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2007
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vol. 55
|
issue 4
247-259
EN
A special type of stem cells, defined as endothelial progenitor cells (EPCs), has been found in the bone marrow and peripheral blood. These EPCs are incorporated into injured vessels and become mature endothelial cells during re-endothelialization and neovascularization processes. Though a complete phenotypic description of EPCs remains unclear, these cells express several surface markers, the most relevant including CD34 and CD133 antigens. Furthermore, EPCs derived from other sources could also give rise to mature endothelial cells, which makes this group of cells more diverse. The recruitment of EPCs from the bone marrow to homing sites of vasculogenesis is subject to regulation by many factors, including chemokines and growth factors. The precise mechanism of EPC mobilization and differentiation is not entirely elucidated and is still under investigation. Recent studies have suggested that EPCs may promote local angiogenesis by secreting angiogenic growth factors in a paracrine manner. The number and function of EPCs can be affected during pathological conditions, including diabetes mellitus, cardiovascular risk factors for ischemic disease, and graft vasculopathy. Additionally, EPC number and migration capacity could be improved by such factors as drugs, physical exercise, and growth factors. Transplantation of EPCs into ischemic tissues may emerge as a promising approach in the therapy of diseases associated with blood vessel disorders.
EN
This article reviews and updates current information on the possible genetic basis for cutaneous lupus erythematosus. The aetiology of this condition remains unknown and is believed to be multifactorial, involving genetic, environmental and retroviral factors. A genetic predisposition is probably the greatest risk factor for this condition. Individual susceptibility to lupus erythematosus may be determined by a combination of specific polymorphisms of genes encoding multiple cytokines, adhesion molecules, and cellular proteins. This condition may lead to an abnormal expression of immunoregulatory molecules and finally results in the development or exacerbation of the disease. Recently also the role of endogenous retroviral sequences in the pathogenesis of autoimmunity has been discussed.
EN
Epigenetic alternations in genomic DNA encompass cytosine methylation in cytosine and guanine (CpG) dinucleotide islands, which are usually extended in the promoter and first exon of genes. The DNA methylation is carried out by DNA methyltransferases (DNMT) and it serves as an epigenetic method of gene expression modulation. The epigenetic alternations in genomic DNA have been implicated in the development of malignant and autoimmune diseases. The epigenetic aberration in regulatory DNA sequences may also be responsible for the emergence of changes in the immune system in patients with systemic lupus erythematosus (SLE). The agents 5-azacytidine (azacitidine) and 5-aza-2?-deoxycytidine (decitabine) belong to inhibitors of methyltransferase. These compounds affect the methylation level of promoter sequences and cause phenotypic changes in peripheral blood mononuclear cells (PBMC), which are similar to those observed in PBMC of SLE patients. The lack of methylcytosine in CpG dinucleotides may be responsible for the antigenic properties of microbial DNA. The presence of low-apoptotic methylated DNA fragments has been identified in plasma of SLE patients. These DNA fragments exhibit antigenic properties and may elicit the humoral response responsible for the flare of SLE. The low methylation of CpG residues in the regulatory sequences may also contribute to the elevated expression of human endogenous retroviruses (HERVs) in PBMC of SLE patients. The HERV components exhibit a profound similarity with nuclear antigens and may be responsible for the enhancement of the production of anti-antinuclear antibodies (ANA). Recent advances in the investigation of epigenetic DNA changes have formed the basis of improved understanding of etiopathogenesis of SLE, which may thereby facilitate improvement in therapeutic principles of this disease.
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