Congenital Diaphragmatic Hernia Lungs Research Articles

Impaired alveolar epithelial cell differentiation in the hypoplastic lung in nitrofen-induced congenital diaphragmatic hernia

Pulmonary hypoplasia is the principal cause of morbidity and mortality in infants with congenital diaphragmatic hernia (CDH). Still, relatively little is known about the mechanisms causing lung hypoplasia associated with CDH. The differentiation from alveolar epithelial cells type II (AECs-II) into alveolar epithelial cells type I (AECs-I) is one of the key processes in lung development in late gestation. It is well known that increased lung expansion promotes differentiation into AECs-I phenotype, whereas reduced lung expansion promotes AECs-II phenotype. The recent availability of cell-specific molecule markers for AECs-I and AECs-II has provided an opportunity to study the various characteristics of these two cell types. To test the hypothesis that the differentiation of AECs-II to AECs-I is impaired in the CDH hypoplastic lung, we investigated molecular markers for AECs-I [ICAM-1, T1alpha, aquaporin 5 (AQP5)] and molecular markers for AECs-II [thyroid transcription factor-1 (Ttf-1), surfactant protein (SP)-B and C] in the nitrofen-induced CDH lung. Fetal rat lungs of normal (n = 7) and nitrofen-treated (n = 14) dams were harvested on embryonic day 21. The expression of the ICAM1, T1alpha, AQP5, SP-B, C and Ttf-1 was analyzed in each lung by real-time reverse transcription polymerase chain reaction. Immunohistochemical studies were performed to evaluate the protein expression level of ICAM1 and Ttf1. Expression levels of ICAM-1, T1alpha and AQP5 were significantly reduced (P < 0.05) in the lungs from nitrofen-treated CDH animals compared to normal controls. ICAM-1 and AQP5 immunohistochemistry showed a diffuse pattern of expression in the alveolar cells in normal lungs. By contrast, the ICAM-1 and AQP5 positive cells were markedly reduced in hypoplastic lungs with CDH. On the other hand, the expression levels of Ttf-1, SP-B and C were significantly (P < 0.05) increased in the lungs from nitrofen-treated CDH animals compared to normal controls. The population of Ttf-1 positive cells was slightly increased in the lungs from nitrofen-treated animals in immunohistochemical study. Our results demonstrate that there is significant reduction in the proportion of AECs-I and increase in the proportion of AECs-II in the hypoplastic lung in the nitrofen-induced CDH. This data provides the first evidence to support the hypothesis that AEC differentiation is impaired in CDH hypoplastic lung.

Serum monocyte chemotactic protein-1 levels in congenital diaphragmatic hernia

To measure serum monocyte chemotactic protein-1 (MCP-1) in patients with congenital diaphragmatic hernia (CDH) and investigate its relationship to the development of persistent pulmonary hypertension (PPH). Serum MCP-1 was measured in 13 neonates with high risk for CDH at the time of diagnosis and postoperatively, and in five age-matched controls using an ELISA system. The 13 CDH subjects were divided into four groups according to the presence of PPH and outcome. Group I (severe-pre group): subjects with severe PPH who died prior to surgery (n = 5); Group II (mild-pre group): subjects with mild PPH controlled by medications (n = 8); Group IIa (severe-post group): subjects who subsequently developed severe PPH postoperatively and died (n = 3); and Group IIb (mild-post group): subjects who continued to have mild PPH controlled by medications. We also examined nitrofen-induced hypoplastic lungs from five rat fetuses with CDH and five control lung specimens for MCP-1 using immunohistochemistry. Mean serum MCP-1 in Group I was (1038.0 +/- 95.8 pg/ml), which was significantly higher than Group II (444.9 +/- 39.7 pg/ml) (P < 0.0001) and controls (147.3 +/- 11.3 pg/ml) (P < 0.0001). Postoperatively, Group IIa was significantly higher than Group IIb from 24 to 120 h postoperatively (P < 0.001). In Group IIb serum MCP-1 did not rise at all between 24 and 120 h postoperatively. Hypoplastic fetal rat CDH lungs had strong expression of MCP-1 compared with control lungs. Up-regulated expression and high circulating levels of MCP-1 in CDH patients with PPH suggest that MCP-1 may play a role in the development of PPH in CDH.

