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

Bioprinting: Development of a novel approach for engineering three-dimensional tissue structures [abstract]

Abstract only availableBioprinting is a tissue engineering technique in which spherical cell aggregates, the "bio-ink", are deposited into biocompatible hydrogels, the "bio-paper", by a 3-axis "bio-printer". The aggregates can be deposited into essentially any 3D configuration, and when comprised of adhesive and motile cells aggregate fusion occurs. This self-organizing, liquid-like nature of these tissues is described on a molecular basis by The Differential Adhesion Hypothesis (DAH). The techniques we have developed are quite unique because of the high degree of automation that has been incorporated into our processes and the variety of engineered tissues that we are capable of creating. Despite automation, the creation of aggregates remains a nontrivial and time intensive process. The entire process of aggregate formation from initial cell culture to mature aggregate ready to be loaded into the printer takes approximately five days. This time is a limiting factor in the potential use of bio-printing as a source of on-demand tissues for clinical applications. A solution to this potential problem lies in the cryopreservation of aggregates. Freezing mediums and freezing protocols were tested and the effect of the freezing process on aggregate fusion was determined. An alternate solution to expedite the bioprinting process could lie in the printing of cell 'sausages', tightly packed cylinders of cells. In this method aggregate preparation is forgone. Elimination of this step could allow for increased time in tissue creation. Cell sausage printing provides another technique that could be incorporated into the fabrication of complex tissues. Our experiments in this novel and developing technology of bioprinting represent steps towards building complex tissues via self-assembly.McNair Scholars Progra

The role of Periostin in regulating the biomechanical properties of cushion tissue

Abstract only availableDuring embryonic heart development the atrio-ventricular (AV) cushions swell and fuse to form the valves and septa of the adult heart. Initially, the cushions appear as swellings on the interior wall of the AV canal and eventually fuse to form the septum and valvular leaflets. The morphogenetic event that the cushions undergo during the fusion process is, in part, driven by the cohesive energy of the tissue, which can be described by the tissue's surface tension. It has been shown earlier that many properties of embryonic tissues can be interpreted by using the analogy that they behave as liquids and it is this analogy that gives rise to apparent tissue surface tension. Periostin is hypothesized to affect cushion tissue surface tension, through its possible binding of the extracellular matrix of the tissue. In this study virus containing the sense strand of Periostin DNA is introduced into hanging drops containing living explants of AV cushion tissue. Overnight the tissue explants rounded up to form spheroids allowing their surface tension to be measured and compared to the surface tension of AV cushion tissue explants exposed to a LacZ promoter control virus. The surface tension was determined using a specifically designed apparatus that measures the viscoelastic response of spherical explants due to a compressive force. It was expected that the increased production of Periostin in the cushion explants due to exposure to the virus will result in an increased surface tension compared to that of explants exposed to the control virus. The preliminary results of the experiment have displayed no significant difference of surface tension between the control virus and the Periostin virus. Since earlier research has shown a significant difference in the rate of fusion of cushions exposed to Periostin DNA virus and those exposed to the control virus, and because fusion time is characterized by the ratio of the surface tension and the viscosity of the tissue, we believe that Periostin may be affecting the viscosity of the tissue explants instead of the surface tension.NSF-REU Program in Biosystems Modeling and Analysi

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

Methodology for the Evaluation of Double-Layered Microcapsule Formability Zone in Compound Nozzle Jetting Based on Growth Rate Ratio

Double-layered microcapsules, which usually consist of a core (polymeric) matrix surrounded by a (polymeric) shell, have been used in many industrial and scientific applications, such as microencapsulation of drugs and living cells. Concentric compound nozzle-based jetting has been favored due to its efficiency and precise control of the coreshell compound structure. Thus far, little is known about the underlying formation mechanism of double-layered microcapsules in compound nozzle jetting. This study aims to understand the formability of double-layered microcapsules in compound nozzle jetting by combining a theoretical analysis and numerical simulations. A linear temporal instability analysis is used to define the perturbation growth rates of stretching and squeezing modes and a growth ratio as a function of the wave number, and a computational fluid dynamics (CFD) method is implemented to model the microcapsule formation process in order to determine the good microcapsule forming range based on the growth ratio curve. Using a pseudobisection method, the lower and upper bounds of the good formability range have been determined for a given materials-nozzle system. The proposed formability prediction methodology has been implemented to model a water-poly (lactide-co-glycolide) (PLGA)-air compound jetting system

