Ectopic bone induction by equine bone protein extract.

Demineralized bone matrix from horse has been reported to be osteoinductive. However, its performance was inferior to autogenous bone graft in terms of new bone formation. In the present experiment, an equine bone protein extract-COLLOSS E was investigated for its osteoinductivity in a rat model. At the mean time, carboxymethyl-cellulose (CMC) was tested as a potential carrier for the protein extract. 18 male Wistar rats (8 weeks) were employed in the experiment. Each rat was implanted randomly with the 2 of the following implants, one on each side of the abdominal muscle. 1) COLLOSS E lyophilisate. 2) PEEK ring holder. 3) 3% or 10% CMC .in gel or lyophilized form 4) COLLOSS E lyophilisate with 3% CMC, implanted as gel or in lyophilized form. 5) COLLOSS E suspension with 10% CMC, implanted as gel or in lyophilized form. The rats were followed up for 21 days. After termination, samples were subjected to macroscopic examination, plain radiograph, micro-CT and histological evaluations. The results showed that PEEK ring or CMC alone could not induce ectopic bone formation. COLLOSS E lyophilisate has a slightly higher (6 out of 7) positive bone formation rate over COLLOSS E/3% CMC (3 out of 5, both gel and lyophilized form), however, the difference is non-significant (p=0.36, Fisher's exact test). 10% CMC with COLLOSS E did not show ectopic bone formation when implanted as gel form (0/8), while 1 positive bone formation was found when implanted as the lyophilized form (1/4). Bone tissue volume ranged from 0 mm(3) to 23.1mm(3) for COLLOSS-E lyophilisate alone and 0 to 29.7mm(3) for COLLOSS E/3%CMC (gel or lyophilized form). We concluded that equine bone protein extract has the ability to induce ectopic bone formation in the rat model. CMC could be a potential carrier, however, further studies are needed to verify the proportion and efficacy.