Spatial and Temporal Expression of Glucocorticoid, Retinoid, and Thyroid Hormone Receptors Is Not Altered in Lungs of Congenital Diaphragmatic Hernia

The degree of associated pulmonary hypoplasia and persistent pulmonary hypertension are major determination factors for survival in congenital diaphragmatic hernia (CDH) patients. Glucocorticoids, thyroid hormone, and vitamin A have been shown to be involved in human lung development. To determine their therapeutic potential in hypoplastic lungs of CDH patients, the temporal and spatial expression of glucocorticoid receptor, thyroid hormone receptors, retinoic acid receptors, and retinoid X receptors were evaluated in lungs of CDH patients, hypoplastic lungs from other causes, and normal lungs. As a series of supportive experiments, the expressions of these receptors were analyzed in lungs of nitrofen-induced CDH rats. Immunohistochemistry (human and rat) and in situ hybridization (rat) demonstrated no overt difference between CDH, hypoplastic, and control lungs, either in the localization nor the timing of the first expression of all analyzed receptors. The mRNA expression of each receptor was detected in all human CDH lungs by quantitative PCR. Our results suggest that, as far as receptors are concerned, hypoplastic lungs of fetuses and newborns with CDH are potentially as responsive to glucocorticoids, thyroid hormone, and retinoic acid as the lungs of normal children.

22 Decreased Neurotrophin Expression in Congenital Diaphragmatic Hernia Human Lung Tissue.

Top of pageAbstract Background: Neurotrophins [nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3)] are growth factors that function as mediators for the development, survival and differentiation of neurons and other types of cells. During normal tissue morphogenesis, neurogenesis and myogenesis proceed as tightly linked processes. In the condition, congenital diaphragmatic hernia (CDH), there is failure of the diaphragm muscle to develop with consequent pulmonary hypoplasia and pulmonary hypertension. The probability that impaired neurogenesis, or coordination of neuro and myogenesis, underlies the disrupted development of the diaphragm muscle in CDH, needs to be explored. Objectives: To determine the expression of neurotrophic factors (NGF, NT-3 and BDNF) in neonatal lung disease; specifically congenital diaphragmatic hernia (CDH), persistent pulmonary hypertension (PPHN) and chronic lung disease (CLD) vs. normal lung tissue. Methods: Immunohistochemical studies for neurotrophin proteins (specific antibody staining using polyclonal rabbit anti-human NGF, BDNF and NT-3) were applied to human neonatal lung tissue samples. The samples included a control group of 18 samples ranging from 23wk EGA to term, a CDH group of 15 samples, a PPHN group of 6 samples and a CLD group of 12 samples. The tissue samples were studied and 4 representative slide fields of aveoli/saccules and 4 of bronchioles were recorded from each sample. These slide fields were then graded (from 0-3) by several blinded observers for intensity of staining. Results: BDNF, NGF and NT-3 immunostaining intensity scores were significantly less in the CDH lung tissue samples (n 15) compared to normal neonatal lung tissue (n 18) (p<0.001). Similarly, PPHN lung tissue (n 6) scored less than normal lung tissue, although not statistically significant; likely due to few samples studied. Chronic lung disease tissue (n 12) did not appear to differ in their neurotrophic staining intensity compared to normal neonatal lung tissue. Conclusion: Neurotrophin expression is decreased in CDH lungs. The decreased expression of neurotrophins in CDH lung tissue suggests they contribute to the abnormality in this condition. Further studies are needed to explore the role of deficient neurotrophin expression in the development of CDH.

Lung Morphology After Late Fetal Tracheal Ligation in Rats

Pulmonary hypoplasia and persistent pulmonary hypertension are the main causes of mortality and morbidity in congenital diaphragmatic hernia (CDH). Prenatal tracheal occlusion accelerates lung growth, but the mechanism remains unknown. In order to be able to establish the accuracy of our experimental model for further molecular biological examinations, we evaluated the histologic structure of 1. fetal lungs subjected to tracheal occlusion compared to 2. normal fetal lungs, 3. hypoplastic lungs in CDH, and 4. normal neonatal lungs. One group of Sprague-Dawley rat fetuses were subjected to intrauterine tracheal ligation (TL) on gestational day 19 (n = 7). Control fetuses were obtained from the same litters as those subjected to TL (n = 8). Another group of pregnant Sprague-Dawley rats were given 100 mg nitrofen on gestational day 9.5 to create CDH (n = 8). All fetuses were delivered by cesarean section on day 21. Lungs from 1-day-old, healthy, non-operated, newborn Sprague-Dawley rats were also examined (n = 6). Lung weight to body weight ratio was significantly higher in the TL lungs (5.0 +/- 0.36 %), compared to control lungs (2.8 +/- 0.15 %), CDH lungs (1.9 +/- 0.12 %), and normal neonatal lungs (4.2 +/- 0.18 %). Volume density of alveolar air space and radial alveolar count (RAC) in TL lungs (52 +/- 1.4 %) (3.3 +/- 0.25) were significantly higher than in control lungs (34 +/- 3.4 %) (2.2 +/- 0.17) and in CDH lungs (16 +/- 1.7 %) (1.7 +/- 0.07). No significant differences were found between the TL and the normal neonatal group (59 +/- 1.4 %) (3.6 +/- 0.11). Fetal lungs after TL showed evidence of growth stimulation with increased volume density of alveolar air space and increased RAC, comparable to findings in normal neonatal lungs.

