The Influence of Zoledoronate and Teripartide on Gd T Cells in Mice

The cause of bisphosphonate-related osteonecrosis of the jaw (BRONJ) is poorly understood. However, since nitrogen-containing bisphosphonates (NBPs) have been shown to reduce bone remodeling and angiogenesis, the suppression of bone turnover and jaw angiogenesis by NBPs has been proposed as an underlying mechanism for BRONJ. Although innate immunity has a critical role in the inflammation process, few studies have investigated the possibility that BRONJ might reflect an immune response. However, in 2012 it was reported that gd T cells, which are a subset of T cells, showed a significant and permanent decline, both in proportion and in absolute number, following infusion of an NBP. Regarding the treatment of BRONJ, although teriparatide, which is a recombinant form of parathyroid hormone that promotes bone growth, has not been widely used in the treatment of BRONJ, there have been a few reports of teriparatide use for the treatment of BRONJ. Administration of teriparatide for the resolution of BRONJ was first described by Harper and Fung in 2007. Subsequently, the administration of teriparatide has been documented in independent case reports. In this study, we analyzed lymphocytes, including gd T cells, which are of the same origin as osteoclasts like all typical immune cells, and we focused on the relationship between innate immunity and NBP and teriparatide treatments, and their effects on inflammatory cytokine production.

Materials and methods: Forty female ICR mice at 12 weeks of age were divided into four groups (n=10 each): vehicle group, zoledronate (an NBP) group, teriparatide group, and zoledronate+teriparatide group. In each group, the drugs were administered for 8 weeks. The right femur was then collected from the mice in each group and immunohistochemical staining was performed using the anti-mouse CD3 antibody. Flow cytometric studies of peripheral blood and thymus were performed using a FACSAria (BD) for analysis of cells labeled with anti-mouse CD45, CD3e, CD19, CD49b, CD4, CD8a, and TCRgd. Serum levels of a total of 23 cytokines were measured using the Bio-Plex® multiplex immunoassay analysis (Bio-Rad).

Results: Immunohistochemical staining and flow cytometric analysis showed that zoledronate decreased, but teriparatide increased the number of T cells in the bone marrow. Zoledronate had no influence on T cell, gd T cell, or B cell populations in peripheral blood; however, teriparatide decreased the population of T cells and increased the populations of gd T cells and B cells. Zoledronate did not influence the populations of double positive (DP)-T cells, double negative (DN)-T cells, or single positive (SP)-T cells in the thymus; however, teriparatide increased the populations of DP-T and DN-T cells, and decreased the population of SP-T cells in the thymus. Serum levels of IL-1ƒÀ, IL-17, and TNF-ƒ¿ were significantly higher, and the serum IL-5 level was significantly lower, in the zoledronate group than in the vehicle group or the teriparatide group. The serum INF-g level was significantly lower in the teriparatide group than in the vehicle or the zoledronate group. Conclusions: Our results showed that treatment with an NBP did not influence B cell or T cell populations, including gd T cell populations, in mouse peripheral blood. However, teriparatide induced an increase in the gd T cell population. If BRONJ involves a loss of gd T cells in the circulation, then the increase in gd T cells that is induced by teriparatide may account for its ability to resolve BRONJ.

References :

1. M. Rossini, et al. Long-term effects of amino-bisphosphonates on circulating gammadelta T cells, Calcif Tissue Int, 91 (2012) 395-399.

2. E. Yamachika,et al. Treatment of Osteonecrosis of the Jaw, J Craniofac Surg, 26 (2015) e575-577.