The Effect of BMP-4 on the Expression of BMP and TGFß Growth Factors and Their Receptors in Cells Isolated From the Human Optic Nerve Head

Abstract

Abstract: : Purpose: Bone morphogenetic proteins (BMPs) were originally identified as osteoinductive cytokines but recently have been shown to be involved in development, morphogenesis, cell proliferation, and apoptosis of a wide variety of tissues and cells. BMPs are members of the TGFß superfamily and act through two distinct transmembrane serine/threonine kinase receptors (BMP-RI and BMP-RII). We have previously reported that BMPs and BMP receptors are expressed by lamina cribrosa cells (LC) and optic nerve head (ONH) astrocytes [(Wordinger et al, Mol. Vis. (2002) 8:241-250)]. Members of the BMP family function in a gene dosage manner during development and participate in ocular development. Heterozygous deficiency of BMP-4 results in anterior segment dysgenesis and elevated IOP. In glaucoma the ONH is altered and BMP-4 may play an important role by interacting with the other members of the TGFß family. The purpose is to determine the effect of BMP-4 treatment on the expression of BMPs, BMPRs, TGFß-2 and TGFß receptors in cells isolated from the human ONH. Methods: Recombinant BMP- 4 (20 ng/ml) was used to treat LC cells, and ONH astrocytes in serum free media for 72 hrs and compared with non-treated control. Total RNA was isolated and subjected to RT-PCR to examine the expression of mRNA for BMPs, BMP receptors, TGFß-2 and TGFß receptors in cultured human LC cells and ONH astrocytes. Western immunoblotting was used to study the expression of BMPs and TGFß-2 proteins. Results: Using semi-quantitative RT- PCR, BMP-4 treatment down-regulated mRNA for BMP-2, BMP-4, BMP-5, BMP-7, BMP-RIα, BMP-RIß, BMP-RII, TGFß-2 and TGFßR-II in the LC Cells. BMP-4 down regulated mRNA for BMP-4 and BMP-5 in ONH astrocytes. Conclusions: BMP-4 treatment causes down regulation of the BMPs, TGFß-2, and their receptors in cells isolated from the human ONH and may be involved in maintaining the normal microenvironment of the ONH. CR: P, F (RJW); E (AFC) Support: NIH Grant EY 12783 and Alcon Research Ltd., Fort Worth, TX.

Keywords: growth factors/growth factor receptors • lamina cribrosa • gene/expression