CFTR gene therapy, a method to rescue lung hypoplasia in congenital diaphragmatic hernia?

despite progress in neonatal care and despite changing concepts in treatment in the recent years, the mortality rate of infants with congenital diaphragmatic hernia (CDH) remains high ([20][1]). Pulmonary hypoplasia and vascular alterations associated with CDH have tremendous postnatal functional

The distribution of matrix metalloproteinases and tissue inhibitors of metalloproteinases in the lungs of congenital diaphragmatic hernia patients and age‐matched controls

In congenital diaphragmatic hernia (CDH), the pathogenesis of abnormal pulmonary morphology is still incompletely understood. Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) are known to play an important role in the turnover of the extracellular matrix (ECM) during development and in remodelling of tissue. The aim of this study was to investigate differences in the expression of MMPs and TIMPs between CDH lungs and controls, against the background of the abnormal pulmonary vasculature in CDH. We studied 12 lungs of term CDH patients who died < 24 h after birth and 11 normal age-matched control lungs, by immunohistochemistry with antibodies against human MMP-1, -2, -9, TIMP-1 and -2. There was a clear increase in the number of MMP-1-reactive capillaries and fibroblasts in CDH lungs compared with controls. In contrast, TIMP-2 reactivity in these structures was decreased in CDH lungs. The arterial endothelium and medial smooth muscle expressed MMP-2, -9 and TIMP-2 in both CDH and control lungs. In small arteries (< 100 microm in diameter), the positive surface area of MMP-2, -9 and TIMP-2 was significantly larger in CDH lungs than in controls. There was no difference in the distribution and expression of TIMP-1 between CDH lungs and normal controls. The differences in staining pattern of MMPs and TIMPs between normal and CDH lungs suggest that these enzymes might play a role in the abnormal remodelling of the interstitium and the pulmonary arteries in CDH lungs. This could contribute to our understanding of the abnormal lung morphology and the occurrence of pulmonary hypertension, which forms one of the major obstacles to the successful treatment of these patients.

Congenital diaphragmatic hernia prevents absorption of distal air space fluid in late-gestation rat fetuses

We hypothesized that congenital diaphragmatic hernia (CDH) may decrease distal air space fluid absorption due to immaturity of alveolar epithelial cells from a loss of the normal epithelial Na+ transport, as assessed by amiloride and epithelial Na+ channel (ENaC) and Na-K-ATPase expression, as well as failure to respond to endogenous epinephrine as assessed by propranolol. Timed-pregnant dams were gavage fed 100 mg of nitrofen at 9.5-day gestation to induce CDH in the fetuses, and distal air space fluid absorption experiments were carried out on 22-day gestation (term) fetuses. Controls were nitrofen-exposed fetuses without CDH. Absorption of distal air space fluid was measured from the increase in 131I-albumin concentration in an isosmolar, physiological solution instilled into the developing lungs. In controls, distal air space fluid absorption was rapid and mediated by beta-adrenoceptors as demonstrated by reversal to fluid secretion after propranolol. Normal lung fluid absorption was also partially inhibited by amiloride. In contrast, CDH fetuses continued to show lung fluid secretion, and this secretion was not affected by either propranolol or amiloride. CDH lungs showed a 67% reduction in alpha-ENaC and beta-ENaC expression, but no change in alpha1-Na-K-ATPase expression. These studies demonstrate: 1) CDH delays lung maturation with impaired distal air space fluid absorption secondary to inadequate Na+ uptake by the distal lung epithelium that results in fluid-filled lungs at birth with reduced capacity to establish postnatal breathing, and 2) the main stimulus to lung fluid absorption in near-term control fetuses, elevated endogenous epinephrine levels, is not functional in CDH fetuses.

