Publications

Mesangial cells organize the glomerular capillaries by adhering to the G domain of laminin alpha5 in the glomerular basement membrane

Kikkawa Y., Virtanen I., Miner J.H.J Cell Biol., 2003

In developing glomeruli, laminin alpha-5 (laminin-521 and -511) replaces laminin alpha-1 (laminin-111) in the glomerular basement membrane (GBM) at the capillary loop stage, a transition required for glomerulogenesis. By the capillary loop stage, laminin-111 is eliminated and at maturity, only laminin-521 is detected in the GBM where it plays a crucial role in maintaining glomerular capillary loop structures. To investigate domain-specific functions of laminin alpha5 during glomerulogenesis, the authors produced transgenic mice that express chimeric laminin composed of laminin alpha-5 domains fused to the human laminin alpha-1 globular (G) domain (Mr51). When bred onto the Lama5 -/- background, Mr51 supported GBM formation, preventing the breakdown that normally occurs in Lama5 -/- glomeruli. In addition, podocytes exhibited their typical arrangement in a single cell layer epithelium adjacent to the GBM, but the convolution of glomerular capillaries did not occur. Instead, capillaries were distended and exhibited a ballooned appearance, a phenotype similar to that observed in the total absence of mesangial cells, suggesting that the G domain of laminin alpha-5 is essential for mesangial adhesion. Finally, in vitro studies showed that integrin alpha3beta1 and the Lutheran glycoprotein mediate adhesion of mesangial cells to laminin alpha-5. These results elucidate a mechanism whereby mesangial cells organize the glomerular capillaries by adhering to laminin alpha-5 in the GBM.

Laminin isoforms and lung development: All isoforms are not equal

Developmental Biology, 2006

The embryonic lung has abundant laminin isoforms. Studies of embryonic lung explants and organotypic co-cultures show that laminin α1 and laminin 111 are important for epithelial branching morphogenesis and that laminin α2 and laminin 211 have a role in smooth muscle cell differentiation. In vivo studies of laminin α5-deficient mice indicate that this laminin chain, found in laminins 511 and 521, is essential for normal lobar septation in early lung development and normal alveolization and distal epithelial cell differentiation and maturation in late lung development. Laminin α4 null mice do not have obvious lung abnormalities and laminin γ2 null mice have only minimal changes in lung development. It is clear that multiple laminin isoforms are crucial for lung development and that different laminin isoforms exhibit specific, nonoverlapping functions.

Epithelial laminin α5 is necessary for distal epithelial cell maturation, VEGF production, and alveolization in the developing murine lung

Nguyen N.M., Kelley D.G, Schlueter J.A., Meyer M.J., Senior R.M., Miner J.H.Developmental Biology, 2005

Laminin α5 is prominent in the basement membrane of alveolar walls, airways, and pleura in developing and adult lung. To identify roles for laminin α5 in lung development, the authors have generated an inducible lung epithelial cell-specific Lama5 null mouse. Lama5 null embryos exposed to doxycycline from E6.5 died a few hours after birth. Compared to control littermates, Lama5 null mice lungs had dilated, enlarged distal airspaces, but the basement membrane ultrastructure was preserved. Distal epithelial cell differentiation was perturbed, with a marked reduction of alveolar type II cells and a virtual absence of type I cells. Cell proliferation was reduced and apoptosis was increased. Capillary density was diminished, and this was associated with a decrease in total lung VEGF production. Overall, these findings indicate that epithelial laminin α5, independent of its structural function, is necessary for murine lung development, and suggest a role for laminin α5 in signaling pathways that promote alveolar epithelial cell differentiation and VEGF expression.

Synergistic activities of alpha3 and alpha6 integrins are required during apical ectodermal ridge formation and organogenesis in the mouse

Both integrin α6-null mice α3-null mice die at birth, with kidney and lung defects at late stages of development, and skin blistering. To investigate possible overlapping functions between α3 and α6 integrins, we analyzed the phenotype of compound α3−/− and α6−/− mutant embryos. Double homozygous mutant embryos were growth-retarded and displayed several developmental defects not observed in the single mutant animals. The presence of novel phenotypes in double mutant embryos demonstrates the synergism between α3 and α6 integrins and their essential roles in multiple processes during embryogenesis.

A bioengineered niche preserves the quiescence of muscle stem cells and enhances their therapeutic efficacy

Quarta M., Brett J.O., DiMarco R., De Morree A., Boutet S.C. Chacon R. Gibbons M.C.,  Garcia V.A., Su J., Shrager J.B., Heilshorn S., Rando T.A. Nat Biotechnol., 2016

Here, the authors describe a system for maintaining muscle stem cells (MuSCs) in vitro in a potent, quiescent state. They screen for factors that could maintain mouse MuSC quiescence and defined a quiescence medium. The authors also designed artificial muscle fibers (AMFs) that mimic the native myofiber of the MuSC niche. Mouse MuSCs maintained in quiescence medium on AMFs showed enhanced potential for engraftment, tissue regeneration, and self-renewal after transplantation in mice. That also evaluated if the muscle fiber specific membrane protein laminin-211 could maintain MuSCs quiescence. The AMFs were coated with recombinant Integrin α4β1 followed by recombinant laminin-211. Indeed, the results showed similarly prolonged quiescence in vitro and enhanced potency in vivo. When seeded onto the laminin-coated AMFs and cultured for three days, mouse MuSCs showed reduced activation as assessed by EdU incorporation, increased viability as assessed by ATP levels, and higher Pax7 and lower MyoD protein expression when compared to AMFs alone or functionalized with integrin α4β1 only.

