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Liya Pi, Huiming Xia, JianWen Liu, Edward Scott; The Role Of Connective Tissue Growth Factor In Retinal Angiogenesis During Postnatal Development. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4826.
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This study utilizes murine neonatal model to determine the function of connective tissue growth factor (CTGF) in retinal angiogenesis during postnatal development.
The levels of CTGF mRNA and protein were detected by semi-quantitative RT-PCR and immunohistochemistry. Transgenic mice expressing GFP from the CTGF promoter (CTGFp-GFP) were utilized to determine the cellular sources of CTGF. Astrocytes were stained with glial fibrillary acidic protein (GFAP) antibody. Blood vessels were perfused with TRITC-conjugated dextran sulfate or stained with Griffonia simplicifolia isolectin B4 (GSI) to label basal membranes of endothelial cells. In addition, primary CD31+ retinal endothelial cells and astrocytes were isolated and used to test the adhesive and migratory activities of recombinant CTGF proteins in vitro in Boyden chamber assay and cell adhesion assay. Furthermore, antibodies recognizing the C terminus of CTGF protein and rabbit IgG control were injected into the intraocular region between the equator and the corneal limbus of the right eyes of postnatal day 1 (p1) mice carrying GFP under the control of GFAP promoter (GFAPp-GFP). 48 hours later, IgG-treated, CTGF antibody-treated, and collateral retinas were stained with GSI and flatmounted followed by confocal microscopy analysis.
CTGF transcript and protein were barely detected at p0, but increased during postnatal development and reached to a plateau at adult stage. CTGF proteins were distributed in the ganglion cell layer within the first postnatal week and appeared in the inner nuclear layer after that. CTGF expression as indicated by GFP reporter was found in perivascular cells but not astrocytes. CTGF antibody-treated retinas had a 43% decrease of vascular areas and a 2.4-fold decrease of filopodia numbers per 100-um-membrane length as compared with the ones that were injected with control IgG. Large tubules formed by sparse GFAPp-GFP+ astrocytes were also associated with the disturbed filopodial extension at the vascular fronts in CTGF antibody treated mice, indicating that CTGF inhibition affected the remodeling of astrocyte networks in front of nascent blood vessels. In vitro assays show that recombinant CTGF protein promoted the adhesion of primary CD31+ endothelial cells and the migration of primary astrocytes.
CTGF is a vascular specific product, acts on multiple cell types and is important for retinal angiogenesis during postnatal development.
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