Investigation of multiple populations highlight VEGFA polymorphisms to modulate anterior cruciate ligament injury.

Polymorphisms in VEGFA and KDR encoding proteins have been associated with anterior cruciate ligament (ACL) injury risk. We leveraged a collective sample from Sweden, Poland, and Australia to investigate the association of functional polymorphisms in VEGFA and KDR with susceptibility to ACL injury risk. Using a case-control genetic association approach, polymorphisms in VEGFA and KDR were genotyped and haplotypes inferred from 765 controls, and 912 cases clinically diagnosed with ACL rupture. For VEGFA, there was a significant overrepresentation of the rs2010963 CC genotype (p = 0.0001, false discovery rate [FDR]: p = 0.001, odds ratio [OR]: 2.16, 95% confidence interval [CI]: 1.47-3.19) in the combined ACL group (18%) compared to the combined control group (11%). The VEGFA (rs699947 C/A, rs1570360 G/A, rs2010963 G/C) A-A-G haplotype was significantly (p = 0.010, OR: 0.85, 95% CI: 0.69-1.05) underrepresented in the combined ACL group (23%) compared to the combined control group (28%). In addition, the A-G-G construct was significantly (p = 0.036, OR: 0.81, 95% CI: 0.64-1.02) underrepresented in the combined ACL group (12%) compared to the combined CON group (16%). Our findings support the association of the VEGFA rs2010963 CC genotype with increased risk and (ii) the VEGFA A-A-G haplotype with a reduced risk, and are in alignment with the a priori hypothesis. Collectively identifying a genetic interval within VEGFA to be implicated in ACL risk modulation and highlight further the importance of vascular regulation in ligament biology.

Risk modelling further implicates the angiogenesis pathway in anterior cruciate ligament ruptures.

The aim of this study was to explore the interactions between the interleukins and the angiogenesis signalling pathway, following a pathway-based approach. Statistical modelling tools were used to develop a preliminary polygenic risk assessment model for anterior cruciate ligament (ACL) ruptures, incorporating the angiogenesis signalling genes (VEGFA and KDR) and interleukins (IL1B, IL6, IL6R) which also function to regulate angiogenesis. Multivariate logistic regression analysis was used to identify the most informative contributors to ACL rupture risk from a range of eleven potential intrinsic risk factors: age, sex, BMI and eight genetic polymorphisms within five genes, namely, IL1B rs16944 C/T, IL6 rs1800795 G/C, IL6R rs2228145 C/A, VEGFA rs699947 C/A, VEGFA rs1570360 G/A, VEGFA rs2010963 C/G, KDR rs2071559 A/G and KDR rs1870377 T/A. A total of 232 asymptomatic controls (CON) and 234 participants with surgically diagnosed ACL ruptures, of which 135 participants reported a non-contact mechanism of injury (NON subgroup), were previously genotyped for the selected polymorphisms. The polygenic risk model identified the VEGFA rs699947 CC genotype (p = 0.024, odds ratio (OR): 3.35, 95% confidence interval (CI): 1.17-9.62), VEGFA rs2010963 GC genotype (p = 0.049, OR: 2.43, 95% CI: 1.00-5.87), age (p = 0.011, OR: 0.97, 95% CI: 0.95-0.99) and BMI (p = 0.009, OR:1.09, 95% CI: 0.57-2.11) as the most significant predictors of ACL rupture risk from the data included. The results of this study highlight VEGFA, age and BMI as biologically significant components of this network requiring further investigation in the context of musculoskeletal soft tissue injury risk.HighlightsThe findings of this study highlight the VEGFA gene, age and BMI as biologically significant contributors to ACL rupture susceptibility.Upon further validation of these risk factors, they may be included in genetic risk assessment tools to design pre-habilitation strategies, prescribe appropriate treatment strategies after injury or to assess how an individual is likely to respond to load.Polygenic risk models aid in highlighting the components of the complex ECM remodelling pathway requiring further investigation, using a multidisciplinary approach.VEGFA is a key angiogenic protein contributing to ECM homeostasis and may therefore have potential therapeutic implications that need to be explored.

Functional polymorphisms within the inflammatory pathway regulate expression of extracellular matrix components in a genetic risk dependent model for anterior cruciate ligament injuries.

