Vascular endothelial growth factor -634G/C polymorphism associated with osteonecrosis of the femoral head in a Chinese population

Emerging roles of growth factors in osteonecrosis of the femoral head

Osteonecrosis of the femoral head (ONFH) is a potentially disabling orthopedic condition that requires total hip arthroplasty in most late-stage cases. However, mechanisms underlying the development of ONFH remain unknown, and the therapeutic strategies remain limited. Growth factors play a crucial role in different physiological processes, including cell proliferation, invasion, metabolism, apoptosis, and stem cell differentiation. Recent studies have reported that polymorphisms of growth factor-related genes are involved in the pathogenesis of ONFH. Tissue and genetic engineering are attractive strategies for treating early-stage ONFH. In this review, we summarized dysregulated growth factor-related genes and their role in the occurrence and development of ONFH. In addition, we discussed their potential clinical applications in tissue and genetic engineering for the treatment of ONFH.

Association of Specific Genetic Polymorphisms with Atraumatic Osteonecrosis of the Femoral Head: A Narrative Review

INTRODUCTION

Atraumatic ONFH is one of the leading cause of hip morbidity in the working-age group. It is a multi-factorial disease whose root cause can be attributed to single-nucleotide polymorphism. Identifying such polymorphisms could pave the way for new modalities of treatment for ONFH.

METHODOLOGY

Two databases were electronically searched for relevant articles. The articles were screened through titles, abstract and full texts to include the relevant studies. A secondary search was done through the reference list of selected articles.

RESULTS

A total of 52 studies were included among the 181 hits. All 181 were case-control studies. Summary of these studies identifies multiple SNPs which can cause ONFH. There were 117 SNPs in all 181 studies, of which 92 were associated with the causation of ONFH and 25 were protective against ONFH.

CONCLUSION

SNPs play an essential role in causing atraumatic ONFH. Identification of SNP that contribute to causing ONFH may help reduce the disease burden by early identification, diagnosis and treatment, including targeted gene therapy.

Relationship of common variants in VEGFA gene with osteonecrosis of the femoral head: A Han Chinese population based association study

The pathology of non-traumatic osteonecrosis of the femoral head (ONFH) is complex. Several studies have linked some polymorphisms of vascular endothelial growth factors A (VEGFA) with ONFH, but the results are not consistent and are even conflicting. In the study, 22 single nucleotide polymorphisms (SNPs) in VEGFA were genotyped in 1,762 subjects (489 cases and 1,273 controls). Genetic association analyses were performed in single markers and haplotype levels. Stratification analysis was conducted for ONFH patients. Gene by environment interactions were tested between VEGFA and the smoking status of the subjects. Gene expression and eQTL data of significant SNPs were extracted from GTEx to examine their potential biological function. The SNP, rs2010963, was identified to be significantly associated with ONFH (χ² = 11.66, P = 0.0006, OR = 1.29). Haplotypes including rs2010963 were also identified to be correlated with ONFH in the haplotype-based analyses. After stratifying by the causes of ONFH, a significant signal from rs2010963 could only be identified in alcohol-induced patients (P_allelic = 0.0009) but not in steroid-induced patients (P_allelic = 0.055). No significant results were obtained from the gene by environmental interaction analyses. Significant expression differences of VEGFA were identified in multiple human tissues for different genotypes of rs2010963. Our findings indicate that SNP rs2010963 is significantly associated with ONFH.

Association between vascular endothelial growth factor gene polymorphisms and the risk of osteonecrosis of the femoral head: Systematic review

Emerging evidence has shown that vascular endothelial growth factor (VEGF) gene polymorphisms are the key initiators that regulate the expression of the VEGF protein, which has a vital role in osteonecrosis of the femoral head (ONFH). The aim of the present study was to investigate whether polymorphisms of the VEGF genes are associated with the occurrence of ONFH. A comprehensive search was performed on MEDLINE, Embase, Web of Science and China National Knowledge Infrastructure databases before June 2015. Meta-analyses were carried out for the VEGF gene -634G/C polymorphisms (single-nucleotide polymorphism with 3 eligible studies). The pooled odds ratios with 95% confidence intervals (CIs) were used to evaluate the strength of the association. All the eligible studies, involving 1,564 individuals, were identified. According to the inclusion criteria, 3 case-control studies were finally included in the meta-analysis. The present meta-analysis indicates that the VEGF gene -634G/C polymorphism [CC+GC vs. GG: Response rate (RR)=0.79; 95% CI, 0.67-0.92; GG vs. GC: RR=0.83; 95% CI, 0.72-0.97; GG vs. CC: RR=0.82; 95% CI, 0.72-0.93] is associated with the occurrence of ONFH, and the association with the male subgroup (RR=0.78; 95% CI, 0.65-0.94; P=0.009) is more evident. In conclusion, the present meta-analysis suggests that the VEGF gene -634G/C polymorphism has a significant association with ONFH occurrence among the investigated patients (P<0.01).

Gaps and opportunities in the management of the young femoral neck fracture

Femoral neck fractures in young adults are difficult to treat. There are substantial gaps in our knowledge regarding treatment and prevention of young adult femoral neck fractures. Avoiding malunion or nonunion of these fractures after fixation remains a challenge. Currently available fixation techniques may allow for healing to occur, but in a shortened position, with negative consequences on gait mechanics and physical function. Osteonecrosis remains a problem, affecting up to half of patients who sustain femoral neck fractures. Achieving reliable healing may require a reconsideration of fracture fixation implants as well as biological methods to address metabolic, endocrine, and/or genetic abnormalities that may be present in the young adult femoral neck fracture patient. Also, prevention of low-energy femoral neck fractures (e.g. stress fracture) remains an area ripe for investigation.

Cajan leaf combined with bone marrow-derived mesenchymal stem cells for the treatment of osteonecrosis of the femoral head

The aim of the present study was to observe the curative effect of traditional Chinese cajan leaves, combined with administration of bone marrow-derived mesenchymal stem cells (BMSCs), on osteonecrosis of the femoral head (ONFH) in rats and to investigate the underlying mechanisms. A total of 40 rat ONFH models were established through liquid nitrogen freezing and were subsequently divided into groups: A, control; B, treated with cajan leaf; C, treated with BMSCs and D, treated with cajan leaf combined with BMSCs. Samples were obtained 30 days following treatment, and immunohistochemical staining of vascular endothelial growth factor (VEGF) and image analysis were performed. Chondrocytes and vascular endothelial cells were stained as a result of immunohistochemical staining and group D exhibited markedly deeper staining, and a significantly larger number of stained cells, compared with group A. Thus, in the present study, cajan leaf combined with BMSCs was shown to promote VEGF expression and improve ONFH repair.

Association between VEGF -634G/C polymorphism and diseases

Vascular endothelial growth factor (VEGF) is a special heparin-binding growth factor, and can significantly stimulate vasculogenesis and angiogenesis in both cancer and healthy tissues. There have been many studies confirming that the single nucleotide polymorphisms (SNP) of VEGF have a close relationship with the occurrence, development, and prognosis of diseases. According to statistics, the human VEGF gene has at least 30 SNP loci, among which VEGF -634C/G, -936C/T and -2578C/A mutations have been proved to regulate the VEGF plasma levels. Here we review the recent advances in understanding the association between VEGF -634G/C polymorphism and diseases.

An association study between hypoxia inducible factor-1alpha (HIF-1α) polymorphisms and osteonecrosis

Bone hypoxia resulting from impaired blood flow is the final pathway for the development of osteonecrosis (ON). The aim of this study was to evaluate if HIF-1α, the major transcription factor triggered by hypoxia, is genetically implicated in susceptibility to ON. For this we analyzed frequencies of three known HIF-1α polymorphisms: one in exon 2 (C111A) and two in exon 12 (C1772T and G1790A) and their association with ON in a Greek population. Genotype analysis was performed using PCR-RFLP and rare alleles were further confirmed with sequencing. We found that genotype and allele frequency of C1772T and G1790A SNP of HIF-1α (SNPs found in our cohort) were not significantly different in ON patients compared to control patients. Furthermore these SNPs could not be associated with the different subgroups of ON. At the protein level we observed that the corresponding mutations (P582S and A588T, respectively) are not significant for protein function since the activity, expression and localization of the mutant proteins is practically indistinguishable from wt in HEK293 and Saos-2 cells. These results suggest that these missense mutations in the HIF-1α gene are not important for the risk of developing ON.

Genetic risk factors for glucocorticoid-induced osteonecrosis: a meta-analysis

Glucocorticoid-induced osteonecrosis is a common and severe adverse event. We conducted a meta-analysis to investigate whether polymorphisms in target genes were associated with the risk of corticosteroid-induced osteonecrosis. Published literature from PubMed and EMBASE were searched for eligible publications. Pooled odds ratio (OR) and 95% confidence interval (CI) were calculated using a fixed- or random-effects model. There were 23 articles with 35 genes described the relationship between polymorphisms and glucocorticoid-induced osteonecrosis. Meta-analyses were carried out for those SNPs with three or more eligible studies, which included four SNPs located in three genes (PAI-1, MTHFR, ABCB1). The meta-analysis revealed that the PAI-1 4G allele was associated with an increased risk of osteonecrosis compared with the 5G allele (combined studies: OR=1.932, 95% CI=1.145-3.261). The OR for the 4G/4G vs. 5G/5G genotype of PAI-1 was 3.217 (95% CI 1.667-6.209 with combined studies), The relative risk of osteonecrosis was increased in the 4G allele vs. 5G/5G and 4G/4G genotype vs. 5G allele, with odds ratios of 2.304 (95% CI=1.235-4.299) and 2.307 (95% CI=1.527-3.485) in combined studies, respectively. The ABCB1 C3435T genotype distributions available confirmed that the C allele increased osteonecrosis risk compared with the T allele (OR 1.668, 95% CI=1.214-2.293) and TT genotype (OR 2.946, 95% CI=1.422-6.101). There was no evidence for significant association between MTHFR C677T and ABCB1 G2677T/A polymorphisms and risk of osteonecrosis. Results of this meta-analysis indicate that the PAI-1 4G/5G and ABCB1 C3435T polymorphisms may be risk factors for osteonecrosis.

Bone vascularization in normal and disease conditions

Bone vasculature is essential for many processes, such as skeletal development and growth, bone modeling and remodeling, and healing processes. Endothelium is an integral part of bone tissue, expressing a physiological paracrine function via growth factors and chemokines release, and interacting with several cellular lines. Alterations of the complex biochemical interactions between vasculature and bone cells may lead to various clinical manifestations. Two different types of pathologies result: a defect or an excess of bone vasculature or endothelium metabolism. Starting from the molecular basis of the interactions between endothelial and bone cells, the Authors present an overview of the recent acquisitions in the physiopathology of the most important clinical patterns, and the modern therapeutic strategies for their treatments.