Artikel
Effects of sensory and sympathetic neurotransmitters on osteoblast metabolism
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Autoren
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Tanja Niedermair
- Klinik und Poliklinik Orthopädie, Experimentelle Orthopädie, ZMB, BioPark1, Universitätsklinikum Regensburg, Regensburg, Germany
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Raphael Seebröker
- Klinik und Poliklinik Orthopädie, Experimentelle Orthopädie, ZMB, BioPark1, Universitätsklinikum Regensburg, Regensburg, Germany
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Rainer H. Straub
- Klinik und Poliklinik für Innere Medizin I, Experimentelle Rheumatologie und Neuroendokrine Immunologie, Universitätsklinikum Regensburg, Regensburg, Germany
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Joachim Grifka
- Orthopädische Universitätsklinik Regensburg, Asklepios Klinikum Bad Abbach, Bad Abbach, Germany
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Susanne Grässel
- Klinik und Poliklinik Orthopädie, Experimentelle Orthopädie, ZMB, BioPark1, Universitätsklinikum Regensburg, Regensburg, Germany
| Veröffentlicht: | 5. Oktober 2015 |
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Gliederung
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Objectives: In previous studies we found reduced biomechanical bone strength and matrix quality in mice lacking the sensory neurotransmitter substance P (SP) and in mice after chemical inhibition (sympathectomy) of the sympathetic nervous system (SNS). We also detected differences in apoptosis rate and activity of osteoblasts isolated from Tac1-/- (no SP expression) and sympathectomized mice [1]. A similar reduction of bone microarchitecture has been described for alpha-calcitonin gene-related peptide (alpha-CGRP)-deficient mice [2]. Lack of SP or alpha-CGRP and absence of the SNS modulate osteoblast metabolism and result in inferior bone quality. This study further investigates and compares the influence of sensory neurotransmitters SP and alpha-CGRP and the sympathetic neurotransmitter norepinephrine (NE) on osteoblast proliferation, apoptosis and activity in vitro.
Methods: Primary osteoblasts were isolated from female C57Bl/6J mice and cultured in osteogenic medium for 14 and 21 days according to established protocols (Niedermair et al., 2014). Osteoblasts were stimulated with SP (10-8 and 10-10 M), alpha-CGRP (10-8 and 10-10 M) and NE (10-6 and 10-8 M) for the last 24 hours. Proliferation was tested by BrdU labeling method; caspase 3/7-activity was measured to determine apoptosis and alkaline phosphatase (ALP) activity was measured to determine osteoblast bone formation activity.
Results and Conclusion: Proliferation rate of osteoblasts was not affected by stimulation with SP or alpha-CGRP. Stimulation with 10-6 M NE highly upregulated proliferation and 10-8 M NE moderately upregulated proliferation after 14 and 21 days of osteogenic culture. Caspase 3/7-activity was clearly reduced by stimulation with 10-10 M SP, 10-10 M alpha-CGRP, 10-6 M and 10-8 M NE. SP (10-10 M) and alpha-CGRP (10-8 M) reduced ALP activity whereas stimulation with both concentrations of NE did not affect ALP activity at any culture time point.
The sympathetic neurotransmitter NE induces proliferation, presumably mainly via β-adrenergic receptors (AR; 10-6 M) whereas NE does not affect osteoblast matrix forming activity (ALP activity). Both, sensory and sympathetic neurotransmitters affect apoptosis rate of osteoblasts via reduction of caspase 3/7 activity. Our data suggest that the sensory nervous system modulates osteoblast viability (apoptosis) and matrix forming activity (ALP) while the SNS preferentially promotes osteoblast expansion.
