Reindeer bone extract can heal the critical-size rat femur defect

Abstract

Bone extract from reindeer induces new ectopic bone formation (BF) in muscle pouches, but its feasibility in experimental bone lesions has not been evaluated. We investigated the effects of implants, containing 2, 5, 15, 20 or 50 mg of reindeer bone extract in a collagen carrier, on the healing of 8-mm femur defects in 78 rats. We used 30 µg of recombinant human bone morphogenetic protein-2 (rhBMP-2) in a collagen carrier, collagen and untreated defects as controls. Bone healing was evaluated with radiographs, peripheral quantitative computed tomography (pQCT), biomechanics and histology. In comparison with empty defects, the groups receiving bone extracts showed more BF at three weeks and had better bone union (BU), larger mean cross-sectional bone area at the defect site in groups receiving higher doses of extract, showed greater torsional stiffness of the bones and higher maximum breaking load of bones at six weeks. In comparison to all other groups, in the rhBMP-2 group, BF and BU were best at the three- and six-week follow-up, bone area was largest and mechanical test results were best. Although rhBMP-2 is superior for new bone regeneration, native reindeer bone extract is also effective in the six-week follow-up period.

Fig. 1

Radiographs showing new BF induced by different amounts of reindeer bone extract in the rat femur after 6 weeks follow-up. a 2 mg of bone extract, b 5 mg of bone extract, c 15 mg of bone extract, d 20 mg of bone extract, e 50 mg of bone extract, f 30 µg of rhBMP-2, g collagen, h untreated defect

Fig. 2

Histological examination showing quality of new bone induced by different amounts of reindeer bone extract in the rat femur after 6 weeks follow-up. a 2 mg of bone extract, b 5 mg of bone extract, c 15 mg of bone extract, d 20 mg of bone extract, e 50 mg of bone extract, f 30 µg of rhBMP-2, g collagen, h untreated defect. OB old bone, F fibroblastic tissue, CC zone of calcified cartilage, B newly formed bone trabeculae, BM bone marrow. (Original magnification ×10, figures are representative images)