Influence of defatting procedure on immunogenicity of cancellous bone allograft.

[Objective]To explore the influence of defatting procedure on immunogenicity of cancellous bone allograft and the possible mechanism. [Methods]Sixty inbred Lewis rats were killed.Distal femoral metaphyses were resected as cancellous bone grafts.Grafts were divided into four groups (A,B,C and D) randomly with four different procedures respectively.Content of total lipid and total protein in grafts were measured.Forty-eight inbred Fisher344 rats were divided into four groups (A,B,C and D) randomly according to different grouped grafts which were transplanted into double femoral muscle pouches of the recipients.Three rats of each group were killed at the 1,2,4 and 8 weeks post operatively respectively.Proliferation index and ratio of CD4+/CD8+ were tested and histological changes of transplanted grafts were observed.The correlation analysis was performed between proliferation index,CD4+/CD8+ ratio at the 4th post-operative week and the content of total lipid.[Results]Results of measurement showed content of total lipid in four grouped grafts was:groups A BCD and the differences between groups were statistically significant(P0.05).There was no significant difference in protein content between groups(P0.05).Proliferation index increased in the early phase and reached the peak at the 4th post-operative week.Level of proliferation index in four groups was gradiently decreased from group A to group D.At the 4th post-operative week,differences of proliferation index were statistically significant between groups(P0.05),except between group C and group D(P0.05).The changing trend of ratio of CD4+/CD8+ was similar to that of proliferation index.Histological observations showed inflammatory cells infiltrated in early phase gradiently decreased from group A to group D.At the 4th post-operative week,histological observations showed neovascularization in group D.At the 8 weeks post-operatively,more new bone formation was observed in group D. The correlation analysis showed significant positive correlation between proliferation index,CD4+/CD8+ ratio at the 4th post-operative week and the content of total lipid (P0.05).[Conclusion]Defatting procedure could decrease immunogenicity of cancellous bone allografts.Content of total lipid might be an indicator for determining immunogenicity of cancellous bone allografts.