OBJECTIVES: To investigate the functional effect of genetic polymorphisms of the inflammatory pathway on structural extracellular matrix components (ECM) and the susceptibility to an anterior cruciate ligament (ACL) injury. DESIGN: Laboratory study, case-control study. METHODS: Eight healthy participants were genotyped for interleukin (IL)1B rs16944 C>T and IL6 rs1800795 G>C and classified into genetic risk profile groups. Differences in type I collagen (COL1A1), type V collagen (COL5A1), biglycan (BGN) and decorin (DCN) gene expression were measured in fibroblasts either unstimulated or following IL-1ß, IL-6 or tumor necrosis factor (TNF)-α treatment. Moreover, a genetic association study was conducted in: (i) a Swedish cohort comprised of 116 asymptomatic controls (CON) and 79 ACL ruptures and (ii) a South African cohort of 100 CONs and 98 ACLs. Participants were genotyped for COL5A1 rs12722 C>T, IL1B rs16944 C>T, IL6 rs1800795 G>C and IL6R rs2228145 G>C. RESULTS: IL1B high-risk fibroblasts had decreased BGN (p=0.020) and COL5A1 (p=0.012) levels after IL-1ß stimulation and expressed less COL5A1 (p=0.042) following TNF-α treatment. Similarly, unstimulated IL6 high-risk fibroblasts had lower COL5A1 (p=0.012) levels than IL6 low-risk fibroblasts. In the genetic association study, the COL5A1-IL1B-IL6 T-C-G (p=0.034, Haplo-score 2.1) and the COL5A1-IL1B-IL6R T-C-A (p=0.044, Haplo-score: 2.0) combinations were associated with an increased susceptibility to ACL injury in the Swedish cohort when only male participants were evaluated. CONCLUSIONS: This study shows that polymorphisms within genes of the inflammatory pathway modulate the expression of structural and fibril-associated ECM components in a genetic risk depended manner, contributing to an increased susceptibility to ACL injuries.

Are MMP3, MMP8 and TIMP2 gene variants associated with anterior cruciate ligament rupture susceptibility?

OBJECTIVES: Anterior cruciate ligament rupture (ACLR) is a common and severe knee injury which typically occurs as a result of sports participation, primarily via a non-contact mechanism. A number of extrinsic and intrinsic risk factors, including genetics, have been identified thus far. Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteases (TIMPs) play a crucial role in extracellular matrix remodeling of ligaments and therefore the genes encoding MMPs and TIMPs are plausible candidates for investigation with ACL rupture risk. DESIGN: A case-control genetic association study was conducted on 229 (158 male) individuals with surgically diagnosed primary ACLR, ruptured through non-contact mechanisms and 192 (107 male) apparently healthy participants (CON) without any history of ACLR. All participants were physically active, unrelated, self-reported Caucasians. METHODS: All participants were genotyped for four single nucleotide polymorphisms (SNP): MMP3 (rs591058C/T, rs679620 G/A), MMP8 (rs11225395C/T), and TIMP2 (rs4789932 G/A) using standard PCR assays. Gene-gene interactions were inferred. Single-locus association analysis was conducted using the Chi-square test. SNP-SNP interaction effects were analysed using multifactor dimensionality reduction (MDR) method. RESULTS: Genotype frequencies did not significantly differ between cases and controls, however, the MMP3 rs679620 G and rs591058C alleles were significantly overrepresented in cases compared to controls (p=0.021, OR=1.38, 95% CI: 1.05-1.81). CONCLUSIONS: These results support the hypothesis that genetic variation within MMP3 contributes to inter-individual susceptibility to non-contact ACLR. However, these results need to be explored further in larger, independent sample sets.

Interactions between COL5A1 Gene and Risk of the Anterior Cruciate Ligament Rupture.

Collagen alpha-1(V) chain, encoded by the COL5A1 gene, plays a crucial role in abundant fibrillar collagens supporting many tissues in the body containing type I collagen and appears to regulate the association between heterotypic fibers composed of both type I and type V collagen occurring among others in muscles, tendons and ligaments. Taking this fact into consideration we decided to examine the association between COL5A1 rs12722 and rs13946 polymorphisms, individually and as inferred haplotypes, with anterior cruciate ligament rupture risk (ACLR) in professional soccer players. A total of 134 male professional soccer players with surgically diagnosed primary anterior cruciate ligament ruptures and 211 apparently healthy male professional soccer players, who were without any self-reported history of ligament or tendon injury, were included in the study. Both the cases and the healthy controls were recruited from the same soccer teams, of a similar age category, and had a comparable level of exposure to anterior cruciate ligament injury. Genomic DNA was extracted from oral epithelial cells using GenElute Mammalian Genomic DNA MiniprepKit. All samples were genotyped for the rs12722 and rs13946 polymorphisms using a Rotor-Gene realtime polymerase chain reaction. Statistically significant differences in the genotype frequencies for the COL5A1 rs13946 polymorphisms in dominant modes of inheritance occurred (p = 0.039). Statistically significant differences were documented only in the dominant model under the representation tendency of the C-C haplotype in the ACLR group compared to controls (p = 0.038). Our results suggest that variation in the COL5A1 gene may be one of the non-modifiable factors associated with the ACL injury in professional soccer players. The C-C rs12722-rs13946 haplotype provides a protective effect against the ACL tear.

