Association of vascular endothelial growth factor gene polymorphisms with osteoporotic vertebral compression fractures in postmenopausal women

Vascular endothelial growth factor I/D variant and postmenopausal osteoporosis risk in the Turkish population

INTRODUCTION

Postmenopausal osteoporosis (PMOP) is a common metabolic bone disorder manifested by low bone mineral density and increased fracture risks in postmenopausal women. Vascular endothelial growth factor (VEGF) has been shown to play an important role in bone formation. In this study, we investigated the potential association between the VEGF insertion/deletion (I/D) variant (rs35569394) and PMOP in a cohort of postmenopausal Turkish women.

METHODS

This study included 300 women, including 150 PMOP patients and 150 healthy postmenopausal women. A T score was used in the diagnosis of OP. DNA was extracted from all subjects. The VEGF I/D polymorphism was analyzed by the PCR method. The Hardy-Weinberg equilibrium (HWE) test and odds ratio (OR) were analyzed, considering CI 95% and p ≤ 0.05.

RESULTS

The mean age of patients aged between 40 and 74 was 60.32 ± 8.65. The frequency of the I/I, I/D, and D/D genotypes was 7.34% versus 6.66%; 67.33% versus 65.34%; and 25.33% versus 28%, in patients and the control group, respectively. The allele frequencies were I: 41% (patients) and 39.4% (controls); D: 59% (patients) and 60.66% (controls). There was no statistically significant difference in the VEGF - 2549 I/D allele and genotype distribution between patients with PMOP and control subjects (p = 0.349, p = 0.864, respectively).

CONCLUSION

Our results showed that the VEGF I/D variant was not a significant factor in the development of PMOP in a Turkish population sample. These findings need confirmation in other ethnic populations.

Vascular endothelial growth factor control mechanisms in skeletal growth and repair

Vascular endothelial growth factor A (VEGF) is a critical regulator of vascular development and postnatal angiogenesis and homeostasis, and it is essential for bone development and repair. Blood vessels serve both as structural templates for bone formation and they provide essential cells, growth factors and minerals needed for synthesis and mineralization, as well as turnover, of the extracellular matrix in bone. Through its regulation of angiogenesis, VEGF contributes to coupling of osteogenesis to angiogenesis, and it directly controls the differentiation and function of osteoblasts and osteoclasts. In this review, we summarize the properties of VEGF and its receptors that are relevant to bone formation and repair; the roles of VEGF during development of endochondral and membranous bones; and the contributions of VEGF to bone healing during different phases of bone repair. Finally, we discuss contributions of altered VEGF function in inherited disorders with bone defects as part of their phenotypes, and we speculate on what will be required before therapeutic strategies based on VEGF modulation can be developed for clinical use to treat patients with bone growth disorders and/or compromised bone repair. Developmental Dynamics 246:227-234, 2017. © 2016 Wiley Periodicals, Inc.

Osteoblast-derived VEGF regulates osteoblast differentiation and bone formation during bone repair

Osteoblast-derived VEGF is important for bone development and postnatal bone homeostasis. Previous studies have demonstrated that VEGF affects bone repair and regeneration; however, the cellular mechanisms by which it works are not fully understood. In this study, we investigated the functions of osteoblast-derived VEGF in healing of a bone defect. The results indicate that osteoblast-derived VEGF plays critical roles at several stages in the repair process. Using transgenic mice with osteoblast-specific deletion of Vegfa, we demonstrated that VEGF promoted macrophage recruitment and angiogenic responses in the inflammation phase, and optimal levels of VEGF were required for coupling of angiogenesis and osteogenesis in areas where repair occurs by intramembranous ossification. VEGF likely functions as a paracrine factor in this process because deletion of Vegfr2 in osteoblastic lineage cells enhanced osteoblastic maturation and mineralization. Furthermore, osteoblast- and hypertrophic chondrocyte-derived VEGF stimulated recruitment of blood vessels and osteoclasts and promoted cartilage resorption at the repair site during the periosteal endochondral ossification stage. Finally, osteoblast-derived VEGF stimulated osteoclast formation in the final remodeling phase of the repair process. These findings provide a basis for clinical strategies to improve bone regeneration and treat defects in bone healing.