Lack of association of a functionally relevant single nucleotide polymorphism of matrix metalloproteinase-1 promoter with systemic sclerosis (scleroderma)

Analysis of TIMP-1 gene polymorphisms in Italian sclerodermic patients

Systemic sclerosis (SSc) is an autoimmune disease characterized by skin and internal organs fibrosis due to an extracellular matrix (ECM) accumulation of type I collagen. The turnover of the ECM is dependent on the balance between matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs). The disruption of this balance is involved in SSc because higher serum TIMP-1 levels have been demonstrated in SSc patients than in controls. On this basis, we analyzed three polymorphisms: -19A>G, +261C>T, and +372T>C of the TIMP-1 gene in SSc patients (67 females, eight males) and controls (29 females, nine males). The C allele of the +372T>C single nucleotide polymorphism (SNP) was observed at a higher frequency in male patients than in healthy individuals (P=0.02), while no differences were observed in the female subjects. Our findings suggest that the +372T>C polymorphism of the TIMP-1 gene is associated with SSc in male individuals. No association with the clinical characteristics of SSc Italian patients and TIMP-1 gene polymorphisms was observed. Thus, the role of TIMP-1 gene in predisposition to SSc remains controversial.

Matrix metalloproteinase-1 and -3 gene promoter polymorphisms in Japanese patients with periodontitis

BACKGROUND/AIMS

Matrix metalloproteinase (MMP)-1 and MMP-3 have important roles in the connective tissue remodelling and destruction processes in periodontitis. MMP-1 1G/2G (-1607) and MMP-3 5A/6A (-1171) polymorphisms have been identified and appear to influence the transcription of the genes. The aim of this study was to investigate whether these gene promoter polymorphisms were associated with the susceptibility to periodontitis.

MATERIAL AND METHODS

Genomic DNA was obtained from 37 generalised aggressive, 205 slight-to-severe generalised chronic-periodontitis patients and 142 healthy subjects. All subjects were non-smoking Japanese. We genotyped by using TaqMan PCR assay. The statistics were analysed by chi2-test.

RESULTS

We found no significant differences in genotype distributions, allele frequencies, carriage rates and haplotype frequencies in the MMP-1 and the MMP-3 gene promoter polymorphisms among all groups. The distributions of MMP-1 and MMP-3 genotypes in our study were different from those of previously reported in Caucasians or Brazilians, but consistent with previously reported in Japanese.

CONCLUSION

Our data did not support the hypothesis that MMP-1 and/or MMP-3 gene promoter polymorphisms influenced the susceptibility to periodontitis in Japanese patients, indicating MMP-1 and MMP-3 expressions were regulated by complex processes such as cytokine network in periodontal disease rather than gene polymorphisms.

Systemic sclerosis: the susceptible host (genetics and environment)

It is becoming evident that several genetic factors participate in modulating susceptibility to SSc and its clinical manifestations. Some genes that specifically affect ECM metabolism and vascular function may be unique to SSc and scleroderma-related disorders; others, such as those genes involved in regulating immune tolerance, are likely shared with other autoimmune diseases. The effect of genetic variations (or polymorphisms) that are found in most of these genes taken individually will likely have only a small or modest effect on disease risk; only a few genetic variations are expected to be highly penetrant. Moreover, genetic studies in SSc have to deal with the additional issues of heterogeneous phenotypes, low disease prevalence in the general population, and an even greater paucity of multiplex families that makes traditional linkage studies difficult, if not impossible. Alternative approaches include allelic association studies, but conventional case-controls designs may be subject to selection bias and will require large sample sizes if the genes that are under investigation confer only modest (OR = 1.5-2.0) disease risk (Fig. 2). The simultaneous examination of several genes that are biologically relevant to a specific disease process to attain higher aggregate ORs, is one approach that was used in several reports that were cited in this review. The use of family-based controls, such as in the transmission-disequilibrium test (based on assessment of the transmitted or nontransmitted alleles that are associated with disease from heterozygous parents to affected offspring), would provide more robustness to spurious associations from population stratification, but is actually less powerful and efficient than case-control designs. Furthermore, for many late adult-onset diseases the effort required to obtain samples from living parents are for a variety of reasons not trivial. The success of these allelic association-based approaches depends on the identification of likely candidate disease genes (or at least markers in disequilibrium with disease genes), careful definition/ascertainment of disease phenotypes to minimize genetic heterogeneity, and for case-control designs, strategies to account for population stratification or admixture. The identification of candidate genes will be aided by rapid progress in the Human Genome Project and other genome efforts that will eventually identify all human genetic variations. Although this will lead to better understanding of the genes that might be involved in complex diseases, much work is required to understand the basic biology of how disease genotypes become clinical phenotypes. This is especially daunting in complex diseases, such as SSc, where the phenotype (including disease susceptibility and clinical presentation) is influenced by dynamic interactions between genetic variations and environment. Multi-center collaborative efforts with research paradigms that integrate genetic and environmental factors (including sociodemographic variables) will be required to elucidate the contribution of environment and genetics in the pathogenesis of SSc.