Investigation of angiogenesis genes with anterior cruciate ligament rupture risk in a South African population.

The angiogenesis-signalling pathway is a physiological response after mechanical loading to promote matrix remodelling and thereby maintain tissue homeostasis. Studies have shown increased expression of angiogenic molecules in response to loading and in ruptured ligaments. Recently, polymorphisms within the vascular endothelial growth factor A (VEGFA) and kinase insert-domain receptor (KDR) genes were associated with risk of anterior cruciate ligament (ACL) ruptures and Achilles tendinopathy in Caucasian study groups. A case-control genetic association study was conducted on 100 controls and 98 participants with surgically-diagnosed ACL ruptures; of which 51 participants reported non-contact mechanism of injury (NON). All participants were genotyped for five functional polymorphisms: VEGFA (rs699947, rs1570360, rs2010963) and KDR (rs2071559, rs1870377). Haplotypes were inferred. In the male participants, the KDR rs2071559 AG genotype was significantly over-represented (P = 0.048, OR: 1.90, 95% CI: 1.00-3.59) in the controls. Furthermore, the GG genotype was significantly under-represented in the male controls compared to the male ACL group (P = 0.018, OR: 2.77, 95% CI: 1.17-6.55) and the male NON subgroup (P = 0.013, OR: 3.26, 95% CI: 1.24-8.58). Haplotype analysis implicated the KDR gene in all participants and in male participants separately. Collectively, these results implicate the angiogenesis-signalling pathway as a potentially key biological pathway contributing to ACL injury susceptibility.

Modulators of the extracellular matrix and risk of anterior cruciate ligament ruptures.

OBJECTIVES: The extracellular matrix (ECM) of ligaments continuously undergoes remodelling in order to maintain tissue homeostasis. Several key mediators of ECM remodelling were chosen for investigation in the present study. It is thought that polymorphisms within genes encoding signalling molecules may contribute to inter-individual variation in the responses to mechanical loading, potentially altering risk of injury. DESIGN: A genetic association study was conducted on 232 asymptomatic controls (CON) and 234 participants with surgically diagnosed anterior cruciate ligament (ACL) ruptures; of which 135 participants reported a non-contact mechanism of injury (NON subgroup). METHODS: All participants were genotyped for ten variants in eight genes encoding ECM remodelling proteins. Haplotypes and allele combinations were also inferred. RESULTS: The CASP8 rs3834129 ins allele was significantly over-represented in the male CON group compared to the male NON subgroup (p=0.047, OR: 1.46, 95% CI: 1.01-2.12). In female participants, the IL1B rs16944 TT genotype was significantly under-represented in the CON group compared to the NON subgroup (p=0.039, OR: 3.06, 95% CI: 1.09-8.64). Haplotype analysis revealed an under-representation of the CASP8 rs3834129-rs1045485 del-G haplotype in the CON group compared to both the ACL group (p=0.042; haplo.score:2.03) and the NON subgroup (p=0.037; haplo.score:2.09). Furthermore, following a pathway-based approach, genetic variants involved in the cell signalling cascade were associated with ACL injury risk. CONCLUSIONS: The novel independent associations and allele combinations observed implicate the apoptosis and cell signalling cascades as potential contributors to ACL injury susceptibility. Furthermore, these genetic variants may potentially modulate ECM remodelling in response to loading and ultimately contribute to ligament capacity.

Human Genetic Variation, Sport and Exercise Medicine, and Achilles Tendinopathy: Role for Angiogenesis-Associated Genes.

