cumulus cells (2.5-f
old), but not in granulosa cells, resulted from addition of FSH, LH, o
r epidermal growth factor to culture media. Much larger, highly signif
icant (p < 0.01) increases in H-3-thymidine incorporation resulted fro
m exposure of both cumulus cells (18-fold) and granulosa cells (8-fold
) to insulin-like growth factor-I (IGF-I). Addition of IGF-I together
with FSH resulted in additive increases in H-3-thymidine incorporation
in granulosa cells over a wide range of each agonist. In contrast, ad
dition of FSH markedly decreased the stimulatory effect of a maximally
effective concentration of IGF-I on incorporation in cumulus cells. A
ddition of estradiol, either alone or with IGF-I, had no consistent ef
fect on H-3-thymidine incorporation in either cumulus cells or granulo
sa cells. Differentiated functions of cumulus and granulosa cells, inc
luding cumulus expansion (an indicator of hyaluronic acid secretion) a
nd progesterone secretion, were investigated under the same culture co
nditions. FSH was highly effective in stimulation of cumulus cell expa
nsion, with maximal expansion occurring at the lowest concentration te
sted (0.04 mu g/ml). LH was effective only at considerably higher conc
entrations consistent with degree of contamination with FSH. IGF-I was
ineffective in inducing cumulus expansion, either alone or together w
ith FSH. FSH and IGF-I by themselves each stimulated progesterone secr
etion by both cumulus and granulosa cells, with further additive stimu
latory effects by the two agents in combination. On a per cell basis,
cumulus cells produced considerably more progesterone than granulosa c
ells under both basal and hormone-stimulated conditions. The results s
uggest that IGF-I has a dual role in follicle regulation-that ii acts
additively with FSH as an autocrine regulator of granulosa cell growth
and, in the absence of FSH, as a paracrine regulator of cumulus cell
proliferation in small antral follicles. The effect of FSH, by inducin
g cumulus expansion, may terminate further cumulus cell proliferation
before ovulation.