Ion transport across CF and normal murine olfactory and ciliated epithelium

Abstract

The nasal epithelium of the cystic fibrosis (CF) mouse has been used extensively in CF research because it exhibits ion transport defects similar to those of human CF airways. This tissue is composed of approximately 50% olfactory (OE) and approximately 50% ciliated epithelium (CE), and on the basis of previous observations, we hypothesized that a significant fraction of the bioelectric signals from murine nasal tissue may arise from OE rather than CE, while CE is the target tissue for CF gene therapy. We compared the bioelectric properties of isolated OE from the nasal cavity and CE from the nasopharynx in Ussing chamber studies. Hyperabsorption of Na(+) [amiloride response; CF vs. wild type (WT)] was approximately 7.5-fold greater in the OE compared with the CE. The forskolin response in native tissues did not reliably distinguish genotypes, likely due to a cyclic nucleotide-gated cation conductance in OE and a calcium-mediated Cl(-) conductance in CE. By potential difference assay, hyperabsorption of Na(+) (CF vs. WT) and the difference in response to apical 0 Cl(-) buffer (CF vs. WT) were approximately 2-fold greater in the nasal cavity compared with the nasopharynx. Our studies demonstrate that in the CF mouse, both the hyperabsorption of Na(+) and the Cl(-) transport defect are of larger magnitude in the OE than in the CE. Thus, while the murine CF nasal epithelium is a valuable model for CF studies, the bioelectrics are likely dominated by the signals from the OE, and assays of the nasopharynx may be more specific for studying the ciliated epithelium.

Inhaled phosphodiesterase type 5 inhibitors restore chloride transport in cystic fibrosis mice

“…This finding highlights the nasal PD in mouse as a valuable tool to evaluate efficacy of fundamental pharmacological therapies in CF. As the olfactory epithelium in CF mice shows progressive, age-related morphological and functional losses [21], the changes we observed in adult CF mice after treatment with PDE5 inhibitors are not expected to reflect olfactory epithelium modifications.…”

“…The nasal mucosa of our F508del mouse model [10] has proven to be valuable for studying novel therapeutic strategies that aim at activating chloride and/or sodium transport function [7,14]. Recently, concerns on the relevance of the murine nasal mucosa as a human-equivalent model have emerged [21]. These concerns are based on the presence of differential proportions of various cell types constituting the mouse and the human nasal epithelium [22] and, subsequently, on different functional roles played by each cell population subset.…”

“…In contrast, in humans, respiratory epithelium lines the large majority of the nasal cavity with only ,3% of the nasal surface being covered by olfactory epithelium [23]. Therefore, attention has been drawn to the issue that assessing respiratory transepithelial ion transport in the nose of mouse, as during nasal PD measurements, may possibly integrate the contribution of the olfactory neuroepithelium in the generation of bioelectrical signals [21]. We confirmed here that the nasal PD in mouse can be directed at the respiratory epithelium with high density of ciliated epithelial cells found at the site of nasal PD measurement.…”

Human Alveolar Type II Cells Secrete and Absorb Liquid in Response to Local Nucleotide Signaling

“…Ion Transport Measurements-Ussing chamber studies were performed on human AT2 cultures under basal conditions or after the addition of designated reagents under open circuit conditions (27). Basal potential difference (PD) and changes in response to each added reagent were measured, and the equivalent short circuit (I eq ) was calculated as previously described (27,28).…”

Synchrotron phase-contrast X-ray imaging reveals fluid dosing dynamics for gene transfer into mouse airways

“…This novel lung airway-like site could potentially be used for modeling the effects of gene vectors or drugs on ciliated airway function within a tubular lung-like conducting airway, an option identified by others in related studies of mouse nasal electrophysiological function. 23 It should be noted that once fluid reaches the nasopharynx in sufficient volume to fill the airway diameter it is possible for retrograde fluid movement into the contralateral anterior nasal airway due to normal breathing or "sneezing" reactions that produce fluid movement into otherwise un-dosed airway regions.…”