Fetal Lung and Diaphragm Development in Congenital Diaphragmatic Hernia

Congenital Diaphragmatic Hernia (CDH) is a congenital disorder with an incidence of 1 in 2500 live births. Respiratory distress of newborns with CDH is the result of pulmonary hypoplasia and pulmonary hypertension. Hypoplastic lungs are characterized by a decreased number of airways with smaller airspaces, whereas the combination of a decreased number of vascular branches and an increased adventitia and medial thickness of the pulmonary arterial walls result in pulmonary hypertension. The appearance of the CDH lungs suggests that its complete formation is stalled during development. Understanding the basic mechanisms of lung development is mandatory to unravel the origin of CDH. Although the histological abnormalities in CDH lungs have been well described, less is known about the underlying molecular mechanisms. In this review we will discuss the current molecular and genetic background of lung formation, as well as a reflection of this knowledge towards CDH.

Expression of vasoactive mediators during mechanical ventilation in nitrofen-induced diaphragmatic hernia in rats

The high mortality in patients with congenital diaphragmatic hernia (CDH) has been attributed to pulmonary hypoplasia and persistent pulmonary hypertension (PPH). Endothelin-1 (ET-1), nitric oxide (NO), and calcitonin gene-related peptide (CGRP) have been reported to be important vasoactive mediators in the perinatal pulmonary circulation. The exact mechanism by which these vasoactive mediators interact to regulate the perinatal pulmonary vascular tone in CDH with PPH is not fully understood. We hypothesized that the altered pulmonary vascular reactivity in CDH is due to imbalance in vasoactive mediators. This study was designed to investigate mRNA expression of ET-1, eNOS, and CGRP in CDH lung in the perinatal period. A CDH model was induced in pregnant rats following administration of nitrofen. In control animals, the same dose of olive oil was given without nitrofen. Cesarean section was performed on day 21 of gestation. The newborn rats were intubated and ventilated, and ventilation was continued for 1-6 h. Left lungs were collected from both groups at 0, 1, and 6 h after ventilation (n=8 in each group). Reverse transcriptase-polymerase chain reaction on lung tissue was performed to evaluate the relative level of ET-1, eNOS, and CGRP mRNA expression. The results showed a significant increase in ET-1 mRNA in CDH lung at 1 and 6 h after ventilation compared with controls. In CDH lung, eNOS mRNA and CGRP mRNA levels were significantly increased at 1 h but were similar to control values at 6 h after ventilation. The increased expression of vasoconstrictor ET-1 mRNA and vasodilators eNOS mRNA and CGRP mRNA in the CDH lung at 1 h after ventilation suggests that pulmonary vascular tone is rapidly changing after birth. An imbalance in the production of vasoconstrictors and vasodilators by the CDH lung may contribute to high pulmonary vascular resistance.

Expression of Angiogenesis-Related Factors in Lungs of Patients with Congenital Diaphragmatic Hernia and Pulmonary Hypoplasia of Other Causes

Congenital diaphragmatic hernia (CDH) is a congenital disorder, complicated by pulmonary hypoplasia (PH) and pulmonary hypertension. Hypoplastic lungs have fewer and smaller airspaces than normal, with thicker interalveolar septa; the adventitia and media of pulmonary arteries are thickened, and the total size of the pulmonary vascular bed is decreased compared to normal. Although histological abnormalities in PH have been described, less is known about the underlying molecular mechanisms. Therefore, we have investigated a series of proteins, known to be involved in angiogenesis, including von Hippel-Lindau protein (pVHL), hypoxia-inducible factor-1a (HIF-1a), vascular endothelial growth factor (VEGF), fetal liver kinase 1 (Flk-1), and endothelial and inducible nitric oxide synthase (eNOS, iNOS) by immunohistochemistry on paraffin-embedded lung tissue of CDH patients ( n = 13), patients with lung hypoplasia due to other causes ( n = 20), and normal controls ( n = 33). pVHL was expressed more frequently in the arterial smooth muscle cells of CDH lungs compared with both other groups. Furthermore, HIF-1a was expressed less frequently in the endothelium of arteries, veins, and capillaries of CDH lungs as compared with both other groups. No differences were observed in the expression patterns of VEGF, Flk-1, eNOS, and iNOS between the different groups. Our data suggest a role for pVHL and HIF-1a in normal and abnormal pulmonary angiogenesis. The differential expression of these proteins may provide a molecular basis for the histological differences observed in the lung vessels of patients with CDH.

