An Avascular Niche Created by Axitinib-Loaded PCL/Collagen Nanofibrous Membrane Stabilized Subcutaneous Chondrogenesis of Mesenchymal Stromal Cells.

Engineered cartilage derived from mesenchymal stromal cells (MSCs) always fails to maintain the cartilaginous phenotype in the subcutaneous environment due to the ossification tendency. Vascular invasion is a prerequisite for endochondral ossification during the development of long bone. As an oral antitumor medicine, Inlyta (axitinib) possesses pronounced antiangiogenic activity, owing to the inactivation of the vascular endothelial growth factor (VEGF) signaling pathway. In this study, axitinib-loaded poly(ε-caprolactone) (PCL)/collagen nanofibrous membranes are fabricated by electrospinning for the first time. Rabbit-derived MSCs-engineered cartilage is encapsulated in the axitinib-loaded nanofibrous membrane and subcutaneously implanted into nude mice. The sustained and localized release of axitinib successfully inhibits vascular invasion, stabilizes cartilaginous phenotype, and helps cartilage maturation. RNA sequence further reveals that axitinib creates an avascular, hypoxic, and low immune response niche. Timp1 is remarkably upregulated in this niche, which probably plays a functional role in inhibiting the activity of matrix metalloproteinases and stabilizing the engineered cartilage. This study provides a novel strategy for stable subcutaneous chondrogenesis of mesenchymal stromal cells, which is also suitable for other medical applications, such as arthritis treatment, local treatment of tumors, and regeneration of other avascular tissues (cornea and tendon).

Vegfa signaling regulates diverse artery/vein formation in vertebrate vasculatures.

Vascular endothelial growth factor A (Vegfa) signaling regulates vascular development during embryogenesis and organ formation. However, the signaling mechanisms that govern the formation of various arteries/veins in various tissues are incompletely understood. In this study, we utilized transcription activator-like effector nuclease (TALEN) to generate zebrafish vegfaa mutants. vegfaa-/- embryos are embryonic lethal, and display a complete loss of the dorsal aorta (DA) and expansion of the cardinal vein. Activation of Vegfa signaling expands the arterial cell population at the expense of venous cells during vasculogenesis of the axial vessels in the trunk. Vegfa signaling regulates endothelial cell (EC) proliferation after arterial-venous specification. Vegfa deficiency and overexpression inhibit the formation of tip cell filopodia and interfere with the pathfinding of intersegmental vessels (ISVs). In the head vasculature, vegfaa‒/‒ causes loss of a pair of mesencephalic veins (MsVs) and central arteries (CtAs), both of which usually develop via sprouting angiogenesis. Our results indicate that Vegfa signaling induces the formation of the DA at the expense of the cardinal vein during the trunk vasculogenesis, and that Vegfa is required for the angiogenic formation of MsVs and CtAs in the brain. These findings suggest that Vegfa signaling governs the formation of diverse arteries/veins by distinct cellular mechanisms in vertebrate vasculatures.

Vegfa Impacts Early Myocardium Development in Zebrafish.

Vascular endothelial growth factor A (Vegfa) signaling regulates cardiovascular development. However, the cellular mechanisms of Vegfa signaling in early cardiogenesis remain poorly understood. The present study aimed to understand the differential functions and mechanisms of Vegfa signaling in cardiac development. A loss-of-function approach was utilized to study the effect of Vegfa signaling in cardiogenesis. Both morphants and mutants for vegfaa display defects in cardiac looping and chamber formation, especially the ventricle. Vegfa regulates the heart morphogenesis in a dose-dependent manner. Furthermore, the initial fusion of the bilateral myocardium population is delayed rather than endocardium. The results demonstrate that Vegfa signaling plays a direct impact on myocardium fusion, indicating that it is the initial cause of the heart defects. The heart morphogenesis is regulated by Vegfa in a dose-dependent manner, and later endocardium defects may be secondary to impaired myocardium-endocardium crosstalk.

Isolated cleft of the mitral valve: clinical spectrum and course.

We have reviewed the clinical presentations, courses, and outcomes of 90 patients seen at Texas Children's Hospital from 1983 through 2008 who had an isolated cleft of the mitral valve without some form of endocardial cushion defect. Additional congenital cardiac defects were present in 61 of the 90 patients, 35 of whom had a congenital syndrome. Seven patients had isolated cleft of the mitral valve without other intracardiac defects, and in these 7 there was a progressive increase in the degree of mitral regurgitation during a median time of 26.5 months from diagnosis to surgery. The patients ranged from a gestational age of approximately 32 weeks to 21.9 years of age. No death was observed among the 39 surgical patients, including 32 who had additional cardiac defects. There was a significant reduction in the degree of mitral regurgitation in all patients who underwent surgery. Among the 51 patients who did not have surgery, the degree of regurgitation did not change significantly over the course of 1 to 27 years' observation. Isolated cleft of the mitral valve is an uncommon (but not rare) congenital malformation of the mitral valve that can cause all degrees of mitral regurgitation but can be managed medically or surgically.