High-efficiency production of bioactive recombinant human type III collagen in transgenic silkworm cocoons

Collagen, a crucial structural protein in the extracellular matrix (ECM), exhibits exceptional biocompatibility with broad applications in biomedicine and cosmetics, of which type III collagen exhibits ubiquitous distribution across crucial tissues including vasculature and skin, where it performs essential physiological functions. However, high-efficiency production of bioactive recombinant human type III collagen (rhCOLIII) remains challenging. This study developed an effective strategy for synthesizing functional rhCOLIII in genetically engineered silkworms, which was driven by fibroin heavy chain (FibH) expression system, making rhCOLIII specifically expressed in the posterior silk gland (PSG) of silkworms. Moreover, rhCOLIII was successfully secreted into the cocoons at the yield of 7.8 mg/g cocoon shell weight. RNA-seq analysis revealed that differentially expressed genes (DEGs) enriched predominantly in endoplasmic reticulum protein processing pathways. Notably, the purified rhCOLIII protein exhibited excellent cytocompatibility and significantly promoted cell proliferation and migration of NIH/3T3, indicating its potential for accelerating wound healing. Additionally, the commercially important traits of the silkworms also remained unchanged, while the existence of rhCOLIII significantly improved the extensibility and toughness of silk fibers. These findings establish the silkworm bioreactor as a viable platform for high-efficiency production of bioactive rhCOLIII and provide a strategy for synthesizing other functional recombinant proteins.