A Biomimetic Approach Utilizing Pulsatile Perfusion Generates Contractile Vascular Grafts.

Surgical implantation of decellularized cadaveric arteries is routinely used to treat right-sided congenital cardiac lesions. These acellular conduits lack the capacity for somatic growth and are prone to stenosis and calcification, necessitating multiple operations throughout childhood. Islet-1+ cardiovascular progenitor cells (CPCs) have demonstrated the capacity for differentiation into all cell types of the heart and outflow tracts. We hypothesize that CPC seeding of decellularized pulmonary arteries and bioreactor culture under physiologic flow conditions will drive vascular differentiation of CPCs and result in a conduit more suitable for implantation and long-term growth. We began by decellularizing ovine pulmonary arteries and characterizing the composition of the extracellular matrix (ECM). Hemodynamic testing of decellularized vessels in a custom bioreactor was used to define the scaffold mechanical properties over a range of pressures and flow rates. Next, our expanded ovine CPCs were suspended in growth media and injected intramurally into decellularized pulmonary arteries that were subsequently cultured in either static or pulsatile cultures. A combination of immunohistochemistry, real-time polymerase chain reaction (PCR), and tissue bath contraction studies were used to evaluate the bioengineered arteries before transplantation. Pulmonary artery patches from the most favorable culture conditions were then implanted into juvenile sheep to provide proof of concept. Hematoxylin and eosin staining indicated complete removal of cell nuclei (n = 9), whereas double-stranded DNA isolation from tissue homogenates showed 99.1% DNA removal (p < 0.01, n = 4). Furthermore, trichrome and elastin staining verified maintenance of collagen and elastin. Immunohistochemistry and PCR analyses (n = 4 per group) confirmed contractile smooth muscle presence on only our 3-week pulsatile scaffolds via presence of calponin 1 and myosin heavy chain 11. Tissue bath studies demonstrated that smooth muscle contraction generated by our 3-week pulsatile scaffolds (2.23 ± 0.19 g, n = 4) is comparable with native tissue contraction strength (2.78 ± 0.06 g, n = 4). Ovine transplantation confirmed that our graft can be safely implanted, retains contractile smooth muscle cells, and recruits native endothelium. Longer duration of physiologic pulsatile culture drives differentiation of CPCs seeded on ECM conduits toward a mature, contractile phenotype that is maintained for several weeks in vivo. Longer term studies to assess somatic growth potential are needed. Impact statement The current field of vascular transplantation relies on cadaveric and synthetic grafts to treat right-sided congenital cardiac lesions. These grafts do not grow somatically with our patients. This results in multiple reoperations throughout childhood to increase the size of the graft. Our bioengineered alternative demonstrates successful implantation, contractile smooth muscle cells, and a native endothelial layer. This research demonstrates a pilot study confirming the viability of a bioengineered alternative to the current standard of care in the field of vascular transplantation.

MicroRNA Expression in the Infarcted Heart Following Neonatal Cardiovascular Progenitor Cell Transplantation in a Sheep Model of Stem Cell-Based Repair.

Myocardial infarctions affect approximately 735,000 people annually in the United States and have a substantial impact on quality of life. Neonates have an enhanced capability of repairing cardiovascular damage, while adults do not. The mechanistic basis for this age-dependent difference in regenerative capacity remains unknown. Recent studies have shown that microRNAs (miRNAs) play a significant role in regulating the regenerative ability of cardiovascular cells. This report defines the alterations in miRNA expression within the cardiovascular repair zone of infarcted sheep hearts following intracardiac injection of neonatal islet-1+ cardiovascular progenitor cells. Sheep were infarcted via left anterior descending coronary artery ligation. After 3 to 4 weeks of infarction, sheep neonatal islet-1+ cardiovascular progenitor cells were injected into the infarcted area for repair. Cell-treated sheep were euthanized 2 months following cell injection, and their hearts were harvested for the analysis of miRNA and gene expression within the cardiovascular repair zone. Ten miRNAs were differentially regulated in vivo, including miR-99, miR-100, miR-302a, miR-208a, miR-665, miR-1, miR-499a, miR-34a, miR-133a, and miR-199a. These miRNAs promote stemness, cell division, and survival. Several signaling pathways are regulated by these miRNAs, including Hippo, Wnt, and Erythroblastic Leukemia Viral Oncogene B (ERBB). Transcripts encoding Wnt, ERBB, and Neuregulin 1 (NRG1) were elevated in vivo in the infarct repair zone. Wnt5a signaling and ERBB/NRG1 transcripts contribute to activation of Yes-Associated Protein 1. MiRNAs that impact proliferation, cell survival, and signaling pathways that promote regeneration were induced during cardiovascular repair in the sheep model. This information can be used to design new approaches for the optimization of miRNA-based treatments for the heart.