Sport and Exercise Medicine is one of the important subspecialties of 21st century healthcare contributing to improving the physical function, health, and vitality of populations while reducing the prevalence of lifestyle-related diseases. Moreover, sport and exercise are associated with injuries such as Achilles tendinopathy, which is a common tendon injury. The angiogenesis-associated signaling pathway plays a key role in extracellular matrix remodeling, with increased levels of angiogenic cytokines reported after cyclic stretching of tendon fibroblasts. We investigated the variants in angiogenesis genes in relation to the risk of Achilles tendinopathy in two population samples drawn independently from South Africa (SA) and the United Kingdom (UK). The study sample comprised 120 SA and 130 UK healthy controls, and 108 SA and 87 UK participants with Achilles tendinopathy. All participants were genotyped for five functional polymorphisms in the vascular endothelial growth factor, A isoform (VEGFA) (rs699947, rs1570360, rs2010963) and kinase insert-domain receptor (KDR) genes (rs1870377, rs2071559). The VEGFA A-G-G inferred haplotype was associated with an increased risk of Achilles tendinopathy in the SA group (15% in controls vs. 20% in cases, p = 0.048) and the combined SA+UK group (14% in controls vs. 20% in cases, p = 0.009). These new findings implicate the VEGFA gene with Achilles tendinopathy risk, while highlighting the potential biological significance of the angiogenesis signaling pathway in the etiology of Achilles tendinopathy. The evidence suggesting a genetic contribution to the susceptibility of sustaining a tendon injury is growing. We anticipate that high-throughput and multi-omics approaches, building on genomics, proteomics, and metabolomics, may soon uncover the pathophysiology of many diseases in the field of Sports and Exercise Medicine, as a new frontier of global precision medicine.

Towards an Understanding of the Genetics of Tendinopathy.

To date, more than 18 genomic intervals, which underpin the complex myriad of extracellular matrix interactions of tendons, have been implicated in risk models for tendinopathy. It is these relationships that most likely regulate the tissue's response to loading and unloading, thereby dictating the overall capacity of tendons and influencing injury susceptibility. The evidence suggesting a genetic contribution to the susceptibility of sustaining a tendon injury is growing. However, only a few of the loci have been repeated in independent studies, of which some have included a range of musculoskeletal soft tissues injuries. Case-control study designs can be effective in capturing risk, provided that the cases and controls are equally well-defined and carefully considered. The genome consists of 3.6 × 10(9) sequences and therefore we realise that we are far from decoding all the genomic signatures. We are indeed fortunate to be living in such exciting times where high-throughput technologies are at our disposal. Through collaboration, our chances of harnessing these "omics" technologies to further our clinical understanding of tendinopathy will increase.

Genes and Musculoskeletal Soft-Tissue Injuries.

There is mounting evidence suggesting a genetic contribution to the susceptibility of sustaining a musculoskeletal soft-tissue injury. To date, more than 70 loci have been implicated in several injury profiles. The genes implicated through these loci encode a broad spectrum of matrix proteins including collagens and non-collagens. The large majority of these studies have followed a candidate gene case-control study design. A small proportion of these loci have been repeated in independent studies, of which some have included different musculoskeletal injuries. However, the large majority of these studies are underpowered to detect contributions of small effect sizes (odds ratio <2.0). It is therefore critical that large data sets are collected and that consortia are established to effectively pool resources to understand the biological significance of these genetic loci and risk susceptibility. We are in the era of omics and high-throughput technologies but it is only through collaborations that we will realize the clinical significance of the genomic revolution and its application to musculoskeletal soft-tissue injury susceptibility.

The association of genes involved in the angiogenesis-associated signaling pathway with risk of anterior cruciate ligament rupture.

Angiogenesis-associated signaling is a fundamental component in the remodeling of the extracellular matrix in response to loading. Genes encoding protein components within this signaling cascade are therefore suitable candidates for investigation into ACL injury susceptibility: namely, vascular endothelial growth factor A isoform (VEGFA), kinase insert-domain receptor (KDR), nerve growth factor (NGF), and hypoxia inducible factor-1α (HIF1A). A case-control genetic association study was conducted on 227 asymptomatic control participants and 227 participants with surgically diagnosed ACL ruptures of which 126 participants reported a non-contact mechanism of rupture. All participants were genotyped for seven polymorphisms within the four genes. The VEGFA rs699947 CC genotype (p=0.010, OR: 1.92, 95% CI: 1.17-3.17) was significantly over-represented within participants with non-contact ACL ruptures. The VEGFA rs1570360 GA genotype was significantly over-represented in the CON group (p=0.007, OR: 1.70, 95% CI: 1.16-2.50). Furthermore, the KDR rs2071559 GA genotype was significantly over-represented in the female controls (p=0.023, OR: 2.16, 95% CI: 1.11-4.22). Inferred haplotype analyses also implicated genomic regions spanning the VEGFA and KDR genes. These novel findings suggest that regions within VEGFA and KDR may be implicated in the pathophysiology of ACL ruptures; highlighting the potential biological significance of angiogenesis-associated signaling in the aetiology of ACL ruptures.