Continuous intrapulmonary distension with perfluorocarbon accelerates lung growth in infants with congenital diaphragmatic hernia: initial experience

Perfluorocarbons in Research and Clinical Practice: A Narrative Review

Perfluorocarbons (PFCs) are organic liquids derived from hydrocarbons in which some of the hydrogen atoms have been replaced by fluorine atoms. They are chemically and biologically inert substances with a good safety profile. They are stable at room temperature, easy to store, and immiscible in water. Perfluorocarbons have been studied in biomedical research since 1960 for their unique properties as oxygen carriers. In particular, PFCs have been used for liquid ventilation in unusual environments such as deep-sea diving and simulations of zero gravity, and more recently for drug delivery and diagnostic imaging. Additionally, when delivered as emulsions, PFCs have been used as red blood cell substitutes. This narrative review will discuss the multifaceted utilization of PFCs in therapeutics, diagnostics, and research. We will specifically emphasize the potential role of PFCs as red blood cell substitutes, as airway mechanotransducers during artificial placenta procedures, as a means to improve donor organ perfusion during the ex vivo assessment, and as an adjunct in cancer therapies because of their ability to reduce local tissue hypoxia.

Safety and efficacy of perflubron-induced lung growth in neonates with congenital diaphragmatic hernia: Results of a prospective randomized trial

BACKGROUND

Mechanical transduction has been shown to promote fetal lung growth. We examined the safety and efficacy of perflubron-induced lung growth (PILG) in neonates with congenital diaphragmatic hernia (CDH) requiring extracorporeal membrane oxygenation (ECMO).

METHODS

Infants with left-sided CDH requiring ECMO were eligible. Exclusion criteria included active air leak, intracranial hemorrhage, major congenital anomalies, and oxygenation index >25 for 24hours. Perflubron was instilled endotracheally and continuous positive airway pressure was applied without ventilation. Survival to discharge was the primary outcome. Daily chest radiographs were used to quantify lung size (the secondary outcome). Midway through the study our institutional practice shifted toward earlier repair of CDH.

RESULTS

Eight infants were randomized to each arm. In the conventional-ventilation arm, six survived to discharge (75%). In the perflubron arm, four survived (50%); the others succumbed to suprasystemic pulmonary hypertension. No adverse events related to perflubron occurred. Within the perflubron group, 4/8 patients had "late repair" (15-19days of life [DOL]) and 4 had "early repair" (2-3 DOL). "Early repair" patients had similar total lung growth, but accelerated growth and shorter ECMO runs.

CONCLUSION

PILG is safe in CDH and doubles the total lung size on average (accelerated with early repair). Despite amelioration of pulmonary hypoplasia with PILG, pulmonary hypertension persists.

Intrapulmonary instillation of perflurooctylbromide improves lung growth, alveolarization, and lung mechanics in a fetal rabbit model of diaphragmatic hernia

OBJECTIVES

Fetal tracheal occlusion of hypoplastic rabbit lungs results in lung growth and alveolarization although the surfactant protein messenger RNA expression is decreased and the transforming growth factor-β pathway induced. The prenatal filling of healthy rabbit lungs with perfluorooctylbromide augments lung growth without suppression of surfactant protein synthesis. We hypothesizes that Intratracheal perfluorooctylbromide instillation improves lung growth, mechanics, and extracellular matrix synthesis in a fetal rabbit model of lung hypoplasia induced by diaphragmatic hernia.

SETTING AND INTERVENTIONS

On day 23 of gestation, DH was induced by fetal surgery in healthy rabbit fetuses. Five days later, 0.8ml of perfluorooctylbromide (diaphragmatic hernia-perfluorooctylbromide) or saline (diaphragmatic hernia-saline) was randomly administered into the lungs of previously operated fetuses. After term delivery (day 31), lung mechanics, lung to body weight ratio, messenger RNA levels of target genes, assessment of lung histology, and morphological distribution of elastin and collagen were determined. Nonoperated fetuses served as controls.

