pH-neutralizing esophageal irrigations as a novel mitigation strategy for button battery injury.

OBJECTIVES/HYPOTHESIS: Ingestion of button batteries (BB) can rapidly lead to caustic esophageal injury in infants and children, resulting in significant morbidity and mortality. To identify novel mitigation strategies, we tested common weakly acidic household beverages, viscous liquids, and Carafate® for their ability to act as protective esophageal irrigations until endoscopic removal of the BB. STUDY DESIGN: Cadaveric and live animal model. METHODS: Apple juice, orange juice, Gatorade®, POWERADE®, pure honey, pure maple syrup, and Carafate® were screened using a 3 V lithium (3 V-CR2032) BB on cadaveric porcine esophagus. The most promising in vitro options were tested against a saline control in live American Yorkshire piglets with anode-facing placement of the BB on the posterior wall of the proximal esophagus for 60 minutes. BB voltage and tissue pH were measured before battery placement and after removal. The 10 mL irrigations occurred every 10 minutes from t = 5 minutes. Gross and histologic assessment was performed on the esophagus of piglets euthanized 7 ± 0.5 days following BB exposure. RESULTS: Honey and Carafate® demonstrated to a significant degree the most protective effects in vitro and in vivo. Both neutralized the tissue pH increase and created more localized and superficial injuries; observed in vivo was a decrease in both full-thickness injury (i.e., shallower depths of necrotic and granulation tissue) and outward extension of injury in the deep muscle beyond surface ulcer margins (P < .05). CONCLUSIONS: In the crucial period between BB ingestion and endoscopic removal, early and frequent ingestion of honey in the household setting and Carafate® in the clinical setting has the potential to reduce injury severity and improve patient outcomes. LEVEL OF EVIDENCE: NA Laryngoscope, 129:49-57, 2019.

Sequential delivery of immunomodulatory cytokines to facilitate the M1-to-M2 transition of macrophages and enhance vascularization of bone scaffolds.

In normal tissue repair, macrophages exhibit a pro-inflammatory phenotype (M1) at early stages and a pro-healing phenotype (M2) at later stages. We have previously shown that M1 macrophages initiate angiogenesis while M2 macrophages promote vessel maturation. Therefore, we reasoned that scaffolds that promote sequential M1 and M2 polarization of infiltrating macrophages should result in enhanced angiogenesis and healing. To this end, we first analyzed the in vitro kinetics of macrophage phenotype switch using flow cytometry, gene expression, and cytokine secretion analysis. Then, we designed scaffolds for bone regeneration based on modifications of decellularized bone for a short release of interferon-gamma (IFNg) to promote the M1 phenotype, followed by a more sustained release of interleukin-4 (IL4) to promote the M2 phenotype. To achieve this sequential release profile, IFNg was physically adsorbed onto the scaffolds, while IL4 was attached via biotin-streptavidin binding. Interestingly, despite the strong interactions between biotin and streptavidin, release studies showed that biotinylated IL4 was released over 6 days. These scaffolds promoted sequential M1 and M2 polarization of primary human macrophages as measured by gene expression of ten M1 and M2 markers and secretion of four cytokines, although the overlapping phases of IFNg and IL4 release tempered polarization to some extent. Murine subcutaneous implantation model showed increased vascularization in scaffolds releasing IFNg compared to controls. This study demonstrates that scaffolds for tissue engineering can be designed to harness the angiogenic behavior of host macrophages towards scaffold vascularization.

The role of macrophage phenotype in vascularization of tissue engineering scaffolds.

Angiogenesis is crucial for the success of most tissue engineering strategies. The natural inflammatory response is a major regulator of vascularization, through the activity of different types of macrophages and the cytokines they secrete. Macrophages exist on a spectrum of diverse phenotypes, from "classically activated" M1 to "alternatively activated" M2 macrophages. M2 macrophages, including the subsets M2a and M2c, are typically considered to promote angiogenesis and tissue regeneration, while M1 macrophages are considered to be anti-angiogenic, although these classifications are controversial. Here we show that in contrast to this traditional paradigm, primary human M1 macrophages secrete the highest levels of potent angiogenic stimulators including VEGF; M2a macrophages secrete the highest levels of PDGF-BB, a chemoattractant for stabilizing pericytes, and also promote anastomosis of sprouting endothelial cells in vitro; and M2c macrophages secrete the highest levels of MMP9, an important protease involved in vascular remodeling. In a murine subcutaneous implantation model, porous collagen scaffolds were surrounded by a fibrous capsule, coincident with high expression of M2 macrophage markers, while scaffolds coated with the bacterial lipopolysaccharide were degraded by inflammatory macrophages, and glutaraldehyde-crosslinked scaffolds were infiltrated by substantial numbers of blood vessels, accompanied by high levels of M1 and M2 macrophages. These results suggest that coordinated efforts by both M1 and M2 macrophages are required for angiogenesis and scaffold vascularization, which may explain some of the controversy over which phenotype is the angiogenic phenotype.

Decellularization of human and porcine lung tissues for pulmonary tissue engineering.

BACKGROUND: The only definitive treatment for end-stage organ failure is orthotopic transplantation. Lung extracellular matrix (LECM) holds great potential as a scaffold for lung tissue engineering because it retains the complex architecture, biomechanics, and topologic specificity of the lung. Decellularization of human lungs rejected from transplantation could provide "ideal" biologic scaffolds for lung tissue engineering, but the availability of such lungs remains limited. The present study was designed to determine whether porcine lung could serve as a suitable substitute for human lung to study tissue engineering therapies. METHODS: Human and porcine lungs were procured, sliced into sheets, and decellularized by three different methods. Compositional, ultrastructural, and biomechanical changes to the LECM were characterized. The suitability of LECM for cellular repopulation was evaluated by assessing the viability, growth, and metabolic activity of human lung fibroblasts, human small airway epithelial cells, and human adipose-derived mesenchymal stem cells over a period of 7 days. RESULTS: Decellularization with 3-[(3-Cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) showed the best maintenance of both human and porcine LECM, with similar retention of LECM proteins except for elastin. Human and porcine LECM supported the cultivation of pulmonary cells in a similar way, except that the human LECM was stiffer and resulted in higher metabolic activity of the cells than porcine LECM. CONCLUSIONS: Porcine lungs can be decellularized with CHAPS to produce LECM scaffolds with properties resembling those of human lungs, for pulmonary tissue engineering. We propose that porcine LECM can be an excellent screening platform for the envisioned human tissue engineering applications of decellularized lungs.