Infants with bronchopulmonary dysplasia (BPD), showed impaired body growth when compared to control infants. In terms of changes in the biochemical composition of the lung, BPD infants had higher DNA, soluble protein, collagen and desmosine contents as well as increased concentrations of DNA, collagen and desmosine in their lungs when compared to the growth patterns obtained for the lungs of control infants. Pathologically BPD was classified into 4 grades. Grade I BPD, was a phase of acute lung injury, grades II and III were proliferative phases. In grade IV BPD, lung structure returned towards normal. Evidence of fibrosis was seen by a significant increase in collagen concentration in grades II and III while desmosine concentration was seen to increase in grades III and IV suggesting that the increase in collagen and desmosine contents in the lungs of BPD infants may be controlled by two different mechanisms. Collagen type I/III ratio was seen to decrease progressively from grade II to grade IV BPD in comparison to age matched controls, indicating a higher proportion of type III collagen in the lungs of infants with BPD. From the clinical analysis and the results obtained from discriminant analysis procedure, it was seen that there was a high degree of correlation between the continuation of the disease and collagen accumulation in the lungs suggesting that pulmonary fibrosis with excessive collagen accumulation is an integral part of BPD. This fibrotic process seemed to correlate significantly with assisted ventilation and high oxygen supplementation received by the infants, but it was difficult to assess the individual contribution of the two treatments in the pathogenesis of BPD. Other variables such as severity of the initial disease and the length of survival of the infants, made the assessment of individual contribution much more difficult. / Medicine, Faculty of / Pathology and Laboratory Medicine, Department of / Graduate

This study was designed to examine the hypothesis that the amount of amniotic fluid present during gestation is critical to normal lung growth and maturation. On day 16 of gestation the amniotic sacs of the right or left uterine horns of timed pregnant Sprague-Dawley rats were punctured with a 20 gauge needle. The fetuses of the opposite horn served as controls. On day 21 of gestation (one day prior to natural delivery) the fetuses were delivered by Cesarean section. An unbalanced, mixed model analysis of variance was performed on the data collected from each fetus. Probability values of less than 0.05 between control and experimental animals were considered significant. Amniotic sac puncture resulted in a significant loss of amniotic fluid as indicated by reduced amniotic fluid volume on day 21. Experimental body weight was significantly reduced indicating fetal growth retardation. Lung growth was also retarded as indicated by significantly reduced lung weight to body weight ratios and lung volume to body weight ratios following amniotic sac puncture. There was a reduction in the amount of fluid present within the experimental lungs. There appeared to be no significant effect on the structural units of the lung as indicated by no significant difference between control and experimental fetal lungs in terms of cell number, cell size, total protein to body weight ratio, maturation of type II cells, volume fraction of saccular air, saccular wall, conducting air and nonparenchyma, airspace size, saccular surface area to body weight ratio and surface to volume ratio. Thus, loss of amniotic fluid significantly affected lung growth, more than it affected overall body growth, without having an effect on lung maturation. / Medicine, Faculty of / Pathology and Laboratory Medicine, Department of / Graduate

A Cannabis sativa é a droga ilícita usada com maior frequência por gestantes. O Delta9-tetrahidrocanabinol é o canabinóide principal responsável pelos efeitos psicoativos agindo principalmente nos receptores canabinóides 1 no cérebro. O consumo de Cannabis durante a gestação pode afetar o sistema endocanabinóide causando impactos na fase implantacional e no desenvolvimento fetal. Além disso, o Delta9- tetrahidrocanabinol é uma substância que pode atravessar a barreira feto-placentária e estar presente no leite materno. Sabe-se, no entanto, que qualquer estímulo ou insulto em um período crítico de desenvolvimento embrionário-fetal pode representar consequências mais tarde na vida. A fumaça de Cannabis contém elementos tóxicos prejudiciais semelhantes aos da fumaça de cigarro, logo o uso crônico de Cannabis tem sido associado