A comparison of airway pressures for inflation fixation of developing mouse lungs for stereological analyses

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.

The fix is not yet in: recommendation for fixation of lungs within physiological/pathophysiological volume range in preclinical pulmonary structure-function studies

Quantitative characterization of lung structures by morphometrical or stereological analysis of histological sections is a powerful means of elucidating pulmonary structure-function relations. The overwhelming majority of studies, however, fix lungs for histology at pressures outside the physiological/pathophysiological respiratory volume range. Thus, valuable information is being lost. In this perspective article, we argue that investigators performing pulmonary histological studies should consider whether the aims of their studies would benefit from fixation at functional transpulmonary pressures, particularly those of end-inspiration and end-expiration. We survey the pressures at which lungs are typically fixed in preclinical structure-function studies, provide examples of conditions that would benefit from histological evaluation at functional lung volumes, summarize available fixation methods, discuss alternative imaging modalities, and discuss challenges to implementing the suggested approach and means of addressing those challenges. We aim to persuade investigators that modifying or complementing the traditional histological approach by fixing lungs at minimal and maximal functional volumes could enable new understanding of pulmonary structure-function relations.

Reduced SARS-CoV-2 disease outcomes in Syrian hamsters receiving immune sera: Quantitative image analysis in pathologic assessments

There is a need to standardize pathologic endpoints in animal models of SARS-CoV-2 infection to help benchmark study quality, improve cross-institutional comparison of data, and assess therapeutic efficacy so that potential drugs and vaccines for SARS-CoV-2 can rapidly advance. The Syrian hamster model is a tractable small animal model for COVID-19 that models clinical disease in humans. Using the hamster model, the authors used traditional pathologic assessment with quantitative image analysis to assess disease outcomes in hamsters administered polyclonal immune sera from previously challenged rhesus macaques. The authors then used quantitative image analysis to assess pathologic endpoints across studies performed at different institutions using different tissue processing protocols. The authors detail pathological features of SARS-CoV-2 infection longitudinally and use immunohistochemistry to quantify myeloid cells and T lymphocyte infiltrates during SARS-CoV-2 infection. High-dose immune sera protected hamsters from weight loss and diminished viral replication in tissues and reduced lung lesions. Cumulative pathology scoring correlated with weight loss and was robust in distinguishing IgG efficacy. In formalin-infused lungs, quantitative measurement of percent area affected also correlated with weight loss but was less robust in non-formalin-infused lungs. Longitudinal immunohistochemical assessment of interstitial macrophage infiltrates showed that peak infiltration corresponded to weight loss, yet quantitative assessment of macrophage, neutrophil, and CD3+ T lymphocyte numbers did not distinguish IgG treatment effects. Here, the authors show that quantitative image analysis was a useful adjunct tool for assessing SARS-CoV-2 treatment outcomes in the hamster model.

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.