Immunomodulatory Effects of Clinically Used Fat Emulsion to Promote Angiogenesis and Osteogenesis for Bone Repair

Bone defects have become a leading cause of disability and mortality. The pro-inflammatory state and impaired vascularization are major factors hindering bone defect repair. However, current bone regeneration materials lack the ability to regulate the osteoimmune microenvironment and promote vascularized bone regeneration. In this study, we employed clinically used fat emulsion (FE), which is intravenously administered to provide nutrition and energy for patients, to investigate the effect of immunomodulation on promoting angiogenesis and osteogenesis. Results from RT-qPCR analysis and immunofluorescence staining demonstrated that FE exhibited potent anti-inflammatory effects by reducing the expression of the pro-inflammatory marker inducible nitric oxide synthase (iNOS) and upregulating the expression of the anti-inflammatory marker transforming growth factor-beta (TGF-β). Endothelial tube formation and scratch assays demonstrated that FE promoted angiogenesis and cell migration by releasing vascular endothelial growth factor (VEGF) within the inflammatory microenvironment. Alkaline phosphatase (ALP) and alizarin red S (ARS) staining revealed that FE facilitated ALP activity and calcium nodule formation by releasing bone morphogenetic protein-2 (BMP-2) within the inflammatory microenvironment. These findings may prove promising and cost-effective for the clinical treatment of bone defects.