Releasing Behavior of Lipopolysaccharide from Gelatin Modulates Inflammation, Cellular Senescence, and Bone Formation in Critical-Sized Bone Defects in Rat Calvaria.

Naoyuki Matsumoto,Tomonari Tanaka,Yoshiya Hashimoto,Jianxin Zhao,Yoshitomo Honda

doi:10.3390/ma13010095

Naoyuki Matsumoto, Tomonari Tanaka + Show 3 more

Open Access

https://doi.org/10.3390/ma13010095

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Abstract

Lipopolysaccharide (LPS) is a well-known strong inducer of inflammation. However, there is little information regarding how LPS-release behavior affects cellular senescence at the affected area. In this paper, we demonstrate that a vacuum-heating technique (dehydrothermal treatment) can be utilized to prepare an LPS sustained-release gelatin sponge (LS-G). LPS sustained release from gelatin leads to the long-term existence of senescent cells in critical-sized bone defects in rat calvaria. Three types of gelatin sponges were prepared in this study: a medical-grade gelatin sponge with extremely low LPS levels (MG), LS-G, and a LPS rapid-release gelatin sponge (LR-G). Histological (H-E) and immunohistochemical (COX-2, p16, and p21) staining were utilized to evaluate inflammatory reactions and cellular senescence one to three weeks after surgery. Soft X-ray imaging was utilized to estimate new bone formation in the defects. The LR-G led to stronger swelling and COX-2 expression in defects compared to the MG and LS-G at 1 week. Despite a small inflammatory reaction, LS-G implantation led to the long-term existence of senescent cells and hampered bone formation compared to the MG and LR-G. These results suggest that vacuum heating is a viable technique for preparing different types of materials for releasing bacterial components, which is helpful for developing disease models for elucidating cellular senescence and bone regeneration.

Highlights

Bacterial infection is a major obstacle to bone fracture healing [1,2] and bone-regeneration therapies [3]
Our results demonstrate that different LPS release behaviors alter inflammatory reactions, and cellular senescence and bone formation in critical-sized bone defects in rat calvaria
The sustained release of LPS is coincident with the failure of bone formation for up to 3 weeks

Summary

Introduction

Bacterial infection is a major obstacle to bone fracture healing [1,2] and bone-regeneration therapies [3]. It is a consensus that bacterial components modulate bone metabolisms. Despite the development of various antibacterial materials [4], antibiotic use occasionally exhibits poor effectiveness in terms of preventing recurrent infections [5] and implant failures [6]. Further elucidation of the mechanisms between chronic inflammation induced by residual bacterial components and bone regeneration is crucial for preparing advanced biomaterials for bone regeneration therapy. Lipopolysaccharide (LPS), which is a typical outer-cell membrane of Gram-negative bacterial endotoxins, is a latent contaminant in many treatments and surgeries in the medical field [7].

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