ABSTRACT
Parathyroid hormone (PTH) regulation of matrix metalloproteinase-13 (MMP-13) expression in osteoblasts contributes to normal bone turnover. The PTH response region of the rat MMP-13 gene spans nucleotides (nt) -148 to -38 and supports binding of numerous transcription factors, including Runx2, necessary for osteoblast differentiation, c-Fos/c-Jun, and Ets-1. These trans-acting proteins mediate hormone induction via incompletely defined combinatorial interactions. Within this region, adjacent to the distal Runx2 site, is a homopolymeric(dA:dT) element (-119/-110 nt) that conforms to the consensus site for the novel transcription factor nuclear matrix protein-4/cas interacting zinc finger protein (Nmp4/CIZ). This protein regulates bone cell expression of type I collagen and suppresses BMP2-enhanced osteoblast differentiation. The aim of this study was to determine whether Nmp4/CIZ contributes to MMP-13 basal transcription and PTH responsiveness in osteoblasts. Electrophoretic mobility shift analysis confirms Nmp4/CIZ binding within the MMP-13 PTH response region. Mutation of the Nmp4/CIZ element decreases basal activity of an MMP-13 promoter-reporter construct containing the first 1329 nt of the 5'-regulatory region, and overexpression of Nmp4/CIZ protein enhances the activity of the wild-type promoter. The same mutation of the homopolymeric(dA:dT) element enhances the MMP-13 response to PTH and PGE(2). Overexpression of Nmp4/CIZ diminishes hormone induction. Mutation of both the homopolymeric(dA:dT) element and the adjacent Runx2 site further augments the PTH response. On the basis of these data and previous studies, we propose that Nmp4/CIZ is a component of a multiprotein assemblage or enhanceosome within the MMP-13 PTH response region and that, within this context, Nmp4/CIZ promotes both basal expression and hormonal synergy.
Subject(s)
Collagenases/metabolism , Gene Expression Regulation , Nuclear Matrix-Associated Proteins/metabolism , Osteoblasts/metabolism , Parathyroid Hormone/physiology , Trans-Activators/metabolism , Transcription Factors/metabolism , 3T3 Cells , Animals , Collagenases/genetics , Enhancer Elements, Genetic/genetics , Enhancer Elements, Genetic/physiology , Matrix Metalloproteinase 13 , Mice , Osteoblasts/cytology , Promoter Regions, Genetic , Rats , Response Elements/genetics , Response Elements/physiology , Transcription, Genetic/physiology , Tumor Cells, Cultured , Zinc Fingers/physiologyABSTRACT
The relationship between bone and the kidney in renal osteodystrophy is a complex interplay of kidney to bone connections, bone to kidney connections, and cell to cell connections. In addition, such interactions have a profound effect on the vasculature. In this review, we discuss the role of the bone morphogenetic proteins (BMPs) in the skeleton, kidney, and vasculature. In addition, we propose that deficiencies of these BMPs seen in chronic kidney disease (CKD) result in decreased bone remodeling and a compensatory secondary hyperparathyroidism (high turnover state). Treatment of the hyperparathyroidism blocks this compensatory arm and thus decreased bone remodeling occurs (low turnover). We review animal models of CKD in which treatment with BMP-7 resulted in normalization of both high and low turnover states. Finally, we discuss vascular calcification as it relates to bone metabolism. We discuss the roles of BMP-7 and 2 other bone regulatory proteins, osteoprotegerin (OPG) and alpha2-HS glycoprotein (AHSG, human fetuin), in the human vasculature and their implications for vascular calcification.
Subject(s)
Bone Morphogenetic Proteins/metabolism , Bone Remodeling/physiology , Cell Communication/physiology , Chronic Kidney Disease-Mineral and Bone Disorder/metabolism , Glycoproteins/metabolism , Kidney/metabolism , Parathyroid Hormone/metabolism , Receptors, Cytoplasmic and Nuclear/metabolism , Humans , Muscle, Smooth, Vascular/metabolism , Osteoprotegerin , Receptors, Tumor Necrosis FactorABSTRACT
Rare cells are present in human umbilical cord blood that do not express the hematopoietic marker CD45 and in culture do not produce cells of hematopoietic lineage. These umbilical cord multipotent stem cells (UC-MC) behave as multilineage progenitor cells (stem cells) and can be expanded in tissue culture. Exposure to basic fibroblast growth factor (bFGF) and human epidermal growth factor (hEGF) for a minimum of 7 days in culture induces expression of neural and glial markers. Western immunoblots demonstrate expression of both beta-tubulin III and glial fibrillary acidic protein (GFAP). Immunocytochemistry of the cells showed intense labeling to both compounds on the intracellular cytoskeleton. The oligodendrocyte cell surface marker galactocerebroside (Gal-C) was present on most cells. Many cells show dual labeling, expressing both neuronal and glial markers.
Subject(s)
Cell Differentiation , Fetal Blood/cytology , Multipotent Stem Cells/physiology , Neuroglia/metabolism , Neurons/metabolism , Animals , Biomarkers , Cell Culture Techniques/methods , Cell Lineage , Cells, Cultured , Epidermal Growth Factor/pharmacology , Glial Fibrillary Acidic Protein/metabolism , Humans , Multipotent Stem Cells/cytology , Multipotent Stem Cells/drug effects , Nerve Growth Factor/pharmacology , Neuroglia/chemistry , Neurons/chemistry , Tubulin/metabolismABSTRACT
Rare cells are present in human umbilical cord blood that do not express the hematopoietic marker CD45 and in culture do not produce cells of hematopoietic lineage. These umbilical cord multipotent stem cells (UC-MC) behave as multilineage progenitor cells (stem cells) and can be expanded in tissue culture. Exposure to basic fibroblast growth factor (bFGF) and human epidermal growth factor (hEGF) for a minimum of 7 days in culture induces expression of neural and glial markers. Western immunoblots demonstrate expression of both ß-tubulin III and glial fibrillary acidic protein (GFAP). Immunocytochemistry of the cells showed intense labeling to both compounds on the intracellular cytoskeleton. The oligodendrocyte cell surface marker galactocerebroside (Gal-C) was present on most cells. Many cells show dual labeling, expressing both neuronal and glial markers.
