Biomedical subjects

Richard L Goodwin

Publications and source records attributed to Richard L Goodwin.

7 recordsLinked to original sources

PubMed2007

Periostin regulates collagen fibrillogenesis and the biomechanical properties of connective tissues.

Periostin is predominantly expressed in collagen-rich fibrous connective tissues that are subjected to constant mechanical stresses including: heart valves, tendons, perichondrium, cornea, and the periodontal ligament (PDL). Based on these data we hypothesize that periostin can regulate collagen I fibrillogenesis and thereby affect the biomechanical properties of connective tissues. Immunoprecipitation and immunogold transmission electron microscopy experiments demonstrate that periostin is capable of directly interacting with collagen I. To analyze the potential role of periostin in collagen I fibrillogenesis, gene targeted mice were generated. Transmission electron microscopy and morphometric analyses demonstrated reduced collagen fibril diameters in skin dermis of periostin knockout mice, an indication of aberrant collagen I fibrillogenesis. In addition, differential scanning calorimetry (DSC) demonstrated a lower collagen denaturing temperature in periostin knockout mice, reflecting a reduced level of collagen cross-linking. Functional biomechanical properties of periostin null skin specimens and atrioventricular (AV) valve explant experiments provided direct evidence of the role that periostin plays in regulating the viscoelastic properties of connective tissues. Collectively, these data demonstrate for the first time that periostin can regulate collagen I fibrillogenesis and thereby serves as an important mediator of the biomechanical properties of fibrous connective tissues.

Adenoviridae↗

PubMed2006

Epicardial development in the rat: a new perspective.

Development of the epicardium is critical to proper heart formation. It provides all of the precursor cells that form the coronary system and supplies signals that stimulate cardiac myocyte proliferation. The epicardium forms from mesothelial cells associated with the septum transversum and is referred to as the proepicardium (PE). Two different methods by which these PE cells colonize the developing heart have been described. In avians, PE cells form a bridge to the heart over which PE cells migrate onto the heart. In fish and mammals, PE cells form vesicles of cells that detach from the mesothelium, float through the pericardial cavity, and attach to the heart. A previous study of rat PE development investigated this process at the histological level. Protein markers have been developed since this study. Thus, we investigated this important developmental process coupled with these new markers using other visualization techniques such as scanning electron microscopy (SEM) and confocal microscopy. Finally, a novel, three-dimensional (3-D) culture system was used to confirm the identity of the PE cells. In this study, we found convincing evidence that the rat PE cells directly attach to the heart in a manner similar to that observed in avians.

Animals↗

PubMed2005

LEK1 protein expression in normal and dysregulated cardiomyocyte mitosis.

A defining characteristic of embryonic cells is their ability to divide rapidly, even in tissues such as cardiac muscle, which cannot divide once fully differentiated. This suggests that regulators of cell division differ in embryonic and differentiated cells. LEK1 is a member of an emerging family of proteins with diverse functions but shared structural domains, including numerous leucine zippers, a nuclear localization site, and a functional Rb-binding domain. LEK1 is expressed ubiquitously in the developing mouse embryo from the earliest stages of differentiation through birth. It is absent in adult tissues, even those that maintain active cell division. We hypothesize that LEK1 is a regulator of mitosis restricted to the developing embryo and early neonate. Here, using BrdU incorporation, we show that LEK1 protein downregulation in cardiac myocytes correlates directly with cessation of DNA synthesis between neonatal days 6 and 10. In contrast, in an immortalized cardiac cell line (HL1 cells), both BrdU incorporation and LEK1 protein expression persist, and actively dividing cells express LEK1. However, BrdU incorporation can be decreased in these cells by treatment with a morpholino targeting LEK1 mRNA. These data suggest a role for LEK1 in regulating the normal embryonic cardiomyocyte cell cycle and in promoting continued mitosis in transformed, abnormally dividing cardiomyocytes.

Animals↗

PubMed2005

Three-dimensional model system of valvulogenesis.

