IN-VIVO NASAL POTENTIAL DIFFERENCE - TECHNIQUES AND PROTOCOLS FOR ASSESSING EFFICACY OF GENE-TRANSFER IN CYSTIC-FIBROSIS

Cystic fibrosis (CF) is a monogenetic disease that is associated with chronic airways disease and early death, The pulmonary disease reflect s mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, and associated abnormal epithelial ion transport, includ ing defective cAMP-mediated (CFTR) Cl- secretion and an accelerated ra te of basal Na+ transport, With the development of vectors for gene th erapy, the airway epithelium of CF patients has been targeted for stud ies of gene transfer, The biological efficacy of gene transfer of the normal CFTR cDNA into CF respiratory epithelia can be assessed by in v ivo measurements of the transepithelial potential difference (PD), a p arameter of ion transport that reflects the expression and function of CFTR, This paper describes techniques that can be used to discriminat e in vivo between the ion transport phenotype of normal subjects and p atients with cystic fibrosis, Protocols are outlined to allow assessme nt of individual components of the electrolyte transport phenotype, i. e., the magnitude of the basal and cAMP-mediated (CFTR) Cl- secretion, and the rate of Na+ transport, The physiologic basis of the protocols and important technical features of these measurements are defined, I f performed properly, the in vivo nasal PD technique clearly discrimin ates between normal subjects and cystic fibrosis patients, and can yie ld estimates of the biological efficacy of gene transfer to achieve co rrection of the electrolyte transport defects in CF patients.