Estrogen regulates insulin-like growth factor 1, platelet-derived growth factor A and B, and their receptors in the vascular wall

Sex-specific and hormone-related differences in vascular remodelling in atherosclerosis

Atherosclerosis, a lipid-driven inflammatory disease, is the main underlying cause of cardiovascular diseases (CVDs) both in men and women. Sex-related dimorphisms regarding CVDs and atherosclerosis were observed since more than a decade ago. Inflammatory mediators such as cytokines, but also endothelial dysfunction, vascular smooth muscle cell migration and proliferation lead to vascular remodelling but are differentially affected by sex. Each year a greater number of men die of CVDs compared with women and are also affected by CVDs at an earlier age (40-70 years old) while women develop atherosclerosis-related complications mainly after menopause (60+ years). The exact biological reasons behind this discrepancy are still not well-understood. From the numerous animal studies on atherosclerosis, only a few include both sexes and even less investigate and highlight the sex-specific differences that may arise. Endogenous sex hormones such as testosterone and oestrogen modulate the atherosclerotic plaque composition and the frequency of such plaques. In men, testosterone seems to act like a double-edged sword as its decrease with ageing correlates with an increased risk of atherosclerotic CVDs, while testosterone is also reported to promote inflammatory immune cell recruitment into the atherosclerotic plaque. In premenopausal women, oestrogen exerts anti-atherosclerotic effects, which decline together with its level after menopause resulting in increased CVD risk in ageing women. However, the interplay of sex hormones, sex-specific immune responses and other sex-related factors is still incompletely understood. This review highlights reported sex differences in atherosclerotic vascular remodelling and the role of endogenous sex hormones in this process.

Platelet Derived Growth Factor BB: A "Must-have" Therapeutic Target "Redivivus" in Ovarian Cancer

BACKGROUND

We aimed to validate PDGF-BB protein expression by RNAscope, a sensitive method for PDGF-BB mRNA evaluation on paraffin embedded (FFPE) specimens of ovarian tumors.

MATERIALS AND METHODS

Seventy-five FFPE ovarian cancer biopsies were assessed by immunohistochemistry followed by PDGF-BB mRNA RNAscope validation.

RESULTS AND CONCLUSION

Dual PDGF-BB expression in tumor and stromal cells have been observed, being highly suggestive for PDGF-BB mediated stromal-tumor cells reciprocal interaction in ovarian cancer (p=0.008). It seems that the nuclear expression of the PDGF-BB represents a negative prognostic factor in ovarian tumors. Being a controversial issue in the literature, PDGF-BB nuclear expression detected by immunohistochemistry was validated by RNAscope in situ hybridization. More than 65% of cases had PDGF-BB mRNA amplification, confirming immunohistochemical results. We herein validated PDGF-BB as a potential therapeutic and prognostic tool of ovarian cancer aggressiveness.

Estrogen Effects on Skeletal Muscle Insulin-Like Growth Factor–1 and Myostatin in Ovariectomized Rats

Previous work showed that estrogen replacement attenuates muscle growth in immature rats. The present study examined muscle insulin-like growth factor–1 (IGF-1) and myostatin expression to determine whether these growth regulators might be involved in mediating estrogen’s effects on muscle growth. IGF-1 and myostatin message and protein expression in selected skeletal muscles from 7-week-old sham-ovariectomized (SHAM) and ovariectomized rats that received continuous estrogen (OVX/E2) or solvent vehicle (OVX/CO) from an implant for 1 week or 5 weeks was measured. In the 1-week study, ovariectomy increased IGF-1 mRNA expression in fast extensor digitorum longus and gastrocnemius muscles; the increase was reversed by estrogen replacement. A similar trend was observed in the slow soleus muscle, although the change was not statistically significant. In contrast to mRNA, muscle IGF-1 protein expression was not different between SHAM and OVX/ CO animals in the 1-week study. One week of estrogen replacement significantly decreased IGF-1 protein level in all muscles examined. Myostatin mRNA expression was not different among the 1-week treatment groups. One week of estrogen replacement significantly increased myostatin protein in the slow soleus muscle but not the fast extensor digitorum longus and gastrocnemius muscles. There was no treatment effect on IGF-1 and myostatin expression in the 5-week study; this finding suggested a transient estrogen effect or upregulation of a compensatory mechanism to counteract the estrogen effect observed at the earlier time point. This investigation is the first to explore ovariectomy and estrogen effects on skeletal muscle IGF-1 and myostatin expression. Results suggest that reduced levels of muscle IGF-1 protein may mediate estrogen’s effect on growth in immature, ovariectomized rats. Increased levels of muscle myostatin protein may also have a role in mediating estrogen’s effects on growth in slow but not fast skeletal muscle.

