The effect of TGF-β1 polymorphism on systemic sclerosis: a systematic review and pooled analysis of available literature.

Transforming growth factor-β1 (TGF-β1) plays an important role in the pathogenesis of systemic sclerosis (SSc). To investigate whether TGF-β1 gene promoter polymorphisms were associated with the susceptibility of SSc, we performed a meta-analysis based on all available studies through PubMed, Elsevier Science Direct, Embase, and Chinese Biomedical, China National Knowledge Infrastructure and Google Scholar with the last report up to March 15, 2013. Crude odds ratios with 95% confidence intervals were used to estimate the strength of the association. A fixed or random effects model was adopted according to heterogeneity test. Heterogeneity among studies was evaluated using I (2) . Meta-regression was used to explore potential sources of between-study heterogeneity. Publication bias was estimated using Begg's and Egger's test. Totally, seven papers with 663 SSc patients and 908 healthy controls were subjected to the final analysis. These studies encompass seven for TGF-β1 codon 10, three for codon 25 and three for -509C/T. We failed to detect any association of these promoter polymorphism with SSc susceptibility. For TGF-β1 codon 10 polymorphism, subgroup analyses by race, genotype testing method and classification of SSc were further performed. Similarly, no association was observed. Significant heterogeneity was detected among the studies in all genetic models of TGF-β1 codon 10 polymorphism. Publication bias was absent. Taken together, our meta-analysis did not provided an evidence of confirming association between TGF-β1 (codon 10, codon 25, -509C/T) gene polymorphism and SSc. Nevertheless, due to smaller sample sizes, larger sample studies including different ethnic groups should be considered in future to confirm our results.