a efeitos deletérios sobre o sistema respiratório. Embora vários estudos abordarem os efeitos da exposição à Cannabis sativa, escassos são aqueles que estudam a exposição gestacional e seus efeitos na prole. Além disso, os efeitos da Cannabis sativa sobre o desenvolvimento pulmonar são pouco conhecidos. O objetivo deste estudo é analisar os efeitos do uso da Cannabis sativa no desenvolvimento pulmonar da prole de camundongos, cujas mães foram expostas no período de gestação e analisar os efeitos no próprio tecido pulmonar dessas mães. Camundongos fêmeas grávidas (BALB/c) com aproximadamente 3 meses foram expostas à fumaça de Cannabis sativa ou ar filtrado por um período de 13 dias. Após as exposições os pulmões e os fetos das fêmeas grávidas foram coletados e o perfil inflamatório pulmonar avaliado no lavado broncoalveolar. As análises morfologia tecidual foram conduzidas e avaliadas utilizando os parâmetros estereológicos do volume pulmonar total, volume total e densidade de volume dos compartimentos pulmonares (parênquima pulmonar, vias aéreas, vasos sanguíneos, espaços aéreos alveolares, septos alveolares, áreas de superfície total e densidade de superfície dos alvéolos). Adicionalmente foram incluídas as análises de dissector físico para a estimativa de volume médio alveolar, densidade numérica e o número total de alvéolos para as proles com 20 e 60 dias de idade. As análises estereológicas das fêmeas grávidas mostraram um aumento significativo no volume total pulmonar, no volume total dos septos e no volume total dos espaços aéreos alveolares, quando comparados com as fêmeas grávidas expostas ao ar filtrado (grupo controle). Nos fetos com 18 dias de idade gestacional, houve uma diminuição significativa no volume total pulmonar, no volume total e na densidade de volume de sacos alveolares, no volume total e na densidade de volume de mesênquima, quando comparados com o grupo controle. Na prole com 20 dias de idade, houve um aumento no volume total, na densidade de volume e de superfície das vias aéreas, quando comparados com o grupo controle. Na prole com 60 dias de idade, houve um aumento no volume total do espaço aéreo alveolar, na densidade de volume do espaço aéreo alveolar, na densidade de superfície dos septos alveolares e na estimativa do número total de alvéolos, quando comparados com o grupo controle. Já os parâmetros de densidade de volume dos septos alveolares, área de superfície total dos septos alveolares e espessura dos septos alveolares, mostraram-se diminuídas quando comparados com o grupo controle. Os resultados mostraram que a exposição à fumaça de Cannabis é capaz de induzir alterações morfológicas no tecido pulmonar de camundongos (BALB/c) fêmeas grávidas e nas suas respectivas proles / Cannabis sativa is the illicit drug most frequently used by pregnant women. Delta9-tetrahydrocannabinol is the main cannabinoid responsible for psychoactive effects and acts mainly on the cannabinoid 1 receptors in the brain. Cannabis use during pregnancy can affect the endocannabinoid system causing impacts on the implantation phase and fetal development. In addition, Delta9-tetrahydrocannabinol is a substance that can cross the fetal-placental barrier and be present in breast milk. It is known, however, that any stimulus or insult in a critical period of embryonic-fetal development can have consequences later in life. Cannabis smoke contains harmful toxic elements similar to those of cigarette smoke, so chronic use of Cannabis has been associated with deleterious effects on the respiratory system. Although several studies address the effects of exposure to Cannabis sativa, few are those who study gestational exposure and its effects on offspring. In addition, the Cannabis sativa effects on lung development are poorly understood. The aim of this study is to analyze the effects of Cannabis sativa on the mice offspring lung development whose mothers were exposed during the gestation period and to analyze the effects on the lung tissue of these mothers. Pregnant female mice (BALB / c) with approximately 3 months were exposed to Cannabis sativa smoke or filtered air for 13 days. After the exposures the lungs and fetuses of the pregnant females were collected and the lung inflammatory profile evaluated in the bronchoalveolar lavage. The tissue morphology analyzes were conducted and evaluated using the stereological parameters of total lung volume, total volume and volume density of lung compartments (lung parenchyma, airways, blood vessels, alveolar air spaces, alveolar septa, total surface areas and alveoli surface density). In