Shared gene expression profiles in developing heart valves and osteoblast progenitor cells

Abstract

The atrioventricular (AV) valves of the heart develop from undifferentiated mesenchymal endocardial cushions, which later mature into stratified valves with diversified extracellular matrix (ECM). Because the mature valves express genes associated with osteogenesis and exhibit disease-associated calcification, we hypothesized the existence of shared regulatory pathways active in developing AV valves and in bone progenitor cells. To define gene regulatory programs of valvulogenesis relative to osteoblast progenitors, we undertook Affymetrix gene expression profiling analysis of murine embryonic day (E)12.5 AV endocardial cushions compared with E17.5 AV valves (mitral and tricuspid) and with preosteoblast MC3T3-E1 (subclone4) cells. Overall, MC3T3 cells were significantly more similar to E17.5 valves than to E12.5 cushions, supporting the hypothesis that valve maturation involves the expression of many genes also expressed in osteoblasts. Several transcription factors characteristic of mesenchymal and osteoblast precursor cells, including Twist1, are predominant in E12.5 cushion. Valve maturation is characterized by differential regulation of matrix metalloproteinases and their inhibitors as well as complex collagen gene expression. Among the most highly enriched genes during valvulogenesis were members of the small leucine-rich proteoglycan (SLRP) family including Asporin, a known negative regulator of osteoblast differentiation and mineralization. Together, these data support shared gene expression profiles of the developing valves and osteoblast bone precursor cells in normal valve development and homeostasis with potential functions in calcific valve disease.

How to Make a Heart Valve: From Embryonic Development to Bioengineering of Living Valve Substitutes

“…Apoptosis in the OFT cushions is substantial at later fetal stages, consistent with ongoing remodeling processes (Poelmann and Gittenberger-de Groot 2005;Aikawa et al 2006;Jain et al 2011). Early overlapping gene expression patterns become restricted (Lincoln et al 2004;Chakraborty et al 2008). The transition from EC growth to remodeling requires calcineurin/NFATc1 signaling in the endocardium (de la Pompa et al 1998;Ranger et al 1998;Chang et al 2004), notably through the regulation of RANKL and Cathepsin K expression (Lange and Yutzey 2006).…”

“…From E11.5 onward, the ECs expand by mesenchyme proliferation driven by Bmp/TGF-b, Egf, Nf1/ras, and Wnt signaling (Gitler et al 2003;Iwamoto et al 2003;Jackson et al 2003;Krenz et al 2005;Alfieri et al 2010) and the combined activities of highly expressed mesenchyme-specific transcription factors, including Msx1/2, Runx2, Sox9, Twist1, and Tbx20 (Gitler et al 2003;Lincoln et al 2007;Shelton and Yutzey 2007;Chakraborty et al 2008Chakraborty et al , 2010. Septation of the OFT and AV junctions into separate R-L ventricular inlets is mediated by fusion of the EC structures.…”

“…The transition from EC growth to remodeling requires calcineurin/NFATc1 signaling in the endocardium (de la Pompa et al 1998;Ranger et al 1998;Chang et al 2004), notably through the regulation of RANKL and Cathepsin K expression (Lange and Yutzey 2006). Interstitial cell progenitors show transcriptional profiles normally associated with cartilage and tendon lineages (Lincoln et al 2006b;Chakraborty et al 2008). Expression of Sox9 is necessary for early interstitial cell proliferation and, subsequently, expression of cartilage matrix proteins (Akiyama et al 2004;Lincoln et al 2007), and scleraxis is required for tendinous cord specification (Levay et al 2008).…”

Notch pathway regulation of chondrocyte differentiation and proliferation during appendicular and axial skeleton development

“…Digoxygenin-labeled probes were amplified from mouse limb cDNA. The Col1a1 probe has been described previously (29). The in situ probes and PCR primers used are listed in Table S1.…”

Calcific Aortic Valve Disease

“…LDL receptor-related protein (LRP) signalling in bone is regulated through the canonical Wnt pathway. Wnt, a growth factor involved in bone and heart development (Clevers, 2006, Chakraborty et al, 2008, binds to receptors composed of frizzled protein and either of LRP5 or LRP6. This inhibits β-catenin degradation and leads to its accumulation and subsequent entry into the cellular nucleus.…”