Characteristics of pulmonary microvascular structure in postnatal yaks

Abstract

Yaks are typical plateau-adapted animals, however the microvascular changes and characteristics in their lungs after birth are still unclear. Pulmonary microvasculature characteristics and changes across age groups were analysed using morphological observation and molecular biology detection in yaks aged 1, 30 and 180 days old in addition to adults. Results: Our experiments demonstrated that yaks have fully developed pulmonary alveolar at birth but that interalveolar thickness increased with age. Immunofluorescence observations showed that microvessel density within the interalveolar septum in the yak gradually increased with age. In addition, transmission electron microscopy (TEM) results showed that the blood–air barrier of 1-day old and 30-days old yaks was significantly thicker than that observed at 180-days old and in adults (P < 0.05), which was caused by the thinning of the membrane of alveolar epithelial cells. Furthermore, Vegfa and Epas1 expression levels in 30-day old yaks were the highest in comparison to the other age groups (P < 0.05), whilst levels in adult yaks were the lowest (P < 0.05). The gradual increase in lung microvessel density can effectively satisfy the oxygen requirements of ageing yaks. In addition, these results suggest that the key period of yak lung development is from 30 to 180 days.

Study of Transcriptomic Analysis of Yak (Bos grunniens) and Cattle (Bos taurus) Pulmonary Artery Smooth Muscle Cells under Oxygen Concentration Gradients and Differences in Their Lung Histology and Expression of Pyruvate Dehydrogenase Kinase 1-Related Factors

“…VEGF not only increases vascular permeability but also promotes the proliferation and differentiation of vascular smooth muscle cells, thereby promoting neovascularization [68][69][70]. Together with the experimental results, the structure of the lungs determines whether yaks can adapt to the hypoxic environment of the plateau [51,71,72]. The expression of HIF-1α and VEGF in the epithelial cells of terminal fine bronchioles of yaks is relatively high compared with that in cattle, which is conducive to the protection of bronchioles and the enrichment of the soft tube mechanism in yaks under the hypoxic environment of the plateau and facilitates the contraction of bronchioles.…”

“…This may be closely related to the adaptation of yaks to the hypoxic environment of the plateau and reduces water consumption during respiration. At the same time, studies have shown that abundant dilated capillaries and large numbers of erythrocytes in the alveolar septa are conducive to increased alveolar ventilation and oxygen transport [51][52][53][54][55][56]. We measured the percentage of alveolar septa at all levels of the peribronchiolar alveoli in yaks after H&E, Masson, and PAS staining, observing a highly significant difference compared to that of cattle, and we also observed that the alveolar septa in yaks between adjacent alveoli was rich in capillaries, and that the number of red blood cells was higher than that of cattle.…”