Cystic Fibrosis Human Organs-on-a-Chip

Abstract

Cystic fibrosis (CF) is an autosomal recessive disease caused by mutations in the cystic fibrosis transmembrane regulator (CFTR) gene: the gene product responsible for transporting chloride and bicarbonate ions through the apical membrane of most epithelial cells. Major clinical features of CF include respiratory failure, pancreatic exocrine insufficiency, and intestinal disease. Many CF animal models have been generated, but some models fail to fully capture the phenotypic manifestations of human CF disease. Other models that better capture the key characteristics of the human CF phenotype are cost prohibitive or require special care to maintain. Important differences have been reported between the pathophysiology seen in human CF patients and in animal models. These limitations present significant limitations to translational research. This review outlines the study of CF using patient-derived organs-on-a-chip to overcome some of these limitations. Recently developed microfluidic-based organs-on-a-chip provide a human experimental model that allows researchers to manipulate environmental factors and mimic in vivo conditions. These chips may be scaled to support pharmaceutical studies and may also be used to study organ systems and human disease. The use of these chips in CF discovery science enables researchers to avoid the barriers inherent in animal models and promote the advancement of personalized medicine.

Keywords: CFTR; cystic fibrosis; organ-on-a-chip; personalized medicine.

Figure 1

Classification of CFTR mutations. A schematic showing six categories of CFTR mutations [4].

Figure 2

Microfluidic-based organ-on-a-chip. (A) Schematic showing a protocol of standardized photolithography and soft lithography techniques to fabricate a microfluidic device [55]. Patient-derived lung airway epithelial cells obtained from CF (F508del/F508del) and non-CF donors (B), pancreatic ductal epithelial cells (C) [55], aggregated pancreatic islets (D) [55], and aggregated acinar cells (E) were cultured in microfluidic devices and monitored for CFTR function (B`–C` [55]) using an iodide efflux assay. Insulin (D`) [55] and amylase secretion (E`) are also shown. To help cell attachment in the channel, the cells were coated with collagen prior to seeding. (ELISA analysis with p-values: ** < 0.005; number of samples: n = 3; Data represented as mean ± SD).

Figure 3

Generating a smart PDMS by modifying a hydrophobic PDMS surface. PDMS is a highly hydrophobic material (A). When the PDMS surface is exposed to oxygen plasma for 30 s, it becomes highly hydrophilic (contact angle = 13.3°). It returns to a hydrophobic status within 3 days (B; black dotted line). However, the polyvinyl alcohol (PVA) coated PDMS surface maintained a hydrophilic status for over 3 months ((B); red solid line). (p-values: * <0.05, ** <0.005, *** <0.0005; number of samples: n = 3 in each condition; data represented as mean ± SD).

Figure 4

Schematic of lung-on-a-chip models to represent the unique microenvironments throughout the respiratory tract. Four separate microfluidic devices represent four functionally distinct regions of the lung. The alveoli are lined by epithelial type II cells (arrowhead) and type I cells (arrow) that are in close proximity to the endothelial cells lining the capillaries containing red blood cells (*). Each lung-on-a-chip model contains different epithelial cell types specialized for region specific functions with distinct cell populations in the subepithelial compartment to mimic the unique cell–cell interactions seen in spatio-regionally distinct lung microenvironments.

Figure 5

In vitro co-culturing model, pancreas-on-a-chip [55]. The pancreas-on-a-chip is composed of two cell culture chambers and a thin layer of porous membrane. Patient-derived pancreatic ductal epithelial cells were plated in the top chamber and polarized on the porous membrane over 4 days. By adding patient-derived islets in the bottom chamber, it mimics the in vivo structure.

Figure 6

In vitro co-culturing model, gut-on-a-chip. (A) A schematic representation of human intestinal mucosa with associated vasculature. (B) A novel gut-on-a-chip model was designed to mimic the in vivo structure of the human intestinal mucosa. This system allows researchers to co-culture intestinal epithelial cells and endothelial cells in the same chip.