. Treatment of newborn rats with a VEGF receptor inhibitor causes pulmonary hypertension and abnormal lung structure. Am J Physiol Lung Cell Mol Physiol 283: L555-L562, 2002. First published April 19, 2002 10.1152/ajplung.00408.2001.-To determine whether disruption of vascular endothelial growth factor (VEGF)-VEGF receptor (VEGFR) signaling in the newborn has long-term effects on lung structure and function, we injected 1-day-old newborn rat pups with a single dose of Su-5416, a VEGFR inhibitor, or vehicle (controls). Lungs from infant (3-wk-old) and adult (3-to 4-mo-old) rats treated with Su-5416 as newborns showed reductions in arterial density (82 and 31%, respectively) and alveolar counts (45 and 29%) compared with controls. Neonatal treatment with Su-5416 increased right ventricle weight to body wt ratios (4.2-fold and 2.0-fold) and pulmonary arterial wall thickness measurements (2.7-fold and 1.6-fold) in infant and adult rats, respectively, indicating marked pulmonary hypertension. We conclude that treatment of newborn rats with the VEGFR inhibitor Su-5416 impaired pulmonary vascular growth and postnatal alveolarization and caused pulmonary hypertension and that these effects were long term, persisting well into adulthood.angiogenesis; postnatal lung development; alveogenesis; bronchopulmonary dysplasia; pulmonary vascular development; vascular endothelial growth factor

The etiology and pathogenesis of the vascular lesions characterizing primary pulmonary hypertension (PPH), an often fatal pulmonary vascular disease, are largely unknown. Plexiform lesions composed of proliferating endothelial cells occur in between 20 and 80% of the cases of this irreversible pulmonary vascular disease. Recently, technology to assess monoclonality has allowed the distinction between cellular proliferation present in neoplasms from that in reactive nonneoplastic tissue. To determine whether the endothelial cell proliferation in plexiform lesions in PPH is monoclonal or polyclonal, we assessed the methylation pattern of the human androgen receptor gene by PCR (HUMARA) in proliferated endothelial cells in plexiform lesions from female PPH patients (n = 4) compared with secondary pulmonary hypertension (PH) patients (n = 4). In PPH, 17 of 22 lesions (77%) were monoclonal. However, in secondary PH, all 19 lesions examined were polyclonal. Smooth muscle cell hyperplasia in pulmonary vessels (n = 11) in PPH and secondary PH was polyclonal in all but one of the examined vessels. The monoclonal expansion of endothelial cells provides the first marker that allows the distinction between primary and secondary PH. Our data of a frequent monoclonal endothelial cell proliferation in PPH suggests that a somatic genetic alteration similar to that present in neoplastic processes may be responsible for the pathogenesis of PPH.

Hyperoxia disrupts vascular and alveolar growth of the developing lung and contributes to the development of bronchopulmonary dysplasia (BPD). Endothelial progenitor cells (EPC) have been implicated in repair of the vasculature, but their role in lung vascular development is unknown. Since disruption of vascular growth impairs lung structure, we hypothesized that neonatal hyperoxia impairs EPC mobilization and homing to the lung, contributing to abnormalities in lung structure. Neonatal mice (1-day-old) were exposed to 80% O2at Denver's altitude (= 65% at sea level) or room air for 10 days. Adult mice were also exposed for comparison. Blood, lung, and bone marrow were harvested after hyperoxia. Hyperoxia decreased pulmonary vascular density by 72% in neonatal but not adult mice. In contrast to the adult, hyperoxia simplified distal lung structure neonatal mice. Moderate hyperoxia reduced EPCs (CD45−/Sca-1+/CD133+/VEGFR-2+) in the blood (55%; P < 0.03), bone marrow (48%; P < 0.01), and lungs (66%; P < 0.01) of neonatal mice. EPCs increased in bone marrow (2.5-fold; P < 0.01) and lungs (2-fold; P < 0.03) of hyperoxia-exposed adult mice. VEGF, nitric oxide (NO), and erythropoietin (Epo) contribute to mobilization and homing of EPCs. Lung VEGF, VEGF receptor-2, endothelial NO synthase, and Epo receptor expression were reduced by hyperoxia in neonatal but not adult mice. We conclude that moderate hyperoxia decreases vessel density, impairs lung structure, and reduces EPCs in the circulation, bone marrow, and lung of neonatal mice but increases EPCs in adults. This developmental difference may contribute to the increased susceptibility of the developing lung to hyperoxia and may contribute to impaired lung vascular and alveolar growth in BPD.

