Effect of epidermal growth factor receptor signaling pathway inhibitor gefitinib on fracture healing in rats

Abstract

Objective To observe the effect of epidermal growth factor receptor (EGFR) signal pathway inhibitor gefitinib on femoral fracture healing in rats. Methods Eighty SD rats were divided into experimental group (n=40) and control group (n=40) by random number table. An open femur fractured model was established by cutting the middle part of the femoral shaft and placing 1 mm Kirschner wire through medial and lateral femoral patella incision. Rats in the experimental group were given gefitinib (100 mg· kg-1· d-1), an inhibitor of epidermal growth factor receptor (EGFR) signaling pathway, and rats in the control group were given equal doses of methylcellulose. The X-ray examination was performed before femoral and serum specimens were collected at 1, 2, 3, 4, and 6 weeks. Bone fracture healing was evaluated by Lane and Sandhu X ray scoring and biomechanical test. Then the tissue morphology was observed by HE staining, safranin fast green staining, and microCT detection. The bone volume (BV), bone volume fracture (BV/TV), trabecular number (Tb. N), trabecular thickness (Tb. Th), and trabecular separation (Tb. Sp) were measured by MicroCT. The levels of serum BALP, PINP, TRACP5b, and CTX were measured by Elisa. Results The X-ray scores of the experimental group (1.26±0.54, 4.94±1.16, and 8.23±1.17) were significantly higher than those in the control group (0.91±0.52, 4.11±1.18, and 7.08±0.86) at 1, 2 and 3 weeks after the fracture (P<0.05). The failure load of experimental group at 3 and 4 weeks after fracture [(38.65±1.07)N , (63.63±7.74)N] were significantly larger than those of the control group [ (29.47+ 1.00)N, (45.42+ 3.26)N](P<0.05). The callus formation in the experimental group was obvious and the healing process of the fracture was faster than that of the control group according to HE and safranin fast green staining. The results of microCT showed that in the experimental group, BV was significantly higher at 2 and 3 weeks after fracture [(59.30±6.54)mm3 and (43.08±2.33)mm3] than those in control group [(42.39±7.82)mm3 and (33.43±5.94)mm3]; BV / TV at 2, 3, and 4 weeks after fracture[(0.61±0.06)%, (0.55±0.05)%, and (0.53±0.04)%] were significantly higher than those in the control group [(0.48±0.07)%, (0.44±0.07)%, and (0.43±0.03)%]; Tb. N at 2, 3, and 4 weeks after fracture [(2.05±0.11)/mm, (1.86±0.18)/mm, and (2.034 ±0.26)/mm]were significantly higher than those in control group [(1.63±0.21)/mm, (1.32±0.21)/mm, and (1.65±0.08)/mm)]; Tb. Th at 2, 3, and 4 weeks after fracture [(0.33±0.02)mm, (0.33±0.03)mm, and (0.27±0.02)mm] were significantly higher than those in the control group [(0.27 ±0.03)mm, (0.28±0.02)mm, and 0.23±0.01)mm]; Tb. Sp at 3 weeks after fracture [(0.39±0.07)mm] was significantly higher than that in the control group [(0.30±0.03)mm](P<0.05). The levels of serum BALP in experimental group at 2 and 3 weeks after fracture [(2.57±0.14)ng/ml, (3.47±0.26)ng/ml] were significantly higher than those of control group [(2.07±0.19)ng/ml, (2.77±0.29)ng/ml]; the PINP at 1, 2, and 3 weeks after fracture in the experimental group [(2 216.50±96.68)pg/ml, (2 692.33±136.76)pg/ml, and (3 196.75±221. 90)pg/ml] were significantly higher than those of the control group[(1 969.50+ 89.34)pg/ml, (2 241.33±107.86)pg/ml, and(2 603.25±361.60)pg/ml]; the levels of TRACP5b [(11.58±0.47)ng/ml] and CTX [(8.02±0.40)ng/ml] at 1 week after fracture were higher than those of the control group [(10.33±0.53)ng/ml, (7.11±0.36)ng/ml](P<0.05). Conclusion Gefitinib can promote the maturation of osteoblasts and the early reabsorption function of osteoclasts to induce bone formation in advance and accelerate the fracture healing. Key words: Receptor, epidermal growth factor; Fracture healing; Gefitinib