Role of MT1-MMP in estrogen-mediated cellular processes of intimal hyperplasia

BACKGROUND

Hormone replacement therapy increases intimal hyperplasia (IH) following vascular intervention. Matrix metalloproteinases (MMPs) play a role in IH development. We have shown estrogen up-regulates MT1-MMP expression, a transmembrane protein that activates MMP-2, and increases vascular smooth muscle cell (VSMC) collagen invasion via increased MMP-2 activity. Here we hypothesize inhibition of MT1-MMP will prevent hormonally-stimulated increased MMP-2 activation and the downstream cellular processes of IH pathogenesis.

METHODS

VSMCs from a postmenopausal donor were transfected with MT1-MMP or negative control siRNAs, treated with estrogen (Est), analyzed by q-PCR, Western blot, zymography, migration, invasion, and proliferation assays.

RESULTS

Est treatment of MT1-MMP silenced cells still resulted in increased MT1-MMP expression (C = 41% ± 4%; Est = 52% ± 2%; P < 0.05). Silencing of MT1-MMP decreased basal MMP-2 activity (nonsilenced = 100%; MT1-silenced = 87% ± 3%; P < 0.05) but had no effect on basal invasion or proliferation. Est treatment of MT1-MMP silenced cells still resulted in increased MMP-2 activity (C = 87% ± 3%; Est = 101% ± 4%; P < 0.05) and invasion (C = 89% ± 6%; Est = 109% ± 3%; P < 0.05) compared with MT1-MMP silenced control cells. However, silencing of MT1-MMP did inhibit Est- and serum-stimulated proliferation (C = 106% ± 18%; Est = 104% ± 16%; FBS = 121% ± 24%; P = NS).

CONCLUSION

Silencing of MT1-MMP in aged VSMCs results in impaired but not complete inhibition of basal and Est-stimulated increases in MMP-2 activity. Other mechanisms appear to be playing a role in hormonally-regulated cellular processes of IH pathogenesis. Future studies will target other signaling cascades, with the goal of identifying mechanisms responsible for hormonally-modulated unbalanced MMPs. In vivo manipulation of the expression patterns of MT1-MMP will be examined for the prevention of IH in animal models of vascular disease.

Syndecan-1: an inhibitor of arterial smooth muscle cell growth and intimal hyperplasia

OBJECTIVE

Arterial injury induces smooth muscle cell (SMC) proliferation, migration, and intimal accumulation of cells and extracellular matrix. These processes are regulated by the administration of the glycosaminoglycans heparin and heparan sulfate, but little is known about the role of endogenous heparan sulfate proteoglycans in the vessel wall. We investigated the response to carotid injury of syndecan-1-null mice to assess the function of one of a conserved family of transmembrane heparan and chondroitin sulfate proteoglycans.

METHODS AND RESULTS

Syndecan-1-null mice developed a large neointimal lesion after injury, whereas wild-type mice made little or none. This was accompanied by a significant increase in both medial and intimal SMC replication. Cultured syndecan-1-null SMCs showed a significant increase in proliferation in response to PDGF-BB, thrombin, FGF2, EGF, and serum. In response to thrombin, PDGF-BB, and serum syndecan-1-null SMCs expressed more PDGF-B chain message than did wild-type SMCs. Downregulation of PDGF-BB or PDGFRbeta inhibited thrombin-, PDGF-BB-, and serum-induced DNA synthesis in syndecan-1-null SMCs.

