Faculty : Departmental- Primary

Nevis L. Fregien, Ph.D.

Research in my laboratory focuses on understanding the molecular control of commitment, differentiation and replacement of ciliated epithelial cells in the airway. Every breath we take exposes our airway and lungs to noxious and pathogenic agents from the environment. A pseudostratified epithelium lining the respiratory tract provides the first line of defense. This epithelium contains many different cell types including ciliated, basal, goblet and Clara cells that work in concert to protect the airway by mucociliary clearance (MCC). Secretory cells emit sticky, viscous mucus that entraps invading particles while the wave-like beating of the cilia on ciliated cells propels the mucus with the trapped particles out of the airway. The ratio of secretory to ciliated cells is critical to ensure maximal MCC efficiency and a healthy airway. The balance of ciliated and secretory cells is established during embryogenesis. These cell types differentiate from common progenitors of the foregut endoderm during lung development. The time that cell fates are determined is not clear, but the differentiation of each cell type is most likely influenced by many factors including cell-cell interactions and growth factor signaling that modulate the expression of cell specific transcription factors and genes that carry out differentiated cell-specific functions. In many airway pathologies, including asthma and smoke exposure, the ratio of ciliated to secretory cells decreases and MCC efficiency decreases due to insufficient numbers of cilia to efficiently propel the increasing mucus layer and ensnared noxious particles out of the airway, resulting in the accumulation of mucus in the airway and disease progression. Understanding the molecular basis for the loss of ciliated cells is not fully understood, but minimizing or preventing ciliated cell loss could be of great therapeutic benefit.

My laboratory is focused on characterizing the molecular events that control the commitment, differentiation and regeneration of ciliated cells in the airway. Our studies are centered on the expression of the FoxJ1 gene. The expression of this gene is tightly controlled during ciliated cell differentiation, precedes the expression of the ciliated phenotype, and is required for ciliogenesis. We use primary normal human airway epithelial cells for these experiments because they can be de-differentiated and redifferentiated in vitro, using air:liquid interface culture conditions. We have recently found that FoxJ1 expression is linked to the formation of apical junctions. Based on these results, we propose a novel signaling pathway between junction formation and FoxJ1 transcription to control ciliogenesis.

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Figure 1. AJC formation in NHBE cells. Transwell cultures of NHBE cells were plated in BEGM medium. The next day, samples were fed :A, BEGM; B, ALI medium; and C, BEGM medium + 0.25 mM Ca2+. Cells were incubated overnight, fixed and AJC stained with anti-ZO-1 (Alexa 488, Green channel) and anti-FOXJ1 (Alexa 555, red channel). All micrographs were imaged with identical settings. ZO-1 is assembled into AJC upon a switch to high Ca2+ containing media. However, FOXJ1 expression is only detectable in the fully differentiated cells (panel D).

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Figure 2. Diagram of ciliated cell differentiation and loss of ciliated cells in disease.

Select Publications

Electronic Cigarettes Enhance Replication of Mycobacterium abscessus in Airway Epithelial Cells. Korukonda A, Zhang C, Rodriguez L, Guerrero A, Campos M, Holt G, Fregien NL, Conner G, Mirsaeidi M.Am J Respir Cell Mol Biol. 2019 Jun;60(6):717-719. doi: 10.1165/rcmb.2018-0339LE.PMID: 3114984

Modulation of Wnt signaling is essential for the differentiation of ciliated epithelial cells in human airways. Schmid A, Sailland J, Novak L, Baumlin N, Fregien N, Salathe M.Version 2. FEBS Lett. 2017 Nov;591(21):3493-3506. doi: 10.1002/1873-3468.12851. Epub 2017 Oct

Gefitinib, an EGFR Tyrosine Kinase inhibitor, Prevents Smoke-Mediated Ciliated Airway Epithelial Cell Loss and Promotes Their Recovery. Valencia-Gattas M, Conner GE, Fregien NL.PLoS One. 2016 Aug 17;11(8):e0160216. doi: 10.1371/journal.pone.0160216. eCollection 2016.PMID: 27532261

IL-13 Inhibits Multicilin Expression and Ciliogenesis via Janus Kinase/Signal Transducer and Activator of Transcription Independently of Notch Cleavage. Gerovac BJ, Fregien NL.Am J Respir Cell Mol Biol. 2016 Apr;54(4):554-61. doi: 10.1165/rcmb.2015-0227OC.PMID: 26414872

View published research articles by Dr. Fregien in the National Library of Medicine.