Transdermal peptide conjugated to human connective tissue growth factor with enhanced cell proliferation and hyaluronic acid synthesis activities produced by a silkworm silk gland bioreactor.

Human connective tissue growth factor (CTGF) is a secreted cysteine-rich peptide that stimulates cell proliferation, migration, and extracellular matrix production during tissue development, differentiation, angiogenesis, implantation, wound healing, and fibrosis processes, with broad application in the medical and cosmetic medical fields. However, the production of CTGF is currently limited by its low yield and purity in current bioreactors. In this study, two genetically modified silkworm strains were generated harboring artificially designed CTGF-8ht and pepCTGF-8ht genes, respectively, that contain an enhanced His-tag with eight histidine residues with or without a transdermal peptide (pep). Both recombinant CTGF-8ht and pepCTGF-8ht proteins were successfully expressed in the silkworm silk gland and cocoon, and could be easily extracted and purified from the cocoon by single-affinity immunoprecipitation column chromatography, achieving a purity of more than 95%. Moreover, compared with CTGF-8ht protein, pepCTGF-8ht protein exhibited better cell proliferation activity by activating the extracellular signal-regulated kinase (ERK) pathway and enhanced hyaluronic acid synthesis activity by upregulating hyaluronan synthase 3 expression; moreover, the addition of pep significantly improved the transmembrane ability of CTGF-8ht protein. These results should help to promote the application prospects of CTGF and further guide the design and development of protein drugs from silkworm and other bioreactor systems. KEY POINTS : A silkworm bioreactor was optimized to produce connective tissue growth factor (CTGF) The transgene contained an enhanced 8-His-tag and transmembrane peptide (pep) Recombinant CTGF was easily purified with maintained or higher biological activity.