Function blocking autoantibodies against matrix metalloproteinase-1 in patients with systemic sclerosis

Systemic sclerosis is characterized by fibrosis and systemic autoimmunity; however, roles of autoantibodies in the development of fibrosis remain unknown in systemic sclerosis. The net accumulation of extracellular matrix is dependent on the balance between the synthesis and degradation of extracellular matrix components, the latter process regulated by matrix metalloproteinases. Matrix metalloproteinase-1 (interstitial collagenase-1) can initiate degradation of collagen types I-III that are major extracellular matrix constituents in affected skin of systemic sclerosis. In this study, we tested the hypothesis that systemic autoimmunity in systemic sclerosis induced anti-matrix metalloproteinase-1 autoantibodies that inhibited matrix metallo-proteinase-1 activity, resulting in collagen accumulation. Enzyme-linked immunosorbent assay using human recombinant matrix metalloproteinase-1 revealed that IgG anti-matrix metalloproteinase-1 autoantibody levels were significantly elevated in sera from patients with systemic sclerosis, but not patients with active systemic lupus erythematosus or dermatomyositis, relative to normal controls. IgG anti-matrix metalloproteinase-1 autoantibody levels were significantly higher in patients with diffuse cutaneous systemic sclerosis than those found in patients with limited cutaneous systemic sclerosis. Furthermore, IgG anti-matrix metalloproteinase-1 antibody levels significantly correlated with the extent of fibrosis in the skin, lung, and renal blood vessels. The presence of IgG anti-matrix metalloproteinase-1 autoantibody in sera from systemic sclerosis patients was confirmed by immunoblotting analysis. Remarkably, IgG anti-matrix metalloproteinase-1 autoantibody in sera from systemic sclerosis patients inhibited matrix metalloproteinase-1 collagenase activity. Collectively, the results of this study suggest that anti-matrix metalloproteinase-1 autoantibody contributes to the development of fibrosis by inhibiting matrix metalloproteinase-1 collagenase activity and reducing the extracellular matrix turnover and suggest that the presence of anti-matrix metalloproteinase-1 autoantibody in systemic sclerosis is the link between systemic autoimmunity and fibrosis.

The genetics of systemic sclerosis

The etiopathogenesis of systemic sclerosis (SSc) is unclear. With no definitive evidence supporting an environmental cause, recent attention has focused on genetic factors. Familial clustering and ethnic influences have been demonstrated. Human leukocyte antigen (HLA) associations exist but are more related to the presence of particular autoantibodies rather than to the disease. In addition, no single major histocompatibility complex (MHC) allele predisposes to SSc in all ethnic groups. The role of microchimerism in SSc is a novel yet unproven hypothesis that may be related to intergenerational HLA compatibility. Recent studies investigating polymorphisms in genes coding for extracellular matrix proteins and cell-signaling molecules implicate non-MHC areas in SSc pathogenesis. The data reviewed suggest that SSc is a multigenic complex disorder.