MEASUREMENTS AND MAIN RESULTS

Fetal instillation of perfluorooctylbromide in hypoplastic lungs resulted in an improvement of lung-to-body weight ratio (0.016 vs 0.013 g/g; p = 0.05), total lung capacity (23.4 vs 15.4 μL/g; p = 0.03), and compliance (2.4 vs 1.2 mL/cm H2O; p = 0.007) as compared to diaphragmatic hernia-saline. In accordance with the results from lung function analysis, elastin staining of pulmonary tissue revealed a physiological distribution of elastic fiber to the tips of the secondary crests in the diaphragmatic hernia-perfluorooctylbromide group. Likewise, messenger RNA expression was induced in genes associated with extracellular matrix remodeling (matrix metalloproteinase-2, tissue inhibitor of metalloproteinase-1, and tissue inhibitor of metalloproteinase-2). Surfactant protein expression was similar in the diaphragmatic hernia-perfluorooctylbromide and diaphragmatic hernia-saline groups. Distal airway size, mean linear intercept, as well as airspace and tissue fractions were similar in diaphragmatic hernia-perfluorooctylbromide, diaphragmatic hernia-saline, and control groups.

CONCLUSIONS

Fetal perfluorooctylbromide treatment improves lung growth, lung mechanics, and extracellular matrix remodeling in hypoplastic lungs, most probably due to transient pulmonary stretch, preserved fetal breathing movements, and its physical characteristics. Perfluorooctylbromide instillation is a promising approach for prenatal therapy of lung hypoplasia.

Skeletal muscle tissue engineering: which cell to use?

Tissue-engineered skeletal muscle is urgently required to treat a wide array of devastating congenital and acquired conditions. Selection of the appropriate cell type requires consideration of several factors which amongst others include, accessibility of the cell source, in vitro myogenicity at high efficiency with the ability to maintain differentiation over extended periods of time, susceptibility to genetic manipulation, a suitable mode of delivery and finally in vivo differentiation giving rise to restoration of structural morphology and function. Potential stem-progenitor cell sources include and are not limited to satellite cells, myoblasts, mesoangioblasts, pericytes, muscle side-population cells, CD133(+) cells, in addition to embryonic stem cells, mesenchymal stem cells, amniotic fluid stem cells and induced pluripotent stem (iPS) cells. The relative merits and inherent limitations of these cell types within the field of tissue-engineering are discussed in the light of current research. Recent advances in the field of iPS cells should bear the fruits for some exciting developments within the field in the forthcoming years.

What can imaging tell us about physiology? Lung growth and regional mechanical strain

The interplay of mechanical forces transduces diverse physico-biochemical processes to influence lung morphogenesis, growth, maturation, remodeling and repair. Because tissue stress is difficult to measure in vivo, mechano-sensitive responses are commonly inferred from global changes in lung volume, shape, or compliance and correlated with structural changes in tissue blocks sampled from postmortem-fixed lungs. Recent advances in noninvasive volumetric imaging technology, nonrigid image registration, and deformation analysis provide valuable tools for the quantitative analysis of in vivo regional anatomy and air and tissue-blood distributions and when combined with transpulmonary pressure measurements, allow characterization of regional mechanical function, e.g., displacement, strain, shear, within and among intact lobes, as well as between the lung and the components of its container-rib cage, diaphragm, and mediastinum-thereby yielding new insights into the inter-related metrics of mechanical stress-strain and growth/remodeling. Here, we review the state-of-the-art imaging applications for mapping asymmetric heterogeneous physical interactions within the thorax and how these interactions permit as well as constrain lung growth, remodeling, and compensation during development and following pneumonectomy to illustrate how advanced imaging could facilitate the understanding of physiology and pathophysiology. Functional imaging promises to facilitate the formulation of realistic computational models of lung growth that integrate mechano-sensitive events over multiple spatial and temporal scales to accurately describe in vivo physiology and pathophysiology. Improved computational models in turn could enhance our ability to predict regional as well as global responses to experimental and therapeutic interventions.

Absorbable versus nonabsorbable mesh repair of congenital diaphragmatic hernias in a growing animal model

INTRODUCTION

The repair of large congenital diaphragmatic hernia frequently results in patch disruption and recurrence as patients grow in size. Absorbable meshes allow for ingrowth of endogenous tissue as they are degraded, providing a more natural and durable repair. The aim of this study was to compare the characteristics of the new diaphragmatic tissue between an absorbable biologic mesh and a nonabsorbable mesh for repairing diaphragmatic hernia in a growing animal model.

METHODS

The left hemi-diaphragm of twenty 2-month-old Yucatan pigs was nearly completely resected. Small intestinal submucosa (SIS; Cook Biotech, Lafayette, IN) and expanded polytetrafluoroethylene (ePTFE; W.L. Gore & Associates, Flagstaff, AZ) were randomly assigned to cover the defect in 10 animals each, and were survived for 6 months. During necropsy, newly formed diaphragmatic tissue was evaluated and compared between the two groups.