P09.02: Accuracy of magnetic resonance imaging for measuring fetal lamb lungs and organs

Congenital diaphragmatic hernia (CDH) is associated with a high mortality rate (over 50%). Prediction is more or less correlated to lung volume at 26 weeks, currently based on lung-to-head ratio (LHR) (Metkus, J Ped Surg 1996; 31: 148–152). Alternatively, lung volume measurement is performed by magnetic resonance imaging (MRI). (Mahieu-Caputo BJOG 2001; 108: 863–868). We conducted an experimental study to determine agreement and precision of MRI fetal organs volume determination versus volume determination at macroscopy (necropsy). In a total of 9 sheeps under general anaesthesia, 14 fetal lambs underwent MRI. Lungs where measured in T2 weighted images in several planes (axial, coronal and sagittal), livers and kidneys where measured in one plane. Lungs where divided in hypoplastic lungs (DH was created at a mean gestational age (GA) of 73 days, n = 10), and normal lungs (n = 18). Necropsy was done less then 24 hours after MRI (at a mean GA of 120 days). At necropsy, organ volumes where determined by the volume displacement method. Ranges volume at necropsy, means ± SD, bias (mean of the difference necropsy volume-MRI volume) and precision (SD of the difference), are represented. Analysis is made according to Bland and Altman (The Lancet 1986; i: 307–310). There was a better agreement in small volumes (Kidney, bias = 2.01) comparing to bigger volumes (Liver, bias = − 35.49) and when lung volumes where measured in the axial plane (bias = − 15.58) comparing to coronal (bias = − 20.22) or sagittal planes (bias = − 26.62). Normal lung volumes in axial planes showed a better agreement comparing to CDH lungs, but this was not the case in the coronal or the sagittal planes. Bland and Altman analyses showed no clinically important systematic errors in the MRI measurements. MRI performed in the axial plane is reliable in predicting CDH as well as normal lung volumes in fetal lamb.

Pulmonary elastin expression is decreased in the nitrofen-induced rat model of congenital diaphragmatic hernia

Background/purpose Babies with congenital diaphragmatic hernia (CDH) suffer from pulmonary hypoplasia and pulmonary hypertension. Elastin is a critical component of the extracellular matrix (EM) involved in pulmonary development and mechanics. Because CDH lungs are developmentally immature and have reduced compliance, the authors hypothesized that elastin deposition would be reduced and disorganized in the nitrofen rat model of CDH. Methods Time-dated pregnant Sprague-Dawley rats were fed 100 mg of nitrofen on day 9 of gestation. Control rats did not receive nitrofen. The authors analyzed three groups of rats (n = 10 for each group): (1) control (C), (2) nitrofen no CDH (NC), and (3) nitrofen-induced CDH (CDH). On day 21.5 (term, 22 days), the fetuses were delivered by cesarean section, and the fetal lung was harvested. Elastin content, mRNA expression, and distribution were assessed with desmosine analysis, Northern blot analysis, and Hart’s staining, respectively. Results The mean desmosine content in picomole desmosine per milligram protein (pmD/mgP) ± SD was 30 ± 6.8 (C, n = 10), 25.1 ± 10.1 (NC, n = 10), and 21.6 ± 6.4 (CDH, n = 10). The comparison between CDH and controls was statistically significant ( P = .026). Northern blot analysis showed decreased mRNA expression in the CDH sample. Hart’s staining showed developmentally immature CDH lungs with less elastin deposition and disorganized distribution. Conclusions Pulmonary elastin expression is decreased and disorganized in the nitrofen-induced rat model of CDH. The decreased expression appears to be regulated at the level of transcription. Altered mechanical forces may be responsible for mediating the expression of elastin in CDH.

Decreased expression of voltage-gated K+ channels in pulmonary artery smooth muscles cells in nitrofen-induced congenital diaphragmatic hernia in rats.