addition, physical dissector analyzes were used to estimate the mean alveolar volume, numerical density and the total number of alveoli for offspring at 20 and 60 days of age. Stereological analyzes of pregnant females showed a significant increase in total lung volume, total septal volume and alveolar air spaces total volume when compared to pregnant females exposed to filtered air (control group). In fetuses with 18 days gestational age, there was a significant decrease in total lung volume, total volume and volume density of saccules, total volume and volume density of mesenchymal stroma when compared to the control group. In the 20-day-old offspring, there was an increase in total volume, volume density and surface density of airway when compared to the control group. In the 60-day-old offspring, there was an increase in total alveolar airspace volume, alveolar airspace volume density, alveolar septal surface density, and total alveolar number estimation, as compared to the control group. The alveolar septa volume density, alveolar septa total surface area and alveolar septa thickness were decreased when compared to the control group. The results showed that exposure to Cannabis smoke is able to induce morphological changes in the lung tissue of pregnant (BALB / c) mice and their respective offspring

Justificativa do estudo: Existem evidências crescentes de redução de fluxos expiratórios em crianças nascidas pré-termo sem doenças respiratórias neonatais. O seguimento destes pacientes sugere que haja um catch-up de função pulmonar durante os primeiros anos de vida. Objetivos: Medir a função pulmonar de lactentes pré-termo sadios (sem patologias respiratórias neonatais) durante os primeiros dois anos de vida e analisar o efeito de dados perinatais no crescimento pulmonar destes pacientes. Delineamento: Estudo de coorte prospectivo com controles históricos. Pacientes e métodos: Foram recrutados neonatos pré-termo menores de 34 semanas de idade gestacional que não necessitaram de ventilação mecânica ou oxigenoterapia prolongada no período neonatal. O grupo controle consistiu de lactentes normais a termo menores de três anos. Duas medidas longitudinais de função pulmonar foram realizadas após 40 semanas e após os 12 meses de idade corrigida., através da técnica de Compressão Torácica Rápida Os principais testes estatísticos utilizados na análise dos dados foram a análise de covariância e a regressão linear. Resultados: Os lactentes pré-termo apresentaram redução nos fluxos expiratórios forçados, com volumes pulmonares normais, em ambos os testes. A melhora da função pulmonar entre os testes foi semelhante entre os dois grupos. O uso breve de oxigênio no período neonatal foi associado a uma melhora nos fluxos e a exposição ao tabagismo antes do nascimento, a fluxos mais reduzidos. Conclusões: Fluxos expiratórios persistentemente reduzidos na presença de capacidades vitais normais e a ausência de catch-up no crescimento pulmonar dos pacientes pré-termo sugerem que o nascimento pré-termo per se está relacionado a um desenvolvimento pulmonar alterado. / Rationale: There is growing evidence of reduced expiratory flows in preterm infants without respiratory troubles at birth. Longitudinal follow-up of these children suggests there is a catch-up of lung function in the first years of life. Objectives: To measure lung function in healthy preterm infants (without neonatal respiratory disease) in the first two years of life, and analyze the effect of perinatal variables in lung growth of these group. Study: Prospective cohort study with historic controls. Patients and methods: Preterm infants less than 34 gestational weeks and with no need for mechanical ventilation or prolonged oxygen support after birth were recruited. Controls consisted of less than three year-old healthy term infants. Longitudinal lung function measures were carried out after 40 weeks and 12 months of corrected gestational age, through the Rapid Thoracic Compression Technique. The main statistical tests used were covariance analysis and linear regression. Results: Preterm infants showed reduced expiratory flows and normal lung volumes in both tests. The improvement of lung function between the two tests were similar in both groups. Brief oxygen use in the neonatal period was associated with better flows, and antenatal smoking exposure was associated to more reduced flows. Conclusions: Persistently reduced flows in the presence of normal forced vital capacity and the absence of catch-up growth in airway function suggest that premature birth is associated with altered lung development.

