Keratinocyte growth factor expression by the bovine corpus luteum

The fibroblast growth factor family: involvement in the regulation of folliculogenesis

Several growth factors have been identified as local regulators of follicle development and ovulation. Fibroblast growth factor (FGF) family members are potent mitogens and are involved in cell differentiation, cell migration and angiogenesis in many tissues and organs. In addition to FGF-2, which is the most-studied FGF, other important members are FGF-1, -5, -7, -8, -9 and -10. A number of studies have indicated that FGFs play important roles in regulating the initiation of primordial follicle growth, oocyte and follicle survival, granulosa and theca cell proliferation and differentiation, corpus luteum formation, steroidogenesis and angiogenesis. The purpose of this review is to highlight the importance of the FGFs on mammalian female reproduction, providing a better understanding of the roles of this family in ovarian physiology and female fertility.

Expression of fibroblast growth factor receptors during development and regression of the bovine corpus luteum

There is evidence that fibroblast growth factors (FGFs) are involved in the regulation of growth and regression of the corpus luteum (CL). However, the expression pattern of most FGF receptors (FGFRs) during CL lifespan is still unknown. The objective of the present study was to determine the pattern of expression of ‘B’ and ‘C’ splice variants of FGFRs in the bovine CL. Bovine CL were collected from an abattoir and classed as corpora hemorrhagica (Stage I), developing (Stage II), developed (Stage III) or regressed (Stage IV) CL. Expression of FGFR mRNA was measured by semiquantitative reverse transcription-polymerase chain reaction and FGFR protein was localised by immunohistochemistry. Expression of mRNA encoding the ‘B’ and ‘C’ spliced forms of FGFR1 and FGFR2 was readily detectable in the bovine CL and was accompanied by protein localisation. FGFR1C and FGFR2C mRNA expression did not vary throughout CL lifespan, whereas FGFR1B was upregulated in the developed (Stage III) CL. FGFR3B, FGFR3C and FGFR4 expression was inconsistent in the bovine CL. The present data indicate that FGFR1 and FGFR2 splice variants are the main receptors for FGF action in the bovine CL.

Fibroblast growth factor-9, a local regulator of ovarian function

Fibroblast growth factor 9 (FGF9) is widely expressed in embryos and fetuses and has been shown to be involved in male sex determination, testicular cord formation, and Sertoli cell differentiation. Given its male gender bias, the ovary has not been reported to express FGF9, nor has a role in ovarian function been explored. We report here that FGF9 mRNA and protein are present in the rat ovary and provide evidence that supports a role for FGF9 in ovarian progesterone production. FGF9 mRNA levels as determined by real-time PCR were high in 4-d-old rat ovaries, thereafter declining and stabilizing at levels approximately 30% of d 4 levels at d 12-25. Levels of FGF9 mRNA in the ovary were significantly higher than that present in adult testis, at all ages studied. The FGF9 receptors FGFR2 and FGFR3 mRNAs were present in postnatal and immature rat ovary and appeared to be constitutively expressed. FGF9 protein was localized to theca, stromal cells, and corpora lutea and FGFR2 and FGFR3 proteins to granulosa cells, theca cells, oocytes, and corpora lutea, by immunohistochemistry. Follicular differentiation induced by gonadotropin treatment reduced the expression of FGF9 mRNA by immature rat ovaries, whereas the estrogen-stimulated development of large preantral follicles had no significant effect. In vitro, FGF9 stimulated progesterone production by granulosa cells beyond that elicited by a maximally stimulating dose of FSH. When the granulosa cells were pretreated with FSH to induce LH receptors, FGF9 was found not to be as potent as LH in stimulating progesterone production, nor did it enhance LH-stimulated production. The combined treatments of FSH/FGF9 and FSH/LH, however, were most effective at stimulating progesterone production by these differentiated granulosa cells. Analyses of steroidogenic regulatory proteins indicate that steroidogenic acute regulatory protein and P450 side chain cleavage mRNA levels were enhanced by FGF9, providing a mechanism of action for the increased progesterone synthesis. In summary, the data are consistent with a paracrine role for FGF9 in the ovary.

Changes in fibroblast growth factor 2 and its receptors in bovine follicles before and after GnRH application and after ovulation

The aim of this study was to evaluate the expression pattern of fibroblast growth factor 2 (FGF2), its receptor variants (FGFR1IIIc, FGFR2IIIc) and nucleolin in time-defined follicle classes before and after GnRH application and after ovulation in the cow. Ovaries containing preovulatory follicles or new corpora lutea (CL) were collected at approximately 0, 4, 10, 20 and 25 h (follicles) and 60 h (new CL) relative to injection of GnRH to induce an LH surge (n = 5 animals per group). The expressions of FGF2 and FGFR1IIIc mRNA were significantly up-regulated only in the follicle group 4 h after GnRH (during the LH surge) with a significant down-regulation immediately afterwards. Western blot analyses showed two protein bands with at 22 and 18 kDa with apparent up-regulation beginning with the LH surge (4 h) and maximum levels 20 h after GnRH. FGF2 protein in follicles collected at 0 h (before LH surge) was localised in theca tissue (endothelial and pericytes of blood vessels) but not in granulosa cells (GCs). The FGF2 staining (by immunohistochemistry) pattern changed dramatically after the LH surge for a short period (about 2 days) and FGF2 protein was localised dominantly in the nucleus of many GCs, while most capillary endothelial cells were FGF2 immunonegative. In conclusion, the novel observation of FGF2 up-regulation and the distinct change in FGF2 localisation from theca (cytoplasm of endothelial cells) to the nucleus of GCs after the LH surge may be important for survival of GCs or for the transition of the GCs to luteal cells.

