The ability to fabricate perfusable, small-diameter vasculature is a foundational step toward generating human tissues/organs for clinical applications. Currently, it is highly challenging to generate vasculature integrated with smooth muscle and endothelium that replicates the complexity and functionality of natural vessels. Here, a novel method for directly printing self-standing, small-diameter vasculature with smooth muscle and endothelium is presented through combining tailored mussel-inspired bioink and unique “fugitive-migration” tactics, and its effectiveness and advantages over other methods (i.e., traditional alginate/calcium hydrogel, post-perfusion of endothelial cells) are demonstrated. The biologically inspired, catechol-functionalized, gelatin methacrylate (GelMA/C) undergoes rapid oxidative crosslinking in situ to form an elastic hydrogel, which can be engineered with controllable mechanical strength, high cell/tissue adhesion, and excellent bio-functionalization. The results demonstrate the bioprinted vascular construct possessed numerous favorable, biomimetic characteristics such as proper biomechanics, higher tissue affinity, vascularized tissue manufacturing ability, beneficial perfusability and permeability, excellent vasculoactivity, and in vivo autonomous connection (~2 weeks) as well as vascular remodeling (~6 weeks). The advanced achievements in creating biomimetic, functional vasculature illustrate significant potential toward generating a complicated vascularized tissue/organ for clinical transplantation.

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Hypoxia induced mitogenic factor (HIMF) is a member of the FIZZ/resistin/RELM family of proteins that we have shown to have potent mitogenic, angiogenic, and vasoconstrictive effects in the lung vasculature. In the current report, we identified Bruton's tyrosine kinase (BTK) as a functional HIMF binding partner through glutathione S-transferase (GST)-HIMF pull-down studies and mass spectrometry. Using primary cultured HIMF-stimulated murine bone marrow cells, we demonstrated that HIMF causes redistribution of BTK to the leading edge of the cells. HIMF stimulation induced BTK autophosphorylation, which peaked at 2.5 min. A transwell migration assay showed that treatment with recombinant murine HIMF induced migration of primary cultured bone marrow cells that was completely blocked by the BTK inhibitor, LFM-A13. Our results demonstrate BTK as the first known functional binding partner of the HIMF/FIZZ family of proteins and that HIMF acts as a chemotatic molecule in stimulating the migration of myeloid cells through activation of the BTK pathway.

Cell-based therapies have been employed with conflicting results. Whether direct injection of ex-vivo expanded autologous marrow stromal cells (MSCs) would improve the function of ischemic myocardium and enhance angiogenesis is not well defined. In a porcine model of chronic ischemia, MSCs were isolated and cultured for 4 weeks. Sixteen animals were random divided into two groups to receive either direct intramyocardial injection of autologous MSCs, or equal volumes and injections sites of saline. Cine MRI and epicardial echocardiography were performed just prior to the injections and again 6 weeks later at the time of sacrifice at which point tissue was also analyzed. Myocardial function as assessed by regional wall thickening (as measured by dobutamine stress echocardiograms) demonstrated a 40.9% improvement after cell treatment of the ischemic zone (p = 0.016) whereas the saline treated animals only had a 3.7% change (p = 0.82) compared to baseline. The left ventricular ejection fractions of MSC group showed 19.5% improvement from baseline 35.9 ± 3.8% to 42.9 ± 5.8% (p = 0.049). Increased vascularity was found in the MSC group compared to controls (0.80 ± 0.30 vs 0.50 ± 0.19 capillary/myocyte ratio, p = 0.018). Direct injection of autologous MSCs promotes angiogenesis and enhances the functional improvements following chronic myocardial ischemia. This suggests that the angiogenesis engendered by cell treatment may be physiologically meaningful by improving the contractility of ischemic myocardium.

