Spermidine supplementation and voluntary activity differentially affect obesity-related structural changes in the mouse lung

Obesity is associated with lung function impairment and respiratory diseases; however, the underlying pathophysiological mechanisms are still elusive, and therapeutic options are limited. This study examined the effects of prolonged excess fat intake on lung mechanics and microstructure and tested spermidine supplementation and physical activity as intervention strategies. C57BL/6N mice fed control diet (10% fat) or high-fat diet (HFD; 60% fat) were left untreated or were supplemented with 3 mM spermidine, had access to running wheels for voluntary activity, or a combination of both. After 30 wk, lung mechanics was assessed, and left lungs were analyzed by design-based stereology. HFD exerted minor effects on lung mechanics and resulted in higher body weight and elevated lung, air, and septal volumes. The number of alveoli was higher in HFD-fed animals. This was accompanied by an increase in epithelial, but not endothelial, surface area. Moreover, air-blood barrier and endothelium were significantly thicker. Neither treatment affected HFD-related body weights. Spermidine lowered lung volumes as well as endothelial and air-blood barrier thicknesses toward control levels and substantially increased the endothelial surface area under HFD. Activity resulted in decreased volumes of lung, septa, and septal compartments but did not affect vascular changes in HFD-fed mice. The combination treatment showed no additive effect. In conclusion, excess fat consumption induced alveolar capillary remodeling indicative of impaired perfusion and gas diffusion. Spermidine alleviated obesity-related endothelial alterations, indicating a beneficial effect, whereas physical activity reduced lung volumes apparently by other, possibly systemic effects.

Evaluating acellular versus cellular perfusate composition during prolonged ex vivo lung perfusion after initial cold ischaemia for 24 hours

Normothermic ex vivo lung perfusion (EVLP) has developed as a powerful technique to evaluate particularly marginal donor lungs prior to transplantation. In this study, acellular and cellular perfusate compositions were compared in an identical experimental setting as no consensus has been reached on a preferred technique yet. Porcine lungs underwent EVLP for 12 h on the basis of an acellular or a cellular perfusate composition after 24 h of cold ischaemia as defined organ stress. During perfusion, haemodynamic and respiratory parameters were monitored. After EVLP, the lung condition was assessed by light and transmission electron microscopy. Aerodynamic parameters did not show significant differences between groups and remained within the in vivo range during EVLP. Mean oxygenation indices were 491 ± 39 in the acellular group and 513 ± 53 in the cellular group. Groups only differed significantly in terms of higher pulmonary artery pressure and vascular resistance in the cellular group. Lung histology and ultrastructure were largely well preserved after prolonged EVLP and showed only minor structural alterations which were similarly present in both groups. Prolonged acellular and cellular EVLP for 12 h are both feasible with lungs prechallenged by ischaemic organ stress. Physiological and ultrastructural analysis showed no superiority of either acellular or cellular perfusate composition.

Intra-amniotic administration of exogenous pulmonary surfactant for improving in lung maturity of fetal rabbits with intrauterine infection caused by premature rupture of membranes

This study was to investigate the effect of intra-amniotic administration of pulmonary surfactant (PS) on lung maturation in conditions of experimentally induced premature rupture of membranes (PROM) and intrauterine infection of rabbits. To establish animal (rabbit) models of intrauterine infection caused by PROM, E. coli was intrauterinely injected in 24-and 26-day pregnant animals. Twenty healthy pregnancy adult Japanese white rabbits were divided into three groups: the infection group (8 rabbits), infection group with intra-amniotic PS administration (8 rabbits) and healthy controls (4 rabbits). Ultrastructure changes in the lung were observed under an electron microscope 19.5 hours after intervention. The results showed that the lung infection levels of fetal rabbits in the infection group and the infection group with PS had no significant difference. Bacillus bodies and infiltrated inflammatory cells can be occasionally seen in the alveoli, bronchial lumen, and cytoplasm.The type II alveolar epithelial cells (AT-II) were decreased in the infection group than that in control group. Lamellar bodies showed vacuolation changes and different levels of apoptosis. In the infection group with PS, the count of AT-II did not show an obvious decrease. Lamellar bodies increased, and different secretion forms appeared. Also, there was little apoptosis and no obvious collagen fiber hyperplasia in antenatal administration of PS group. We believe that once PROM has happened, intrauterine infection and inflammation stimulated a cascade reaction on the fetal lung, leading to abnormal changes in the alveolar ultrastructure. Intra-amniotic administration of PS can improve the fetal lung ultrastructure and its maturity.