The newborn with congenital diaphragmatic hernia (CDH) is at high risk of developing persistent pulmonary hypertension (PPH). Recently, smooth muscle K(+) channels have been implicated in hypoxic pulmonary vasoconstriction in adults. We hypothesized that the hyperreactivity of the newborn pulmonary vasculature in CDH might reflect a relatively low level of smooth muscle K(+) channel activity because of hypoxemia, which could give rise to excessive smooth muscle cell depolarisation and lead to failure of the pulmonary vasculature to adapt to extrauterine life. We therefore investigated K(+) channel subunits in pulmonary artery smooth muscle cells (PASMC) in the nitrofen-induced CDH lung in rats. The CDH model was induced in pregnant rats after administration of 100 mg nitrofen on day 9.5 of gestation (term = 22 days). Dexamethasone (0.25 mg/kg) was given on days 18.5 and 19.5 of gestation. Cesarean section was performed on day 21. Fetuses were divided into three groups: group I, normal control; group II, nitrofen-induced CDH; and group III, nitrofen-induced CDH with antenatal dexamethasone treatment. Reverse transcription polymerase chain reaction (RT-PCR) was performed to evaluate the relative amount of the potassium channels Kv1.2, Kv2.1, and KvCa mRNA. Indirect immunohistochemistry was performed using a laser scanning confocal microscope with anti-Kv1.2, -Kv2.1, and -KvCa antibodies. In the CDH lung, Kv1.2, Kv2.1, and KvCa immunoreactivity was markedly decreased in PASMC compared with controls. Relative mRNA levels of potassium channel anti-Kv1.2, -Kv2.1, and -KvCa were significantly decreased in the CDH lung compared with controls (p<0.05). Dexamethasone treatment increased Kv1.2, Kv2.1, and KvCa immunoreactivity and mRNA levels in the CDH lung. Changes in voltage-gate K(+) channel subunits expression in the CDH lung suggest that potassium channels may play an important role in the development of pulmonary hypertension. Antenatal dexamethasone may modulate pulmonary vascular tone in the CDH hypoplastic lung by selectively upregulating local expression of Kv1.2, Kv2.1, and KvCa.

Upregulated expression of EGF and TGF-? in the proximal respiratory epithelium in the human hypoplastic lung in congenital diaphragmatic hernia

Newborn infants with congenital diaphragmatic hernia (CDH) still have a high mortality rate. Epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) are peptide growth factors involved in the fetal lung growth and development. The EGF and TGF-alpha have been reported to promote pulmonary branching activity and alveolar type-II pneumocyte proliferation. Epidermal growth factor and TGF-alpha immunoreactivity and mRNA expression in the bronchial and bronchiolar epithelium is maximal during early fetal life and barely detectable in the proximal airways of neonatal lung. The purpose of this study was to determine protein and gene expression of EGF and TGF-alpha in CDH lung in order to elucidate the potential role of these growth factors in the pathogenesis of pulmonary hypoplasia in CDH. Lung tissue specimens were obtained from archival lung tissue from 11 patients with CDH and 5 controls. Indirect immunohistochemistry was performed using ABC method with anti-EGF and anti-TGF-alpha antibodies. In situ hybridization was performed using EGF and TGF-alpha specific digoxigenin-labeled oligonucleotide probes. The most striking difference between hypoplastic CDH lung and control lung was the strong EGF and TGF-alpha mRNA expression and immunoreactivity in the bronchial and bronchiolar epithelium in CDH lung. The upregulated protein and gene expression of EGF and TGF-alpha in the proximal airways in the CDH hypoplastic lung suggests persistence of fetal stage of pulmonary airway development in CDH.

Effect of epidermal growth factor on pulmonary hypoplasia in experimental diaphragmatic hernia

