title: Biphasic influence of dexamethasone exposure on embryonic vertebrate skeleton development.
abstract: Dexamethasone (Dex) has anti-inflammatory and immunomodulatory properties against many conditions. There is a potential teratogenic risk, however, for pregnant women receiving Dex treatment. It has been claimed that Dex exposure during pregnancy could affect osteogenesis in the developing embryo, which still remains highly controversial. In this study, we employed chick embryos to investigate the effects of Dex exposure on skeletal development using combined in vivo and in vitro approach. First, we demonstrated that Dex (10(-8)-10(-6)μmol/egg) exposure resulted in a shortening of the developing long bones of chick embryos, and it accelerated the deposition of calcium salts. Secondly, histological analysis of chick embryo phalanxes exhibited Dex exposure inhibited the proliferation of chondrocytes, increased apoptosis of chondrocytes and osteocytes, and led to atypical arranged hypertrophic chondrocytes. The expression of genes related to skeletogenesis was also analyzed by semi-quantitative RT-PCR. The expression of ALP, Col1a2 and Col2a1 was decreased in the Dex treated phalanxes. A detectable increase was observed in Runx-2 and Mmp-13 expression. We next examined how Dex affected the different stages of skeletogenesis in vitro. Utilizing limb bud mesenchyme micromass cultures, we determined that Dex exposure exerted no effect on apoptosis but impaired chondrogenic cell proliferation. Interestingly, low dose of Dex moderately prompted nodule formation as revealed by alcian blue staining, but higher doses of Dex significantly inhibited similar chondrogenic differentiation. Dex exposure did not induce apoptosis when the chondrogenic precursors were still at the mesenchymal stage, however, cell viability was suppressed when the mesenchyme differentiated into chondrocytes. Alizarin red staining revealed that the capacity to form mineralized bone nodules was correspondingly enhanced as Dex concentrations increased. The mRNA level of Sox-9 was slightly increased in mesenchymal cell mass treated by low concentration of Dex. Mmp-13 expression was obviously up-regulated by Dex in both mesenchymal cells and primary chondrocyte cultures. And Col10a1 expression was also increased by Dex exposure in chondrocyte. In summary, we have revealed that different concentrations of Dex exposure during early gestation could exert a biphasic effect on vertebrate skeletal development.
authors.affiliation: Department of Histology & Embryology, Key Laboratory for Regenerative Medicine of the Ministry of Education, School of Medicine, Jinan University, Guangzhou 510632, PR China.
authors.forename: Xin
authors.initials: X
authors.lastname: Cheng
authors.affiliation: Department of Histology & Embryology, Key Laboratory for Regenerative Medicine of the Ministry of Education, School of Medicine, Jinan University, Guangzhou 510632, PR China.
authors.forename: Jian-Long
authors.initials: JL
authors.lastname: Chen
authors.affiliation: Department of Histology & Embryology, Key Laboratory for Regenerative Medicine of the Ministry of Education, School of Medicine, Jinan University, Guangzhou 510632, PR China.
authors.forename: Zheng-Lai
authors.initials: ZL
authors.lastname: Ma
authors.affiliation: Department of Histology & Embryology, Key Laboratory for Regenerative Medicine of the Ministry of Education, School of Medicine, Jinan University, Guangzhou 510632, PR China.
authors.forename: Zhao-Long
authors.initials: ZL
authors.lastname: Zhang
authors.affiliation: Department of Histology & Embryology, Key Laboratory for Regenerative Medicine of the Ministry of Education, School of Medicine, Jinan University, Guangzhou 510632, PR China.
authors.forename: Shun
authors.initials: S
authors.lastname: Lv
authors.affiliation: Department of Histology & Embryology, Key Laboratory for Regenerative Medicine of the Ministry of Education, School of Medicine, Jinan University, Guangzhou 510632, PR China.
authors.forename: Dong-Mei
authors.initials: DM
authors.lastname: Mai
authors.affiliation: Department of Histology & Embryology, Key Laboratory for Regenerative Medicine of the Ministry of Education, School of Medicine, Jinan University, Guangzhou 510632, PR China.
authors.forename: Jia-Jia
authors.initials: JJ
authors.lastname: Liu
authors.affiliation: Division of Cell and Developmental Biology, University of Dundee, Dundee DD1 5EH, UK.
authors.forename: Manli
authors.initials: M
authors.lastname: Chuai
authors.affiliation: Stem Cell and Regeneration Thematic Research Programme, School of Biomedical Sciences, Chinese University of Hong Kong, Shatin, Hong Kong.
authors.forename: Kenneth Ka Ho
authors.initials: KK
authors.lastname: Lee
authors.affiliation: Stem Cell and Regeneration Thematic Research Programme, School of Biomedical Sciences, Chinese University of Hong Kong, Shatin, Hong Kong.
authors.forename: Chao
authors.initials: C
authors.lastname: Wan
authors.affiliation: Department of Histology & Embryology, Key Laboratory for Regenerative Medicine of the Ministry of Education, School of Medicine, Jinan University, Guangzhou 510632, PR China; Institute of Fetal-Preterm Labor Medicine, Jinan University, Guangzhou 510632, PR China. Electronic address: yang_xuesong@126.com.
authors.forename: Xuesong
authors.initials: X
authors.lastname: Yang
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000187:drug effects* / Q000196:embryology*; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D049109:Cell Proliferation / Q000187:drug effects / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002642:Chick Embryo; D019902:Chondrocytes / Q000187:drug effects* / Q000502:physiology; D003907:Dexamethasone / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D047108:Embryonic Development / Q000187:drug effects* / Q000502:physiology; D005260:Female; D005938:Glucocorticoids / Q000633:toxicity; D011247:Pregnancy
chemical_list: D005938:Glucocorticoids; D003907:Dexamethasone
keywords: Chick embryo; Chondrogenesis; Dexamethasone; Micromass culture; Osteogenesis