Additive Effect of Parathyroid Hormone and Zoledronate Acid on Prevention Particle Wears-Induced Implant Loosening by Promoting Periprosthetic Bone Architecture and Strength in an Ovariectomized Rat Model

Abstract

Implant-generated particle wears are considered as the major cause for the induction of implant loosening, which is more susceptible to patients with osteoporosis. Monotherapy with parathyroid hormone (PTH) or zoledronate acid (ZOL) has been proven efficient for preventing early-stage periprosthetic osteolysis, while the combination therapy with PTH and ZOL has exerted beneficial effects on the treatment of posterior lumbar vertebral fusion and disuse osteopenia. However, PTH and ZOL still have not been licensed for the treatment of implant loosening to date clinically. In this study, we have explored the effect of single or combined administration with PTH and ZOL on implant loosening in a rat model of osteoporosis. After 12 weeks of ovariectomized surgery, a femoral particle-induced periprosthetic osteolysis model was established. Vehicle, PTH (5 days per week), ZOL (100 mg/kg per week), or combination therapy was utilized for another 6 weeks before sacrifice, followed by micro-CT, histology, mechanical testing, and bone turnover examination. PTH monotherapy or combined PTH with ZOL exerted a protective effect on maintaining implant stability by elevating periprosthetic bone mass and inhibiting pseudomembrane formation. Moreover, an additive effect was observed when combining PTH with ZOL, resulting in better fixation strength, higher periprosthetic bone mass, and less pseudomembrane than PTH monotherapy. Taken together, our results suggested that a combination therapy of PTH and ZOL might be a promising approach for the intervention of early-stage implant loosening in patients with osteoporosis.

Keywords: implant loosening; osteolysis; osteoporosis; parathyroid hormone (1-34); zoledronate (ZOL).

Figure 1

The establishment of the OVX model was confirmed by radiological and histomorphological analysis. (A) The representative 3D and 2D micro-CT images of distal femurs were demonstrated from the sham group and the OVXS groups. (B) The BMD and BV/TV values of micro-CT images were quantified. (C) The representative images of H&E staining from both groups were performed. Upper ×40, lower ×200 magnification. Scale bar = 500 μm (upper) and 100 μm (lower). (D) The bodyweight of rats from 0 to 12 weeks after OVX in both groups. The representative images of the uterus (E) and weight (F) were obtained at the time of sacrifice in both groups. Values are expressed as mean ± SD, n=3; *p<0.05, **p<0.01, compared with the sham group.

Figure 2

The positive effects of combined or single treatment with PTH and ZOL on inhibiting particle-induced fixation strength loss of the implant in OVX rats. The schematic image of the biomechanical testing device (A) and the representative loading force–displacement curve (B) were displayed. The maximal fixation strength (C) and stiffness (D) of samples were collected and analyzed. Values expressed are means ± SD; *p < 0.05, n=5; **p < 0.01, significantly different compared between two groups. "ns", no significant difference.

Figure 3

The beneficial effect of combined therapy or monotherapy on preventing particles-induced peri-implant bone loss was observed radiologically in OVX rats. (A) The representative X-ray images from the NC, OVX, O+T, PTH, ZOL, and P+Z groups were exhibited. (B) The representative 3D and 2D micro-CT images of peri-implant bone mass in distal femurs were demonstrated from the six groups. (C) The quantification of the BMD, BV/TV, BS/BV, Conn.D, SMI, Tb.N, Tb.Th and Tb.Sp values was analyzed. Values expressed are means ± SD, n=5; *p < 0.05, **p < 0.01, significantly different compared between two groups. "ns", no significant difference.

Figure 4

Histomorphology of combined therapy or monotherapy on protecting particle-induced peri-implant osteolysis. (A) H&E staining (upper ×40, lower ×200 magnification) and (B) Masson staining (upper 40×, lower ×200 magnification) were used for the histological analysis. Scale bar= 500 μm (upper) and 100 μm (lower). (C) BIC, B.Ar/T.Ar, and mean thickness of the pseudomembrane were quantified. Values expressed are means ± SD, n=5; **p < 0.01, significantly different compared between two groups. "ns", no significant difference.

Figure 5

Different effects of combined therapy or monotherapy on bone formation and osteoclast formation in the animal model. (A) Representative images of alizarin red (red) and calcein (green) labels were observed. (B) Representative images of TRAP staining were presented. The (C) MAR, (D) MS/BS, (E) N.Oc/BS and (F) OcS/BS were analyzed with sections. Values expressed are means ± SD, n=5; *p<0.05, **p<0.01, significantly different compared with the O+T group. "ns", no significant difference.

Figure 6

The effects of combined therapy or monotherapy on the expression of OCN (A) and RANKL (B) in peri-implant bone. Representative IHC staining images of OCN and RANKL were visualized.

Figure 7

The effects of combined or single treatment on serum levels of GLA-OCN and CTX-1 in the animal model. The serum levels of GLA-OCN (A) and CTX-1 (B) were measured using ELISA. Values expressed are means ± SD; n=5~6; *p<0.05, **p<0.01, significantly different compared between two groups. "ns", no significant difference.