Hylaluronan-based heparin-incorporated hydrogels for generation of axially vascularized bioartificial bone tissues : in vitro and in vivo evaluation in a PLDLLA-TCP-PCL-composite system

摘要

Smart matrices are required in bone tissueengineeredudgrafts that provide an optimal environment forudcells and retain osteo-inductive factors for sustained biologicaludactivity. We hypothesized that a slow-degradingudheparin-incorporated hyaluronan (HA) hydrogel can preserveudBMP-2; while an arterio–venous (A–V) loop canudsupport axial vascularization to provide nutrition for a bioartificialudbone graft. HA was evaluated for osteoblastudgrowth and BMP-2 release. Porous PLDLLA–TCP–PCLudscaffolds were produced by rapid prototyping technologyudand applied in vivo along with HA-hydrogel, loaded withudeither primary osteoblasts or BMP-2. A microsurgicallyudcreated A–V loop was placed around the scaffold, encasedudin an isolation chamber in Lewis rats. HA-hydrogel supportedudgrowth of osteoblasts over 8 weeks and allowedudsustained release of BMP-2 over 35 days. The A–V loopudprovided an angiogenic stimulus with the formation ofudvascularized tissue in the scaffolds. Bone-specific genesudwere detected by real time RT-PCR after 8 weeks.udHowever, no significant amount of bone was observedudhistologically. The heterotopic isolation chamber in combinationudwith absent biomechanical stimulation mightudexplain the insufficient bone formation despite adequateudexpression of bone-related genes. Optimization of theudinterplay of osteogenic cells and osteo-inductive factorsudmight eventually generate sufficient amounts of axiallyudvascularized bone grafts for reconstructive surgery.