Studying the proliferative ability of human bone marrow derived mesenchymal stem cells in hypoxic conditions can help us achieve the effective regeneration of ischemic injured myocardium. Cardiac-type fatty acid binding protein (FABP3) is a specific biomarker of muscle and heart tissue injury. This protein is purported to be involved in early myocardial development, adult myocardial tissue repair and responsible for the modulation of cell growth and proliferation. We have investigated the role of FABP3 in human bone marrow derived mesenchymal stem cells under ischemic conditions. MSCs from 12 donors were cultured either in standard normoxic or modified hypoxic conditions, and the differential expression of FABP3 was tested by quantitative rtPCR and western blot. We also established stable FABP3 expression in MSCs and searched for variation in cellular proliferation and differentiation bioprocesses affected by hypoxic conditions. We identified: 1) the FABP3 differential expression pattern in the MSCs under hypoxic conditions; 2) over-expression of FABP3 inhibited the growth and proliferation of the MSCs; however, improved their survival in low oxygen environments; 3) the cell growth factors and positive cell cycle regulation genes, such as PCNA, APC, CCNB1, CCNB2 and CDC6 were all down-regulated; while the key negative cell cycle regulation genes TP53, BRCA1, CASP3 and CDKN1A were significantly up-regulated in the cells with FABP3 overexpression. Our data suggested that FABP3 was up-regulated under hypoxia; also negatively regulated the cell metabolic process and the mitotic cell cycle. Overexpression of FABP3 inhibited cell growth and proliferation via negative regulation of the cell cycle and down-regulation of cell growth factors, but enhances cell survival in hypoxic or ischemic conditions.

Objectives This study sought to investigate whether Treg cells provide a protective and supportive role when co-transplanted with MSCs. Methods In a porcine model of chronic ischemia, autologous MSCs were isolated and expanded ex vivo for 4 wks. Autologous Treg cells were freshly isolated from 100 ml of peripheral blood and purified by fluorescence-activated cell sorting. MSCs and Treg cells were then co-transplanted into the chronic ischemic myocardium of Yorkshire pigs by direct intramyocardial injection (1.2 × 108 MSCs plus an average of 1.5 million Treg cells in 25 injection sites). Animals were sacrificed 6 weeks post-injection to study the fate of the cells and compare the effect of combined MSCs +Treg cells transplantation versus MSCs alone. Results The co- injection of MSCs along with Tregs was safe and no deleterious side effects were observed. Six weeks after injection of the cell combination, spherical MSCs clusters with thin layer capsules were found in the injected areas. In animals treated with MSCs only, the MSC clusters were less organized and not encapsulated. Immunofluorescent staining showed CD25+ cells among the CD90+ (MSC marker) cells, suggesting that the injected Treg cells remained present locally, and survived. Factor VIII positive cells were also prevalent suggesting new angiogenesis. We found no evidence that co-injections were associated with the generation of cardiac myocytes. Conclusions The co-transplantation of Treg cells with MSCs, dramatically increased the MSC survival rate, proliferation, and augmented their role in angiogenesis, which suggesting a new way for future clinical application of cell-based therapy.

We consider the initial boundary value problem of a simplified nematic liquid crystal flow in a bounded, smooth domain Ω ⊂ ℝ2. Given any k distinct points in the domain, we develop a new inner‐outer gluing method to construct solutions that blow up exactly at those k points as t goes to a finite time T. Moreover, we obtain a precise description of the blowup. © 2021 Wiley Periodicals LLC.

Background Marrow stromal cells (MSCs) are reportedly able to improve ventricular function after MI through the paracrine effect or regenerating myocytes. However, the evidence to prove that is scant. In this animal study, we employed MSCs isolated from transgenic pigs designed to express enhanced green fluorescent proteins as the donor to study the fate of the cells after allogeneic transplantation. Methods Green MSCs prepared from transgenic pigs were allogeneically transplanted into chronic ischemic myocardium of eight Yorkshire pigs by direct intramyocardial injection (total 1.2 × 108 cells in 2.5 ml of saline, with 25 injection sites). Cohorts of two animals were sacrificed at 1, 2, 4, 6 wks and 3 months after injection to study the fate of the injected cells. Results Allogeneic injection of the green MSCs is safe, no observable side effects or signs of graft versus host disease were observed. By dapi counterstained frozen senctions, the green cells were found migrating from the injected area into deeper layers of myocardium over the course of 1 to 6 weeks. By immunofluorescent staining, the green cells were associated with smooth muscle actin or vWF positive cells, suggesting that the transplanted cells were contributing to the formation of new vessels. We found no evidence that these cells were associated with the new generation of cardiac myocytes. Three months after injection, clusters of MSCs still can be found in the middle layer of ischemic myocardium, however, no unlimited cell growth was found. Conclusions Allogeneic transplantation of green MSCs can be safely used to elucidate the mechanisms of cell-based therapy. The benefits of this therapy appear mainly due to the angiogenesis not the regeneration of cardiac myocytes.