Endodermal growth factors promote endocardial precursor cell formation from precardiac mesoderm

AbstractWe previously demonstrated that the initial emergence of endocardial precursor cells (endocardial angioblasts) occurred within the precardiac mesoderm and that the endodermal secretory products promoted delamination of cells from the precardiac mesoderm and expression of endothelial lineage markers [Dev. Biol. 175 (1996), 66]. In this study, we sought to extend our original study to the identification of candidate molecules derived from the endoderm that might have induced endocardial precursor cell formation. We have detected expression of transforming growth factors β (TGFβ) 2, 3, and 4 in anterior endoderm at Hamburger and Hamilton (H-H) stage 5 by RT-PCR. To address the role of growth factors known to be present in the endoderm, precardiac mesodermal explants were isolated from H-H stage 5 quail embryos and cultured on the surface of collagen gels with serum-free defined medium 199. Similar to the effect of explants cocultured with anterior endoderm, when cultured with TGFβs 1–3 (3 ng/ml each), explants formed QH-1 (anti-quail endothelial marker)-positive mesenchymal cells, which invaded the gel and expressed the extracellular marker, cytotactin (tenascin). Another member of the TGFβ superfamily, bone morphogenetic protein-2 (BMP-2; 100 ng/ml), did not induce QH-1-positive mesenchymal cell formation but promoted formation of an epithelial monolayer on the surface of the collagen gel; this monolayer did not express QH-1. Explants treated with vascular endothelial growth factor (VEGF165, 100 ng/ml) also did not invade the gel but formed an epithelial-like outgrowth on the surface of the gel. However, this monolayer did express the QH-1 marker. Fibroblast growth factor-2 (FGF-2; 250 ng/ml)-treated explants expressed QH-1 and exhibited separation of the cells on the surface of the gel. Finally, a combination of TGFβs and VEGF enhanced formation of QH-1-positive cord-like structures within the gel from mesenchyme that had previously invaded the gel. Luminization of the cords, however, was not clearly evident. These findings suggest that TGFβs, among the growth factors tested, mediate the initial step of endocardial formation, i.e., delamination of endothelial precursor cells from precardiac mesoderm, whereas VEGF may primarily effect early vasculogenesis (cord-like structure formation)

Formation and Early Morphogenesis of Endocardial Endothelial Precursor Cells and the Role of Endoderm

AbstractThe formation of endocardial endothelium in quail embryos was investigated usingin vivoandin vitrosystems. Based on the expression of an quail endothelial marker, QH-1, the initial emergence of endothelial precursor cells in the embryo occurs at stage 7+(two somites) in the posterior parts of the bilateral heart forming regions. Cells that expressed the QH-1 antigen were mesenchymal and positioned between the mesodermal epithelium of the heart region and the endoderm. By confocal microscopy, an asymmetrical distribution of QH-1 positive cells was observed between the two heart regions: specifically between 7+and 8−, more precursor cells were seen in the right region than the left. Endothelial precursor cells did not appear outside of the heart forming regions until stage 8−(three somites). Free, mesenchymal-like endothelial precursor cells intrinsic to the heart regions also expressed two extracellular antigens, JB3, a fibrillin-like protein, and cytotactin, both associated with segments of the primary heart tube where endothelial cells “re-transform” back to a mesenchymal phenotype during cardiac cushion tissue formation. Between stages 8 and 9 (four to seven somites), (1) QH-1 positive cells within the heart forming region established vascular-like connections with QH-1 positive cells located outside of the heart region, as initially shown by Coffin and Poole (1988), (2) after fusion of the heart regions, a plexus of QH-1 positive cells was formed ventral to the foregut, and (3) the definitive endocardial lining of the primary heart tube formed directly from the ventral plexus of endothelial precursor cells. Because the QH-1 positive, endothelial precursor cells of each heart forming region were always in close association with anterior endoderm, we sought to determine if the endoderm mediated the formation of precursor cells committed to a cardiac endothelial lineage as reflected by their expression of QH-1, JB3 antigen, and cytotactin. To test this hypothesis, precardiac mesodermal explants were isolated from stage 5 heart forming regions prior to their expressing of either endocardial or myocardial markers and cultured on the surface of collagen gels in the presence or absence of endoderm. In the absence of endoderm, precardiac mesoderm of each stage 5 explant remained epithelial, formed contractile tissue, but did not exhibit any QH-1 positive cells or mesenchymal cells. Conversely, when cocultured with endoderm or endoderm conditioned medium, in addition to the formation of contractile tissue, the explant formed mesenchymal cells. The latter invaded the gel lattice and, asin vivo,expressed QH-1 antigen, JB3 antigen, and cytotactin. These findings suggest that endoderm induces mesoderm of the heart fields to undergo an epithelial to mesenchyme transformation that results in the segregation of myocardial and endocardial precursor cells

