Hip fractures are the most devastating result of osteoporosis and often the first step in a downward spiral of lost ambulation and independence, institutionalization, and secondary medical morbidity and mortality. Within one year of hip fracture, 50% of patients will be unable to walk without assistance, 25% will require long-term care, and 20% will have died. One potent regulator of bone formation is physical loading (Krahl et al. 1994); however, the cellular sensing mechanism directing mechanotransduction has proven to be elusive. Our laboratory is one of the first to demonstrate that the osteocyte primary cilium plays a major role in this process (Malone et al. 2007). The primary cilium is a solitary cellular extension present in virtually every cell in the body, but its function has yet to be fully characterized. As osteocyte mechanosensors, these organelles act synergistically with other known regulators of bone metabolism. Our contribution is to elucidate the primary cilium microdomain?s role in osteocyte mechanotransduction and identify the intracellular signaling mechanisms involved. This contribution is significant because it catalyzes a continuum of research leading to novel pharmacologic therapeutics that potentiate mechanical loading at a molecular level. The long-term goal of this project is to determine how primary cilia contribute to bone mechanosensing and capitalize on this knowledge to develop novel therapies. The overall objective of this application is to exploit the molecular mechanisms identified in the last funding period to sensitize osteocyte primary cilia and identify osteocyte-cilia specific therapeutic targets. We will achieve this objective by establishing the potential of osteocyte cilia therapeutics in vivo (SA1), enhancing osteocyte-specificity through molecular manipulation of the intraciliary signaling system (SA2), and ensuring that ciliary strategies do not have adverse effects on bone biology (SA3). At the conclusion of this project, we expect to contribute potential pharmacologic agents that target unique characteristics of the osteocyte microdomain to bias bone formation without adverse effects to normal physiology. Osteoporosis prevention will dramatically increase patient quality of life, reduce morbidity, and cut health care costs. A collateral benefit will be extending this knowledge to applications in other cell types to develop treatments for numerous cilia-associated diseases.

Public Health Relevance

Osteoporosis is a devastating disease that causes significant social costs and human suffering. Primary cilia are solitary cellular antennae that have recently been shown to sense a variety of extracellular signals in bone and other tissues, including mechanical stimulation. In this project we will establish the potential of osteocyte cilia therapeutics in vivo, enhance therapeutic osteocyte-specificity through molecular manipulation of the intraciliary signaling system, and ensure that ciliary strategies do not have adverse effects on bone biology.

National Institute of Health (NIH)
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Research Project (R01)
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Nicks, Kristy
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Columbia University (N.Y.)
Biomedical Engineering
Biomed Engr/Col Engr/Engr Sta
New York
United States
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Moore, Emily R; Zhu, Ya Xing; Ryu, Han Seul et al. (2018) Periosteal progenitors contribute to load-induced bone formation in adult mice and require primary cilia to sense mechanical stimulation. Stem Cell Res Ther 9:190
Moore, Emily R; Jacobs, Christopher R (2018) The primary cilium as a signaling nexus for growth plate function and subsequent skeletal development. J Orthop Res 36:533-545
Moore, Emily R; Yang, Yuchen; Jacobs, