A comparative study of autogenous, allograft and artificial bone substitutes on bone regeneration and immunotoxicity in rat femur defect model

Abstract

Repair and reconstruction of large bone defect were often difficult, and bone substitute materials, including autogenous bone, allogenic bone and artificial bone, were common treatment strategies. The key to elucidate the clinical effect of these bone repair materials was to study their osteogenic capacity and immunotoxicological compatibility. In this paper, the mechanical properties, micro-CT imaging analysis, digital image analysis and histological slice analysis of the three bone grafts were investigated and compared after different time points of implantation in rat femur defect model. Autogenous bone and biphasic calcium phosphate particular artificial bone containing 61.4% HA and 38.6% β-tricalcium phosphate with 61.64% porosity and 0.8617 ± 0.0068 g/cm³ density (d ≤ 2 mm) had similar and strong bone repair ability, but autogenous bone implant materials caused greater secondary damage to experimental animals; allogenic bone exhibited poor bone defect repair ability. At the early stage of implantation, the immunological indexes such as Immunoglobulin G, Immunoglobulin M concentration and CD4 cells' population of allogenic bone significantly increased in compared with those of autologous bone and artificial bone. Although the repair process of artificial bone was relatively inefficient than autologous bone graft, the low immunotoxicological indexes and acceptable therapeutic effects endowed it as an excellent alternative material to solve the problems with insufficient source and secondary trauma of autogenous bone.

Keywords: allogenic bone; artificial bone; autogenous bone; bone defect repair; immunotoxicity; osteogenesis.

Figure 1.

(A) Macroscopic images for the implanted materials. (B) SEM images of the implanted materials. (C) EDS mapping images for the implanted materials. (D) Antigen removal by freezing at 80°C. (E, F) the implantation process of the materials

Figure 2.

Digital radiography observation of mouse bone defects after implantation with different materials. (A) Digital radiography images for autogenous bone group. (B) Digital radiography images for artificial bone group. (C) Digital radiography images for allograft bone group

Figure 3.

Micro-CT 3D reconstruction analysis for each group of materials during femoral implantation. (A) images at 4 weeks; (B) images at 12 weeks; (C) images at 40 weeks. Implant orifice and longitudinal section were shown in red rectangle. The image of hydroxyapatite was shown in green on the longitudinal section of artificial bone. (D−I) Micro-CT parameters of new bone formation inside the graft. Data were presented as mean ± SD by t-test (n = 3). **P < 0.01; *P < 0.05

Figure 4.

The observation of tissue section after implantation (H&E staining). (A) observation of histological sections at 4 weeks. (B) Observation of histological sections at 12 weeks. (C) Observation of histological sections at 40 weeks

Figure 5.

Compression test of femur in animals of different groups. (A−C) The change of load with displacement of autogenous bone at 4, 12 and 26 weeks. (D−F) The change of load with displacement of artificial bone at 4, 12 and 26 weeks. (G−I) The change of load with displacement of allograft bone at 4, 12 and 26 weeks. (J) Maximum broken force derived from the curve of compression test. (K) Statistical analysis of changes in femoral compressive strength of animals in each group. (L) Statistical analysis of changes in femoral compressive modulus of animals in each group. Data were presented as mean ± SD by t-test (n = 3). *P < 0.05

Figure 6.

Immunoglobulin content analysis. (A) IgG content; (B) IgM content. Data were presented as mean ± SD by t-test (n = 6). *P < 0.05

Figure 7.

CD4 and CD8 lymphocyte typing. (A, B) Lymphocyte typing for autogenous bone at 4 and 26 weeks. (C, D) Lymphocyte typing for artificial bone at 4 and 26 weeks. (E, F) Lymphocyte typing for allogenic bone at 4 and 26 weeks. (G, H) Contents of CD4 and CD8 at 4 and 26 weeks. Data were presented as mean ± SD by t-test (n = 5). **P < 0.01; *P < 0.05