Biocompatibility of porous polyethylene implants tissue-engineered by extracellular matrix and VEGF

Rapid ingrowth of blood vessels and low inflammatory response are considered major prerequisites for successful implantation of biomaterials in reconstructive surgery. Aim of the present study was to evaluate whether tissue-engineered porous polyethylene (PPE) implants providing extracellular matrix components (ECM) and vascular endothelial growth factor (VEGF) in vivo improve microvascular ingrowth and mechanical integration with regard to initial inflammatory responses. PPE implants (3 x 3 x 0.1 mm(3), pore size approximately 100-200 microm) were tissue-engineered by incorporation of ECM components (GFR-Matrigel) adding recombinant murine VEGF (1 microg/mL) and grafted into dorsal skinfold chamber preparations of C57BL/6 mice. Control animals received uncoated implants or implants coated with ECM components alone (n = 6 per group). Using in vivo fluorescence microscopy angiogenic activity and inflammatory leukocyte-endothelial cell interactions were analyzed for 2weeks. Finally, mechanical integration was quantified by measurement of dynamic desintegration strengths at the host-implant border. Functional vessel density, red blood cell velocity, and vessel diameters increased continuously in all groups indicating that rapid microvascular integration of PPE occurred even without incorporation of ECM or VEGF. However, a transient initial inflammatory response with increased leukocyte-endothelial cell adherence on day 7 in uncoated control implants was efficiently reduced by incorporation of ECM and VEGF. Measurement of dynamic breaking strengths revealed no significant differences between the groups although there was a tendency to improved mechanical integration in tissue-engineered implants. Therefore, novel tissue- engineered constructs of PPE implants providing ECM and VEGF in high local concentrations can increase biocompatibility especially under unfavorable conditions for implantation.