Combining keratinocyte growth factor transfection into the airways and tracheal occlusion in a fetal sheep model of congenital diaphragmatic hernia

Excessive Reversal of Epidermal Growth Factor Receptor and Ephrin Signaling Following Tracheal Occlusion in Rabbit Model of Congenital Diaphragmatic Hernia

Congenital diaphragmatic hernia (CDH) causes severe pulmonary hypoplasia from herniation of abdominal contents into the thorax. Tracheal occlusion (TO) for human CDH improves survival, but morbidity and mortality remain high, and we do not fully understand the cellular pathways and processes most severely impacted by CDH and TO. We created a left diaphragmatic hernia (DH) in rabbit fetuses with subsequent TO and collected left lung sections for NextGen mRNA sequencing. DH, TO, and DHTO fetuses had comparable body and organ growth to control except for lower lung weights in DH (p<0.05). Of 13,687 expressed genes, DHTO had 687 differentially expressed genes compared to DH, but no other group-group comparison had more than 10. Considering genes in combination, many of the genes reduced in DH were more highly expressed in DHTO than in control. Benchmarking fetal rabbit lung gene expression to published lung development data, both DH and DHTO lungs were more highly correlated with the gene expression of immature lung. DNA synthesis was upregulated in DHTO compared to DH and ribosome and protein synthesis pathways were downregulated. DH reduced total and epithelial cell proliferation by half and two-thirds respectively, and DHTO increased proliferation by 2.5 and 3.4-fold respectively. Signaling pathways downregulated by DH and upregulated in DHTO were epidermal growth factor receptor signaling, ephrin signaling, and cell migration; however, levels of ephrin and EGFR signaling in DHTO exceeded that of control. Identification and inhibition of the ligands responsible for this dysregulated signaling could improve lung development in CDH.

The Effect of Transplacental Administration of Glucagon-Like Peptide-1 on Fetal Lung Development in the Rabbit Model of Congenital Diaphragmatic Hernia

Objective: Glucagon-like peptide-1 (GLP-1) increases surfactant protein expression in type 2 pneumocytes. Herein, we determine if transplacental GLP-1 treatment accelerates lung growth in the fetal rabbit model of congenital diaphragmatic hernia (DH). Methods: Time-mated does had an induction of DH on day 23 followed by daily GLP-1 or placebo injection until term. At that time, the does were weighed, fetal blood was obtained for GLP-1 assay, and the lungs were dissected. Fetal outcome measures were lung-to-body-weight ratio (LBWR), morphometry, and Ki67 and surfactant protein B (SPB) expression. Results: Maternal weight loss in the GLP-1 group was 7.1%. Fetal survival was lower in GLP-1 fetuses compared to placebo controls (27/85, 32% vs. 35/57, 61%; p < 0.05). Fetal GLP-1 levels were increased 3.6-fold. The LBWR of GLP-1 DH fetuses fell within the range of DH placebo fetuses (1.166 ± 0.207% vs. 1.312 ± 0.418%), being significantly lower than that of placebo-exposed unoperated fetuses (2.280 ± 0.522%; p < 0.001). GLP-1 did not improve airway morphometry. GLP-1 DH lungs had a reduced adventitial and medial thickness within the range of controls, and lesser muscularization of vessels measuring 30-60 µm. There were no differences in Ki67 and SPB expression. Conclusion: GLP-1 at this dosage improves peripheric pulmonary vessel morphology in intra-acinar vessels with no effect on airway morphometry but with significant maternal and fetal side effects. Thus, it is an unlikely medical strategy.

Medical interventions to reverse pulmonary hypoplasia in the animal model of congenital diaphragmatic hernia: A systematic review

We aimed to systematically review all published pre-clinical research on prenatal medical treatment of pulmonary hypoplasia in congenital diaphragmatic hernia (CDH). Background The neonatal mortality due to isolated CDH remains high. Whether fetal endoscopic tracheal occlusion (FETO) reduces mortality is still to be demonstrated. Therefore more potent preferentially medical therapy would be welcomed. Methods We searched MEDLINE (Pubmed), Embase and the Web of Science including all studies from the earliest date (1951) to December 2013. Article quality was assessed using the modified CAMRADES checklist. Inclusion criteria were those animal studies addressing prenatal medical interventions and principal variables were confirmation of a diaphragmatic defect, lung to body weight ratio (LBWR), formal airway morphometry or DNA/protein content. Results In total 983 articles were identified. Following abstract review, 96 articles were assessed by two authors in agreement with a third for eligibility. Of these, 43 were included in the final analysis. The median number of study quality checklist items (maximum 10) scored was 4 (IQ range: 2-5). Thirty (69.8%) of studies were in the nitrofen rat. The majority were treated with vitamins or glucocorticoids. Single studies reported some improvement in lung morphology with alternative therapies. It was impossible to identify a pattern in animal model selection or creation, mode, time point or duration of treatment and readouts. Only one study reported a sample size calculation. Conclusion Comparison in pre-clinical studies in CDH is challenging due to methodological variation. Agreed standardized methods need to be applied in future investigation of new medical therapies.

Pulmonary alveolar and vascular morphometry after gel plug occlusion of the trachea in a fetal rabbit model of CDH

PURPOSE

Tracheal occlusion (TO) induces lung growth in congenital diaphragmatic hernia (CDH) but is also associated with drawbacks. We devised a temporary gel plug that induced lung growth when placed in the fetal trachea. This study evaluates the effects of temporary versus permanent TO on histologic radial alveolar count (RAC) and vascular morphometrics.

