HISTOLOGY AND HISTOPATHOLOGY

Cellular and Molecular Biology

 

Neurotrophins, airway smooth muscle and the fetal breathing-like movements

M.R. Inanlou, M. Baguma-Nibasheka, M.-M. Keating and B. Kablar

Dalhousie University, Faculty of Medicine, Department of Anatomy and Neurobiology, Halifax, NS, Canada

Offprint requests to: Dr. Boris Kablar, Dalhousie University, Faculty of Medicine, Department of Anatomy and Neurobiology, 5850 College Street, Halifax, NS, Canada B3H 1X5. e-mail: bkablar@dal.ca


Summary. Central nervous system and skeletal muscles secrete a group of polypeptide hormones called neurotrophins (NTs). More recent studies show that NTs and their receptors are also expressed in the lung, suggesting a role for NTs in lung development. To examine the role of NTs during normal and diseased lung organogenesis, we employed wild-type and amyogenic mouse embryos (designated as Myf5-/-:MyoD-/-). Amyogenic embryos completely lacked skeletal muscles and were not viable after birth due to the respiratory failure secondary to lung hypoplasia. To examine the importance of lung-secreted NTs during normal and hypoplastic lung organogenesis, immunohistochemistry was employed. Distribution of NTs and their receptors was indistinguishable between normal and hypoplastic lungs. To further examine the importance of non-lung-secreted NTs (e.g., from the skeletal muscle and CNS) in lung organogenesis, in utero injections of two NTs were performed. The exogenously introduced NTs (i.e., non-lung-secreted) did not appear to improve development of the lung in amyogenic embryos. Moreover, immunohistochemistry showed significantly reduced number of airway smooth muscle cells (ASMCs) in hypoplastic lungs of amyogenic embryos, suggesting that the number of ASMCs is primarily regulated by the fetal breathing-like movements (i.e., mechanical factors). Histol Histopathol 21, 931-940 (2006)

Key words: Lung hypoplasia, Mouse embryo, Myf5 and MyoD, Neurotrophins, Smooth muscle cells

DOI: 10.14670/HH-21.931