The pentapeptide KTTKS promoting the expressions of type I collagen and transforming growth factor-β of tendon cells

Pentapeptide KTTKS, a subfragment of type I collagen propeptide, has been demonstrated to promote the extracellular release of collagen in fibroblasts. The present study was designed to investigate the effect and molecular mechanism of KTTKS on type I collagen expression of rat Achilles tendon cells. Genes related to the upregulation of collagen expression such as transforming growth factor-β (TGF-β), and mRNA-binding proteins (mRBP) E1 and K were also examined. MTT assay revealed cell viability was not affected by KTTKS treatment. Protein expression of type I collagen was determined by immunocytochemistry and Western blot analysis. Results showed that KTTKS induced type I collagen expression of tendon cells. The mRNA expressions of α1(I) procollagen, TGF-β, mRBP K, as determined by reverse transcription-polymerase chain reaction (RT-PCR), were also enhanced after KTTKS treatment. The stability of preexisting α1(I) procollagen mRNA after the addition of α-amanitin was analyzed by RT-PCR at 24 and 48 h. Results showed that KTTKS slowed down the degradation of α1(I) procollagen mRNA (p = 0.021). Furthermore, the concentration of TGF-β in conditioned medium, as determined by enzyme-linked immunosorbent assay, increased dose dependently in cells treated with KTTKS (p = 0.001). In conclusion, KTTKS promotes the expression of type I collagen and maintains its mRNA stability in a process associated with the upregulation of TGF-β.