RESULTS

At necropsy, the animals had tripled their weight. Patch disruption and herniation occurred in 3 animals in the ePTFE group and none in the SIS group. The SIS mesh had better integration to the chest wall (2.8 ± 0.2 versus 1.3 ± 0.3), more muscle growth within the newly formed diaphragmatic tissue (1.9 ± 0.2 versus 0.4 ± 0.2), and less fibrotic tissue (2.1 ± 0.5 versus 3.4 ± 0.4) than ePTFE. There was no difference between SIS and ePTFE in terms of adhesion scores to the lung (2 ± 0.4 versus 2.4 ± 0.4) and liver (1.8 ± 0.3 versus 2.2 ± 0.5).

CONCLUSION

SIS allows for tissue ingrowth from surrounding tissue as it degrades, providing a more durable repair with 30% less incidence of herniation in a porcine model. As the diaphragm grows, SIS resulted in a more natural repair of the defect with more tissue growth, better tissue integration, and a comparable adhesion formation to ePTFE.

A comparative analysis of cartilage engineered from different perinatal mesenchymal progenitor cells

We sought to compare engineered cartilaginous constructs derived from different perinatal mesenchymal progenitor cell (MPC) sources. Ovine MPCs isolated from amniotic fluid (AF, n = 8), neonatal bone marrow (BM, n = 6), and preterm umbilical cord blood (CB, n = 12) were expanded and comparably seeded onto synthetic scaffolds. Constructs were maintained in chondrogenic media containing transforming growth factor-beta. After 12-15 weeks, specimens were compared with native fetal hyaline and elastic cartilage by gross inspection, histology, immunohistochemistry, and quantitative extracellular matrix (ECM) assays. MPCs from AF proliferated significantly faster ex vivo when compared to MPCs from the other sources. Chondrogenic differentiation was evident in all groups, as shown by toluidine blue staining and expression of aggrecan, cartilage proteoglycan link protein, and collagen type II. Quantitatively, all engineered specimens had significantly lower levels of glycosaminoglycans than native hyaline cartilage. Elastin levels in AF-based constructs (156.0 +/- 120.4 microg/mg) were comparable to that of native elastic cartilage (235.8 +/- 54.2 microg/mg), both of which were significantly higher than in BM- and CB-based specimens. We conclude that the ECM profile of cartilage engineered from perinatal MPCs is highly dependent on cell source. ECM peculiarities should be considered when designing the optimal cartilaginous bioprosthesis for use in perinatal surgical reconstruction.

Congenital diaphragmatic hernia

The incidence of congenital diaphragmatic hernia (CDH) may be as high as 1 in 2000. Over the past two decades, antenatal diagnosis rates have increased, the pathophysiology of CDH has become better understood, and advances in clinical care, including foetal surgery, have occurred. However, there remains a paucity of randomised controlled trials to provide evidence-based management guidelines. Reports of improved survival rates appear to be confined to a select subset of CDH infants, surviving to surgical repair, while the overall mortality, at over 60%, appears to be unchanged, largely due to the often forgotten 'hidden mortality' of CDH. The significant long-term morbidity in surviving infants has become apparent, and the need for long-term multidisciplinary follow up established. A total of 10% of cases may present later in life, and misdiagnosis on initial chest X-ray may lead to significant morbidity.

Predicting inadequate long-term lung development in children with congenital diaphragmatic hernia: an analysis of longitudinal changes in ventilation and perfusion

PURPOSE

Infants born with congenital diaphragmatic hernia (CDH) demonstrate a wide variability in postnatal catch-up lung growth. The goals of this study were to assess the pulmonary development of children born with CDH using sequential ventilation-perfusion (V/Q) scintigraphy and to identify the perinatal factors that correspond to a progressive V/Q mismatch.

METHODS

The records of 137 patients seen between 1990 and 2005 in a multidisciplinary CDH clinic were reviewed. Changes in the ipsilateral V/Q quotient were compared in 46 patients who had 2 or more studies with the following variables: sex, patch repair, laterality, gestational age, and use of extracorporeal membrane oxygenation. An abnormal V/Q quotient was defined as greater than 1.2 (reference range, 0.8-1.2).