Welcome to The new anatomist

No abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34282/1/1_ftp.pd

Role of periostin

Periostin, also termed osteoblast-specific factor 2, is a matricellular protein with known functions in osteology, tissue repair, oncology, cardiovascular and respiratory systems, and in various inflammatory settings. However, most of the research to date has been conducted in divergent and circumscribed areas meaning that the overall understanding of this intriguing molecule remains fragmented. Here, we integrate the available evidence on periostin expression, its normal role in development, and whether it plays a similar function during pathologic repair, regeneration, and disease in order to bring together the different research fields in which periostin investigations are ongoing. In spite of the seemingly disparate roles of periostin in health and disease, tissue remodeling as a response to insult/injury is emerging as a common functional denominator of this matricellular molecule. Periostin is transiently upregulated during cell fate changes, either physiologic or pathologic. Combining observations from various conditions, a common pattern of events can be suggested, including periostin localization during development, insult and injury, epithelial–mesenchymal transition, extracellular matrix restructuring, and remodeling. We propose mesenchymal remodeling as an overarching role for the matricellular protein periostin, across physiology and disease. Periostin may be seen as an important structural mediator, balancing appropriate versus inappropriate tissue adaption in response to insult/injury

Roles of Proteoglycans and Glycosaminoglycans in Wound Healing and Fibrosis

A wound is a type of injury that damages living tissues. In this review, we will be referring mainly to healing responses in the organs including skin and the lungs. Fibrosis is a process of dysregulated extracellular matrix (ECM) production that leads to a dense and functionally abnormal connective tissue compartment (dermis). In tissues such as the skin, the repair of the dermis after wounding requires not only the fibroblasts that produce the ECM molecules, but also the overlying epithelial layer (keratinocytes), the endothelial cells, and smooth muscle cells of the blood vessel and white blood cells such as neutrophils and macrophages, which together orchestrate the cytokine-mediated signaling and paracrine interactions that are required to regulate the proper extent and timing of the repair process. This review will focus on the importance of extracellular molecules in the microenvironment, primarily the proteoglycans and glycosaminoglycan hyaluronan, and their roles in wound healing. First, we will briefly summarize the physiological, cellular, and biochemical elements of wound healing, including the importance of cytokine cross-talk between cell types. Second, we will discuss the role of proteoglycans and hyaluronan in regulating these processes. Finally, approaches that utilize these concepts as potential therapies for fibrosis are discussed

The many facets of the matricelluar protein periostin during cardiac development, remodeling, and pathophysiology

Periostin is a member of a growing family of matricellular proteins, defined by their ability to interact with components of the extracellular milieu, and with receptors at the cell surface. Through these interactions, periostin has been shown to play a crucial role as a profibrogenic molecule during tissue morphogenesis. Tissues destined to become fibrous structures are dependent on cooperative interactions between periostin and its binding partners, whereas in its absence, these structures either totally or partially fail to become mature fibrous entities. Within the heart, fibrogenic differentiation is required for normal tissue maturation, remodeling and function, as well as in response to a pathological myocardial insult. In this review, aspects related to the function of periostin during cardiac morphogenesis, remodeling and pathology are summarized

Mutations in DCHS1 Cause Mitral Valve Prolapse

SUMMARY Mitral valve prolapse (MVP) is a common cardiac valve disease that affects nearly 1 in 40 individuals1–3. It can manifest as mitral regurgitation and is the leading indication for mitral valve surgery4,5. Despite a clear heritable component, the genetic etiology leading to non-syndromic MVP has remained elusive. Four affected individuals from a large multigenerational family segregating non-syndromic MVP underwent capture sequencing of the linked interval on chromosome 11. We report a missense mutation in the DCHS1 gene, the human homologue of the Drosophila cell polarity gene dachsous (ds) that segregates with MVP in the family. Morpholino knockdown of the zebrafish homolog dachsous1b resulted in a cardiac atrioventricular canal defect that could be rescued by wild-type human DCHS1, but not by DCHS1 mRNA with the familial mutation. Further genetic studies identified two additional families in which a second deleterious DCHS1 mutation segregates with MVP. Both DCHS1 mutations reduce protein stability as demonstrated in zebrafish, cultured cells, and, notably, in mitral valve interstitial cells (MVICs) obtained during mitral valve repair surgery of a proband. Dchs1+/− mice had prolapse of thickened mitral leaflets, which could be traced back to developmental errors in valve morphogenesis. DCHS1 deficiency in MVP patient MVICs as well as in Dchs1+/− mouse MVICs result in altered migration and cellular patterning, supporting these processes as etiological underpinnings for the disease. Understanding the role of DCHS1 in mitral valve development and MVP pathogenesis holds potential for therapeutic insights for this very common disease