Background/purpose Currently, tracheal occlusion (TO) is a potent stimulus for fetal lung growth but also a rather invasive and high-risk procedure. The aim of this study was to investigate a new and much less invasive therapeutic strategy, namely the maternal intraperitoneal administration of epidermal growth factor (EGF) and its effect on pulmonary hypoplasia in the nitrofen-induced congenital diaphragmatic hernia (CDH) rat model, especially its effect on type II pneumocytes. Methods CDH was induced by maternal administration of a single oral dose (100 mg) of nitrofen on day 8.5 of pregnancy. Four groups of pregnant rats were designed on day 18.5: normal control (n = 4), CDH (n = 4), CDH plus Dex (n = 4), CDH plus EGF (n = 8). All fetuses were delivered by cesarean section on day 21. Accordingly, there were 4 groups of fetuses: normal controls (n = 33), nitrofen-induced CDH (n = 19), CDH plus Dex treatment (n = 15), and CDH plus EGF treatment (n = 24). Lung tissue weight (LW) and body weight (BW) of each fetus were recorded, lung histologic and morphometric evaluations were performed, and image analysis was combined after lung processing. Transmission electron microscopy was used for ultrastructural observation, especially type II pneumocytes. Results CDH was observed in 58 of the 94 rat fetuses (61.7%). Lw/Bw of CDH group was significantly lower than those of Dex and EGF ( P < .05). The lungs of CDH fetuses showed marked hypoplasia, in contrast to improved mesenchymal differentiation in that of Dex and EGF fetuses. Statistical differences of these morphologic parameters (RAC, MTBD, interstitial%, and alveoli%) were found ( P < .05). As to ultrastructural features, type II cells of CDH lungs had few if any lamellar bodies and cytoplasmic organelles, and showed evidence of abundant glycogen granules. The sparse type II cells also showed cytoplasmic degenerative changes. By contrast, type II cells of EGF lungs showed numerous mitochondria, abundant lamellar bodies (surfactant) and deficiency of glycogen granules, and displayed prominent microvillous projections and pitlike depressions. The density of type II pneumocyte were 65 ± 4.5, 31 ± 3.1, and 8 ± 1.5 for EGF, Dex, and CDH, respectively (EGF v Dex, P < .05; EGF v CDH, P < 0.01). Conclusions Compared with TO, prenatal EGF administration as a much less-invasive therapeutic strategy had shown marked improvement in pulmonary hypoplasia and promotion of type II pneumocyte differentiation in the nitrofen-induced CDH rat model. Thus, EGF could improve the prognosis of CDH by means of promoting pulmonary hypoplasia and improving the surfactant deficiency, which suggested a potential role in the clinical treatment of CDH.

Pulmonary surfactant protein A, B, and C mRNA and protein expression in the nitrofen-induced congenital diaphragmatic hernia rat model.

Neonates with congenital diaphragmatic hernia (CDH) suffer from a diaphragmatic defect, lung hypoplasia, and pulmonary hypertension, with poor lung function forming the major clinical challenge. Despite prenatal diagnosis and advanced postnatal treatment strategies, the mortality rate of CDH is still high. CDH has been subject of extensive research over the past decades, but its etiology remains unknown. A major problem with CDH is the failure to predict the individual response to treatment modalities like high-frequency ventilation, inhaled nitric oxide, and extracorporeal membrane oxygenation. In this study, we tested the possibility that CDH lungs are surfactant protein deficient, which could explain the respiratory failure and difficulties in treating CDH infants. We investigated this hypothesis in the nitrofen-induced CDH rat model and assessed the cellular concentrations of surfactant protein (SP)-A, -B, and -C mRNA with a quantitative radioactive in situ hybridization technique. No differences were observed between control and CDH lungs for SP mRNA expression patterns. The cellular concentration (mean OD) of SP-A and SP-B mRNA was similar at all stages whereas the mean OD of SP-C mRNA and the volume fraction of cells (% Area) expressing SP mRNA was higher in CDH lungs at term. Immunohistochemical analysis revealed no differences between control and CDH lungs for SP protein expression. No differences in the mean OD or % Area for the SP mRNAs were found between the ipsi- and contralateral side of CDH lungs. We conclude that there is no primary deficiency of surfactant proteins in the nitrofen-induced CDH rat model.

Gene expression of fibroblast growth factors 10 and 7 is downregulated in the lung of nitrofen-induced diaphragmatic hernia in rats

Background/purpose Newborns with congenital diaphragmatic hernia (CDH) still have a high mortality rate, which has been attributed to pulmonary hypoplasia and pulmonary hypertension. Fibroblast growth factors (FGFs) are essential components of the gene network that regulates lung development. Recent studies suggest that the new member of FGF family, FGF-10, plays a fundamental role in branching morphogenesis and is essential for lung formation. FGF-10-deficient mice exhibit complete absence of lungs. FGF-7 promotes epithelial proliferation and expansion leading to the formation of cystlike structures. The aim of this study was to determine the gene level expression of FGF-10 and FGF-7 in the lung of nitrofen-induced CDH. Methods Congenital diaphragmatic hernia (CDH) was induced in pregnant rats after administration of 100 mg of nitrofen on day 9.5 of gestation (term, 22 days). In control animals, the same dose of olive oil was given without nitrofen. Cesarean section was performed on day 21 of gestation. The fetuses were divided into 3 groups: normal controls (n = 16), nitrofen induced without CDH (n = 16), and nitrofen-induced CDH (n = 16). Total RNA and DNA were extracted from the lung in each group and measured. mRNA was extracted from total RNA. Reverse transcription polymerase chain reaction (RT-PCR) was performed to evaluate mRNA expressions of FGF-10 and FGF-7. Levels of mRNA were expressed as a ratio of the band density divided by that of β-actin, a house-keeping gene. Results FGF-10 mRNA expression was decreased significantly in CDH lung (2.914 ± 0.320) compared with controls (4.062 ± 0.307; P < .05) and nitrofen induced without CDH lung (3.923 ± 0.250; P < .01). FGF-7 mRNA expression was decreased significantly in CDH lung (0.777 ± 0.097) compared with controls (1.028 ± 0.093; P < .01). Conclusions Decreased gene expression of FGF-10 and FGF-7 in the hypoplastic lung suggests that pulmonary hypoplasia in nitrofen-induced CDH rat may be caused by reduced synthesis of FGF-10 and FGF-7 during lung morphogenesis.

