Comparative Study Of HA, BCP And TCP Three-Dimensional Scaffolds On Osteogenesis

BackgroundIt is a troublesome problem for the orthopedic surgeon to cure large bone defects. Metal scaffolds with strong mechanical strength are mainly used in weight-bearing areas including limbs and joints. However, owing to huge difference from natural bone and poor degradation, metal materials are prone to stress-shielding and bone resorption for mismatching with surrounding tissue, thus limiting their use on bone repair. Many researchers pay attention to bioactive ceramics for its high biological activity and histocompatibility, especially on the non-weight bearing bones such as calvarial bone and maxillofacial bone. Multiple studies have verified their repair effects, but comparative studies on the similar ceramics are rare. In this study,bone repair effect of the three promising ceramics including hydroxyapatite (HA), biphasic calcium phosphates (BCP) and tricalcium phosphate (TCP) are investigated to search promising bone alterative materials. And inactive hydroxyapatite (HA) was used as control.ObjectiveOsteogenic effect of the four creamics including inactive HA, HA, BCP and TCP were investigated through in vitro and in vivo studies to provide experimental base for the clinical repair of non-weight bearing bone defects.MethodsMicrostructures and mechanical capacities of the four biomaterials were detected by SEM and mechanical tests respectively. The third passage osteoblasts obtained from calvarial bone of new born SD rats were seeded on the surface of the four biomaterials at the density of 1×105 cells, osteoblasts were used in in vitro study. MTT, ALP activity and the expression of osteogenic related genes were evaluated at week 1,2 and 3. In addition, cell viability and cell actin cytoskeleton were also detected by FDA/PI staining and rhodamine phalloidin/Hoechst 33258 staining. Furthermore,40 SD rats (300±10g) were randomly divided into four groups (10 rats per group) in the study. Critical-sized defects were created on the parietal bone of SD rats, and rats in group A, B, C and D were implanted with HA, BCP, TCP and inactive HA. At month 1,2 and 3 post-operation, therapeutic effect on repair of calvarial defect were assessed with cone beam computed tomography (CBCT), gross morphological examination, micro-CT, histological and immunohistochemical staining.ResultsCompared with TCP, HA and inactive HA showed superior properties in mechanical tests, and BCP ranked the second. In the in vitro study, BCP exerted best promotive effect on osteoblasts, but BCP and TCP evaluated ALP level most notably. However, inactive HA displayed lowest bioactivity. In the in vivo study, no obvious difference on bone repair was found through CBCT and gross morphological examination. However, BCP exerted higher structure linear density and bone mineral density than other scaffolds via micro-CT, and more new bone formation was found on the BCP group, less new bone formation was found on the HA and TCP groups. On the contrary, more fibroblasts and inflammation cells were found in the inactive HA group.ConclusionBCP shows higher bioactivity in vitro and better calvarial repair effect in vivo than other scaffolds, suggesting that HA, BCP, TCP scaffolds are all caplable of non-weight bearing bone pepair, and BCP exerted the best repair result on non-weight bearing bone defects.