METHODS

Experimental CDH was created surgically in 64 New Zealand White rabbit fetuses on gestational day (GD) 24. On GD 27, these fetuses were randomized to intratracheal instillation of a fibrin gel plug (GP), tracheal suture ligation (SL), intratracheal instillation of normal saline (NS), or sham amniotomy (SH). Non-manipulated fetuses served as controls (NM). Histologic lung sections were assessed blindly for RAC and relative arterial adventitial thickness (%AT) as a variable for vascular remodelling. Results were statistically compared.

RESULTS

RAC was significantly lower in the ipsilateral lung of SH fetuses than in the contralateral lung (p = 0.011). Mean RAC was higher after SL (p < 0.001) and GP (p = 0.03) compared to SH. Furthermore, %AT was higher in GP (50 ± 28, p < 0.001) and SL (45 ±2 6, p = 0.003) fetuses than in controls (36 ± 19).

CONCLUSION

Temporary and permanent TO leads to increased RAC; this effect was more pronounced with permanent TO. Both interventions were associated with an increased %AT. These findings may explain the adverse clinical effects of TO, despite causing accelerated lung growth.

Candidate diseases for prenatal gene therapy

Prenatal gene therapy aims to deliver genes to cells and tissues early in prenatal life, allowing correction of a genetic defect, before irreparable tissue damage has occurred. In contrast to postnatal gene therapy, prenatal application may target genes to a large population of stem cells, and the smaller fetal size allows a higher vector to target cell ratio to be achieved. Early gestation delivery may allow the development of immune tolerance to the transgenic protein, which would facilitate postnatal repeat vector administration if needed. Moreover, early delivery would avoid anti-vector immune responses which are often acquired in postnatal life. The NIH Recombinant DNA Advisory Committee considered that a candidate disease for prenatal gene therapy should pose serious morbidity and mortality risks to the fetus or neonate, and not have any effective postnatal treatment. Prenatal gene therapy would therefore be appropriate for life-threatening disorders, in which prenatal gene delivery maintains a clear advantage over cell transplantation or postnatal gene therapy. If deemed safer and more efficacious, prenatal gene therapy may be applicable for nonlethal conditions if adult gene transfer is unlikely to be of benefit. Many candidate diseases will be inherited congenital disorders such as thalassaemia or lysosomal storage disorders. However, obstetric conditions such as fetal growth restriction may also be treated using a targeted gene therapy approach. In each disease, the condition must be diagnosed prenatally, either via antenatal screening and prenatal diagnosis, for example, in the case of hemophilias, or by ultrasound assessment of the fetus, for example, congenital diaphragmatic hernia. In this chapter, we describe some examples of the candidate diseases and discuss how a prenatal gene therapy approach might work.

Vector systems for prenatal gene therapy: choosing vectors for different applications

This chapter gives a comparative review of the different vector systems applied to date in prenatal gene therapy experiments highlighting the need for versatility and choice for application in accordance with the actual aim of the study. It reviews the key characteristics of the four main gene therapy vector systems and gives examples for their successful application in prenatal gene therapy experiments.

Organ targeted prenatal gene therapy--how far are we?

Prenatal gene therapy aims to deliver genes to cells and tissues early in prenatal life, allowing correction of a genetic defect, before long-term tissue damage has occurred. In contrast to postnatal gene therapy, prenatal application can target genes to a large population of dividing stem cells, and the smaller fetal size allows a higher vector-to-target cell ratio to be achieved. Early-gestation delivery may allow the development of immune tolerance to the transgenic protein which would facilitate postnatal repeat vector administration if needed. Targeting particular organs will depend on manipulating the vector to achieve selective tropism and on choosing the most appropriate gestational age and injection method for fetal delivery. Intra-amniotic injection reaches the skin, and other organs that are bathed in the fluid however since gene transfer to the lung and gut is usually poor more direct injection methods will be needed. Delivery to the liver and blood can be achieved by systemic delivery via the umbilical vein or peritoneal cavity. Gene transfer to the central nervous system in the fetus is difficult but newer vectors are available that transduce neuronal tissue even after systemic delivery.

Keratinocyte growth factor (KGF) gene therapy mediated by an attenuated form of Salmonella typhimurium ameliorates radiation induced pulmonary injury in rats

The aim of this study is to investigate the effect of KGF (Keratinocyte growth factor) gene therapy mediated by the attenuated Salmonella typhimurium Ty21a on radiation-induced pulmonary injury in rats model. Sprague-Dawley rats were divided into three groups: TPK group (treated with TPK strain, attenuated Salmonella typhimurium Ty21a-recombined human KGF gene); TP group (treated with TP strain, attenuated Salmonella typhimurium Ty21a-recombined blank plasmid); and Saline group (treated with saline). After intraperitoneal administration for 48 h, the thoraxes of the rats were exposed to X-ray (20 Gy), and the rats were administered again two weeks after radiation. On the 3rd, 5th, 7th, 14th and 28th day after radiation, the rats were sacrificed and lung tissues were harvested. Histological analysis was performed, MDA contents and SOD activity were detected, mRNA levels of KGF, TGF-β, SP-A and SP-C were measured by Real-time RT-PCR, and their concentrations in the BALF were quantified with ELISA. Administration of TPK strain improved the pathological changes of the lung on the 28th day. In the TPK group, KGF effectively expressed since the 3rd day, MDA contents decreased and SOD activity increased significantly, on the 7th day and 14th day respectively. SP-A and SP-C expression elevated, whereas TGF-β expression was inhibited in the TPK group. These results suggest that this novel gene therapy of KGF could ameliorate radiation-induced pulmonary injury in rats, and may be a promising therapy for the treatment of radiative pulmonary injury.