Enhancement of Bone-Forming Ability on Beta-Tricalcium Phosphate by Modulating Cellular Senescence Mechanisms Using Senolytics.

Xinchen Wang,Jianxin Zhao,Hidetoshi Morikuni,Yoshiya Hashimoto,Aki Nishiura,Yoshitomo Honda,Naoyuki Matsumoto

doi:10.3390/ijms222212415

Xinchen Wang, Jianxin Zhao + Show 5 more

Open Access

https://doi.org/10.3390/ijms222212415

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Abstract

Various stresses latently induce cellular senescence that occasionally deteriorates the functioning of surrounding tissues. Nevertheless, little is known about the appearance and function of senescent cells, caused by the implantation of beta-tricalcium phosphate (β-TCP)—used widely in dentistry and orthopedics for treating bone diseases. In this study, two varying sizes of β-TCP granules (<300 μm and 300–500 μm) were implanted, and using histological and immunofluorescent staining, appearances of senescent-like cells in critical-sized bone defects in the calvaria of Sprague Dawley rats were evaluated. Parallelly, bone formation in defects was investigated with or without the oral administration of senolytics (a cocktail of dasatinib and quercetin). A week after the implantation, the number of senescence-associated beta-galactosidase, p21-, p19-, and tartrate-resistant acid phosphatase-positive cells increased and then decreased upon administrating senolytics. This administration of senolytics also attenuated 4-hydroxy-2-nonenal staining, representing reactive oxygen species. Combining senolytic administration with β-TCP implantation significantly enhanced the bone formation in defects as revealed by micro-computed tomography analysis and hematoxylin-eosin staining. This study demonstrates that β-TCP granules latently induce senescent-like cells, and senolytic administration may improve the bone-forming ability of β-TCP by inhibiting senescence-associated mechanisms.

Highlights

Bone defects attributed to periodontitis, trauma, surgery, or congenital malformations are a crucial clinical issue [1]
Images captured utilizing a field emission-scanning electron microscope (FE-SEM) proved that these granules differed in size but had similar smooth surfaces (Figure 1B)
The present study demonstrated that the implantation of β-TCP granules induced senescent cells in critical-sized bone defects in rat calvaria; the oral administration of DQ to rats, implanted with β-TCP granules, markedly inhibited cellular senescence induction mechanisms and promoted bone regeneration

Summary

Introduction

Bone defects attributed to periodontitis, trauma, surgery, or congenital malformations are a crucial clinical issue [1]. Autogenous bone grafting is the gold standard clinical procedure for repairing bone defects, but the limited availability of donor bone hamper further operation [2]. Calcium phosphate (CaP)-based scaffolds, such as beta-tricalcium phosphate (β-TCP) [4], alpha-tricalcium phosphate [5], hydroxyapatite [6], and octacalcium phosphate [7], have been studied as bone graft substitutes because of their high biocompatibility, biosafety, and long shelf life [8]. The β-TCP scaffold has occasionally been used in clinical practice for periodontal defects, as it exhibits excellent osteoconductive properties [9]. When compared with that of the autogenous bone graft, the osteogenic capacity of β-TCP is insufficient, limiting its further use [10].

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