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J Cell Physiol. 2019 Apr 23. doi: 10.1002/jcp.28652. [Epub ahead of print]

IL-6 counteracts the inhibitory effect of IL-4 on osteogenic differentiation of human adipose stem cells.

Author information

1
Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands.
2
Department of Oral and Maxillofacial Surgery, Amsterdam University Medical Centers (Amsterdam UMC)/ACTA, location VUmc, Amsterdam Movement Sciences, Amsterdam, The Netherlands.
3
Department of Dental Materials Science, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands.
4
Department of Physiology, Amsterdam Cardiovascular Sciences, Amsterdam University Medical Centers (Amsterdam UMC), Amsterdam, The Netherlands.

Abstract

Fracture repair is characterized by cytokine production and hypoxia. To better predict cytokine modulation of mesenchymal stem cell (MSC)-aided bone healing, we investigated whether interleukin 4 (IL-4), IL-6, and their combination, affect osteogenic differentiation, vascular endothelial growth factor (VEGF) production, and/or mammalian target of rapamycin complex 1 (mTORC1) activation by MSCs under normoxia or hypoxia. Human adipose stem cells (hASCs) were cultured with IL-4, IL-6, or their combination for 3 days under normoxia (20% O 2 ) or hypoxia (1% O 2 ), followed by 11 days without cytokines under normoxia or hypoxia. Hypoxia did not alter IL-4 or IL-6-modulated gene or protein expression by hASCs. IL-4 alone decreased runt-related transcription factor 2 (RUNX2) and collagen type 1 (COL1) gene expression, alkaline phosphatase (ALP) activity, and VEGF protein production by hASCs under normoxia and hypoxia, and decreased mineralization of hASCs under hypoxia. In contrast, IL-6 increased mineralization of hASCs under normoxia, and enhanced RUNX2 gene expression under normoxia and hypoxia. Neither IL-4 nor IL-6 affected phosphorylation of the mTORC1 effector protein P70S6K. IL-4 combined with IL-6 diminished the inhibitory effect of IL-4 on ALP activity, bone nodule formation, and VEGF production, and decreased RUNX2 and COL1 expression, similar to IL-4 alone, under normoxia and hypoxia. In conclusion, IL-4 alone, but not in combination with IL-6, inhibits osteogenic differentiation and angiogenic stimulation potential of hASCs under normoxia and hypoxia, likely through pathways other than mTORC1. These results indicate that cytokines may differentially affect bone healing and regeneration when applied in isolation or in combination.

KEYWORDS:

hASCs; interleukin-4; interleukin-6; osteogenic differentiation; oxygen tension

PMID:
31016754
DOI:
10.1002/jcp.28652

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