Biomedical subjects

Vineeth Rajkumar

Publications and source records attributed to Vineeth Rajkumar.

4 recordsLinked to original sources

PubMed2006

Increased endogenous angiogenic response and hypoxia-inducible factor-1alpha in human critical limb ischemia.

OBJECTIVE: The potent physiologic endogenous angiogenic response to ischemic stimuli is often suboptimal, and therefore, a better understanding of the basic mechanisms is essential for the use in therapeutic angiogenesis. Hypoxia-inducible factor-1 (HIF-1) is a major transcription factor that promotes ischemia-driven angiogenesis and is induced when the HIF-1alpha subunit is upregulated. However, little is known about the endogenous angiogenic response and the role of HIF-1alpha in human critical limb ischemia (CLI). We aimed to investigate the extent of the angiogenic response and the expression of HIF-1alpha in the lower limbs of CLI patients. METHOD: Skeletal muscle biopsy specimens were obtained from the lower limbs of 12 patients with CLI and 12 patients without limb ischemia (controls), with ethical committee approval. Microvessel density (MVD) was determined by using endothelial marker anti-CD31, and HIF-1alpha expressions were determined by immunohistochemistry. MVD was measured as the median number of microvessels in x200 magnification fields. Five random fields per section and three sections per biopsy specimen were analyzed. Enzyme-linked immunoabsorbent assay and Western blotting were used to quantify the HIF-1alpha levels. Colocalization between cell-specific antigens was investigated by double immunofluorescence labelling by using confocal microscopy. Statistical analyses were performed with the Mann-Whitney U test. RESULTS: The CLI group have significantly higher MVD, with an increase of 2.7-fold compared with the controls (P < 0.001). HIF-1alpha expression was significantly increased in CLI muscles (P < 0.001) and was localized to vascular endothelial cells. CONCLUSIONS: Our findings suggest that the endogenous angiogenic response occurs in CLI. The increased HIF-1alpha level and colocalization to vascular endothelial cells suggest that HIF-1alpha plays a role in the physiologic endogenous angiogenic response in CLI. Therefore, augmentation of the HIF-1alpha pathway may be an important aspect in therapeutic angiogenesis.

Aged↗

PubMed2004

Extra-cellular matrix in vascular networks.

The vascular network is a series of linked conduits of blood vessels composed of the endothelium, a monolayer of cells that adorn the vessel lumen and surrounding layer(s) of mesenchymal cells (vascular smooth muscle, pericytes and fibroblasts). In addition to providing structural support, the mesenchymal cells are essential for vessel contractility. The extracellular matrix is a major constituent of blood vessels and provides a framework in which these various cell types are attached and embedded. The composition and organization of vascular extracellular matrix is primarily controlled by the mesenchymal cells, and is also responsible for the mechanical properties of the vessel wall, forming complex networks of structural proteins which are highly regulated. The extracellular matrix also plays a central role in cellular adhesion, differentiation and proliferation. This review examines the cellular and extracellular matrix components of vessels, with specific emphasis on the regulation of collagen type I and implications in vascular disease.

Animals↗

PubMed2003

Monocyte chemoattractant protein 3 as a mediator of fibrosis: Overexpression in systemic sclerosis and the type 1 tight-skin mouse.

OBJECTIVE: To determine the gene-expression profile in dermal fibroblasts from type 1 tight-skin (Tsk1) mice, and to examine the expression and potential fibrotic activity of monocyte chemoattractant protein 3 (MCP-3) in Tsk1 mouse and human systemic sclerosis (SSc) skin. METHODS: Complementary DNA microarrays (Atlas 1.2) were used to compare Tsk1 fibroblasts with non-Tsk1 littermate cells at 10 days, 6 weeks, and 12 weeks of age. Expression of MCP-3 protein was assessed by Western blotting of fibroblast culture supernatants, and localized in the mouse and human skin biopsy samples by immunohistochemistry. Activation of collagen reporter genes by MCP-3 was explored in transgenic mouse fibroblasts and by transient transfection assays. RESULTS: MCP-3 was highly overexpressed by neonatal Tsk1 fibroblasts and by fibroblasts cultured from the lesional skin of patients with early-stage diffuse cutaneous SSc. Immunolocalization confirmed increased expression of MCP-3 in the dermis of 4 of 5 Tsk1 skin samples and 14 of 28 lesional SSc skin samples, compared with that in matched healthy mice (n = 5) and human controls (n = 11). Proalpha2(I) collagen promoter-reporter gene constructs were activated by MCP-3 in transgenic mice and by transient transfection assays. This response was maximal between 16 and 24 hours of culture and mediated via sequences within the proximal promoter. The effects of MCP-3 could be diminished by a neutralizing antibody to transforming growth factor beta. CONCLUSION: We demonstrate, for the first time, overexpression of MCP-3 in early-stage SSc and in Tsk1 skin, and suggest a novel role for this protein as a fibrotic mediator activating extracellular matrix gene expression in addition to promoting leukocyte trafficking. This chemokine may be an important early member of the cytokine cascade driving the pathogenesis of SSc.

Adult↗

PubMed2002

Prostacyclin derivatives prevent the fibrotic response to TGF-beta by inhibiting the Ras/MEK/ERK pathway.

The SMAD-mediated induction of connective tissue growth factor (CTGF), a fibroproliferative cytokine, by transforming growth factor (TGF)beta is required for the development of sustained fibrosis in humans. Here, we show that in fibroblasts, activation of the Ras/MEK/ERK pathway is required for the SMAD-mediated induction of CTGF by TGFbeta2. We then show that activation of protein kinase A (PKA) in fibroblasts is able to block Ras/MEK/ERK signaling and abolish the fibrotic response. Previously, we found that prostacyclin agonists were able to prevent the induction of CTGF in fibroblasts, and in patients with the fibrotic disease scleroderma. Here, we confirm the in vitro and in vivo antifibrotic effects of prostacyclin derivatives and show that these effects are due to PKA-dependent inhibition of the Ras/MEK/ERK pathway. Ras/MEK/ERK does not directly affect SMAD signaling. The coordinate and varied biological responses to TGFbeta are in part due to the interactions of signaling pathways within target cells. Specific inhibition of fibroblast Ras/MEK/ERK signaling might prevent fibrosis while leaving other physiological effects of TGFbeta unaltered.

Animals↗