Inhibition of type I procollagen production by tRNA^Val CTE-HSP47 ribozyme

Background: Fibrosis characteristically occurs in the advanced stages of chronic inflammatory diseases, occasionally as the primary lesion, and frequently determines the disease prognosis. Fibrotic lesions consist mostly of collagen, and therefore it may be possible to prevent or treat fibrosis by inhibiting collagen production. Of the currently available therapeutic approaches, however, none is sufficiently effective and specific for inhibition of collagen. Heat shock protein 47 (HSP47) is a collagen-specific molecular chaperone that has been reported to play a pivotal role in secretion of procollagen molecules. Therefore, we have tried to suppress its function to inhibit these various types of collagen. Methods: We have developed a novel type of ribozyme by ligating a hammerhead sequence to a tRNA^Val promoter to facilitate displacing the ribozyme from nucleus to cytoplasm and to constitutive transport element, a binding motif of helicase which unwinds mRNA to render the target sequence on the mRNA accessible to the ribozyme. Results: The ribozyme thus constructed showed strong activity to cleave HSP47 mRNA and suppress the secretion of type I procollagen in the human primary fibroblast. Conclusion: We suggest applicability of this ribozyme as a new modality for antifibrosis therapy.