Justificativa do estudo: Existem evidências crescentes de redução de fluxos expiratórios em crianças nascidas pré-termo sem doenças respiratórias neonatais. O seguimento destes pacientes sugere que haja um catch-up de função pulmonar durante os primeiros anos de vida. Objetivos: Medir a função pulmonar de lactentes pré-termo sadios (sem patologias respiratórias neonatais) durante os primeiros dois anos de vida e analisar o efeito de dados perinatais no crescimento pulmonar destes pacientes. Delineamento: Estudo de coorte prospectivo com controles históricos. Pacientes e métodos: Foram recrutados neonatos pré-termo menores de 34 semanas de idade gestacional que não necessitaram de ventilação mecânica ou oxigenoterapia prolongada no período neonatal. O grupo controle consistiu de lactentes normais a termo menores de três anos. Duas medidas longitudinais de função pulmonar foram realizadas após 40 semanas e após os 12 meses de idade corrigida., através da técnica de Compressão Torácica Rápida Os principais testes estatísticos utilizados na análise dos dados foram a análise de covariância e a regressão linear. Resultados: Os lactentes pré-termo apresentaram redução nos fluxos expiratórios forçados, com volumes pulmonares normais, em ambos os testes. A melhora da função pulmonar entre os testes foi semelhante entre os dois grupos. O uso breve de oxigênio no período neonatal foi associado a uma melhora nos fluxos e a exposição ao tabagismo antes do nascimento, a fluxos mais reduzidos. Conclusões: Fluxos expiratórios persistentemente reduzidos na presença de capacidades vitais normais e a ausência de catch-up no crescimento pulmonar dos pacientes pré-termo sugerem que o nascimento pré-termo per se está relacionado a um desenvolvimento pulmonar alterado. / Rationale: There is growing evidence of reduced expiratory flows in preterm infants without respiratory troubles at birth. Longitudinal follow-up of these children suggests there is a catch-up of lung function in the first years of life. Objectives: To measure lung function in healthy preterm infants (without neonatal respiratory disease) in the first two years of life, and analyze the effect of perinatal variables in lung growth of these group. Study: Prospective cohort study with historic controls. Patients and methods: Preterm infants less than 34 gestational weeks and with no need for mechanical ventilation or prolonged oxygen support after birth were recruited. Controls consisted of less than three year-old healthy term infants. Longitudinal lung function measures were carried out after 40 weeks and 12 months of corrected gestational age, through the Rapid Thoracic Compression Technique. The main statistical tests used were covariance analysis and linear regression. Results: Preterm infants showed reduced expiratory flows and normal lung volumes in both tests. The improvement of lung function between the two tests were similar in both groups. Brief oxygen use in the neonatal period was associated with better flows, and antenatal smoking exposure was associated to more reduced flows. Conclusions: Persistently reduced flows in the presence of normal forced vital capacity and the absence of catch-up growth in airway function suggest that premature birth is associated with altered lung development.

Justificativa do estudo: Existem evidências crescentes de redução de fluxos expiratórios em crianças nascidas pré-termo sem doenças respiratórias neonatais. O seguimento destes pacientes sugere que haja um catch-up de função pulmonar durante os primeiros anos de vida. Objetivos: Medir a função pulmonar de lactentes pré-termo sadios (sem patologias respiratórias neonatais) durante os primeiros dois anos de vida e analisar o efeito de dados perinatais no crescimento pulmonar destes pacientes. Delineamento: Estudo de coorte prospectivo com controles históricos. Pacientes e métodos: Foram recrutados neonatos pré-termo menores de 34 semanas de idade gestacional que não necessitaram de ventilação mecânica ou oxigenoterapia prolongada no período neonatal. O grupo controle consistiu de lactentes normais a termo menores de três anos. Duas medidas longitudinais de função pulmonar foram realizadas após 40 semanas e após os 12 meses de idade corrigida., através da técnica de Compressão Torácica Rápida Os principais testes estatísticos utilizados na análise dos dados foram a análise de covariância e a regressão linear. Resultados: Os lactentes pré-termo apresentaram redução nos fluxos expiratórios forçados, com volumes pulmonares normais, em ambos os testes. A melhora da função pulmonar entre