Stereological analysis of the naked mole-rat Heterocephalus glaber lung provides evidence of altered surfactant function and late alveolarization

Naked mole-rats (NMR; Heterocephalus glaber) exhibit unique biological traits such as resistance to cancer, exceptional longevity, and high tolerance to low-oxygen environments. However, little is known of the lung structure of this eusocial species. Here, the lungs of adult NMR were qualitatively examined using light and electron microscopy, followed by structural quantification of the alveolar region by means of stereology. One queen (> 18 years) was also included in the study. The data normalized to body weight (BW) was furthermore compared to that of young and old mice (Mus musculus) as well as the expression of genes of surfactant proteins. Qualitatively, NMR showed larger conducting airways compared to mice. Additionally, alveolar septa with a double-layered capillary network were observed in NMR, indicating microvascular maturation and late alveolarization. Stereological analysis of the lung parenchyma revealed a lower septal surface area and alveolar epithelial type II (AEII) cell number per BW in NMR compared to mice. However, in NMR, the AEII cells were larger with a higher content of lamellar bodies, resulting in more intracellular surfactant per BW. Furthermore, the expression of surfactant protein B (Sfptb) was prominently higher in NMR. The queen showed a larger mean alveolar volume, but no other age-related structural alterations were observed. The results indicate that NMR are capable of late alveolarization, which is in line with their good regenerative potential. Additionally, NMR have more intracellular surfactant and higher expression of Sftpb, suggesting functional alterations in their surfactant system possibly as an environmental adaptation.

• Geltinger, F.
• Holtze, S.
• Hildebrandt, T. B.
• Ochs, M.
• Brandenberger, C.