Exercise enhance the ectopic bone formation of calcium phosphate biomaterials in muscles of mice

Abstract

Objective: To investigate whether exercise can enhance ectopic bone formation of calcium phosphate (Ca-P) biomaterials in muscles of mice.

Methods: Firstly, ten transient receptor potential vanilloid subfamily member 1 (TRPV1) knockout mice (group KO) and ten C57BL/6 mice (group WT) were randomly chosen, 10μg Ca-P biomaterials were implanted into the thigh muscle pouch of each mouse which was far away from femur; after that, all animals were kept in open field for free exploration 5min, and the movement time and distance were automatically analyzed. Ten weeks later, the Ca-P samples were harvested for histological staining and immunochemistry. Secondly, the Ca-P biomaterials were implanted into the thigh muscle pouch of C57BL/6 mice the same as previous operation, and then randomly divided into two groups: running group and non-running group (n=10); in running group, all mice run 1h as a speed of 6m/h in a treadmill for 10weeks. Ten weeks later, the blood was collected to detect the interleukin-4 (IL-4) and IL-12 levels by enzyme linked immunosorbent assay (ELISA), and the samples were harvested for histological staining.

Results: In groups KO and WT, both the movement time and distance were significant higher in group KO than that in group WT (P<0.05); furthermore, the histology staining results showed that lots of new bone and bone marrow tissues were observed in group KO, but only bone matrix-like substances were observed in group WT. In running group and non-running group, the ELISA results indicated that the immunological genes, both IL-4 and IL-12 levels were significant higher in running group than that in non-running group (P<0.05); besides that, more new bone tissues were observed in running group than that in non-running group.

Conclusion: Knockout of TRPV1 in mice could reduce algesia and induce the stronger athletic ability of mice, causing better osteoinductivity of Ca-P biomaterials both in TRPV1^-/- mice and running mice; according to this, we want to offer a proposal to patients who suffer from bone defects and artificial bone transplantation: do moderate exercise, don't convalesce all the time.

Keywords: Ca-P biomaterials; Exercise; Osteoinduction; TRPV1.