Valvular defects are among the most common and deleterious of all cardiac malformations. The early cardiac cushions are located in the atrioventricular (AV) canal of the embryonic heart. These cushions contain cells that are the primordia of the cardiac valves and membranous septa. Significant progress has been made in delineating the molecular mechanisms that regulate the early steps of cushion formation; however, little is known about how these cushions differentiate into valve leaflets. Here, a new three-dimensional collagen tube culturing system was tested for its ability to sustain the development and maturation of the AV cushion anlagen. We report that AV cushion tissues grown within the collagen tube scaffold recapitulate aspects of AV valve development both at the molecular and morphological levels. Furthermore, our results indicate that valve leaflet formation in the tube model is dependent on the presence of cardiac myocytes.

Animals↗

PubMed2003

Novel 3D culture system for study of cardiac myocyte development.

Insufficient myocardial repair after pathological processes contributes to cardiovascular disease, which is a major health concern. Understanding the molecular mechanisms that regulate the proliferation and differentiation of cardiac myocytes will aid in designing therapies for myocardial repair. Models are needed to delineate these molecular mechanisms. Here we report the development of a model system that recapitulates many aspects of cardiac myocyte differentiation that occur during early cardiac development. A key component of this model is a novel three-dimensional tubular scaffold engineered from aligned type I collagen strands. In this model embryonic ventricular myocytes undergo a transition from a hyperplastic to a quiescent phenotype, display significant myofibrillogenesis, and form critical cell-cell connections. In addition, embryonic cardiac myocytes grown on the tubular substrate have an aligned phenotype that closely resembles in vivo neonatal ventricular myocytes. We propose that embryonic cardiac myocytes grown on the tube substrate develop into neonatal cardiac myocytes via normal in vivo mechanisms. This model will aid in the elucidation of the molecular mechanisms that regulate cardiac myocyte proliferation and differentiation, which will provide important insights into myocardial development.

Actin Cytoskeleton↗

PubMed2002

Functional diversification during evolution of the murine alpha(1)-proteinase inhibitor family: role of the hypervariable reactive center loop.

Alpha(1)-proteinase inhibitor (alpha(1)-PI) is a member of the serpin superfamily of serine proteinase inhibitors that are involved in the regulation of a number of proteolytic processes. Alpha(1)-PI, like most serpins, functions by covalent binding to, and inhibition of, target proteinases. The interaction between alpha(1)-PI and its target is directed by the so-called reactive center loop (RCL), an approximately 20 residue domain that extends out from the body of the alpha(1)-PI polypeptide and determines the inhibitor's specificity. Mice express at least seven closely related alpha(1)-PI isoforms, encoded by a family of genes clustered at the Spi1 locus on chromosome 12. The amino acid sequence of the RCL region is hypervariable among alpha(1)-PIs, a phenomenon that has been attributed to high rates of evolution driven by positive Darwinian selection. This suggests that the various isoforms are functionally diverse. To test this notion, we have compared the proteinase specificities of individual alpha(1)-PIs from each of the two mouse species. As predicted from the positive Darwinian selection hypothesis, the various alpha(1)-PIs differ in their ability to form covalent complexes with serine proteinases, such as elastase, trypsin, chymotrypsin, and cathepsin G. In addition, they differ in their binding ability to proteinases in crude snake venoms. Importantly, the RCL region of the alpha(1)-PI polypeptide is the primary determinant of isoform-specific differences in proteinase recognition, indicating that hypervariability within this region drives the functional diversification of alpha(1)-PIs during evolution. The possible physiological benefits of alpha(1)-PI diversity are discussed.

Amino Acid Sequence↗

PubMedDate not supplied

A novel tubular scaffold for cardiovascular tissue engineering.

We have developed a counter rotating cone extrusion device to produce the next generation of three-dimensional collagen scaffold for tissue engineering. The device can produce a continuously varying fibril angle from the lumen to the outside of a 5-mm-diameter collagen tube, similar to the pattern of heart muscle cells in the intact heart. Our scaffold is a novel, oriented, type I collagen, tubular scaffold. We selected collagen because we believe there are important signals from the collagen both geometrically and biochemically that elicit the in vivo -like phenotypic response from the cardiomyocytes. We have shown that cardiomyocytes can be cultured in these tubes and resemble an in vivo phenotype. This new model system will provide important information leading to the design and construction of a functional, biologically based assist device.

Biocompatible Materials↗