RESULTS

Abnormal V/Q scans were identified in 28 (61%) of the 46 patients at the time of the last V/Q study. Patients who underwent a patch repair had nearly 7 times the risk (P < .001) of developing an ipsilateral V/Q mismatch. The use of extracorporeal membrane oxygenation had a variable effect on the probability of an abnormal V/Q study finding. No other variable was significant.

CONCLUSIONS

Many children with CDH develop significant and progressive V/Q mismatches. Although some perinatal variables appear to be predictive of this phenomenon, they may simply be surrogates for a greater degree of pulmonary hypoplasia present at birth. This subpopulation of CDH survivors is an identifiable group clearly at risk and thus requires long-term follow-up.

Fetal cartilage engineering from amniotic mesenchymal progenitor cells

We determined whether cartilage could be engineered from mesenchymal progenitor cells (MPCs) normally found in amniotic fluid. Mesenchymal amniocytes were isolated from ovine amniotic fluid samples (n = 5) and had their identity confirmed by immunocytochemistry. Cells were expanded and then cultured as micromass pellets (n = 5) in a chondrogenic medium containing transforming growth factor-beta2 (TGF-beta2) and insulin growth factor-1 (IGF-1) for 6-12 weeks. Pellets derived from fetal dermal fibroblasts (n = 4) were cultured under identical conditions. Additionally, expanded mesenchymal amniocytes were seeded onto biodegradable polyglycolic acid scaffolds (n = 5) and maintained in the same chondrogenic medium within a rotating bioreactor for 10-15 weeks. Engineered specimens were analyzed quantitatively and compared with native fetal hyaline cartilage samples (n = 5). Statistical analysis was by the unpaired Student's t-test (p < 0.05). The isolated cells stained positively for vimentin and cytokeratins-8 and -18, but negatively for CD31. Micromass pellets derived from mesenchymal amniocytes exhibited chondrogenic differentiation by both standard and matrix-specific staining. In contrast, these findings could not be replicated in dermal fibroblast-based pellets. The engineered constructs derived from mesenchymal amniocytes similarly displayed histological evidence of chondrogenic differentiation and maintained their original size and three-dimensional architecture. Quantitative assays of the engineered constructs revealed lower concentrations of collagen type II, but similar amounts of glycosaminoglycans, elastin, and DNA, when compared to native fetal hyaline cartilage. We conclude that mesenchymal amniocytes can be used for the engineering of cartilaginous tissue in vitro. Cartilage engineering from the amniotic fluid may become a practical approach for the surgical treatment of select congenital anomalies.

The immediate and long-term outcomes of newborns with congenital diaphragmatic hernia

In spite of the innovations in the management of newborns with congenital diaphragmatic hernia (CDH) presenting with respiratory distress at birth, mortality and ongoing morbidity still remain high. This is a retrospective analysis of newborns with CDH to determine the immediate and long-term outcomes among survivors. Medical records of newborns with CDH and respiratory distress at birth between January 1993 and March 2002 were reviewed retrospectively. There were 45 newborns, 29 males and 16 females. Eleven newborns (24%) died during the period of preoperative stabilization, 9 from pulmonary hypoplasia and 2 with complex anomalies who were not resuscitated. Surgery was performed in 34 newborns (76%). Three died postoperatively from severe pulmonary hypoplasia and pulmonary hypertension. Eleven newborns (24%) had sepsis from coagulative-negative staphylococci. Thirty-one of 43 newborns (72%) with isolated CDH were discharged home. Twenty-seven of 31 survivors (87%) had adverse long-term outcome and 2 late deaths were from pulmonary complications. Twenty-nine of 43 newborns (67%) with isolated CDH survived. The principal determinant of survival was pulmonary hypoplasia. Eighty-seven percent of survivors have associated morbidity including ongoing pulmonary, nutritional and neuro-developmental problems. Nevertheless preoperative stabilization and delayed surgery have been a satisfactory mode of management.

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 β-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 α-ENaC and β-ENaC expression, but no change in α1-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.

Rescue of the Hypoplastic Lung by Prenatal Cyclical Strain

We determined the effects of sustained and cyclical prenatal mechanical strain on the hypoplastic lung of the ovine model of congenital diaphragmatic hernia. Over a period of 4 weeks in late gestation, repeated cyclical tracheal occlusion for 23 hours with 1-hour release stimulated minimal growth, but promoted maturation with the development of a saccular lung. In contrast, a cycle consisting of 47 hours with 1-hour release induced optimal lung growth and morphologic maturation of the hypoplastic lung parenchyma. Sustained occlusion resulted in exaggerated lung growth, exceeding that of unaffected controls, and abnormal alveolar development. The extent of induction of lung growth by mechanical strain was inversely proportional to the number of alveolar type II cells remaining in the lung epithelium. These studies show that, although mechanical strain is capable of inducing lung growth and differentiation, cyclical strain is a prerequisite for normal development and that mechanically induced growth occurs at the expense of the alveolar type II cell. We conclude that cyclical strain may allow optimal alveolar development while maintaining a population of alveolar type II cells and may thus facilitate an improvement in postnatal lung function in infants with congenital diaphragmatic hernia.

