Radiomorphometry and biomechanical assessment of recombinant human bone morphogenetic protein 2 and polymer in rabbit radius ostectomy model

The study objective was to determine the mechanical integrity and radiopacity of regenerated bone within critical-sized defects (CSDs) in radii of rabbits using recombinant human bone morphogenetic protein 2 (rhBMP-2) with a porous, biodegradable poly(D,L-lactic acid) (PDLLA) carrier (designated PLA). Twenty millimeter, unilateral radial ostectomies were created in 96 skeletally mature New Zealand white rabbits. The rabbits were randomly assigned to six treatment groups with two euthanasia periods. Treatment groups included unfilled defect (n = 8), segmental autograft (n = 8), PLA + 0 microg rhBMP-2 (n = 8), PLA + 17 microg rhBMP-2 (n = 8), PLA + 35 microg rhBMP-2 (n = 8), and PLA + 70 microg rhBMP-2 (n = 8). The radiopacity was significantly greater for the 35- and 70-microg rhBMP-2 groups at 4 weeks compared to unfilled controls, PLA only, and 17-microg rhBMP-2 groups and equivalent to the autograft. At 8 weeks all groups receiving rhBMP-2 were equivalent to the autograft and significantly greater than unfilled defects and PLA alone. Similarly, the biomechanical analysis indicated significantly greater torque at failure for the 35-microg rhBMP-2 group compared to all other groups at 4 weeks. By 8 weeks all groups receiving rhBMP-2 and autograft had significantly greater torque than unfilled controls and PLA alone. These radiomorphometric and biomechanical results indicate PLA may be a suitable carrier for rhBMP-2 used for skeletal regeneration.

Recombinant human bone morphogenetic protein-2 and collagen for bone regeneration

The study reported describes a combination of recombinant human bone morphogenetic protein-2 (rhBMP-2) and collagen (C) to regenerate bone. Unilateral critical-sized defects (CSDs) were prepared in radii of 32 skeletally mature New Zealand white rabbits. Rabbits were divided evenly among four treatments: autograft, absorbable C (Helistat), 35 microg of rhBMP-2 combined with absorbable C (rhBMP-2/C), and untreated CSDs. The two euthanasia periods were 4 and 8 weeks. Radiographs were taken the day of surgery, every 2 weeks, and at term and the percent of radiopacity was measured. Data analysis revealed a time-dependent increase in the percent radiopacity with rhBMP-2/C. Histological examination revealed the rhBMP-2/C treatment regenerated osseous contour by 8 weeks. According to quantitative histomorphometry, the CSD and C groups had significantly less new bone than either autograft or rhBMP-2/C (p < or = 0.05). The results suggest that rhBMP-2/C could be an effective therapy to restore segmental bone defects.

Charged beads enhance cutaneous wound healing in rhesus non-human primates

Enhanced cutaneous wound healing by positively charged cross-linked diethylaminoethyl dextran beads (CLDD) was studied in a standardized incisional wound model in 20 adult and 20 geriatric Macaca mulatta (rhesus) partitioned equally over five time periods. Physiologic saline served as a control. Soft-tissue linear incisions were prepared between and 1 cm inferior to the scapulae. There were four incisions per rhesus; each incision was 1.5 cm long with 1 cm of undisturbed tissue between incisions, and both the experimental CLDD and physiologic saline treatments were administered to each rhesus. The incision treatments were either CLDD and soft-tissue closure with 4-0 BioSyn sutures or sterile physiologic saline and closure with 4-0 BioSyn sutures. The hypothesis was CLDD would enhance cutaneous wound repair. Verification of the hypothesis consisted of clinical examinations and histologic and tensiometric evaluations on biopsy specimens at 10 and 15 days, whereas 5-day and 2- and 4-month groups were assessed clinically and biopsy specimens were assessed histologically. The clinical course of healing for all groups was unremarkable. At 10 days, incisions in adult rhesus treated with CLDD had a 30-percent greater tensile strength compared with the physiologic saline-treated incisions (p = 0.01), whereas for geriatric rhesus, the CLDD treatment proved to be 15 percent greater in tensile strength compared with the physiologic saline cohort (p = 0.11). By day 15, incisions in adult rhesus were 26 percent stronger than the saline treatment group (p = 0.07), and the difference was 36 percent (p = 0.02) for the geriatric rhesus. From 5 through 15 days, histologic observations revealed a gradual decrease in quantity and integrity of CLDD, with no remnants of CLDD at either 2 or 4 months. Macrophages and multinucleated giant cells were localized in the dermis and were associated with the CLDD. These cells decreased commensurately with the decrease of CLDD beads. The data suggest that CLDD can enhance significantly the tensile properties of healing cutaneous wounds in both adult and geriatric rhesus. Moreover, if the wound healing is enhanced in geriatric patients, this finding may be clinically germane to conditions where wound healing is compromised, such as in diabetics and patients on steroids.

Comparison of porous bone mineral and biologically active glass in critical-sized defects

Several materials have been proposed as therapies to augment alveolar bone and to promote periodontal regeneration. However, there are an insufficient number of studies that effectively evaluated these therapies. Consequently, the purpose of this study was to compare bone regeneration promoted by porous bone mineral and biologically active glass. Unilateral critical-sized defects (CSDs) were prepared in the radii of 24 rabbits, divided evenly between 2 time periods (4 and 8 weeks) and between 2 treatment groups (porous bone mineral and biologically active glass). Evaluations consisted of clinical examinations, standardized radiography at baseline and every 2 weeks thereafter, as well as histology and histomorphometry. Data were analyzed by an unpaired Student t-test with significance established at P < or = 0.05. We determined that CSDs treated with porous bone mineral were significantly more radiopaque than biologically active glass-treated sites at both 4 and 8 weeks. Moreover, the amount of new bone was significantly greater at both 4 and 8 weeks in the porous bone mineral groups than in the biologically active glass groups. We concluded that in the rabbit radius CSD wound model, porous bone mineral appears to be more effective than biologically active glass in regenerating bone.