Expression of fibroblast growth factor 1 (FGF1) and FGF7 in mature follicles during the periovulatory period after GnRH in the cow

The aim of this study was to evaluate the expression pattern of mRNA for fibroblast growth factor 1 (FGF1), FGF7, and their receptor variants (FGFR2IIIb) in time-defined follicle classes before LH surge, between LH surge and ovulation, and in the early corpus luteum (CL) in the cow. The ovaries were collected by transvaginal ovariectomy (n=5 cows/group), and the follicles (n=5, one follicle/cow) were classified into the following groups: before GnRH administration (before LH surge); 3-5 h after GnRH (during LH surge); 10 h after GnRH; 20 h after GnRH; 25 h after GnRH (periovulation), and early CL (Days 2-3). The mRNA expression was analyzed by quantitative real-time PCR (RotorGene 3000). The mRNA expression of FGF1 showed no significant differences in the follicle groups examined, but increased significantly at the early CL phase. A transient increase in FGF7 mRNA expression was observed 3-5 h after GnRH and again in the early CL phase. In contrast, the expression of FGFR2IIIb was constant throughout the period from the final growth of the follicle to early CL formation. The results of this study suggest that FGF1 and FGF7 may be involved differently in the process of follicle maturation and CL formation, which is strongly dependent on angiogenesis.

Regulation of endometrial fibroblast growth factor 7 (FGF-7) and its receptor FGFR2IIIb in gilts after sex steroid replacements, and during the estrous cycle and early gestation

The aim of this study was to characterize the effect of ovarian steroids and early gestation on the expression of fibroblast growth factor 7 (FGF-7) and its receptor (FGFR2IIIb) in the porcine endometrium. In Experiment 1, gilts were ovariectomized (OVX) on day 10 of the estrous cycle and treated thereafter with vehicle (VEH), progesterone (P4), estradiol benzoate (EB), or P4+EB. Days 12 and 20 cyclic gilts (C12 and C20) were used to determine the influence of physiologically low and high plasma estradiol and progesterone concentrations on their expression. In Experiment 2, the expression of FGF-7 and FGFR2IIIB was characterized on days 1 (G 1) and 12 (G 12) of gestation. FGF-7 and FGFR2IIIb mRNA were quantified by quantitative real-time RT-PCR, and localization of FGF-7 protein in steroid-treated and early pregnant gilts was performed by immunohistochemistry. VEH-gilts expressed both FGF-7 and FGFR2IIIB mRNA. We found a significant effect of EB, but no effects of P4 or P4+EB on the mRNA expression of FGF-7. FGFR2IIIb mRNA significantly decreased after the EB and combined P4+EB treatments, compared to P4 only substituted animals. Day 12 cyclic gilts showed significantly higher FGF-7 and FGFR2IIIb mRNA expression compared with day 20 gilts. Between day 1 and 12 of gestation, FGF-7 mRNA expression differed highly while FGFR2IIIb transcripts only varied significantly. FGF-7 protein was localized in endometrial epithelia, vascular smooth muscle, and the endothelium of different types of blood vessels. Staining was weak in VEH and P4 treated gilts, whereas it was prominent following EB and P4+EB. FGF-7 antibody strongly stained the luminal epithelium on day 12 of gestation. In summary, FGF-7 and FGFR2IIIb mRNA expression is regulated differently by exogenous ovarian steroids, assuming progesterone in connection with a specific amount of 17beta-estradiol, whereas the receptor seems to be inhibited by estradiol. Both transcripts coordinately increased during the progesterone dominated phase on day 12 both in cyclic and early pregnant gilts. We conclude that estradiol and progesterone are involved in the regulation of this ligand-receptor system, which might have an important role in preparing endometrial tissue for implantation in gilts.

Expression and localization of fibroblast growth factor (FGF) family members during the final growth of bovine ovarian follicles

The aim of this study was to investigate the possible participation of fibroblast growth factor (FGF) family members: FGF1, FGF2, and FGF7, and their receptor variants: FGFR, FGFR2IIIb, and FGFR2IIIc in theca interna (TI) and granulosa cell (GC) compartments of bovine follicles during final growth. A classification of follicles into five groups (<0.5; >0.5-5; >5-20; >20-180; >180 ng/ml, respectively) was performed according to the follicular fluid (FF) oestradiol-17beta (E) content. The mRNA expression and protein localization was analyzed by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. FGF1 mRNA expression was relatively high in TI and lower in GC, and without any regulatory change for both tissue compartments during final follicular growth. The FGF1 protein could be predominantly localized in the cytoplasm of GC, in smooth muscle cells of blood vessels, in the rete ovarii, and at a lesser degree in theca cells. FGF2 mRNA in TI increased significantly in large follicles and was low and without any regulatory change in GC. FGF7 mRNA expression was relatively high in TI and very low in GC. For FGF7 in mature follicles a marked staining of the TI and the basal layers of the GC could be demonstrated. The mRNA signal for the FGFR in TI increased significantly with beginning of E production (E > 0.5-5 ng/ml FF) and was without any regulatory change in GC. The mRNA expression of FGFR2IIIb was relatively high in GC and increased significantly during final growth of follicles in contrast to the TI with very low expression. The FGFR2IIIc mRNA expression in TI and GC was relatively high but without any clear change. Our results suggest that FGF growth factor family members are involved in process of folliculogenesis and especially during final growth of the preovulatory (dominant) follicle by stimulation of angiogenesis and GC survival and proliferation.