title: Role of biphasic calcium phosphate ceramic-mediated secretion of signaling molecules by macrophages in migration and osteoblastic differentiation of MSCs.
abstract: The inflammatory reaction initiates fracture healing and could play a role in the osteoinductive effect of calcium phosphate (CaP) ceramics, which has been widely confirmed; however, the underlying mechanism has not been fully elucidated. In this study, various signaling molecules from macrophages under the stimulation of osteoinductive biphasic calcium phosphate (BCP) ceramic and its degradation products were examined and evaluated for their influence on the migration and osteoblastic differentiation of mesenchymal stem cells (MSCs). The results of cellular experiments confirmed that the gene expression of most inflammatory factors (IL-1, IL-6 and MCP-1) and growth factors (VEGF, PDGF and EGF) by macrophages were up-regulated to varying degrees by BCP ceramic and its degradation products. Cell migration tests demonstrated that the conditioned media (CMs), which contained abundant signaling molecules secreted by macrophages cultured on BCP ceramic and its degradation products, promoted the migration of MSCs. qRT-PCR analysis indicated that CMs promoted the gene expression of osteogenic markers (ALP, COL-I, OSX, BSP and OPN) in MSCs. ALP activity and mineralization staining further confirmed that CMs promoted the osteoblastic differentiation of MSCs. The present study confirmed the correlation between the inflammatory reaction and osteoinductive capacity of BCP ceramic. The ceramic itself and its degradation products can induce macrophages to express and secrete various signaling molecules, which then recruit and promote the MSCs to differentiate into osteoblasts. Compared with BCP conditioned media, degradation particles played a more substantial role in this process. Thus, inflammation initiated by BCP ceramic and its degradation products could be necessary for osteoinduction by the ceramic.
  
  
  
  It is known that the inflammatory reaction initiates fracture healing. The aim of this study was to examine whether osteoinductive BCP ceramics could cause macrophages to change their secretion patterns and whether the secreted cytokines could affect migration and osteoblastic differentiation of MSCs. Moreover, the duration of inflammation could be influenced by the local ionic environment and the degradation products of the implant. Our experimental results revealed the correlation between the inflammatory reaction and osteoinductive capacity of BCP ceramic. The ceramic itself and its degradation products can induce macrophages to express and secrete various signaling molecules, which then recruit and promote the MSCs to differentiate into osteoblasts. Compared with ionic microenvironment, degradation particles played a more substantial role in this process. Therefore, the appropriate inflammation initiated by BCP ceramic and its degradation products could be essential for osteoinduction by the ceramic. We believe that the present study improves the understanding of the effect of biomaterial-mediated inflammation on MSC migration and differentiation and established a preliminary correlation between the immune system and osteoinduction by biomaterials.
authors.affiliation: National Engineering Research Center for Biomaterials, Sichuan University, Chengdu 610064, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.affiliation: National Engineering Research Center for Biomaterials, Sichuan University, Chengdu 610064, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Liu
authors.affiliation: Department of Ophthalmology, West China Hospital of Sichuan University, Chengdu 610041, China. Electronic address: guobohx@163.com.
authors.forename: Bo
authors.initials: B
authors.lastname: Guo
authors.affiliation: National Engineering Research Center for Biomaterials, Sichuan University, Chengdu 610064, China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Yang
authors.affiliation: National Engineering Research Center for Biomaterials, Sichuan University, Chengdu 610064, China.
authors.forename: Xuening
authors.initials: X
authors.lastname: Chen
authors.affiliation: National Engineering Research Center for Biomaterials, Sichuan University, Chengdu 610064, China. Electronic address: zxd7303@163.com.
authors.forename: Xiangdong
authors.initials: X
authors.lastname: Zhu
authors.affiliation: National Engineering Research Center for Biomaterials, Sichuan University, Chengdu 610064, China.
authors.forename: Yujiang
authors.initials: Y
authors.lastname: Fan
authors.affiliation: National Engineering Research Center for Biomaterials, Sichuan University, Chengdu 610064, China.
authors.forename: Xingdong
authors.initials: X
authors.lastname: Zhang
mesh_terms: D000818:Animals; D002113:Calcification, Physiologic / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects*; D002465:Cell Movement / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002516:Ceramics / Q000494:pharmacology*; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005786:Gene Expression Regulation / Q000187:drug effects; D006882:Hydroxyapatites / Q000494:pharmacology*; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D018613:Microscopy, Confocal; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D000067996:RAW 264.7 Cells; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D016207:Cytokines; D006882:Hydroxyapatites; C074950:hydroxyapatite-beta tricalcium phosphate
keywords: BCP ceramic; MSCs; Macrophages; Migration; Osteoblastic differentiation; Signaling molecules