Postnatal pulmonary distension for the treatment of pulmonary hypoplasia: pilot study in the neonatal piglet model

BACKGROUND

Accelerated lung growth has previously been demonstrated after fetal tracheal occlusion. The purpose of this study was to determine if short-term perfluorocarbon (PFC) distension could increase lung growth postnatally in neonatal piglets.

METHODS

Eleven piglets aged 5 to 8 days were divided into 3 groups: (a) controls (n = 4), (b) PFC x 6 hours (n = 3), and (c) PFC x 12 hours (n = 4). A right posterolateral thoracotomy was performed and a pressure-monitoring catheter was placed in the posterior segment of the right upper lobe. Perfluorocarbon was infused and a mean intrabronchial pressure of 12 mm Hg (range, 5-21 mm Hg) was maintained. The control piglets also had a thoracotomy with right upper lobe bronchus dissection without ligation or PFC distension. All piglets were injected with [3H]-thymidine 3 hours before killing. Both right and left posterior segments of each upper lobe were analyzed for their respective amount of total DNA by fluorometry. Rates of DNA synthesis for each segment were determined by precipitating incorporated [3H]-thymidine with 5% trichloroacetic acid and reporting this value by the total amount of DNA. The differential lung DNA synthesis rate was calculated as (right posterior segment/left posterior segment) x 100. Statistical analysis consisted of 1-way analysis of variance and Student's t tests with significance at P < or = .05.

RESULTS

Heart rate, mean arterial pressure, temperature, oxygen saturation, pH, PCO2 , and PO2 were similar in all 3 groups. Lung DNA synthesis was nearly doubled in the PFC x 6 hours group compared with controls (302% vs 165%, P = .05). Animals in the PFC x 12 hours group experienced a 261% increase (P = NS).

CONCLUSION

Short-term PFC distension in neonatal piglets resulted in increased DNA synthesis within 6 hours presumably because of stretch-induced mechanisms.

Evidence-based management of infants with congenital diaphragmatic hernia

The mortality rate associated with congenital diaphragmatic hernia (CDH) varies widely between centers and remains relatively high despite widespread use of new therapeutic modalities. Many of these have been implemented without properly controlled studies. Over the past 10 to 15 years, only 9 randomized trials enrolling a total of approximately 250 infants with CDH have been published. The limited evidence available suggests that better outcomes are observed by delivering infants with CDH at experienced centers, by delaying surgical repair until hemodynamic and respiratory stability is achieved, and by the judicious utilization of nonaggressive mechanical ventilation and permissive hypercapnea. Other therapeutic modalities, such as high frequency oscillatory ventilation, inhaled nitric oxide, and ECMO, may provide additional advantages for selected infants. There is a dire need to establish networks of centers that manage enough infants with CDH, to conduct appropriately sized randomized trials that can answer some of the critical questions about the management and long-term outcome of these infants.

Insulinlike growth factor I gene expression is increased in the fetal lung after tracheal ligation

BACKGROUND/PURPOSE

The mortality and morbidity in congenital diaphragmatic hernia are mainly caused by pulmonary hypoplasia. To improve clinical results, further methods inducing lung growth may have to be used. The aim of this report was to evaluate the expression of insulinlike growth factor I (IGF-I), estrogen receptor alpha, estrogen receptor beta, growth hormone receptor, and thioredoxin in a rat model of hypoplastic, hyperplastic, and normal fetal lungs to improve understanding of lung growth.

METHODS

Hypoplastic diaphragmatic hernia lungs were created by giving nitrofen by gavage to pregnant rats on day 9.5. Hyperplastic lungs were achieved by intrauterine tracheal ligation of rat fetuses on day 19. All lungs were harvested on gestational day 21. Total nucleic acids were extracted by proteinase K digestion and extraction in phenol/chloroform. The total nucleic acids mixture was hybridized with radioactively labeled RNA probes, and the radioactivity of the hybrids was compared with the respective standard curve of known amounts of in vitro synthesized mRNA. Immunohistochemistry staining was performed for IGF-I.

