Anabolic Effects of Peniel 2000, a Peptide That Regulates TGF-β1 Signaling on Intervertebral Disc Degeneration

Abstract

An in vitro study with bovine intervertebral disc (IVD) cells and an in vivo study with a rabbit disc degeneration model on the extracellular matrix metabolism by a biglycan-derived peptide (Peniel 2000; P2K). To investigate the mechanism for P2K-induced increases in extracellular matrix and in vitro and in vivo effects of the peptide on IVD. Transforming growth factor-β (TGF-β) has a functional versatility on the metabolism of IVD cells, suggesting that the regulation of TGF-β signaling is important in IVD degeneration. P2K was explored by an in silico drug discovery strategy to regulate TGF-β signaling. The putative target of P2K was verified by Biacore 3000 analysis and affinity purification using biotin-P2K. A monolayer culture system of bovine IVD cells was used to demonstrate the mechanism underlying the anabolic effects of P2K. Smad signaling and extracellular matrix metabolism of the IVD cells were investigated by Western blot and reverse transcription-polymerase chain reaction, respectively. The in vivo effect of P2K on degenerated disc was investigated using a rabbit model of disc degeneration. In 14 New Zealand white rabbits, disc degeneration was induced by percutaneous annular punctures. After 4 weeks, 3 consecutive discs in the same animal were treated with 5% lactose or P2K per disc. Twelve weeks after the treatment, the regenerative activity in the disc was examined by radiography, magnetic resonance imaging, and biochemical and histological analyses. Direct binding of P2K to an active form of TGF-β1 was shown. Type II collagen and aggrecan were increased in TGF-β1/P2K-treated bovine IVD cells, compared with nontreated and TGF-β1-treated cells.In in vivo analysis, a single injection of P2K increased the disc height (P < 0.001) on the radiographs and improved the magnetic resonance imaging grade (P < 0.05) compared with controls. Biochemical analysis, showed a significant increase in PG content because of P2K treatment (P < 0.05). Histological analysis using disc degeneration grades demonstrated improvement in P2K-treated discs (P <0.01). A novel peptide, P2K, regulating TGF-β1 signaling had an anabolic effect on bovine IVD cells and rabbit degenerated discs. The results suggest that P2K has considerable potential as a treatment of degenerative disc disease.