Human Osteoblastic Cells Propagate Intercellular Calcium Signals by Two Different Mechanisms

• Published in: Journal of bone and mineral research 2000-06, Vol.15 (6), p.1024-1032
• Main Authors: Jørgensen, Niklas R., Henriksen, Zanne, Brot, Christine, Eriksen, Erik F., Sørensen, Ole H., Civitelli, Roberto, Steinberg, Thomas H.
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Bone Marrow Cells - cytology; Bone Marrow Cells - drug effects; Bone Marrow Cells - metabolism; calcium; Calcium Signaling; Cells, Cultured; cell‐cell communication; Fundamental and applied biological sciences. Psychology; gap junctions; Gap Junctions - metabolism; Humans; Intracellular Fluid - metabolism; Kinetics; osteoblast; Osteoblasts - cytology; Osteoblasts - drug effects; Osteoblasts - metabolism; P2 receptors; Rats; Receptors, Purinergic P2 - metabolism; Receptors, Purinergic P2Y2; Skeleton and joints; Space life sciences; Stromal Cells - cytology; Stromal Cells - drug effects; Stromal Cells - metabolism; Vertebrates: osteoarticular system, musculoskeletal system
• ISSN: 0884-0431; 1523-4681
• DOI: 10.1359/jbmr.2000.15.6.1024

Effective bone remodeling requires the coordination of bone matrix deposition by osteoblastic cells, which may occur via soluble mediators or via direct intercellular communication. We have previously identified two mechanisms by which rat osteoblastic cell lines coordinate calcium signaling among cells: autocrine activation of P2 (purinergic) receptors leading to release of intracellular calcium stores, and gap junction‐mediated communication resulting in influx of extracellular calcium. In the current work we asked whether human osteoblastic cells (HOB) were capable of mechanically induced intercellular calcium signaling, and if so, by which mechanisms. Upon mechanical stimulation, human osteoblasts propagated fast intercellular calcium waves, which required activation of P2 receptors and release of intracellular calcium stores but did not require calcium influx or gap junctional communication. After the fast intercellular calcium waves were blocked, we observed slower calcium waves that were dependent on gap junctional communication and influx of extracellular calcium. These results show that human osteoblastic cells can propagate calcium signals from cell to cell by two markedly different mechanisms and suggest that these two pathways may serve different purposes in coordinating osteoblast functions.