The essential role for endothelial cell sprouting in coronary collateral growth.

RATIONALE: Coronary collateral growth is a natural bypass for ischemic heart diseases. It offers tremendous therapeutic benefit, but the process of coronary collateral growth isincompletely understood due to limited preclinical murine models that would enable interrogation of its mechanisms and processes via genetic modification and lineage tracing. Understanding the processes by which coronary collaterals develop can unlock new therapeutic strategies for ischemic heart disease. OBJECTIVE: To develop a murine model of coronary collateral growth by repetitive ischemia and investigate whether capillary endothelial cells could contribute to the coronary collateral formation in an adult mouse heart after repetitive ischemia by lineage tracing. METHODS AND RESULTS: A murine model of coronary collateral growth was developed using short episodes of repetitive ischemia. Repetitive ischemia stimulation resulted in robust collateral growth in adult mouse hearts, validated by high-resolution micro-computed tomography. Repetitive ischemia-induced collateral formation compensated ischemia caused by occlusion of the left anterior descending artery. Cardiac function improved during ischemia after repetitive ischemia, suggesting the improvement of coronary blood flow. A capillary-specific Cre driver (Apln-CreER) was used for lineage tracing capillary endothelial cells. ROSA mT/mG reporter mice crossed with the Apln-CreER transgene mice underwent a 17 days' repetitive ischemia protocol for coronary collateral growth. Two-photon and confocal microscopy imaging of heart slices revealed repetitive ischemia-induced coronary collateral growth initiated from sprouting Apelin+ endothelial cells. Newly formed capillaries in the collateral-dependent zone expanded in diameter upon repetitive ischemia stimulation and arterialized with smooth muscle cell recruitment, forming mature coronary arteries. Notably, pre-existing coronary arteries and arterioles were not Apelin+, and all Apelin+ collaterals arose from sprouting capillaries. Cxcr4, Vegfr2, Jag1, Mcp1, and Hif1⍺ mRNA levels in the repetitive ischemia-induced hearts were also upregulated at the early stage of coronary collateral growth, suggesting angiogenic signaling pathways are activated for coronary collaterals formation during repetitive ischemia. CONCLUSIONS: We developed a murine model of coronary collateral growth induced by repetitive ischemia. Our lineage tracing study shows that sprouting endothelial cells contribute to coronary collateral growth in adult mouse hearts. For the first time, sprouting angiogenesis is shown to give rise to mature coronary arteries in response to repetitive ischemia in the adult mouse hearts.

Variation in Bacterial Respiratory Culture Results in Children With Neurologic Impairment.

OBJECTIVES: To examine bacterial respiratory cultures in children with neurologic impairment (NI) (eg, cerebral palsy), both with and without tracheostomies, who were hospitalized with acute respiratory infections (ARIs) (eg, pneumonia) and to compare culture results across hospitals and age groups. METHODS: This multicenter retrospective cohort study included ARI hospitalizations for children aged 1 to 18 years with NI between 2007 and 2012 who had a bacterial respiratory culture obtained within 2 days of admission. Data from 5 children's hospitals in the Pediatric Health Information System Plus database were used. Organisms consistent with oral flora and nonspeciated organisms were omitted from analysis. The prevalence of positive respiratory culture results and the prevalence of organisms identified were compared across hospitals and age groups and in subanalyses of children with and without tracheostomies by using generalized estimating equations to account for within-patient clustering. RESULTS: Of 4900 hospitalizations, 693 from 485 children had bacterial respiratory cultures obtained. Of these, 54.5% had positive results, although this varied across hospitals (range 18.6%-83.2%; P < .001). Pseudomonas aeruginosa and Staphylococcus aureus were the most commonly identified organisms across hospitals and age groups and in patients with and without tracheostomies. Large variation in growth prevalence was identified across hospitals but not age groups. CONCLUSIONS: The bacteriology of ARI in hospitalized children with NI differs from that of otherwise healthy children. Significant variation in prevalence of positive bacterial respiratory culture results and organism growth were observed across hospitals, which may be secondary to local environmental factors and microbiology reporting practices.

Discharge Before Return to Respiratory Baseline in Children With Neurologic Impairment.

BACKGROUND: Children with neurologic impairment (NI) are commonly hospitalized with acute respiratory infections (ARI). These children frequently require respiratory support at baseline and are often discharged before return to respiratory baseline. OBJECTIVE: To determine if discharge before return to respiratory baseline is associated with reutilization among children with NI hospitalized with ARI. METHODS: This single-center retrospective cohort study included children with NI aged 1 to 18 years hospitalized with ARI who required increased respiratory support between January 2010 and September 2015. The primary exposure was discharge before return to respiratory baseline. The primary outcome was 30-day hospital reutilization. A generalized estimating equation was used to examine the association between exposure and outcome while accounting for within-patient clustering and patient-level clinical complexity and illness severity. RESULTS: In the 632 hospitalizations experienced by 366 children, children were discharged before return to respiratory baseline in 30.4% of hospitalizations. Compared with those hospitalizations in which children were discharged at baseline, hospitalizations with a discharge before return to respiratory baseline were more likely to be for privately insured, technology-dependent children with respiratory comorbidities. Compared with discharges at respiratory baseline, discharges with increased respiratory support had no difference in 30-day reutilization (32.8% vs 31.8%; P = .81; adjusted OR 0.80, 95% CI 0.51-1.26). CONCLUSIONS: Among children with NI hospitalized with ARI, discharge before return to respiratory baseline was common, but it was not associated with hospital reutilization. Return to respiratory baseline may not be a necessary component of discharge criteria in this population.

Microstereolithography and characterization of poly(propylene fumarate)-based drug-loaded microneedle arrays.

Drug-loaded microneedle arrays for transdermal delivery of a chemotherapeutic drug were fabricated using multi-material microstereolithography (µSL). These arrays consisted of twenty-five poly(propylene fumarate) (PPF) microneedles, which were precisely orientated on the same polymeric substrate. To control the viscosity and improve the mechanical properties of the PPF, diethyl fumarate (DEF) was mixed with the polymer. Dacarbazine, which is widely used for skin cancer, was uniformly blended into the PPF/DEF solution prior to crosslinking. Each microneedle has a cylindrical base with a height of 700 µm and a conical tip with a height of 300 µm. Compression test results and characterization of the elastic moduli of the PPF/DEF (50:50) and PPF/drug mixtures indicated that the failure force was much larger than the theoretical skin insertion force. The release kinetics showed that dacarbazine can be released at a controlled rate for five weeks. The results demonstrated that the PPF-based drug-loaded microneedles are a potential method to treat skin carcinomas. In addition, µSL is an attractive manufacturing technique for biomedical applications, especially for micron-scale manufacturing.