S1-3 Effects and Mechanisms of Depression on Bone Fracture Healing in Rats

Objective:To explore the effect of depression on fracture healingand forecast its agnostic mechanism.Methods:Rats(Sprague Dawley,female,8-month-old,(242.6±11.2)g)wererandomly divided into Control(group A),Sham Control(group B)and Depression(group C)groups.Upper 1/3 transverse tibia fracture model and intramedullaryfix were applied to Group A and C and sham operations(similar surgeries with no fracture and fix)were applied to Group B.The serum calcium(Ca),phosphorus(P)and alkaline phosphatase(ALP)were measured on day 7,14,and 21 after operation;the tibia image(DR)and pathology(HE stain)were examined onday14,28,and 56 after operation;the Biomechanics(three-point bending test)were implemented on day 35 and 56 after operation;and the Micro-CT were performed on day 28 and 56 after operation.Results:The tibia image(DR)showed no significant difference in callus volume between Groups A and C on Day 14 after operation(P>0.05,n=10),but had significant difference on Day 28 and 56 after operation(P<0.05,n=10).HE staining showed significantly worse recovery of the fracture zone in Group C than in Group A on Day 14,28,and 56 after operation.The results from three point bending experiment revealed a significantly worse recovery of all bending indices(stiffness,strength,deflection,load,and movement)of Group C than the control Group A on Day 35 and 56 after operation(P<0.05,n=10).Micro-CTalsoshowed that the osteogenesis indicators such as bone volume fraction,thickness of trabecular bone,and number of trabecular bone were significantly lower in Group C than that in the control group A on Day 28 and 56 after operation(P<0.05,n=10).The volume of interstitial bone trabecular space and area of trabecular bone of Group C was significantly greater than that of control Group A(P<0.05,n=10).The serum P and ALP concentrations of Group C were significantly lower than those of group Bon Day 7(P<0.05,P<0.01,n=10),14(P<0.05,P<0.01,n=10),and 21(P<0.05,P<0.01,n=10)after operation,while the serum Ca concentrations did not show any signifi cant changes(P>0.05,n=10).Conclusion:Depression may delay the primary callus and tibia fracture healing through an effect on the metabolism of phosphorus which caused a down-regulation of serum P and ALP concentrations in rats.These results provide a novel underlying mechanism and also a potential therapeutic strategy for depression caused delay of bone fracture healing.