At this dose, a significant amount of PDGF-BB was detected in the media for the duration of the cell culture period (9 days)

At this dose, a significant amount of PDGF-BB was detected in the media for the duration of the cell culture period (9 days). dose of PDGF-BB in the presence of the delivery system. In the presence of canine tendon fibroblasts, the delivery system prolonged the period of PDGF-BB release from fibrin matrices, thus demonstrating that cells are able to liberate PDGF-BB retained by the HBDS. Sustained delivery of PDGF-BB promoted increased cell proliferation at a dose of 0.125 and 1.25 g/mL compared to fibrin without delivery system. Collagen synthesis was enhanced by PDGF-BB at a dose of 0.125 and 1.25 g/mL, however there was an enhancement over fibrin without the delivery system only at the lower dose. == Conclusions == These results demonstrate that this PDGF-BB released from fibrin matrices made up of a HBDS is usually biologically active and can modulate both cell proliferation and extracellular matrix synthesis, both of which are key factors in the process of tendon repair. Keywords:drug delivery, fibrin, growth factor, tissue engineering == INTRODUCTION == Intrasynovial tendon injuries are at best risk of failure in the first three weeks after surgical repair due to repair-site rupture. Loss of function during flexor tendon healing of intact repairs is typically due to repair-site elongation or adhesion formation between the tendon surface and the digital sheath. Previous work has shown that controlled passive motion after repair is effective in reducing adhesion formation and maintaining digital range of motion (13). However, attempts to improve the strength of repair (and hence reduce repair-site elongation) by modifying rehabilitation variables have been unsuccessful, as the immature repair site has failed to respond to increasing levels of appliedin vivoload (47). Clinical and experimental Rabbit Polyclonal to c-Met (phospho-Tyr1003) studies have suggested that future strategies for accelerating the repair process be directed toward altering the biological environment of the sutured tendon (820). Growth factors have been shown to be powerful regulators of biological function and their presence in tissues is usually highly regulated in both time and space. We hypothesized that controlled delivery of growth factors may enhance tendon fibroblast proliferation and extracellular matrix synthesis. This could accelerate tendon healing and reduce the risk of tendon repair-site elongation and rupturein vivo. Patterns of various growth factors, such as platelet-derived growth factor BB (PDGF-BB), basic fibroblast growth factor (bFGF), transforming growth factor 1, and vascular endothelial growth factor, vary dramatically over the time course of tendon healing (21). However, the endogenous factors released during the process of repair have been insufficient to restore the tendons structural characteristics in the first few weeks following injury. Manipulation of the repair environment of dense regular connective tissues through the use of exogenous growth factor delivery from drug delivery systems has shown promise Ginsenoside Rb2 for stimulating collagen synthesis Ginsenoside Rb2 and increasing the stiffness and strength of the repair site. Further, previous authors have noted substantial improvement when growth factor release is maintained for a prolonged period of time during healing (812,14,19,2224). In our previous reports we showed that: 1) PDGF-BB stimulates flexor tendon fibroblast proliferation and collagen synthesisin vitro(24), 2) sustained delivery of PDGF-BB in repaired flexor tendons improves range of motion(25),and 3) sustained delivery of PDGF-BB in repaired flexor tendons promotes collagen synthesis and cell proliferation(26). However, we did not demonstrate an increase in repair site strength due to PDGF-BB. The lack of improvement in repair site strength with PDGF-BB treatment may have been due to sub-optimal release kinetics and/or growth factor dosage. Based on these studies, we chose to comprehensively characterize the release kinetics and the biologic activity of PDGF-BBin vitro.To manipulate the release characteristics of the growth factor, we chose a fibrin matrix as the scaffold for the delivery system and a heparin-based delivery system (HBDS) to sequester the PDGF-BB and control its release over a two week period. We have previously used this delivery system for controlled delivery of bFGF and neurotrophins to promote neurite extension and nerve regeneration in the rat following sciatic nerve injury or spinal cord injury (2729). In the current study, we examine both the range of conditions over which delivery of PDGF-BB can be modulated using this HBDS, as well as the biological effect Ginsenoside Rb2 that PDGF-BB, released from this system, has on canine tendon fibroblastsin vitro.Our goal.