Defective Bone Repair in C57Bl6 Mice With Acute Systemic Inflammation

Abstract

Background Bone repair is initiated with a local inflammatory response to injury. The presence of systemic inflammation impairs bone healing and often leads to malunion, although the underlying mechanisms remain poorly defined. Our research objective was to use a mouse model of cortical bone repair to determine the effect of systemic inflammation on cells in the bone healing microenvironment. Question/Purposes (1) Does systemic inflammation, induced by lipopolysaccharide (LPS) administration affect the quantity and quality of regenerating bone in primary bone healing? (2) Does systemic inflammation alter vascularization and the number or activity of inflammatory cells, osteoblasts, and osteoclasts in the bone healing microenvironment? Methods Cortical defects were drilled in the femoral diaphysis of female and male C57BL/6 mice aged 5 to 9 months that were treated with daily systemic injections of LPS or physiologic saline as control for 7 days. Mice were euthanized at 1 week (Control, n = 7; LPS, n = 8), 2 weeks (Control, n = 7; LPS, n = 8), and 6 weeks (Control, n = 9; LPS, n = 8) after surgery. The quantity (bone volume per tissue volume [BV/TV]) and microarchitecture (trabecular separation and thickness, porosity) of bone in the defect were quantified with time using microCT. The presence or activity of vascular endothelial cells (CD34), macrophages (F4/80), osteoblasts (alkaline phosphatase [ALP]), and osteoclasts (tartrate-resistant acid phosphatase [TRAP]) were evaluated using histochemical analyses.The institution of one or more of the authors (JEH, PAM) has received, during the study period, funding from the Fonds de recherche Santé Québec. The remaining authors certify that neither he or she, nor a member of his or her immediate family, has funding or commercial associations (consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article. Results Only one of eight defects was bridged completely 6 weeks after surgery in LPS-injected mouse bones compared with seven of nine defects in the control mouse bones (odds ratio [OR], 0.04; 95% CI, 0.003-0.560; p = 0.007). The decrease in cortical bone in LPS-treated mice was reflected in reduced BV/TV (21% ± 4% vs 39% ± 10%; p\0.01), increased trabecular separation (240 ± 36 lm vs 171 ± 29 lm; p \ 0.01), decreased trabecular thickness (81 ± 18 lm vs 110 ± 22 lm; p = 0.02), and porosity (79% ± 4% vs 60% ± 10%; p \ 0.01) at 6 weeks postoperative. Defective healing was accompanied by decreased CD34 (1.1 ± 0.6 vs 3.4 ± 0.9; p\0.01), ALP (1.9 ± 0.9 vs 6.1 ± 3.2; p = 0.03), and TRAP (3.3 ± 4.7 vs 7.2 ± 4.0; p = 0.01) activity, and increased F4/80 (13 ± 2.6 vs 6.8 ± 1.7; p \ 0.01) activity at 2 weeks postoperative. Conclusion The results indicate that LPS-induced systemic inflammation reduced the amount and impaired the quality of bone regenerated in mouse femurs. The effects were associated with impaired revascularization, decreased bone turnover by osteoblasts...

Defective bone repair in mast cell-deficient Cpa3Cre/+ mice

“…The relatively low abundance of macrophages under healing conditions in the absence of mast cells in Cpa3 Cre/+ mice in the current study, and previously in Kit W-sh mice, suggests an interdependence between the two lineages. This conjecture is further supported by the increase in both mast cells and macrophages in bone defects in WT mice administered lipopolysaccharide (LPS) [35]. The timeframe and pattern of distribution of F4/80 positive cells in the current study closely resembled that of “osteomacs” in a similar model of cortical bone repair [36].…”

Defective bone repair in diclofenac treated C57Bl6 mice with and without lipopolysaccharide induced systemic inflammation

“…Metabolic activity of mast cells (c) and vascular endothelial cells (d) exposed to increasing concentrations of diclofenac was assessed using the AlamarBlue assay. (Behrends et al, 2017). Taken together, these data suggest that sustained treatment with a therapeutic dose of NSAID will inhibit basal and LPS-induced catabolism by OC and macrophages during bone repair.…”

<p>Ultra-Small Lysozyme-Protected Gold Nanoclusters as Nanomedicines Inducing Osteogenic Differentiation</p>

“…41 TRAP is a histochemical biomarker of osteoclastogenesis. [42][43][44] The overexpression of TRAP has also been suggested to be involved in the bone resorptive activity of osteoclasts. 45,46 To verify the effects of lysozyme and Lys-AuNCs on inhibiting the negative influence of osteoporosis, a typical macrophagelike cell line (Raw 264.7) was used ( Figure 5).…”