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

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.

Augmentation of Bone Regeneration by Depletion of Stress-Induced Senescent Cells Using Catechin and Senolytics

“…LS-Gs containing 12.42 EU/mg of LPS were prepared as reported previously [ 17 ]. Our previous study revealed that LS-G could retain LPS in similar bone defects for at least three weeks.…”

“…This discrepancy might be due to the difference in the bonding between LPS and gelatin. Recently, we identified that reagent-grade gelatin contains a small amount of LPS [ 17 ]. We fabricated vacuum-heated gelatin sponges (LS-G) [ 17 ] because dehydrothermal treatment using vacuum heating is known to enhance ester bonding between carboxyl and hydroxyl groups of molecules [ 25 ].…”

“…LPS stimulation potentially impairs bone healing [ 13 ]. Recently, we reported that the long-term presence of LPS in bone defects alters the induction of SIPS cells using two fabricated different LPS-gelatin sponges that released LPS at a distinct speed in vivo [ 17 ]. Compared with LPS rapid-release gelatin sponges, LPS sustained-release gelatin sponges (hereafter designated as LS-G) even with extremely low quantity of LPS generates more SIPS cells and causes less bone regeneration despite insignificant inflammation.…”

Gas Permeability of Mold during Freezing Process Alters the Pore Distribution of Gelatin Sponge and Its Bone-Forming Ability

“…LPS, which is an outer-cell membrane of Gram-negative bacteria, is an established strong stimulant for modulating the immune system and inducing inflammation [ 35 , 36 ], which diverges bone formation that is primarily dependent on its dose and sustained condition to the matrix materials [ 36 , 37 , 38 ]. We have previously reported that even tiny contaminations involving minute amounts of LPS in gelatin sponges remarkably hindered bone formation in a similar bone defect model [ 38 ]. Xu et al also reported that the combined use of the NF-κB activator and gelatin augmented severe inflammation [ 39 ].…”

Neurorestoration Approach by Biomaterials in Ischemic Stroke

“…What is already a certainty today is the safety of many of the components of biomaterials and cells (for example, adipose cells) supported by biomaterials in animals (Zhao et al, 2019;Kupikowska-Stobba and Lewińska, 2020;Otake et al, 2020). These results led us to argue that the gap between animals and humans in this context will be closed soon.…”