Impact of litter size on survival, growth and lung alveolarization of newborn mouse pups

Establishment of a Rabbit Model of Rib Tethering-induced Early-onset Scoliosis: Insights into Lung Evaluation Using Design-based Stereology

STUDY DESIGN

Experimental study.

OBJECTIVE

To create an early-onset scoliosis (EOS) rabbit model and use a design-based stereological method to quantitatively assess lung structure changes at 24 weeks of age.

SUMMARY OF BACKGROUND DATA

Scoliosis affects thoracic and lung development, impacting children's chest and lung growth.

MATERIALS AND METHODS

EOS was induced via rib tethering in 4-week-old rabbits with ongoing CT scans and weight measures. Lungs were extracted postfixation for volume estimation and tissue sampling, followed by microscopic analysis of lung morphology.

RESULTS

The mean Cobb angle increased with the rabbits' growth. The EOS group showed significant decreases in total and right lung volumes. Quantitative lung stereology revealed reduced volumes of lung parenchyma and nonparenchymal tissue in all lobes. Alveolar duct volumes decreased significantly in multiple lobes, and alveolar septal volume was notably reduced in the right upper, middle, and lower lobes. The alveolar septal area decreased, and septal thickness increased in the EOS group. Alveoli numbers dropped, with variable changes in mean alveolar volume across lobes. Vascular lumen volume decreased in the right middle and lower lobes, and blood vessel and perivascular tissue volumes were significantly reduced in the right lung. Vessel diameter changes varied across lobes, with significant decreases in the right middle and lower lobes and increases in the left upper and lower lobes. Vascular endothelial surface area decreased in the left lower, right middle, and right lower lobes, with increased vessel and perivascular tissue thickness in the left upper and lower lobes compared with the right lobes.

CONCLUSION

The EOS rabbit model demonstrated reduced lung volume, impaired alveolarization, septal thickening, and vascular changes, indicating scoliosis's negative impact on thoracic and lung development, especially on the concave lung.

Design-Based Stereology of the Lung in the Hyperoxic Preterm Rabbit Model of Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is a complex condition frequently occurring in preterm newborns, and different animal models are currently used to mimic the pathophysiology of BPD. The comparability of animal models depends on the availability of quantitative data obtained by minimally biased methods. Therefore, the aim of this study was to provide the first design-based stereological analysis of the lungs in the hyperoxia-based model of BPD in the preterm rabbit. Rabbit pups were obtained on gestation day 28 (three days before term) by cesarean section and exposed to normoxic (21% O2, n = 8) or hyperoxic (95% O2, n = 8) conditions. After seven days of exposure, lung function testing was performed, and lungs were taken for stereological analysis. In addition, the ratio between pulmonary arterial acceleration and ejection time (PAAT/PAET) was measured. Inspiratory capacity and static compliance were reduced whereas tissue elastance and resistance were increased in hyperoxic animals compared with normoxic controls. Hyperoxic animals showed signs of pulmonary hypertension indicated by the decreased PAAT/PAET ratio. In hyperoxic animals, the number of alveoli and the alveolar surface area were reduced by one-third or by approximately 50% of control values, respectively. However, neither the mean linear intercept length nor the mean alveolar volume was significantly different between both groups. Hyperoxic pups had thickened alveolar septa and intra-alveolar accumulation of edema fluid and inflammatory cells. Nonparenchymal blood vessels had thickened walls, enlarged perivascular space, and smaller lumen in hyperoxic rabbits in comparison with normoxic ones. In conclusion, the findings are in line with the pathological features of human BPD. The stereological data may serve as a reference to compare this model with BPD models in other species or future therapeutic interventions.