title: Dextran-coated fluorapatite crystals doped with Yb3+/Ho3+ for labeling and tracking chondrogenic differentiation of bone marrow mesenchymal stem cells in vitro and in vivo.
abstract: Upconversion fluorescent nanoparticles are becoming more widely used as imaging contrast agents, owing to their high resolution and penetration depth, and avoidance of tissue auto-fluorescence and photodamage to cells. Here, we synthesized upconversion fluorescent crystals from rare-earth Yb3+ and Ho3+ co-doped fluorapatite (FA:Yb3+/Ho3+) suitable for long-term tracking and monitoring cartilage development (chondrogenesis) in bone marrow mesenchymal stem cells (BMSCs) in vitro and in vivo. We initially determined the structure, morphology and luminescence of the products using X-ray powder diffraction, transmission electron microscopy and two-photon confocal microscopy. When excited at 980 nm, FA:Yb3+/Ho3+ crystals exhibited distinct upconversion fluorescence peaks at 543 nm and 654 nm. We then conjugated FA:Yb3+/Ho3+ crystals with dextran to enhance hydrophilicity, biocompatibility and cell penetration. Next, we employed the dextran-coated FA:Yb3+/Ho3+ crystals in labeling and tracking chondrogenic differentiation processes in BMSCs stably expressing green fluorescent protein (BMSCsGFP) in vitro and in vivo. Labeled BMSCsGFP were shown to reproducibly exhibit chondrogenic differentiation potential in RT-PCR analysis, histological assessment and immunohistochemistry. We observed continuous luminescence from the FA:Yb3+/Ho3+ upconversion crystals at 4 weeks and 12 weeks post transplantation in BMSCsGFP, while GFP fluorescence in both control and crystal-treated groups significantly decreased at 12 weeks after BMSCsGFP transplantation. We therefore demonstrate the high biocompatibility and stability of FA:Yb3+/Ho3+ crystals in tracking and monitoring BMSCs chondrogenesis in vitro and in vivo, highlighting their excellent cell labeling potential in cartilage tissue engineering.
authors.affiliation: Institute of Sports Medicine, Beijing Key Laboratory of Sports Injuries, Peking University Third Hospital, 49 North Garden Road, Haidian District, Beijing 100191, People's Republic of China.
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Hu
authors.affiliation: Institute of Sports Medicine, Beijing Key Laboratory of Sports Injuries, Peking University Third Hospital, 49 North Garden Road, Haidian District, Beijing 100191, People's Republic of China.
authors.forename: Jingxian
authors.initials: J
authors.lastname: Zhu
authors.affiliation: Department of Biomedical Engineering, College of Engineering, Peking University, 5 Yiheyuan Road, Haidian District, Beijing 100871, People's Republic of China.
authors.forename: Xiyu
authors.initials: X
authors.lastname: Li
authors.affiliation: Institute of Sports Medicine, Beijing Key Laboratory of Sports Injuries, Peking University Third Hospital, 49 North Garden Road, Haidian District, Beijing 100191, People's Republic of China.
authors.forename: Xin
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Institute of Sports Medicine, Beijing Key Laboratory of Sports Injuries, Peking University Third Hospital, 49 North Garden Road, Haidian District, Beijing 100191, People's Republic of China.
authors.forename: Qingyang
authors.initials: Q
authors.lastname: Meng
authors.affiliation: Medical and Healthy Analysis Centre, Peking University, 38 Xueyuan Road, Haidian District, Beijing 100191, People's Republic of China.
authors.forename: Lan
authors.initials: L
authors.lastname: Yuan
authors.affiliation: Institute of Sports Medicine, Beijing Key Laboratory of Sports Injuries, Peking University Third Hospital, 49 North Garden Road, Haidian District, Beijing 100191, People's Republic of China.
authors.forename: Jiying
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Institute of Sports Medicine, Beijing Key Laboratory of Sports Injuries, Peking University Third Hospital, 49 North Garden Road, Haidian District, Beijing 100191, People's Republic of China.
authors.forename: Xin
authors.initials: X
authors.lastname: Fu
authors.affiliation: Institute of Sports Medicine, Beijing Key Laboratory of Sports Injuries, Peking University Third Hospital, 49 North Garden Road, Haidian District, Beijing 100191, People's Republic of China.
authors.forename: Xiaoning
authors.initials: X
authors.lastname: Duan
authors.affiliation: Department of Biomedical Engineering, College of Engineering, Peking University, 5 Yiheyuan Road, Haidian District, Beijing 100871, People's Republic of China. Electronic address: haifeng.chen@pku.edu.cn.
authors.forename: Haifeng
authors.initials: H
authors.lastname: Chen
authors.affiliation: Institute of Sports Medicine, Beijing Key Laboratory of Sports Injuries, Peking University Third Hospital, 49 North Garden Road, Haidian District, Beijing 100191, People's Republic of China. Electronic address: aoyingfang@163.com.
authors.forename: Yingfang
authors.initials: Y
authors.lastname: Ao
mesh_terms: D000818:Animals; D001031:Apatites / Q000737:chemistry*; D001672:Biocompatible Materials / Q000737:chemistry; D002356:Cartilage / Q000473:pathology; D002454:Cell Differentiation; D002465:Cell Movement; D002470:Cell Survival; D019902:Chondrocytes / Q000166:cytology*; D020219:Chondrogenesis; D003460:Crystallization; D003911:Dextrans / Q000737:chemistry*; D049452:Green Fluorescent Proteins / Q000737:chemistry; D006695:Holmium / Q000737:chemistry*; D059630:Mesenchymal Stem Cells / Q000166:cytology*; D051379:Mice; D008819:Mice, Nude; D018613:Microscopy, Confocal; D011208:Powders; D051381:Rats; D017207:Rats, Sprague-Dawley; D023822:Tissue Engineering / Q000379:methods; D014945:Wound Healing; D014961:X-Ray Diffraction; D015018:Ytterbium / Q000737:chemistry*
chemical_list: D001031:Apatites; D001672:Biocompatible Materials; D003911:Dextrans; D011208:Powders; D049452:Green Fluorescent Proteins; C025105:fluorapatite; D015018:Ytterbium; D006695:Holmium
keywords: BMSCs; Chondrogenic differentiation; In vivo imaging; Upconversion fluorescence