Development of a mechanically stable support for the osteoinductive biomaterial COLLOSS E.

The application of bone graft substitutes with osteoinductive properties is of high importance for the repair of large bone defects. COLLOSS E, a protein lyophilizate extracted from equine long bones, exhibits an osteoinductive potential which has been proven in several studies. In this work, a mechanically stable, but biodegradable support for COLLOSS E has been developed aiming at a bone graft substitute that retains shape and size when coming in contact with body fluids. Mineralization of collagen type I, isolated from horse tendon, resulted in a stable collagen hydroxyapatite nanocomposite. By means of freeze drying, this composite was used to prepare 3D scaffolds which can be filled with the cotton-wool like COLLOSS E material. These scaffolds exhibit a porous microstructure and a good mechanical stability in dry and wet state. Cell culture experiments with human bone marrow stromal cells (hBMSC) revealed the cytocompatibility of the newly developed composite material. Cells were able to adhere, proliferate and differentiate into the osteoblastic lineage. The osteoinductive nature of COLLOSS E has been demonstrated by a significant higher activity of the osteogenic marker alkaline phosphatase (ALP) on combined scaffolds (mineralized collagen scaffolds filled with COLLOSS E) compared to pure scaffolds. The combination of COLLOSS E with scaffolds made of a collagen hydroxyapatite composite results in a synthetic bone graft substitute which can be completely remodelled into vital bone tissue opening an interesting new possibility for the therapy of bone defects.

Instrumented anterior lumbar interbody fusion with equine bone protein extract.

STUDY DESIGN: Randomized and self-controlled study with anterior lumbar interbody fusion in a porcine model. OBJECTIVE: To determine the osteoinductive potential of an equine bone protein extract in anterior interbody spinal fusion. SUMMARY OF BACKGROUND DATA: Interbody spinal fusion with bone graft transplantation is a common spine procedure. Complications related to bone graft harvesting are still a major concern. Equine demineralized bone matrix has been reported to be osteoinductive. However, the application of equine bone protein extract in spine fusion has not been documented. In this experiment, we evaluated equine bone protein extract in a porcine spinal fusion model. METHODS: Due to their size and availability, we chose 12 normal Danish landrace pigs, each weighing 50 kg, as our experimental animals. Lumbar spine interbody fusion of L3/4, L4/5 using titanium alloy cages and pedicle screws instrumentation was performed on each pig. Cages packed with either autograft or equine bone protein extract (COLLOSS E; OSSACUR AG, Oberstenfeld, Germany) were randomly assigned to the 2 levels anteriorly. The pigs were followed for 3 months. After sacrifice, radiograph, microcomputed tomography, and histomorphometry were used to evaluate the spine segments. RESULTS: All pigs went through the observation without major complications. Radiograph examination after 12 weeks revealed no implant breakage, loosening, or spinal deformity. Microcomputed tomography scanning showed that cages with COLLOSS E had the same fusion rate (11/12) as those with autograft. Three-dimensional evaluation from microcomputed tomography found a significant difference only in trabecular thickness; trabeculae from COLLOSS E-filled cages were much thinner (P = 0.04). Histologic evaluations demonstrated longitudinally formed bone trabeculae in both autograft and COLLOSS E-filled cages. Bone volume calculation from histomorphometry correlates well with that from microcomputed tomography results (R = 0.5; P = 0.01). CONCLUSION: In this porcine model, COLLOSS E is as effective as autograft for anterior spinal fusion.

Repair of sheep long bone cortical defects filled with COLLOSS, COLLOSS E, OSSAPLAST, and fresh iliac crest autograft.

COLLOSS and COLLOSS E are osteoinductive bone void fillers consisting of bone collagen and noncollagenous proteins from bovine and equine bone, respectively. The aim of this study was to compare COLLOSS, COLLOSS E, iliac bone autograft, sintered beta tricalcium phosphate (beta-TCP; OSSAPLAST), and COLLOSS E plus OSSAPLAST. Materials were placed for 4, 8, or 24 weeks in 5-mm cortical bone defects in sheep long bones. Histological sections in a plane perpendicular to the long axis of the bone were used to measure the total repair area (original defect plus callus) and the area of bone within the total repair area. The incidence of defect union was also evaluated. At 4 and 8 weeks, defects treated with COLLOSS and COLLOSS E with or without OSSAPLAST had total repair and bone areas equivalent to autograft, and larger than OSSAPLAST-treated defects. At 8 weeks, the incidence of defect union was higher in defects treated with autograft or COLLOSS E plus OSSAPLAST than in untreated defects. At 24 weeks, the incidence of union was 100% in all treatment groups and 0% in untreated defects. The incidence of union was related to the degree of remodeling between 8 and 24 weeks. This was greater in all treated than nontreated defects. In conclusion, COLLOSS and COLLOSS E were equivalent to each other and to autograft, and superior to beta-TCP, in this study model.

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.