Novel prediction and treatment methods for fetuses with congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a rare condition occurring in approximately 1 in 2,500 live births. This condition is characterized bydefect in the diaphragm as a result of failed closure during the embryonic period of development. In the majority of cases the defect is located on the left side (85%), whereas right (14%) and bilateral defects (1%)are more rare. Because of the defect, abdominal organs, such as stomach, bowels, liver and spleen can herniate towards the chest cavity. This leads to impaired pulmonary development (pulmonary hypoplasia) with important consequences after birth. Besides respiratory insufficiency as a result of the hypoplasia these neonates often also develop pulmonary hypertension. In approximately 40% of cases there are associated anomalies, sometimes as part of syndrome and these cases the prognosis is very poor.Nevertheless, despite optimal neonatal care in around 30% of neonates with isolated CDH the disease is too severe to survive after birth. Nowadays in most Western countries this conditionis diagnosed before birth. In order to give an individualized prediction of the prognosis, most methods are measuring the lung area or volume either with ultrasound or with magnetic resonance imaging (MRI). The moststudied method is using a ratio between the lung area and the head circumference (lung-to-head ratio; LHR), which is expressed as a percentage of what is to be expected in a normally developed fetus (observed/expected: o/e LHR). However, this method does not provide information regarding the pulmonary vasculature, hence the occurrence of pulmonary hypertension. Immediately after birth the lungs will start to function and the oxygen levels in the blood will rise shortly thereafter. This triggers therelease of vasodilating factors as endothelin derived NO and prostacyclin, thereby increasing the pulmonary blood flow. One can mimic this phenomenon by administering oxygen to the mother and this vascular reactivity can be measured using Doppler ultrasound. In the first part of this thesis (chapter 2 and 3) we focused on the lung reactivityin normally developed fetuses in order to create normative ranges. The induced changes in blood flow can be measured either by assessing the resistance in a single vessel (deltaPI) or by evaluating the lung perfusion on a transverse section at the level of the lung (deltaFMBV). We hypothesized that in the majority of fetuses the lungs become reactive with advancing gestation. However both methods are hampered by an important variability between the individual measurements. This variation is betweenfetuses, but also when assessing the same fetus after a 4 or 8 weeks interval. The implementation of this test into routine clinical practice is difficult, given that it is not possible to describe normal pattern of lung reactivity. Secondary to the herniation of abdominal organs there is also a shift of the heart axis and in left sided (LCDH) cases this coincides with smaller left cardiac structures. In chapter 4 we used a noveltechnique, namely velocity vector imaging (VVI), to determine whether the cardiac contractility is influenced by these geometrical changes. Based on our results we concluded that there is no evidence for cardiac dysfunction in LCDH. On the contrary, the left ventricle is apparently compensating for its smaller size in order to maintain normal flow towards the systemic circulation. Since right sided CDH (RCDH) is so rare, there is limited data available regarding cardiac development in these fetuses. In chapter 5 we describe a series of RCDH cases in which we performed an extensive echocardiographic examination. Similar to what is reported in fetuses with LCDH, we could document significant smaller cardiac structures on the side of the defect. Both the right ventricle, as well as the pulmonary valve, is smaller than in gestational age matched controls. In addition, VVI showed also normal ventricular contractility and no evidence for cardiac dysfunction (chapter 4 and 5). In the final clinical part of this thesis (chapter 6) we reviewed all RCDH cases that were evaluated in two large centers (Leuven and Barcelona) during a decade. Both centers are offering fetal therapy (FETO) in case of severe lung hypoplasia. In the group that was expectantly managed before birth, O/E LHR appeared to be the only independent predictor of postnatal survival. Based on this largerseries we suggest that using a prediction algorithm specific for RCDH seems essential. In case of severe hypoplasia there appears to be a beneficial effect of FETO (17 vs. 42% survival). However due to its rareness it seems very difficult to confirm this finding in a formal randomized clinical trial. FETO remains anyway an invasive procedure and in about half of the fetuses the effect is not enough for postnatal survival. The second part of this thesis was focused on theuse of cell therapy with amniotic fluid derived stem cells to improve pulmonary development. The first study (chapter 7) showedthat it is possible to isolate and expand these cells on a routine basis from AF samples of fetuses with CDH. There were no differences in growth potential, cell surface markers and differentiation capacity comparedto normal fetuses. Furthermore, the cells could be labeled with cell markers, which allowed identification of the cells after injection in a rabbit model. In the final chapter (chapter 8) we evaluated the effect of adding intra-tracheal injection of stem cells to tracheal occlusion in a rabbit model for CDH. In the group treated with stem cells we observed an increased number of alveoli, without any signs of toxicity. Further research is necessary to unravel the underlying causes of this observation.status: publishe