Conditioned media from endothelial progenitor cells cultured in simulated microgravity promote angiogenesis and bone fracture healing

Abstract

Background Paracrine signaling from endothelial progenitor cells (EPCs) is beneficial for angiogenesis and thus promotes tissue regeneration. Microgravity (MG) environment is found to facilitate the functional potentials of various stem or progenitor cells. The present study aimed to elucidate the effects of MG on pro-angiogenic properties and fracture repair capacities of conditioned media (CM) from EPCs. Methods Human peripheral blood-derived EPCs were cultured under MG or normal gravity (NG) followed by analysis for angiogenic gene expression. Furthermore, the serum-free CM under MG (MG-CM) or NG (NG-CM) were collected, and their pro-angiogenic properties were examined in human umbilical vein endothelial cells (HUVECs). In order to investigate the effects of MG-CM on fracture healing, they were injected into the fracture gaps of rat models, and radiography, histology, and mechanical test were performed to evaluate neovascularization and fracture healing outcomes. Results MG upregulated the expression of hypoxia-induced factor-1α (HIF-1α) and endothelial nitric oxide synthase (eNOS) and promoted NO release. Comparing to NG-CM, MG-CM significantly facilitated the proliferation, migration, and angiogenesis of HUVECs through NO-induced activation of FAK/Erk1/2-MAPK signaling pathway. In addition, MG-CM were verified to improve angiogenic activities in fracture area in a rat tibial fracture model, accelerate fracture healing, and well restore the biomechanical properties of fracture bone superior to NG-CM. Conclusion These findings provided insight into the use of MG bioreactor to enhance the angiogenic properties of EPCs’ paracrine signals via HIF-1α/eNOS/NO axis, and the administration of MG-CM favored bone fracture repair. Graphical abstract

Deferoxamine accelerates endothelial progenitor cell senescence and compromises angiogenesis

“…Considering that DFO compromised the angiogenic activity of EPCs, we then examined whether four-day DFO treatment altered the expression of angiogenic proteins such as vascular endothelial growth factor (VEGF), Fms-related receptor tyrosine kinase 1 (Flt-1), kinase insert domain receptor (KDR) and TEK receptor tyrosine kinase (TIE2) in EPCs ( Figure 3C – 3F ). DFO strongly downregulated VEGF, the major angiogenic factor in EPCs, consistent with the notion that EPCs primarily promote angiogenesis through their paracrine functions [ 17 , 18 ]. Flt-1, KDR and TIE2 levels were also moderately reduced in DFO-induced senescent EPCs.…”

Slight up‐regulation of Kir2.1 channel promotes endothelial progenitor cells to transdifferentiate into a pericyte phenotype by Akt/mTOR/Snail pathway

“…More researchers showed that CD44, CD31 and vWF were all related to the differentiation of EPCs into endothelial cells 20–22 . Subsequently, we found that the expression of EPC‐related marker molecules CD44, CD31 and vWF decreased significantly after promoting the expression of EPC Kir2.1.…”

Effect of Microgravity on Endothelial Cell Function, Angiogenesis, and Vessel Remodeling During Wound Healing

“…The functional association of identified miRNAs targeting specific mRNAs revealed that a series of miRNAs (hsa-mir-496, hsa-mir-151a, hsa-miR-296-3p, hsa-mir-148a, hsa-miR-365b-5p, hsa-miR-3687, hsa-mir-454, hsa-miR-155-5p, and hsa-miR-145-5p) differentially regulated the genes involved in cell adhesion, angiogenesis, cell cycle, JAK-STAT signaling, MAPK signaling, NO signaling, and VEGF signaling, finally favoring angiogenesis ( Kasiviswanathan et al, 2020 ). In a study on endothelial progenitor cells, cultured in simulated microgravity, a facilitation of functional angiogenic properties has been reported, with increased HIF-1α and eNOS/NO induced FAK/ERK1/2 pathway upregulation in HUVEC ( Kong et al, 2021 ).…”

“…However, their effectiveness in human patients remains to be established ( Jo et al, 2021 ; Mazini et al, 2021 ; Ullah et al, 2021 ). The proposal of proangiogenic paracrine secretion by stem and precursor cells cultured in microgravity has been provided ( Ratushnyy et al, 2018 ; Kong et al, 2021 ).…”