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[rhDNase: scientific background, cloning and production]
1Pulmonary research, South San Francisco, CA 94080, USA.
Abstract:
Despite the hopes raised by the first attempts in gene therapy, direct correction of the defect in CFTR protein associated with cystic fibrosis is still beyond clinical reach. Therefore we have to set upon the consequences of the defect. Respiratory distress and progressive lung destruction in cystic fibrosis can be accounted for by infectious exacerabations and the accumulation of viscous purulent secretions in the airways. For a long time we have known that purulent secretions that accumulate in the airways of patients with cystic fibrosis contain large amounts of DNA, a complex macromolecule that contributes mostly to the viscosity and hinders the mucociliary function. Hence we hypothesized that enzymatic cleaving of DNA molecules by desoxyribonuclease (DNase) should reduce the viscosity of sputum, and slow or prevent the deterioration of pulmonary function. Using the techniques of molecular biology and genetic engineering, we identified the gene of human DNase I, which was cloned in mammalian cells to produce large amounts of a glycosylated protein for therapeutic use. Catalytic amounts of rhDNase greatly reduce the viscosity of purulent cystic fibrosis sputum, transforming it within minutes from a nonflowing viscous gel to a flowing liquid. This effect was associated with a decrease in size of DNA fragments in the sputum. Our studies suggested that inhalation of a rhDNase aerosol might be a simple direct approach to reduce the viscosity of purulent secretions and thereby help patients with cystic fibrosis clear their airways and breathe more easily.
Insights
Recombinant human deoxyribonuclease (rhDNase) thins cystic fibrosis mucus by breaking down DNA. This enzyme therapy helps patients clear airways and breathe easier, offering a new treatment approach.
Area of Science:
- Biochemistry
- Molecular Biology
- Pulmonology
Context:
- Cystic fibrosis (CF) involves defective CFTR protein, leading to respiratory distress and lung damage.
- Airway secretions in CF patients are viscous due to accumulated DNA, impairing mucociliary function.
- Gene therapy for direct CFTR correction remains clinically challenging.
Purpose:
- To investigate the potential of enzymatic DNA cleavage to reduce sputum viscosity in cystic fibrosis.
- To develop a therapeutic approach targeting the consequences of the CFTR defect.
Summary:
- Human deoxyribonuclease I (DNase) gene was identified and cloned for therapeutic production of recombinant human DNase (rhDNase).
- rhDNase effectively reduces the viscosity of purulent CF sputum by cleaving DNA molecules.
- Treatment transforms viscous sputum into a flowing liquid, decreasing DNA fragment size.
Impact:
- Inhaled rhDNase aerosol offers a direct method to improve airway clearance in cystic fibrosis patients.
- This approach may slow pulmonary function deterioration by reducing mucus viscosity.
- rhDNase therapy provides a novel strategy to alleviate respiratory symptoms in CF.