Combined iNO and endothelial progenitor cells improve lung alveolar and vascular structure in neonatal rats exposed to prolonged hyperoxia

Abstract

Background: Stem cells or inhaled nitric oxide (iNO) are reported to improve lung structures in bronchopulmonary dysplasia (BPD) models. We hypothesized that combined iNO and transplanted endothelial progenitor cells (EPCs) might restore lung structure in rats after neonatal hyperoxia. Methods: Litters were separated into eight groups: room air, hyperoxia, hyperoxia + iNO, hyperoxia + iNO + L-NAME, hyperoxia + EPCs, hyperoxia + EPCs + L-NAME, hyperoxia + EPCs + iNO, and hyperoxia + EPCs + iNO + L-NAME. Litters were exposed to hyperoxia from the 21st day, then, sacrificed. EPCs were injected on the 21st day. L-NAME was injected daily for 7 d from the 21st day. Serum vascular endothelial growth factor (VEGF), radial alveolar count (RAC), VIII factor, EPCs engraftment, lung VEGF, VEGFR2, endothelial nitric oxide (eNOS) and SDF-1 expression, and NO production were examined. results: Hyperoxia exposure led to air space enlargement, loss of lung capillaries, and low expression of VEGF and eNOS. Transplanted EPCs, when combined with iNO, had significantly increased engraftment in lungs, compared to EPCs alone, upon hyperoxia exposure. There was improvement in alveolarization, microvessel density, and upregulation of VEGF and eNOS proteins in the hyperoxia-exposed EPCs with iNO group, compared to hyperoxia alone. conclusion: Combined EPCs and iNO improved lung structures after neonatal hyperoxia. This was associated with the upregulation of VEGF and eNOS expression.B ronchopulmonary dysplasia (BPD) is a chronic lung disease associated with significant mortality and morbidity in premature infants. New BPD is characterized by arrested alveolar and vascular growth (vascular hypothesis of BPD) (1,2). Alveolar formation is a highly coordinated process between the development of airways and pulmonary vasculature (3). Exposure to inflammation caused by excessive O 2 supplementation is hypothesized to interfere with the coordinated process of normal human lung development. Neonatal hyperoxia exposure is known to disrupt alveolar formation and growth, providing a useful model for studying BPD (4).Cell-based therapy is a novel approach that offers much promise in the prevention and treatment of BPD, including embryonic stem cells, mesenchymal stem cells, placental stem cells, umbilical cord stem cells, amniotic fluid and amnionderived cells, and lung progenitor cells. Endothelial progenitor cells (EPCs) are precursors of endothelial cells, which have the capacity of self-renewal and proliferation. EPCs is one of the key cells mediating vascular growth, which can mobilize from bone marrow and home to the site of vascular injuries, promoting neovascularization (5). There is data showing that reduced numbers or dysfunction of EPCs at birth is associated with the development of BPD (6,7). In addition, a reduction in the number of EPCs in the bone marrow, circulation and lungs has also emerged in animal models of BPD (8). Evidences that angiogenic cells treatment can restore lung structure have been demonstrated. Balasubramaniam et al...

Nitric oxide and hyperoxic acute lung injury

“…Steudel et al (1999) found the expression and activity of both eNOS and iNOS increased in the adult rat lung following hyperoxia exposure, but Arkovitz et al (1997) found hyperoxia had differential effects on the eNOS and iNOS and hyperoxia was able to decrease eNOS activity . The reduction in eNOS expression was also confirmed by the study of Lu et al (2015). However, the study of Grisafi et al (2012) showed eNOS expression increased in hypoxia-treated rats and L-citrulline further increased eNOS expression in the lung, accompanied by the improvement of lung Arkovitz et al (1997), hyperoxia failed to increase serum NO, but resulted in a small but significant increase in NO production in the BALF.…”

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