Postnatal lung development of rhesus monkey airways: cellular expression of Clara cell secretory protein

Clara cell secretory protein (CCSP) is a protective lung protein that is believed to have antioxidant, immunomodulatory, and anticarcinogenic properties. Evidence suggests that CCSP is involved in mitigating many lung disease states during development including asthma. This study's rationale is to define the distribution and abundance of CCSP in the airway epithelium of the rhesus monkey during postnatal lung development using carefully controlled site-specific morphometric approaches in defined airway regions. Immunoreactive CCSP was found in nonciliated cells and mucous cells, including glands, throughout the airway epithelium at all ages, with proximal and mid-level airways having the highest labeling. Overall airway CCSP levels were low at 1 week and 1 month, doubled between 1 and 3 months, and changed little from 3 months to 3 years. Thus, the critical developmental window for CCSP expression to reach adult levels in the rhesus conducting airways occurs between 1 and 3 months of age.