CONCLUSIONS

These results suggest the possibility that syndecan-1 may limit intimal thickening in injured arteries by suppressing SMC activation through inhibition of SMC PDGF-B chain expression and PDGFRbeta activation.

Aberrant expression of PDGF ligands and receptors in the tumor prone ovary of follitropin receptor knockout (FORKO) mouse

Although PDGF family members play a vital role in cell proliferation, motility and chemotaxis via activation of structurally similar alpha- and beta-receptors, little is known of their function in ovarian regulation and induction of tumorigenesis. Microarray analyses of ovaries from young follitropin receptor knockout (FORKO) mice that are prone to late ovarian tumors upon aging have revealed significant imbalances in PDGF ligands and receptors. We hypothesized that FSH/FSH-R signaling may exert effects partly by regulation of PDGF the family. To further understand their implications for ovarian tumorigenesis, we studied FORKO ovaries and hormonal regulation of the PDGF family members in normal mice, by using RT-PCR, Q-PCR, immunohistochemistry and western blotting. While PDGF-C and PDGFR-alpha increased, PDGFR-beta mRNA and protein decreased significantly in absence of FSH-R signaling. In the normal ovary, PDGFR-alpha was not affected by gonadotropin (eCG) stimulation but PDGF-C and PDGFR-beta decreased. Administration of estradiol decreased PDGF and their receptors. To further probe the differential regulation of PDGF family members by eCG and estradiol, we co-administered eCG with estrogen antagonist, ICI 182780. Increase in PDGFR-alpha in the absence of estradiol suggests direct effects of FSH signaling. During the estrous cycle in mice PDGF-C, PDGF-D and PDGFR-alpha mRNA levels were higher at the proestrous. By IHC, we report for the first time the localization of PDGF-C, PDGFR-alpha and PDGFR-beta protein in mouse ovarian compartments including the surface epithelium that is also altered in mutants. Immunostaining of PDGFRs increased as the follicle developed to preantral stage and declined thereafter. Thus, FSH modulates PDGF family members, partly via E2, suggesting that loss of FSH-R signaling causes an imbalance of PDGF family members predisposing the abnormal ovarian follicular environment for inducing tumorigenesis in aging FORKO mice.

Selective estrogen receptor modulators prevent neointima formation after vascular injury

Exploitation of estrogen's vasculoprotective properties in drug design is difficult due to its adverse effects on endometrium and breast. Selective estrogen receptor modulators (SERM) act as estrogen agonists in some tissues but are anti-estrogenic in others. We investigate here whether tamoxifen, raloxifene, and two novel SERMs, ospemifene and fispemifene, preserve estrogen's beneficial effects on the ovariectomized rat vascular wall, and correlate their effects with natural estrogen (17beta-E2) and a pure anti-estrogen ICI 182,780. All compounds dose-dependently (0.0025-25 mg/kg/day) inhibited neointimal thickening at 7 days after aorta denudation injury. At 28 days, tamoxifen and ospemifene (2.5 mg/kg/day) reduced intimal nuclei number and intimal area equal to 17beta-E2, while raloxifene and fispemifene had no effect. Replacing the drug at 14 days with vehicle did not induce any rebound effect at 28 days, and furthermore, resulted in a smaller neointima with raloxifene and fispemifene. 17beta-E2 and the SERMs also significantly enhanced reendothelialization. All compounds inhibited replication and all but fispemifene inhibited migration of vascular SMC and cells from cultured aortic explants in vitro. Finally, only 17beta-E2 increased the weight of the uterus above that of normal rats. Interestingly, ICI 182,780 also weakly inhibited neointima formation and SMC proliferation at 7 days, suggesting that non-estrogen receptor mediated effects may have also played a role. In conclusion, SERMs have beneficial estrogen agonist effects in the injured vascular wall through their regulation of vascular SMC function and reendothelialization. Early intervention is of particular importance in preventing the injury-response.