Trisomy 21 (T21) causes Down syndrome (DS), but the mechanisms by which T21 produces the different disease spectrum observed in people with DS are unknown. We recently identified an activated interferon response associated with T21 in human cells of different origins, consistent with overexpression of the four interferon receptors encoded on chromosome 21, and proposed that DS could be understood partially as an interferonopathy. However, the impact of T21 on systemic signaling cascades in living individuals with DS is undefined. To address this knowledge gap, we employed proteomics approaches to analyze blood samples from 263 individuals, 165 of them with DS, leading to the identification of dozens of proteins that are consistently deregulated by T21. Most prominent among these proteins are numerous factors involved in immune control, the complement cascade, and growth factor signaling. Importantly, people with DS display higher levels of many pro-inflammatory cytokines (e.g. IL-6, MCP-1, IL-22, TNF-α) and pronounced complement consumption, resembling changes seen in type I interferonopathies and other autoinflammatory conditions. Therefore, these results are consistent with the hypothesis that increased interferon signaling caused by T21 leads to chronic immune dysregulation, and justify investigations to define the therapeutic value of immune-modulatory strategies in DS.

-VEGF signaling inhibition decreases alveolar and vessel growth in the developing lung, suggesting that impaired VEGF signaling may contribute to decreased lung growth in bronchopulmonary dysplasia (BPD). Whether VEGF treatment improves lung structure in experimental models of BPD is unknown. The objective was to determine whether VEGF treatment enhances alveolarization in infant rats after hyperoxia. Two-day-old Sprague-Dawley rats were placed into hyperoxia or room air (RA) for 12 days. At 14 days, rats received daily treatment with rhVEGF-165 or saline. On day 22, rats were killed. Tissue was collected. Morphometrics was assessed by radial alveolar counts (RAC), mean linear intercepts (MLI), and skeletonization. Compared with RA controls, hyperoxia decreased RAC (6.1 Ϯ 0.4 vs. 11.3 Ϯ 0.4, P Ͻ 0.0001), increased MLI (59.2 Ϯ 1.8 vs. 44.0 Ϯ 0.8, P Ͻ 0.0001), decreased nodal point density (447 Ϯ 14 vs. 503 Ϯ 12, P Ͻ 0.0004), and decreased vessel density (11.7 Ϯ 0.3 vs. 18.9 Ϯ 0.3, P Ͻ 0.001), which persisted despite RA recovery. Compared with hyperoxic controls, rhVEGF treatment after hyperoxia increased RAC (11.8 Ϯ 0.5, P Ͻ 0.0001), decreased MLI (42.2 Ϯ 1.2, P Ͻ 0.0001), increased nodal point density (502 Ϯ 7, P Ͻ 0.0005), and increased vessel density (23.2 Ϯ 0.4, P Ͻ 0.001). Exposure of neonatal rats to hyperoxia impairs alveolarization and vessel density, which persists despite RA recovery. rhVEGF treatment during recovery enhanced vessel growth and alveolarization. We speculate that lung structure abnormalities after hyperoxia may be partly due to impaired VEGF signaling. bronchopulmonary dysplasia; lung development; vascular endothelial growth factor; angiogenesis BRONCHOPULMONARY DYSPLASIA (BPD) is the chronic lung disease of infancy that follows ventilator and oxygen therapy for respiratory distress syndrome after premature birth (37). Although the mechanisms that cause BPD are not completely understood, surfactant deficiency, ventilator-induced lung injury, oxygen toxicity, and inflammation are important pathogenic factors (21). Traditionally, BPD has been characterized by severe chronic lung injury with striking fibrosis and cellular proliferation. With advancements in perinatal care including exogenous surfactant administration, improved ventilator management, and antenatal steroids, the clinical course and lung histology of BPD have changed. Infants with BPD now have less severe acute respiratory disease, and at autopsy, lung histology is characterized by arrested lung development including alveolar simplification and dysmorphic vascular growth (1,18,21,37).Mechanisms that impair lung growth and cause persistent abnormalities in lung structure in premature infants with BPD remain poorly understood. Recently, experimental studies have shown that growth of the pulmonary circulation and alveolarization are closely coordinated, as demonstrated by findings that disruption of angiogenesis impairs lung structure (20). Treatment of neonatal rats with antiangiogenic agents, including fumagillin and thalidomide...