title: Sodium-dependent vitamin C transporter SVCT2: expression and function in bone marrow stromal cells and in osteogenesis.
abstract: Ascorbic acid (Vitamin C) has a critical role in bone formation and osteoblast differentiation, but very little is known about the molecular mechanisms of ascorbic acid entry into bone marrow stromal cells (BMSCs). To address this gap in knowledge, we investigated the identity of the transport system that is responsible for the uptake of ascorbic acid into bone marrow stromal cells (BMSCs). First, we examined the expression of the two known isoforms of the sodium-coupled ascorbic acid transporter, namely SVCT1 and SVCT2, in BMSCs (Lin-ve Sca1+ve) and bone at the mRNA level. Only SVCT2 mRNA was detected in BMSCs and bone. Uptake of ascorbic acid in BMSCs was Na(+)-dependent and saturable. In order to define the role of SVCT2 in BMSC differentiation into osteoblasts, BMSCs were stimulated with osteogenic media for different time intervals, and the activity of SVCT2 was monitored by ascorbic acid uptake. SVCT2 expression was up-regulated during the osteogenic differentiation of BMSCs; the expression was maximal at the earliest phase of differentiation. Subsequently, osteogenesis was inhibited in BMSCs upon knock-down of SVCT2 by lentivirus shRNA. We also found that the expression of the SVCT2 could be negatively or positively modulated by the presence of oxidant (Sin-1) or antioxidant (Ascorbic acid) compounds, respectively, in BMSCs. Furthermore, we found that this transporter is also regulated with age in mouse bone. These data show that SVCT2 plays a vital role in the osteogenic differentiation of BMSCs and that its expression is altered under conditions associated with redox reaction. Our findings could be relevant to bone tissue engineering and bone related diseases such as osteoporosis in which oxidative stress and aging plays important role.
authors.affiliation: Department of Orthopaedic Surgery, Georgia health Science University, Augusta, GA 30912, USA. sfulzele@georgiahealth.edu
authors.forename: Sadanand
authors.initials: S
authors.lastname: Fulzele
authors.forename: Paresh
authors.initials: P
authors.lastname: Chothe
authors.forename: Rajnikumar
authors.initials: R
authors.lastname: Sangani
authors.forename: Norman
authors.initials: N
authors.lastname: Chutkan
authors.forename: Mark
authors.initials: M
authors.lastname: Hamrick
authors.forename: Maryka
authors.initials: M
authors.lastname: Bhattacharyya
authors.forename: Puttur D
authors.initials: PD
authors.lastname: Prasad
authors.forename: Ibrahim
authors.initials: I
authors.lastname: Zakhary
authors.forename: Matthew
authors.initials: M
authors.lastname: Bowser
authors.forename: Carlos
authors.initials: C
authors.lastname: Isales
authors.forename: Vadivel
authors.initials: V
authors.lastname: Ganapathy
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001205:Ascorbic Acid / Q000494:pharmacology; D001842:Bone and Bones / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D010012:Osteogenesis / Q000187:drug effects; D010084:Oxidation-Reduction; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D012886:Skull / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D060347:Sodium-Coupled Vitamin C Transporters / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D023822:Tissue Engineering; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D000975:Antioxidants; D020033:Protein Isoforms; D034741:RNA, Small Interfering; D060347:Sodium-Coupled Vitamin C Transporters; D012964:Sodium; D001205:Ascorbic Acid