In vitro transcribed messenger RNA (IVT mRNA) represents an emerging platform technology that can be used for tissue repair by encoding growth factors such as fibroblast growth factor 7 (FGF7) which modulates epithelial repair in the skin and lung via the FGF receptor 2b (FGFR2b). FGFR2b expressing progenitor basal epithelial cells contribute to epithelial repair through self-renewal or differentiation and dysregulation of this process impairs regeneration of the injured epithelium. Therefore, exogenous FGF7 encoded mRNA may improve FGFR2b+ basal bronchial epithelial cell repair. Moreover, modification of IVT mRNA poly(A) tail length and untranslated regions (UTRs) can alter transcript stability and translation efficiency which are important determinants of IVT mRNA potency. This thesis first aimed to investigate the influence of poly(A) tail length and UTR modification on exogenous mRNA translation in human cells. Next, this thesis aimed to investigate the potential of exogenous FGF7 mRNA for basal bronchial epithelial cell repair.
Poly(A) tail length extension of IVT mRNA revealed that the presence of a poly(A) tail is crucial for reporter mRNA translation in human lung cells. Novel UTR modifications improved reporter mRNA translation better than mRNA without UTRs or with gold standard UTR modifications in primary human lung and skin cells. However, mRNA coding sequence was found to influence UTR performance and the same trends were not observed with UTR modified FGF7 mRNA in primary lung cell types.
Primary bronchial epithelial cells translated FGF7 mRNA following non-viral transfection despite not endogenously expressing FGF7. In addition, prophylactic application of FGF7 ameliorated epithelial monolayer scratch wound closure and attenuated injury associated cytotoxicity by upregulating endogenous expression of FGF7 mediated epithelial repair genes including RAC1, PIK3CA, and MAPK1/3.
Together, this thesis demonstrates the feasibility of UTR modification for enhanced mRNA translation and the potential of exogenous growth factor mRNA for the repair of lung epithelial cells.