os testes foi semelhante entre os dois grupos. O uso breve de oxigênio no período neonatal foi associado a uma melhora nos fluxos e a exposição ao tabagismo antes do nascimento, a fluxos mais reduzidos. Conclusões: Fluxos expiratórios persistentemente reduzidos na presença de capacidades vitais normais e a ausência de catch-up no crescimento pulmonar dos pacientes pré-termo sugerem que o nascimento pré-termo per se está relacionado a um desenvolvimento pulmonar alterado. / Rationale: There is growing evidence of reduced expiratory flows in preterm infants without respiratory troubles at birth. Longitudinal follow-up of these children suggests there is a catch-up of lung function in the first years of life. Objectives: To measure lung function in healthy preterm infants (without neonatal respiratory disease) in the first two years of life, and analyze the effect of perinatal variables in lung growth of these group. Study: Prospective cohort study with historic controls. Patients and methods: Preterm infants less than 34 gestational weeks and with no need for mechanical ventilation or prolonged oxygen support after birth were recruited. Controls consisted of less than three year-old healthy term infants. Longitudinal lung function measures were carried out after 40 weeks and 12 months of corrected gestational age, through the Rapid Thoracic Compression Technique. The main statistical tests used were covariance analysis and linear regression. Results: Preterm infants showed reduced expiratory flows and normal lung volumes in both tests. The improvement of lung function between the two tests were similar in both groups. Brief oxygen use in the neonatal period was associated with better flows, and antenatal smoking exposure was associated to more reduced flows. Conclusions: Persistently reduced flows in the presence of normal forced vital capacity and the absence of catch-up growth in airway function suggest that premature birth is associated with altered lung development.

Bronchopulmonary dysplasia (BPD) is a chronic neonatal lung injury (CNLI) affecting infants of < 32 weeks gestation, which has a significant associated morbidity and mortality. The hallmarks of BPD as seen in the current era are arrested alveologenesis and parenchymal thickening. Those most severely affected may develop pulmonary hypertension which worsens the prognosis. No effective preventive therapy exists. Generation of damaging reactive oxygen species is implicated in its development. The more recently recognized reactive nitrogen species may also contribute to this disease. Thus, there is considerable interest in preventive antioxidant therapies, but results to date have not been promising. Newborn rats, exposed to 60% O2 for 14 days, develop a parenchymal injury and pulmonary hypertension that resembles the morphological features of human BPD. Previous studies have shown that following exposure to 60% O2, a pulmonary influx of neutrophils is followed by that of macrophages. Inhibiting the influx of neutrophils prevents the generation of reactive oxygen species, while simultaneously enhancing postnatal lung growth. Other interventions have shown that development of pulmonary hypertension is dependent upon increases in both 8-isoprostane and its downstream regulator of vascular tone, endothelin-1. Gentler ventilation strategies, incorporated to minimize induction of stretch-mediated pro-inflammatory cytokines, have shown benefits of permissive hypercapnia in adult lung injury. Multicentre clinical trials of permissive hypercapnia in neonates have not shown benefit. Therapeutic hypercapnia has been demonstrated to have a protective effect of PaCO2 in both acute studies of ventilator-induced and ischemia-reperfusion injuries in animal models. In the studies reported herein, therapeutic hypercapnia was found to completely protect against CNLI and attenuate 60% O2-induced macrophage-derived protein nitration. The likely nitrating agent was macrophage-derived peroxynitrite. The critical role of peroxynitrite, in the development of chronic neonatal lung injury in this model, was confirmed using a peroxynitrite decomposition catalyst. This protected against the impairments of alveolarization and of pulmonary vascularization induced by 60% O2. These results suggest a more significant role for reactive nitrogen species than previously recognized. Finally, preliminary evidence is presented supporting a role for neutrophil-derived elastase in initiating the macrophage influx in the lungs, required for peroxynitrite generation, during 60% O2-mediated injury.