Development of a convolutional neural network to detect abdominal aortic aneurysms.

Objective: We sought to train a foundational convolutional neural network (CNN) for screening computed tomography (CT) angiography (CTA) scans for the presence of infrarenal abdominal aortic aneurysms (AAAs) for future predictive modeling and other artificial intelligence applications. Methods: From January 2015 to January 2020, a HIPAA (Health Insurance and Accountability Act)-compliant, institutional review board-approved, retrospective clinical study analyzed contrast-enhanced abdominopelvic CTA scans from 200 patients with infrarenal AAAs and 200 propensity-matched control patients with non-aneurysmal infrarenal abdominal aortas. A CNN was trained to binary classification on the input. For model improvement and testing, transfer learning using the ImageNet database was applied to the VGG-16 base model. The image dataset was randomized to sets of 60%, 10%, and 30% for model training, validation, and testing, respectively. A stochastic gradient descent was used for optimization. The models were assessed by testing validation accuracy and the area under the receiver operating characteristic curve. Results: Preliminary data demonstrated a nonrandom pattern of accuracy and detectability. Iterations (≤10) of the model characteristics generated a final custom CNN model reporting an accuracy of 99.1% and area under the receiver operating characteristic curve of 0.99. Misjudgments were analyzed through review of the heat maps generated via gradient weighted class activation mapping overlaid on the original CT images. The greatest misjudgments were seen in small aneurysms (<3.3 cm) with mural thrombus. Conclusions: Preliminary data from a CNN model have shown that the model can accurately screen and identify CTA findings of infrarenal AAAs. This model serves as a proof-of-concept to proceed with potential future directions to include expansion to predictive modeling and other artificial intelligence-based applications.

Long-Term Hypoxia Maintains a State of Dedifferentiation and Enhanced Stemness in Fetal Cardiovascular Progenitor Cells.

Early-stage mammalian embryos survive within a low oxygen tension environment and develop into fully functional, healthy organisms despite this hypoxic stress. This suggests that hypoxia plays a regulative role in fetal development that influences cell mobilization, differentiation, proliferation, and survival. The long-term hypoxic environment is sustained throughout gestation. Elucidation of the mechanisms by which cardiovascular stem cells survive and thrive under hypoxic conditions would benefit cell-based therapies where stem cell survival is limited in the hypoxic environment of the infarcted heart. The current study addressed the impact of long-term hypoxia on fetal Islet-1+ cardiovascular progenitor cell clones, which were isolated from sheep housed at high altitude. The cells were then cultured in vitro in 1% oxygen and compared with control Islet-1+ cardiovascular progenitor cells maintained at 21% oxygen. RT-PCR, western blotting, flow cytometry, and migration assays evaluated adaptation to long term hypoxia in terms of survival, proliferation, and signaling. Non-canonical Wnt, Notch, AKT, HIF-2α and Yap1 transcripts were induced by hypoxia. The hypoxic niche environment regulates these signaling pathways to sustain the dedifferentiation and survival of fetal cardiovascular progenitor cells.

Predicting Baylisascaris procyonis roundworm prevalence, presence and abundance in raccoons (Procyon lotor) of southwestern Ohio using landscape features.

Raccoon roundworm is a leading cause of a neurological disease known as larva migrans encephalopathy in vertebrates. We determined that roundworm prevalence is significantly lower in Beavercreek Township than other townships surveyed, and that mean patch size and proportion of landscape modified by urbanization or by agriculture are good predictors of roundworm prevalence and abundance in raccoons. The proportion of landscape modified by urbanization was the best predictor of roundworm presence. These data will facilitate predictions regarding roundworm prevalence in areas that have not been previously sampled, and contribute to devising management strategies against the spread of raccoon roundworm.