Laminin therapy for the promotion of muscle regeneration

Riederer I., Bonomo A.C., Mouly V., Savino W.FEBS Lett., 2015

Accumulating data show that the local microenvironment plays a major role during muscle regeneration. In the satellite cell niche, a major extracellular matrix protein is laminin. Human myoblasts transplanted into immunodeficient mice are preferentially located in laminin-enriched areas. Additionally, laminin-111 enhances myoblast proliferation in vitro and increases the expression of the α7β1 integrin-type laminin receptor. Intramuscular injection of laminin-111 ameliorates muscular pathology in mdx mice, protecting muscle fibers from damage. Moreover, transplantation of human myoblasts with laminin-111 into Rag/mdx immunodeficient recipients improved the efficacy of myoblast transplantation, increasing the number of human dystrophin-positive myofibres. Taken together, these data strongly indicate that exogenous laminin can ameliorate the regeneration process in different models of muscular dystrophies and can be instrumental for improving cell therapy aiming at repairing the degeneration/regeneration process in skeletal muscle.

FOXC1 maintains the hair follicle stem cell niche and governs stem cell quiescence to preserve long-term tissue-regenerating potential

Lay K., Kumeb T., Fuchsa E.PNAS, 2016

Here, the authors suggest that hair follicle stem cells (HFSCs) have restricted potential in vivo, which they conserve by coupling quiescence to adhesion-mediated niche maintenance, thereby achieving long-term tissue homeostasis. They examine whether parsimonious stem cells use is essential to conserve long-term tissue-regenerating potential during normal homeostasis by conditionally ablating a key transcription factor Forkhead box C1 (FOXC1).  FOXC1-deficient HFSCs spend less time in quiescence, leading to markedly shortened resting periods between hair cycles. The enhanced hair cycling accelerates HFSC expenditure, and impacts hair regeneration in aging mice. Interestingly, although FOXC1-deficient HFs can still form a new bulge that houses HFSCs for the next hair cycle, the older bulge is left unanchored. Hair follicle stem cells lacking the protein FOXC1 can only retain one old bulge in their hair follicles, while normal stem cells can keep up to four. In vitro cell adhesion assay they show that FACS-purified WT and Foxc1-KO HFSCs attach very well to LN-511 with about 6 times higher well area coverage compared to collagen I, fibronectin or Matrigel-coated plates.

Laminin a5 chain is required for intestinal smooth muscle development

Bolcato-Bellemin A-L., Lefebvre O., Arnold C., Sorokin L., Miner J. H., Kedinger M., Simon-Assmann P. Developmental Biology, 2003

Here, the function of the laminin a5 chain in the developing intestine was defined by analyzing laminin a5 -/- mutants and by grafting experiments. The authors show that laminin a5 plays a major role in smooth muscle organization and differentiation, as excessive folding of intestinal loops and delay in the expression of specific markers are observed in laminin a5 -/- mice. Loss of a5 expression was paralleled by ectopic or accelerated deposition of laminin a2 and a4 chains; this may explain why no obvious defects were observed in the villous form and enterocytic differentiation. Lack of the laminin a5 chain was accompanied by a decrease in epithelial a3B1 integrin receptor expression adjacent to the epithelial basement membrane and of Lutheran blood group glycoprotein in the smooth muscle cells, indicating that these receptors are likely mediating the a5 interactions. Taken together, the laminin a5 chain is essential for the normal development of the intestinal smooth muscle.

Switch in Laminin β2 to Laminin β1 Isoforms During Aging Controls Endothelial Cell Functions

Wagner J.U.G., Chavakis E., Rogg E.M, Muhly-Reinholz M., Glaser S.F., Günther S., John D., Bonini F, Zeiher A.M., Schaefer L., Hannocks M-J, Boon R.A., Dimmeler S.Arterioscler Thromb Vasc Biol, 2018

Here, the authors aim to decipher the role of the microenvironment underlying the impairment of endothelial cell functions by aging. RNA sequencing of isolated cardiac endothelial cells derived from young and 18-month-old mouse hearts revealed that aging affects the endothelial expression of genes encoding extracellular matrix proteins, specifically the laminin β1 (Lamb1) and laminin β2 (Lamb2) chains. Whereas Lamb1 was upregulated, Lamb2 was decreased in endothelial cells in old mice compared with young controls. A similar change in expression patterns was observed after induction of acute myocardial infarction. Mimicking aging and injury conditions by plating endothelial cells on laminin β1–containing laminin 411 matrix impaired endothelial cell adhesion, migration, and tube formation and augmented endothelial-to-mesenchymal transition and endothelial detachment compared with laminin 421, which contains the laminin β2 chain. Because laminins can signal via integrin receptors, the authors determined the activation of ITGB1 (integrin β1). Laminin 421 coating induced a higher activation of ITGB1 compared with laminin 411. siRNA-mediated silencing of ITGB1 reduced laminin β2–dependent adhesion, suggesting that laminin β2 more efficiently activates ITGB1. Mimicking age-related modulation of laminin β1 versus β2 chain expression changes the functional properties and phenotype of endothelial cells. The dysregulation of the extracellular matrix during vascular aging may contribute to an age-associated impairment of organ function and fibrosis.

Astrocytic laminin regulates pericyte differentiation and maintains blood brain barrier integrity

Yao Yao, Zu-Lin Chen, Erin H. Norris, Sidney Strickland. Nature Communications, 2014

In this article, conditional knockout mice and an acute adenovirus-mediated knockdown model were used to show that lack of astrocytic laminin, a brain-specific BM component, induces BBB breakdown.