Os recém-nascidos pré-termo extremos, por estarem ainda em uma fase do desenvolvimento pulmonar anterior à alveolização, estão mais vulneráveis a fatores como a hiperoxia, o barotrauma, o volutrauma e, o uso de medicações como os corticosteróides. A ação destes fatores, associada à imaturidade pulmonar, pode alterar a organização estrutural pulmonar, interferindo na alveolização e na organização de fibras elásticas e de colágeno. Estas alterações são comuns à \"nova\" displasia broncopulmonar, patologia freqüente entre os recém-nascidos pré-termo, especialmente os extremos. Criou-se um modelo experimental de restrição nutricional e hiperoxia, em coelhos pré-termo, com o objetivo de analisar os efeitos da restrição nutricional e da hiperoxia sobre a arquitetura pulmonar (número de alvéolos, intercepto linear médio(ILm), área de superfície interna(ASI), espessura de septo interalveolar), especialmente em relação à deposição de fibras elásticas e de colágeno. Após a realização de cesárea, em coelhas New Zealand White, com idade gestacional de 28 dias, seus filhotes foram divididos em 4 grupos, de acordo com a dieta e a concentração de oxigênio administradas: GIA (dieta padrão e FiO2=0,21) (n=120); GIB (dieta padrão e FiO2>0,95) (n=232); GIIA (restrição nutricional e FiO2=0,21) (n=72); GIIB (restrição nutricional e FiO2>0,95) (n=368). A restrição nutricional foi definida como uma redução em 30% de todos os nutrientes, em relação à dieta padrão. Os coelhos foram pesados, diariamente. Após o sacrifício, aos 7 e 11 dias de vida, os pulmões foram removidos, pesados e fixados em formol tamponado 10%, com uma pressão de 30 cm de H2O. O volume pulmonar total foi medido pelo método de deslocamento de água. Nos cortes histológicos utilizou-se as seguintes colorações: hematoxilina-eosina, para contagem do número de alvéolos, ILm, ASI, medida de septo interalveolar; orceína-resorcina modificada para análise de fibras elásticas e picrosirius, para análise de colágeno. Os resultados foram apresentados através de médias e realizou-se ANOVA para comparação dos resultados, considerando-se um p < 0,05 como significante. A restrição nutricional alterou o crescimento somático, reduzindo o ganho de peso e, alterou o crescimento e a morfologia pulmonares, reduzindo o volume pulmonar, o número de alvéolos e a deposição de fibras elásticas e de colágeno aos 7 e 11 dias de vida. A hiperoxia elevou a mortalidade e modificou a arquitetura pulmonar, reduzindo o número de alvéolos e aumentando suas dimensões, bem como aumento da espessura dos septos interalveolares, aos 7 e 11 dias de vida. Aos 11 dias, a hiperoxia reduziu a deposição de colágeno. A restrição nutricional associada à hiperoxia teve os seus efeitos intensificados sobre a redução do número de alvéolos e do depósito de colágeno, aos 7 e 11 dias. Estes resultados ilustram o papel da nutrição como modulador da lesão pulmonar pela hiperoxia, em pulmões em desenvolvimento / Characteristic pathologic findings in bronchopulmonary dysplasia are the presence of alveolization impairment, widened alveolar septa, disordered collagen and elastic fibers deposition. There are likely to be multiple factors that result in the histological changes seen with the development of bronchopulmonary dysplasia, besides the lung imaturity: hyperoxia, volutrauma, barotrauma, nutrition. The aim of this study is to developed an experimental model, in preterm rabbits, to evaluate the effects of nutritional restriction and hyperoxia on lung weight and volume, alveoli number, mean linear intercept (Lm), internal surface area (ISA), alveolar septal thickness, elastic fibers and collagen density. After c-section, 28 days preterm New Zealand White rabbits were randomized into 4 groups: GIA (regular diet and FiO2=0,21) (n=120); GIB (regular diet and FiO2>0,95) (n=232); GIIA (nutritional restriction and FiO2=0,21) (n=72); GIIB (nutritional restriction and FiO2>0,95) (n=368). They were kept in incubators, warmer and humidified oxygen (Plexiglas chamber). Nutritional restriction was defined as caloric-proteic intake limited to 70% of the regular diet. After sacrifice with 7 and 11 days, the lungs were removed and fixed in 10% formalin under 30 cm H2O transtracheal pressure. The total lung volume was measured by displacement water. Lung slices were stained with hematoxylin and eosin for alveoli number, Lm, ISA and alveolar septal thickness; resorcin-orcein for elastic fibers and Picrosirius for collagen (fibers/parenchyma pointy