Repair of bone defect by using vascular bundle implantation combined with Runx II gene-transfected adipose-derived stem cells and a biodegradable matrix.

A large hurdle in orthopedics today is the difficulty of dealing with the non-union of fractured bones. We therefore evaluated the effects of runt-related transcription factor II (Runx II), a factor used to create gene-modified tissue-engineered bone, combined with vascular bundle implantation for repairing segmental bone defects. Adenovirus Runx II gene (Ad-Runx II)-modified rabbit adipose-derived stem cells (ADSCs) were seeded onto polylactic acid/polycaprolacton (PLA/PCL) scaffolds to construct gene-modified tissue-engineered bone. The following four methods were used for repair in rabbit radial-defect (1.5 cm long) models: gene-modified tissue-engineered bone with vascular bundle (Group A), gene-modified tissue-engineered bone (Group B), non-gene-modified tissue-engineered bone with vascular bundle (Group C), and PLA/PCL scaffolds only (Group D). X-ray, histological examination, biomechanics analysis, and micro-angiography were conducted 4, 8, and 12 weeks later to determine angiogenesis and osteogenesis. The volume and speed of production of newly formed bones in Group A were significantly superior to those in other groups, and de-novo vascular network circulation from the vessel bundle through newly formed bone tissue was observed, with the defect being completely repaired. Group B showed a slightly better effect in terms of speed and quality of bone formation than Group C, whereas the bone defect in Group D was replaced by fibrous tissue. The maximal anti-bending strength in Group A was significantly higher than that in the other groups. Runx II gene therapy combined with vascular bundle implantation thus displays excellent abilities for osteoinduction and vascularization and is a promising method for the treatment of bone non-union and defect.