Keratinocyte growth factor-induced proliferation of rat airway epithelium is restricted to Clara cells in vivo

Abstract

Keratinocyte growth factor-induced proliferation of rat airway epithelium is restricted to Clara cells in vivo. H. Fehrenbach, A. Fehrenbach, T. Pan, M. Kasper, R.J. Mason. #ERS Journals Ltd 2002. ABSTRACT: Keratinocyte growth factor (KGF) is a potent mitogen of pulmonary bronchial and alveolar epithelial cells. However, it is unclear which type(s) of airway epithelial cells (AEC) proliferate(s) in response to KGF.AEC proliferation was induced in rats by either endobronchial instillation of 5 mg recombinant human (rHu) KGF per kg body weight or by adenoviral transfer of the human KGF gene (Ad5-HuKGF). Alterations in terminal airway AEC were followed for up to 7 days after rHuKGF, and for up to 28 days after Ad5-HuKGF.Cell proliferation, as assessed by immunohistochemistry (IHC) for incorporated 5-bromo-29-deoxyuridine (BrdU) and quantified by stereology, peaked at days 1-2 and was resolved by day 7 after rHuKGF and by day 21 after Ad5-HuKGF. Double immunofluorescence labelling for BrdU or Ki-67 on the one hand, and for Clara cell specific protein 10 (CC10) and calcitonin-gene related peptide on the other hand, demonstrated that Clara cells, not pulmonary neuroendocrine cells, proliferated in response to human KGF. TUNEL (terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labelling) method in conjunction with IHC for MNF116 failed to detect significant numbers of apoptotic AEC. IHC in conjunction with stereology revealed transient phenotypic alterations with a decrease in CC10, an increase in surfactant protein D and an increase in CD44v6 in AEC.The authors conclude that Clara cells responded to human keratinocyte growth factor in vivo by proliferation as well as by changes in protein expression, whereas no significant response was observed in pulmonary neuroendocrine cells. As Clara cells are intimately involved in airway epithelial repair, ion and fluid transport, and modulate lung inflammation, the potential of human keratinocyte growth factor to protect the lung may in part rely on the response of Clara cells.

Keratinocyte growth factor protects against Clara cell injury induced by naphthalene

“…Human recombinant KGF was shown to stimulate DNA synthesis and proliferation of human bronchial epithelial cells in vitro and of rat and mouse airway epithelium in vivo. It has previously been demonstrated that the KGF-induced stimulation of distal airway epithelial proliferation was restricted to Clara cells, and peaked between days 1 and 2 following intratracheal instillation of KGF into rat lungs in vivo [17]. In the present study, a similar strong induction of mouse Clara cell proliferation in response to exogenous DN23-KGF was observed, as evidenced by both PCNA immunohistochemistry and quantitative real-time RT-PCR for detection of PCNA mRNA expression.…”

“…In rats, the decrease in CC10 mRNA levels appeared to be due to decreased expression per cell, as assessed by in situ hybridisation [34]. Correspondingly, CC10, assessed by quantitative immunohistochemistry, exhibited decreased immunoreactivity per cell in distal rat airway epithelium [17]. In response to intratracheal administration of exogenous KGF in vivo, a quantitative shift from Clara cells exhibiting normal strong staining for CC10 to them exhibiting weak immunoreactivity for CC10 was observed.…”

“…As described previously [17], cross-sections of airways 2 mm in thickness were deparaffinised in xylene and rehydrated in ethanol and PBS. Endogenous peroxidase activity was inactivated using 1% hydrogen peroxide in methanol (Roth, Karlsruhe, Germany; pH 7.2) for 30 min.…”

“…Knowledge is much more limited with regard to the role of KGF in acute airway epithelial injury and repair. KGF was demonstrated to be important for the detoxification of reactive oxygen species [16], and to enhance proliferation in airway cells [17]. Administration of KGF was shown to protect against radiation-induced increases in airway epithelial barrier permeability [18], exert protective effects against oxidant injury [19] and limit allergen-induced alterations in airway epithelial integrity [20].…”

Keratinocyte growth factor and the transcription factors C/EBPα, C/EBPδ, and SREBP-1c regulate fatty acid synthesis in alveolar type II cells

“…The vectors were linearized with EcoRI and transcribed using T7 polymerase for sense control riboprobes. Riboprobes were transcribed with [ 33 P] UTP as described previously (15). Hybridization with radiolabeled sense riboprobes was done as a control.…”