counting). Statistical analysis was done by ANOVA. Level of significance was set at 0,05. Values are means +- sd. It was observed that GIA and GIB (regular diet) put on more weight than nutritional restriction groups from 8th till 11th day of life. Nutritional restriction influenced the ponderal evolution and reduced lung volume, alveoli number, collagen and elastic fibers deposition at 7th and 11th days of life. Hyperoxia elevated the mortality. In relation to lung architetural, the hyperoxia reduced alveoli number and elevated Lm, besides widened alveolar septal at 7th and 11th days of life. At 11th days, hyperoxia reduced collagen deposition, too. Nutritional restriction and hyperoxia had an additive efect on the reduction of alveoli number and collagen deposition. These findings suggest that nutrition has a modulator effect on lung injury by hyperoxia. This study strengthened the contribution of nutrition on preterm lung development

Bronchopulmonary dysplasia (BPD) is a chronic neonatal lung injury (CNLI) affecting infants of < 32 weeks gestation, which has a significant associated morbidity and mortality. The hallmarks of BPD as seen in the current era are arrested alveologenesis and parenchymal thickening. Those most severely affected may develop pulmonary hypertension which worsens the prognosis. No effective preventive therapy exists. Generation of damaging reactive oxygen species is implicated in its development. The more recently recognized reactive nitrogen species may also contribute to this disease. Thus, there is considerable interest in preventive antioxidant therapies, but results to date have not been promising. Newborn rats, exposed to 60% O2 for 14 days, develop a parenchymal injury and pulmonary hypertension that resembles the morphological features of human BPD. Previous studies have shown that following exposure to 60% O2, a pulmonary influx of neutrophils is followed by that of macrophages. Inhibiting the influx of neutrophils prevents the generation of reactive oxygen species, while simultaneously enhancing postnatal lung growth. Other interventions have shown that development of pulmonary hypertension is dependent upon increases in both 8-isoprostane and its downstream regulator of vascular tone, endothelin-1. Gentler ventilation strategies, incorporated to minimize induction of stretch-mediated pro-inflammatory cytokines, have shown benefits of permissive hypercapnia in adult lung injury. Multicentre clinical trials of permissive hypercapnia in neonates have not shown benefit. Therapeutic hypercapnia has been demonstrated to have a protective effect of PaCO2 in both acute studies of ventilator-induced and ischemia-reperfusion injuries in animal models. In the studies reported herein, therapeutic hypercapnia was found to completely protect against CNLI and attenuate 60% O2-induced macrophage-derived protein nitration. The likely nitrating agent was macrophage-derived peroxynitrite. The critical role of peroxynitrite, in the development of chronic neonatal lung injury in this model, was confirmed using a peroxynitrite decomposition catalyst. This protected against the impairments of alveolarization and of pulmonary vascularization induced by 60% O2. These results suggest a more significant role for reactive nitrogen species than previously recognized. Finally, preliminary evidence is presented supporting a role for neutrophil-derived elastase in initiating the macrophage influx in the lungs, required for peroxynitrite generation, during 60% O2-mediated injury.

Os recém-nascidos pré-termo extremos, por estarem ainda em uma fase do desenvolvimento pulmonar anterior à alveolização, estão mais vulneráveis a fatores como a hiperoxia, o barotrauma, o volutrauma e, o uso de medicações como os corticosteróides. A ação destes fatores, associada à imaturidade pulmonar, pode alterar a organização estrutural pulmonar, interferindo na alveolização e na organização de fibras elásticas e de colágeno. Estas alterações são comuns à \"nova\" displasia broncopulmonar, patologia freqüente entre os recém-nascidos pré-termo, especialmente os extremos. Criou-se um modelo experimental de restrição nutricional e hiperoxia, em coelhos pré-termo, com o objetivo de analisar os efeitos da restrição nutricional e da hiperoxia sobre a arquitetura pulmonar (número de alvéolos, intercepto linear médio(ILm), área de superfície interna(ASI), espessura de septo interalveolar), especialmente em relação à deposição de fibras