Evaluation of composite collagen/hydroxy-apatite implantation and nerve growth factor (NGF) delivery on new bone in growth

In this study, a bio-ertittciel bioresorbable composite consisting of a polymer of coffagen/hydroxy-apatite (Col/Hap) enriched with neurotropin - nerve growth factor (NGF), was implanted into the femurs of 73 male Wistar rats, weighing 100-125 g. Implants were left in place for different times. Controls were as foffows: a) contralatera/ femur without any implants; and b) contralateral femur implanted with composite without NGF factor. Therats were euthanizedafter 1, 10 and 30 days and the implant sites and explants were examined clinically, histologicaffy, by scanning electron microscopy and histomorpho metricaffy. The results show stimulated periosteal and enciocorticet woven and lameffar bone formation, which yielded increases in bone mass and decreases in bone marrow. The NGF treatment had greater effects in the femur shafts of older male rats than in younger ones. Additionaffy, we found that NGF increased remodeling activity in the intrecorticet region and induced an increase of intrecorticel cavity numberand area by the end of the study. Since no similar studies appear to have been carried out, it is difficult to correlate our findings with other studies where neurogenic factors are delivered by complex polymer composites. We believe that this proposed system has great advantages in tissue engineering and is very suitable as a biomaterial for fiffing irregular defects in orthopaedic and maxillo-facial surgery, bone replacement and fixation, and as a drug delivery device. edotoxin tested; neurobiological tests; neurofilament outgrowth observed at 30 ng/ml; cell culture: free of bacteria, yeasts, moulds and mycoplasma; preparation: by gel filtration and ion-exchange chromatography, sterilized by 0.2 mm-filtration and lyophilized (100 mg) from 1 ml of 5 mM PBS, pH 6.8. Solubility (0.1 mq/rnl H20) clear, colorless. Implants were left in place for different times, after which termination was performed by cardiac perfusion with Karnovsky's fixative. The bone was dissected to reveal the implant site and subsequently remained in Karnovsky's fixative for another 5 days. One femur from each animal was examined in the scanning electron microscope (SEM). Quantitative evaluations were carried out using a digitizing image analyzing system (DIAS). Total cross-sectional area (T.Ar), marrow area, cortical width, periosteal new bone area, and osteoid surface (O.Pm) were recorded. These parameters were used to calculate the total bone area (TB.Ar), cortical bone area (Ct.Ar), percent cortical area (%Ct.Ar), percent osteoid perimeter (O.Pm/B.Pm), mineral apposition rate (MAR), and bone formation rate per unit of bone surface (BFR/B.Pm). The porosity was defined as intracortical cavities with diameter >30~lm. Intracortical cavity area and cortical area were used to calculate the percent porosity area. Forming osteon number (FON) was the sum of single and double labeled surfaces. Forming osteon number, resorption cavity number, and porosity number were used to calculate the forming osteon density (%RCN) and the ratio of the forming osteon number and resorption number (FON/RCN). Results are presented as mean ± SD. The differences within groups were evaluated statistically using one-way analysis of variance (ANOVA). P>0.05 was considered significant.