Laminin-dystroglycan signaling regulates retinal arteriogenesis

Association of Hepatic Gene Expression with Chemical Concentrations in Wild-Collected Double-Crested Cormorant Embryos using an EcoToxChip Gene Array

Contaminant monitoring programs use wild bird eggs, but determining whether measured concentrations elicit adverse effects relies on extrapolation from toxicity studies with avian model species. Here, we directly evaluated the relationships between whole embryo contaminant concentrations and mRNA expression in liver tissue of the double-crested cormorant (Nannopterum auritum). Eggs collected from three North American sites (one from Lake Erie and two from the Salish Sea) were artificially incubated until pipping. Hepatic mRNA was analyzed with an EcoToxChip quantitative polymerase chain reaction (qPCR) array containing 354 target genes. The remaining embryo was analyzed for mercury and 95 persistent organic contaminants. Lake Erie embryos had higher concentrations of most organic contaminants than those from the Salish Sea. Sparse partial least-squares regression analysis of contaminant and gene expression data indicated that chlorinated hydrocarbons, especially polychlorinated biphenyls (PCBs), were associated with variation in gene expression. Linear correlations revealed consistent pairwise associations between chlorinated contaminants and the expression of nine genes (seven genes with PCBs and two with β-hexachlorocyclohexane). Partial least-squares discriminant analysis identified embryos from the Lake Erie site accurately. Overall, gene expression in embryos from wild-collected eggs was associated with tissue contaminant concentrations, and thus, transcriptomic measurements may serve to identify individuals or populations affected biologically by contaminants.

Mural Wnt/β-catenin signaling regulates Lama2 expression to promote neurovascular unit maturation

Neurovascular unit and barrier maturation rely on vascular basement membrane (vBM) composition. Laminins, a major vBM component, are crucial for these processes, yet the signaling pathway(s) that regulate their expression remain unknown. Here, we show that mural cells have active Wnt/β-catenin signaling during central nervous system development in mice. Bulk RNA sequencing and validation using postnatal day 10 and 14 wild-type versus adenomatosis polyposis coli downregulated 1 (Apcdd1-/-) mouse retinas revealed that Lama2 mRNA and protein levels are increased in mutant vasculature with higher Wnt/β-catenin signaling. Mural cells are the main source of Lama2, and Wnt/β-catenin activation induces Lama2 expression in mural cells in vitro. Markers of mature astrocytes, including aquaporin 4 (a water channel in astrocyte endfeet) and integrin-α6 (a laminin receptor), are upregulated in Apcdd1-/- retinas with higher Lama2 vBM deposition. Thus, the Wnt/β-catenin pathway regulates Lama2 expression in mural cells to promote neurovascular unit and barrier maturation.

Laminin β2 Chain Regulates Cell Cycle Dynamics in the Developing Retina

Vertebrate retinal development follows a highly stereotyped pattern, in which the retinal progenitor cells (RPCs) give rise to all retinal types in a conserved temporal sequence. Ensuring the proper control over RPC cell cycle exit and re-entry is, therefore, crucially important for the generation of properly functioning retina. In this study, we demonstrate that laminins, indispensible ECM components, at the retinal surface, regulate the mechanisms determining whether RPCs generate proliferative or post-mitotic progeny. In vivo deletion of laminin β2 in mice resulted in disturbing the RPC cell cycle dynamics, and premature cell cycle exit. Specifically, the RPC S-phase is shortened, with increased numbers of cells present in its late stages. This is followed by an accelerated G2-phase, leading to faster M-phase entry. Finally, the M-phase is extended, with RPCs dwelling longer in prophase. Addition of exogenous β2-containing laminins to laminin β2-deficient retinal explants restored the appropriate RPC cell cycle dynamics, as well as S and M-phase progression, leading to proper cell cycle re-entry. Moreover, we show that disruption of dystroglycan, a laminin receptor, phenocopies the laminin β2 deletion cell cycle phenotype. Together, our findings suggest that dystroglycan-mediated ECM signaling plays a critical role in regulating the RPC cell cycle dynamics, and the ensuing cell fate decisions.

Designing Cardiovascular Implants Taking in View the Endothelial Basement Membrane

Insufficient endothelialization of cardiovascular grafts is a major hurdle in vascular surgery and regenerative medicine, bearing a risk for early graft thrombosis. Neither of the numerous strategies pursued to solve these problems were conclusive. Endothelialization is regulated by the endothelial basement membrane (EBM), a highly specialized part of the vascular extracellular matrix. Thus, a detailed understanding of the structure–function interrelations of the EBM components is fundamental for designing biomimetic materials aiming to mimic EBM functions. In this review, a detailed description of the structure and functions of the EBM are provided, including the luminal and abluminal interactions with adjacent cell types, such as vascular smooth muscle cells. Moreover, in vivo as well as in vitro strategies to build or renew EBM are summarized and critically discussed. The spectrum of methods includes vessel decellularization and implant biofunctionalization strategies as well as tissue engineering-based approaches and bioprinting. Finally, the limitations of these methods are highlighted, and future directions are suggested to help improve future design strategies for EBM-inspired materials in the cardiovascular field.

Neuronal and glial regulation of CNS angiogenesis and barriergenesis

Neurovascular pathologies of the central nervous system (CNS), which are associated with barrier dysfunction, are leading causes of death and disability. The roles that neuronal and glial progenitors and mature cells play in CNS angiogenesis and neurovascular barrier maturation have been elucidated in recent years. Yet how neuronal activity influences these processes remains largely unexplored. Here, we discuss our current understanding of how neuronal and glial development affects CNS angiogenesis and barriergenesis, and outline future directions to elucidate how neuronal activity might influence these processes. An understanding of these mechanisms is crucial for developing new interventions to treat neurovascular pathologies.