Treatment with
recombinant human deoxyribonuclease I (
rhDNase) is currently used as
therapy for
cystic fibrosis (CF)
lung disease. Hypertonic saline (HS) acts as an
expectorant promoting mucus secretion and augmenting the volume of sputum. We evaluated the individual and combined effects of HS and
rhDNase in vitro on the viscoelasticity of CF sputum. Sputum samples were collected from nine CF patients to use for in vitro testing. Aliquots of CF sputum (0.20 to 0.40 g) were subjected to the following protocols: (1) negative control sample without any treatment; (2) positive control sample, adding 10% volume of
normal saline (
0.9% NaCl); (3) application of hypertonic saline (
HS-3% NaCl); (4) combining approximately 100 nM concentration of
rhDNase with protocols 2 and 3. The samples in protocols 2 through 4 were incubated for 30 min at 37 degrees C. For each protocol, CF sputum was analyzed at baseline and at 30 min for spinnability by filancemeter and viscoelasticity by magnetic microrheometry. Spinnability decreased for the sputum samples that were treated with
rhDNase, in combination with either HS or
normal saline. Treatment with HS alone and combined treatment with
rhDNase and HS decreased log G* (the principal viscoelasticity index) to the same degree. Saline alone and
rhDNase in
normal saline both increased the predicted
cough clearability of the sputum; however, the combined treatment with
rhDNase and hypertonic saline had the best overall effect on
cough clearability. The change in predicted mucociliary clearability, although greatest after HS, was not significant. These in vitro results suggest that combined treatment with
rhDNase and HS should be evaluated further as a potential mucotropic approach to augment the clearance of purulent sputum in CF
lung disease.