RESULTS

The IGF-I mRNA was significantly (P < .01) higher in hyperplastic lungs compared with control and hypoplastic lungs. The latter 2 did not differ. No difference was found between the other mRNA levels in the study groups.

CONCLUSIONS

IGF-I is involved in the accelerated lung growth seen after intrauterine tracheal ligation.

Extracorporeal life support: history and new directions

This review recounts the development of extracorporeal life support (ECLS, ECMO) from the laboratory and early clinical trials to routine clinical application. Lessons from neonatal ECMO have led to better understanding of neonatal lung physiology, improved methods of treatment, and application of ECLS to other patient populations.

Tissue engineering of skeletal muscle using polymer fiber arrays

The purpose of this study was to assess a new scaffold design for muscle tissue engineering: arrays of parallel-oriented polymer microfibers. First, C2C12 skeletal myoblasts were seeded onto single, laminin-coated polypropylene fibers and their growth and alignment were characterized. With the aim of creating skeletal muscle sheets, it was then investigated whether cell layers of single fibers merged when in close proximity to neighboring fibers. The optimal fiber spacing needed to achieve cell alignment with the lowest possible content of scaffold material was established. Further, it was assessed whether such a cell sheet became contractile and whether it survived in vitro for extended periods of time. C2C12 cells, cultured on fibers 10 to 15 microm in diameter, formed up to 50-microm-thick layers of longitudinally aligned cells. Four different groups based on fiber spacing (30 to 35, 50 to 55, 70 to 75, and 90 to 95 microm) were evaluated. Complete cell sheets formed between fibers that were spaced 55 microm apart or less; larger spacing led to no or incomplete sheets. C2C12 cells, seeded onto a 10 x 20 mm fiber array, formed a contractile cell sheet that was maintained in vitro for 70 days. Larger, three-dimensional structures might be created by arranging fibers in several layers or by stacking cellular sheets.

New approaches to managing congenital diaphragmatic hernia

A number of new techniques have been studied for managing newborns with congenital diaphragmatic hernia and respiratory insufficiency. Among these have been the techniques of delayed approach to the repair of the diaphragmatic hernia; permissive hypercapnia; nitric oxide and surfactant administration; intratracheal pulmonary ventilation; liquid ventilation; perfluorocarbon-induced lung growth; and lung transplantation. These interventions are at various stages of development and evaluation of effectiveness. All, however, are being explored in the hopes of improving outcome in patients with congenital diaphragmatic hernia who continue to have significant morbidity and mortality in the newborn period.

Fetal Liver as a Source of Autologous Progenitor Cells for Perinatal Tissue Engineering

Mesenchymal progenitor cells, isolated from adult bone marrow, have been shown to have utility for autologous tissue engineering. The possibility of isolating from the fetal hematopoietic system a cell population with similar potential, which could be used for autologous reconstruction of prenatally diagnosed congenital anomalies, has not been explored to date. Liver stromal cells isolated from a portion of the right lateral hepatic lobe of midgestation fetal lambs were expanded in vitro. Passage 1 cells displayed a uniform fibroblast-like morphology but could be induced to differentiate into skeletal muscle, adipocytes, chondrocytes, and endothelial cells by selective medium supplementation. By manipulating the extracellular matrix in vitro, spontaneously contracting cardiac myocyte-like cells could be generated as well. Multilineage differentiation was confirmed by morphology, protein expression, and upregulation of lineage-specific mRNA. The potential for engineering myocardial tissue was then investigated by transplanting early-passage progenitor cells, organized on a three-dimensional matrix, into the ventricle of an immunocompromised rat utilizing a previously described model of left ventricular tissue engineering. Survival, incorporation into the host myocardium, and cardiomyocytic differentiation of the transplanted cells were confirmed. We have demonstrated that mesenchymal progenitor cells with multilineage potential can be isolated from the fetal liver and have potential utility for autologous tissue engineering.

Nihilism in the 1990s: the true mortality of congenital diaphragmatic hernia

OBJECTIVE

Reported survival in congenital diaphragmatic hernia (CDH) fails to allow for case selection bias. This study reports the incidence of CDH in a geographically defined population over 11 years and assesses the effect of new therapies (high-frequency oscillatory ventilation, extracorporeal membrane oxygenation, inhaled nitric oxide, and delayed surgery) on survival when case selection is avoided.