elásticas e de colágeno. Após a realização de cesárea, em coelhas New Zealand White, com idade gestacional de 28 dias, seus filhotes foram divididos em 4 grupos, de acordo com a dieta e a concentração de oxigênio administradas: GIA (dieta padrão e FiO2=0,21) (n=120); GIB (dieta padrão e FiO2>0,95) (n=232); GIIA (restrição nutricional e FiO2=0,21) (n=72); GIIB (restrição nutricional e FiO2>0,95) (n=368). A restrição nutricional foi definida como uma redução em 30% de todos os nutrientes, em relação à dieta padrão. Os coelhos foram pesados, diariamente. Após o sacrifício, aos 7 e 11 dias de vida, os pulmões foram removidos, pesados e fixados em formol tamponado 10%, com uma pressão de 30 cm de H2O. O volume pulmonar total foi medido pelo método de deslocamento de água. Nos cortes histológicos utilizou-se as seguintes colorações: hematoxilina-eosina, para contagem do número de alvéolos, ILm, ASI, medida de septo interalveolar; orceína-resorcina modificada para análise de fibras elásticas e picrosirius, para análise de colágeno. Os resultados foram apresentados através de médias e realizou-se ANOVA para comparação dos resultados, considerando-se um p < 0,05 como significante. A restrição nutricional alterou o crescimento somático, reduzindo o ganho de peso e, alterou o crescimento e a morfologia pulmonares, reduzindo o volume pulmonar, o número de alvéolos e a deposição de fibras elásticas e de colágeno aos 7 e 11 dias de vida. A hiperoxia elevou a mortalidade e modificou a arquitetura pulmonar, reduzindo o número de alvéolos e aumentando suas dimensões, bem como aumento da espessura dos septos interalveolares, aos 7 e 11 dias de vida. Aos 11 dias, a hiperoxia reduziu a deposição de colágeno. A restrição nutricional associada à hiperoxia teve os seus efeitos intensificados sobre a redução do número de alvéolos e do depósito de colágeno, aos 7 e 11 dias. Estes resultados ilustram o papel da nutrição como modulador da lesão pulmonar pela hiperoxia, em pulmões em desenvolvimento / Characteristic pathologic findings in bronchopulmonary dysplasia are the presence of alveolization impairment, widened alveolar septa, disordered collagen and elastic fibers deposition. There are likely to be multiple factors that result in the histological changes seen with the development of bronchopulmonary dysplasia, besides the lung imaturity: hyperoxia, volutrauma, barotrauma, nutrition. The aim of this study is to developed an experimental model, in preterm rabbits, to evaluate the effects of nutritional restriction and hyperoxia on lung weight and volume, alveoli number, mean linear intercept (Lm), internal surface area (ISA), alveolar septal thickness, elastic fibers and collagen density. After c-section, 28 days preterm New Zealand White rabbits were randomized into 4 groups: GIA (regular diet and FiO2=0,21) (n=120); GIB (regular diet and FiO2>0,95) (n=232); GIIA (nutritional restriction and FiO2=0,21) (n=72); GIIB (nutritional restriction and FiO2>0,95) (n=368). They were kept in incubators, warmer and humidified oxygen (Plexiglas chamber). Nutritional restriction was defined as caloric-proteic intake limited to 70% of the regular diet. After sacrifice with 7 and 11 days, the lungs were removed and fixed in 10% formalin under 30 cm H2O transtracheal pressure. The total lung volume was measured by displacement water. Lung slices were stained with hematoxylin and eosin for alveoli number, Lm, ISA and alveolar septal thickness; resorcin-orcein for elastic fibers and Picrosirius for collagen (fibers/parenchyma pointy counting). Statistical analysis was done by ANOVA. Level of significance was set at 0,05. Values are means +- sd. It was observed that GIA and GIB (regular diet) put on more weight than nutritional restriction groups from 8th till 11th day of life. Nutritional restriction influenced the ponderal evolution and reduced lung volume, alveoli number, collagen and elastic fibers deposition at 7th and 11th days of life. Hyperoxia elevated the mortality. In relation to lung architetural, the hyperoxia reduced alveoli number and elevated Lm, besides widened alveolar septal at 7th and 11th days of life. At 11th days, hyperoxia reduced collagen deposition, too. Nutritional restriction and hyperoxia had an additive efect on the reduction of alveoli number and collagen deposition. These findings suggest that nutrition has a modulator effect on lung injury by hyperoxia. This study strengthened the contribution of nutrition on preterm lung development