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

Can Routine Commercial Cord Blood Banking Be Scientifically and Ethically Justified?

Background to the debate: Umbilical cord blood—the blood that remains in the placenta after birth—can be collected and stored frozen for years. A well-accepted use of cord blood is as an alternative to bone marrow as a source of hematopoietic stem cells for allogeneic transplantation to siblings or to unrelated recipients; women can donate cord blood for unrelated recipients to public banks. However, private banks are now open that offer expectant parents the option to pay a fee for the chance to store cord blood for possible future use by that same child (autologous transplantation.

Human pre-valvular endocardial cells derived from pluripotent stem cells recapitulate cardiac pathophysiological valvulogenesis

Genetically modified mice have advanced our understanding of valve development and disease. Yet, human pathophysiological valvulogenesis remains poorly understood. Here we report that, by combining single cell sequencing and in vivo approaches, a population of human pre-valvular endocardial cells (HPVCs) can be derived from pluripotent stem cells. HPVCs express gene patterns conforming to the E9.0 mouse atrio-ventricular canal (AVC) endocardium signature. HPVCs treated with BMP2, cultured on mouse AVC cushions, or transplanted into the AVC of embryonic mouse hearts, undergo endothelial-to-mesenchymal transition and express markers of valve interstitial cells of different valvular layers, demonstrating cell specificity. Extending this model to patient-specific induced pluripotent stem cells recapitulates features of mitral valve prolapse and identified dysregulation of the SHH pathway. Concurrently increased ECM secretion can be rescued by SHH inhibition, thus providing a putative therapeutic target. In summary, we report a human cell model of valvulogenesis that faithfully recapitulates valve disease in a dish.We thank the Leducq Fondation for supporting Tui Neri, and funding this research under the framework of the MITRAL network and for generously awarding us for the equipment of our cell imaging facility in the frame of their program “Equipement de Recherche et Plateformes Technologiques” (ERPT to M.P.), the Genopole at Evry and the Fondation de la recherche Medicale (grant DEQ20100318280) for supporting the laboratory of Michel Puceat. Part of this work in South Carolina University was conducted in a facility constructed with support from the National Institutes of Health, Grant Number C06 RR018823 from the Extramural Research Facilities Program of the National Center for Research Resources. Other funding sources: National Heart Lung and Blood Institute: RO1-HL33756 (R.R.M.), COBRE P20RR016434–07 (R.R.M., R.A. N.), P20RR016434–09S1 (R.R.M. and R.A.N.); American Heart Association: 11SDG5270006 (R.A.N.); National Science Foundation: EPS-0902795 (R.R.M. and R.A. N.); American Heart Association: 10SDG2630130 (A.C.Z.), NIH: P01HD032573 (A.C. Z.), NIH: U54 HL108460 (A.C.Z), NCATS: UL1TR000100 (A.C.Z.); EH was supported by a fellowship of the Ministere de la recherche et de l’éducation in France.TM-M was supported by a fellowship from the Fondation Foulon Delalande and the Leducq Foundation. P.v.V. was sponsored by a UC San Diego Cardiovascular Scholarship Award and a Postdoctoral Fellowship from the California Institute for Regenerative Medicine (CIRM) Interdisciplinary Stem Cell Training Program II. S.M.E. was funded by a grant from the National Heart, Lung, and Blood Institute (HL-117649). A.T. is supported by the National Heart, Lung, and Blood Institute (R01-HL134664).S