METHODS

A retrospective review of cases from a regional case registry, the Northern Region Congenital Anomaly Survey, was conducted.

RESULTS

A total of 185 cases were identified. Mortality was 62% and did not vary significantly during the study period. Mortality was unaffected by the introduction of new therapies. There was a significant inverse correlation between the rate of elective termination and survival of live borns. The presence of an additional anomaly increased mortality to 79%.

CONCLUSIONS

The mortality of CDH when complete case ascertainment is achieved is unaffected by new therapies. The survival rate is principally determined by the rate of antenatal termination and the incidence of associated anomalies. Reports of improved survival of CDH should be interpreted with caution, as variations in outcome are more likely to be explained by case selection artifact.

A prospective, randomized pilot trial of perfluorocarbon-induced lung growth in newborns with congenital diaphragmatic hernia

BACKGROUND/PURPOSE

Initial laboratory and clinical data suggest that partial liquid ventilation (PLV) can enhance pulmonary function and that lung growth can be induced via distension of the newborn lung using perfluorocarbon in patients with congenital diaphragmatic hernia (CDH). The authors, therefore, performed a prospective, randomized pilot study evaluating PLV and perfluorocarbon-induced lung growth (PILG) in newborns with CDH on extracorporeal life support (ECLS) at 6 medical centers.

METHODS

Patients were selected randomly using a permuted block design to PLV/PILG (n = 8) or conventional mechanical ventilation (CMV/control, n = 5). Patients in the PILG group received daily doses which filled the lungs with perflubron for up to 7 days and were placed on continuous positive airway pressure of 5 to 8 cm H2O. CMV patients were treated with standard mechanical ventilation while on extracorporeal membrane oxygenation (ECMO).

RESULTS

A total of 13 patients were evaluated in this study. All 3 patients enrolled without being on ECLS rapidly transitioned to ECLS. The study, therefore, effectively evaluated PILG (n = 8) versus standard ventilation (control, n = 5) on ECLS. Mean (+/- SE) gestational age was 37 +/- 1 weeks and weight was 3.1 +/- 0.1 kg. Time on ECMO was 9.8 +/- 2.3 days in the PILG and 14.5 +/- 3.5 days (P =.58) in the control group. Survival rate in the PILG group was 6 of 8 (75%), whereas survival rate was 2 of 5 (40%) in the control group (P =.50). The number of days free from the ventilator in the first 28 days (VFD) was 6.3 +/- 3.3 days with PILG and 4.6 +/- 4.6 days with control (P =.9). Causes of death in the PILG group included sepsis and renal failure in one patient and pulmonary hypertension in the other. There were no safety issues, and the deaths in the PILG group did not appear to be related to the administration of perflubron.

CONCLUSIONS

These data show that PILG can be performed safely. The survival rate, VFD, and time on ECMO data, although not conclusive, are encouraging and indicate the need for a definitive trial of this novel intervention in these neonates with high mortality.

Early perfluorodecalin lung distension in infants with congenital diaphragmatic hernia

BACKGROUND/PURPOSE

Pulmonary hypoplasia contributes to mortality in infants with severe congenital diaphragmatic hernia (CDH). Accelerated postnatal lung growth with perfluorocarbon lung distension has been demonstrated in animals. The authors present a study measuring perfluorodecalin distension in neonates with severe CDH on extracorporeal membrane oxygenation (ECMO) support.

METHODS

Six consecutive neonates with CDH requiring ECMO support were recruited. The lungs were filled with perfluorodecalin, and continuous positive airway pressure was applied for 6 to 10 days (mean, 7.7 days +/- 0.7). The perfluorodecalin was exchanged 4 times a day. Radiographic lung projections were measured, and from 2-dimensional measurements an estimated lung volume was calculated using the ECMO cannula as reference.

RESULTS

Perfluorodecalin instillation started soon after starting ECMO support (mean, 13.5 +/- 5.3 hours). The volume required to fill the lungs increased significantly (P <.02). The radiographic dimension of the affected lung increased significantly (mean percentage increase, 272%; P <.02). The contralateral lung dimension also increased (mean percentage increase 51%; P <.02). CDH repair was undertaken on ECMO in all cases. All patients survived (follow-up, 3 to 42 months).

CONCLUSIONS

This protocol of early perfluorodecalin lung distension in infants with severe CDH on ECMO support resulted in significant radiographic lung enlargement. Clinical outcomes are encouraging. Possible mechanisms include alveolar recruitment, alveolar dilatation, and accelerated postnatal lung growth.

Congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a lethal human birth defect. Hypoplastic lung development is the leading contributor to its 30-50% mortality rate. Efforts to improve survival have focused on fetal surgery, advances in intensive care and elective delivery at specialist centres following in utero diagnosis. The impact of abnormal lung development on affected infants has stimulated research into the developmental biology of CDH. Traditionally lung hypoplasia has been viewed as a secondary consequence of in utero compression of the fetal lung. Experimental evidence is emerging for a primary defect in lung development in CDH. Culture systems are providing research tools for the study of lung hypoplasia and the investigation of the role of growth factors and signalling pathways. Similarities between the lungs of premature newborns and infants with CDH may indicate a role for antenatal corticosteroids. Further advances in postnatal therapy including permissive hypercapnia and liquid ventilation hold promise. Improvements in our basic scientific understanding of lung development may hold the key to future developments in CDH care.

Support of respiratory failure in the pediatric surgical patient

Severe respiratory failure in newborn and pediatric patients is associated with significant morbidity and mortality. Basic science laboratory investigation has led to advances in the understanding of ventilator-induced lung injury and in optimizing the supportive use of conventional ventilation strategies. Over the past few years, progress has been made in alternative therapies for supporting children and adults with severe respiratory failure. This review will focus on recent laboratory and clinical data regarding the techniques of lung protective ventilator strategies, inhaled nitric oxide, liquid ventilation, and extracorporeal life support (ECLS, ECMO). Some of these modalities are commonplace, while others may have much to offer the pediatric clinician if their benefit is clearly demonstrated in future clinical trials.

Congenital diaphragmatic hernia

Congenital diaphragmatic hernia occurs in approximately 1 in every 2500 live births and is associated with a reported mortality of almost 35% in live-born patients and a higher mortality when in utero deaths are counted. Ventilator-induced lung injury, pulmonary hypoplasia, and other associated anomalies account for the high death rate. Numerous adjunctive measures have been used to treat these patients. Inhaled vasodilators (nitric oxide), intravenous vasodilators, and fetal therapy have no proven benefit. While animal models of congenital diaphragmatic hernia are surfactant deficient, controversy remains over the use of surfactant in infants. There has been no clinical trial showing any clear benefit with the use of exogenous surfactant in these patients. Similarly, prenatal corticosteroids show some improvements in animal models, but again, there is a complete absence of supportive data to show benefit in humans. Mechanical ventilator strategies that limit ventilator-induced lung injury by avoiding hyperventilation and lung over inflation are the strategies currently in use that have been associated with improved survival. Long-term follow-up of these patients is quite important since gastroesophageal reflux, developmental delay, chronic lung disease, and chest wall deformity are all seen with increased frequency in these children.

Control of embryonic lung branching morphogenesis by the Rho activator, cytotoxic necrotizing factor 1

BACKGROUND

Lung development is sensitive to physiological stresses, and its development may be impaired by physical distortion, as in patients with congenital diaphragmatic hernia. Yet, little is known about how mechanical forces can influence lung morphogenesis. Studies with cultured cells suggest that cytoskeletal tension may play a key role in growth control. Since the small GTPase Rho plays an important role in the control of cell tension generation, we carried out studies to test the hypothesis that changes in Rho-mediated cell tension may influence branching morphogenesis.

METHODS

Embryonic lung buds from timed pregnant Swiss Webster mice were microdissected on Embryonic Day 12 (E12), and whole organs were cultured in serum-free medium in the presence of the Rho activator cytotoxic necrotizing factor 1 (CNF-1) for 48 h. Serial measurements of the degree of epithelial branch formation and tissue maturation were performed using light microscopy and computerized image analysis.

RESULTS

At 48 h, embryonic lungs treated with 2 ng/ml CNF-1 increased their terminal bud count by 236 +/- 18% (P = 0.01) compared with 132 +/- 2% for untreated controls. However, dose-response experiments revealed biphasic behavior: at a higher dose of CNF-1 (200 ng/ml), bud number was actually decreased relative to controls (43 +/- 1%, P < 0.001). Histological analysis revealed that individual glands appeared to be more highly developed at low-dose CNF-1, whereas the high dose produced gland contraction.

CONCLUSIONS

These data support a potential role for Rho and cytoskeletal tension in control of epithelial pattern formation during lung development.