Thrombospondin and Vascular Endothelial Growth Factor Are Cyclically Expressed in an Inverse Pattern During Bovine Ovarian Follicle Development1

Abstract

Angiogenesis does not normally occur in most adult tissues. However, in the ovary, there are cyclical vascular changes including angiogenesis that involve the interaction of numerous cytokines and growth factors. Angiogenic processes are regulated by a balance between pro- and antiangiogenic factors. The purpose of this study was to determine the expression of the antiangiogenic thrombospondin family and proangiogenic vascular endothelial growth factor (VEGF) in various sizes of healthy bovine follicles. Ovaries were collected from slaughterhouse animals and healthy follicles were sorted based on size (< 0.5 cm, small; 0.5-1.0 cm, medium; >1.0 cm, large). Thrombospondin (TSP) protein levels were significantly higher in small follicles. Immunohistochemistry confirmed the granulosa layer as the primary area within the follicle involved in TSP generation and that small follicles had the highest proportion of immunopositive cells. TSP-1 and -2 mRNA levels were significantly higher in small follicles than either medium or large follicles. TSP colocalized with CD36 on granulosa cells (GC) in the follicle and in cultured cells. In contrast with TSP, VEGF expression increased during growth and development of the follicle. FSH stimulated GC expression of TSP, while LH had no effect. In summary, TSP-1 and -2 were coordinately expressed in the extravascular compartment of the ovary during early follicle development. VEGF was inversely expressed, with expression increasing as follicles developed. Regulated expression and localization of these proteins suggests that they may be involved in regulating growth and development of the follicle in a novel fashion.

A novel physiological culture system that mimics luteal angiogenesis

“…Both VEGFA and FGF2 mediate their action through their high affinity tyrosine kinase receptors, namely VEGF receptor (VEGFR)-1 and VEGFR-2 and FGF receptor (FGFR)-1 and FGFR-2 respectively (Ferrara et al 2003, Wiedlocha & Sorenson 2004). In the pre-ovulatory follicle, granulosa cells are the major source of VEGFA, while FGF2 is mainly theca derived (Berisha et al 2000a, Greenaway et al 2005. Contrary to expectation, we have recently showed that FGF2 production, rather than VEGFA, is the dynamic driver during the follicle-luteal transition and early CL development in the cow (Robinson et al 2007).…”

Age-associated changes in bovine oocytes and granulosa cell complexes collected from early antral follicles

“…Hayashi et al [36] reported several marker genes related to the largest follicle as the most viable follicle and the second largest follicles as a subordinate follicles in cows. In addition, several studies have reported genes related to healthy large developing follicles or subordinate follicles [31,34,35,37]. First, we compared the expression of marker genes between the two age groups.…”

“…Of the apoptosis related genes, CCDC80, COL1A1, CTGF, DNAJB1, LGALS9, LTF, LNM, MT2A, MTH11, SOX4, and TIMP2 showed significant differences in expression levels between the two age groups (Supplementary Table 2). Table 3 lists the marker genes for the largest healthy follicles and the subordinate follicles in cows [31][32][33][34][35][36][37], and shows the expression levels of these genes in aged and young cows. All genes associated with subordinate follicles were expressed at lower levels in young cows.…”

Gene expression profiling of bovine preovulatory follicles: gonadotropin surge and prostanoid-dependent up-regulation of genes potentially linked to the ovulatory process

“…In the rat ovary, both TSP-1 and CD36 are localized primarily to the GC layer of antral follicles, while TSP-2 is expressed later during the ovulatory/early luteal phase (Petrik et al 2002). In the bovine, TSPs are co-expressed with CD36 on GC of follicles (Greenaway et al 2005). The specific functional role of CD36 in bovine preovulatory follicles remains to be elucidated.…”