EXPRESSION AND ACTIVITY OF MATRIX METALLO PROTEINASES 2 AND 9 AND THEIR INHIBITORS IN RAT LUNGS DURING THE PERINATAL PERIOD AND IN DIAPHRAGMATIC HERNIA

During lung development, the extracellular matrix undergoes dynamic remodeling. Matrix metalloproteinases (MMPs), and tissue inhibitors of matrix metalloproteinases (TIMPs), are important enzymes that participate in regulating tissue remodeling. There is an abnormal balance of the synthesis and degradation of collagen and elastin in perinatal lung associated with congenital diaphragmatic hernia (CDH). This study was designed to (1) determine the expression and gelatinolytic activity patterns of MMPs 2 and 9 and TIMPs 1 and 2 in rat lungs during the perinatal period, and (2) to test the hypothesis that they are abnormal in nitrofen-induced CDH. Measurements were made using reverse transcriptase-polymerase chain reaction (RT-PCR), Western blotting, and zymography. The mRNA expression and activity of MMP 2 did not change significantly from embryonic day 16 to postnatal day 14. The most striking feature found was the rapid increase in the expression of MMP 9 soon after birth. Measurements were repeated on lung tissue isolated from embryonic rats with nitrofen-induced CDH. The expression and activity of MMPs and TIMPs were similar to control values and thus we conclude that these proteins appear not to be responsible for the altered extracellular matrix and morphological abnormalities noted in CDH lungs at birth.

Matrix metalloproteinase-9 and tissue inhibitor of metalloproteinase-1: expression in the lung of fetal rats with nitrofen-induced diaphragmatic hernia.

The surrounding extracellular matrix of airway wall tissues changes in response to mechanical stresses and hypoxia. The presence of matrix metalloproteinase-9 (MMP-9) and its inhibitor, tissue inhibitor of metalloproteinase-1 (TIMP-1), is correlated with collagen degradation and tissue repair in lung disorders. The aim of this study was to evaluate the expression of MMP-9 and TIMP-1 in the lung of fetal rats with nitrofen-induced congenital diaphragmatic hernia (CDH). Administering 100 mg of nitrofen dissolved in 1 ml olive oil to pregnant Wistar rats on day 9 of gestation induced left-sided CDH in fetal rats. In control animals, the same dose of olive oil was given without nitrofen. Cesarean section was performed on day 21 of gestation. The fetuses were divided into two groups: normal controls (n = 10) and nitrofen-induced left-sided CDH (n = 10). Immunoreactivity of the staining for MMP-9 and TIMP-1 in the lung tissues was semiquantitatively analyzed using the staining scores. The relative amount of MMP-9 or TIMP-1 divided by the amount of beta-actin for each lung sample was measured by using the real-time reverse-transcriptase polymerase chain reaction. The immunoreactivity of MMP-9 was significantly increased in the CDH group (n = 5) compared with the control group (n = 5) (p = 0.031). On the other hand, the immunoreactivity of TIMP-1 in the two groups was not significantly different (n = 0.134). The relative amount of MMP-9 (or TIMP-1) in the CDH group (n = 5) does not differ significantly from that in the control group (n = 5) (p = 0.059, 0.596, respectively), but the relative amount of MMP-9 is higher in the CDH group, although it is not significantly higher. On the other hand, the ratios of MMP-9 to TIMP-1 were significantly higher in the CDH group (p = 0.028). In conclusion, fetal rats with nitrofen-induced CDH, a model of respiratory disorders, manifested the excess of MMP-9 activity due to the absence of TIMP-1 that would suggest a trend toward disruption of the extracellular matrix in the CDH lung tissues.