[Analysis on polymorphism at -509 C/T site of TGF-β1 gene in patients with keloids]

To analyze the polymorphism at -509C/T site of TGF-β1 gene in patients with keloids, and to explore its relationship with the occurrence of keloid and its influence on the plasma level of TGF-β1.

One hundred and sixty-nine patients with keloids and hospitalized from June 2011 to April 2014 were included as keloid group, and 119 healthy blood donors were enrolled as healthy control group. Venous blood of study subjects was collected. The -509C/T genotype of TGF-β1 gene was determined with PCR-restriction fragment length polymorphism technique combined with DNA sequence analysis, and the frequency of allele C or T was calculated. The theoretical frequency of the 3 genotypes CC, CT, and TT was calculated according to the theory of Hardy-Weinberg equilibrium to determine whether the gene frequency of the study subject was group representative or not. The distribution of -509C/T genotype of TGF-β1 gene among patients in keloid group was analyzed by grouping in gender, age, with or without family history of keloid, and the number of keloid respectively. Plasma level of TGF-β1 of all study subjects was determined with ELISA, and the plasma level TGF-β1 of patients with various -509C/T genotypes of TGF-β1 gene in keloid group was analyzed. The relative risk of allele frequency of patients in keloid group was analyzed by Logistic regression analysis, and the other data were processed with chi-square test and t test.

Among the -509C/T genotypes of TGF-β1 gene between subjects in the two groups, the distribution of genotypes CC, CT, and TT was quite similar, and they were respectively 38 cases (22.5%), 79 cases (46.7%), and 52 cases (30.8%) in keloid group and 39 persons (32.8%), 52 persons (43.7%), and 28 persons (23.5%) in healthy control group (χ² = 4.225, P>0.05). The distribution frequency of alleles C and T in the two groups were obviously different, and they were respectively 45.9% and 54.1% in keloid group and 54.6% and 45.4% in healthy control group (χ² = 4.291, P<0.05). The theoretical frequency values of the three kinds of genotypes of CC, CT, and TT were respectively 35 cases (21.0%), 84 cases (49.7%), and 50 cases (29.3%) in keloid group, and 35 persons (29.8%), 59 persons (49.6%), and 25 persons (20.6%) in healthy control group. There were no statistically significant differences between the actual genotype frequency and the theoretical values (with χ² values respectively 0.581 and 1.672, P values above 0.05), showing that the research group reached Hardy-Weinberg equilibrium. Relative risk analysis of allele frequency showed that the risk of suffering from keloid of patients carrying allele C was 1.421 times of that of patients without carrying allele C (odds ratio = 1.421, with 95% confidence interval 1.109-1.983, P < 0.05). The distribution of -509C/T genotypes of TGF-β1 gene among patients in keloid group was similar by grouping in gender, age, and number of keloid (with χ² values 0.895-5.008, P values above 0.05). Between patients with or without family history of keloid, the differences of distribution frequencies of genotypes CC and CT were significantly different, which were respectively 61.8% (21/34) and 37.8% (51/135) in patients with family history of keloid and 14.7% (5/34) and 34.1% (46/135) in patients without a family history of keloid, with χ² values respectively 6.391 and 4.835, P values below 0.05; the distribution frequency of genotype TT was close (χ² = 0.292, P > 0.05). The plasma level of TGF-β1 of patients in keloid group was (42 ± 9) µg/L, which was significantly higher than that of people in healthy control group \[(34 ± 8) µg/L, t = 4.408, P < 0.05\]. In keloid group, the plasma level of TGF-β1 in patients with genotype CC and that of patients with genotype CT was quite similar, which were respectively (43 ± 9) and (40 ± 9) µg/L (t = 0.680, P > 0.05), and they were significantly higher than that of patients with genotype TT \[(34 ± 8) µg/L, with t values respectively 2.676 and 2.137, P values below 0.05\].

TGF-β1 gene -509C/T polymorphism was shown to be present in patients with keloids who were admitted to our hospital. It was shown to influence the plasma level of TGF-β1 in patients. The individuals who carry TGF-β1 allele C may increase the risk of developing keloid by promoting the expression of TGF-β1.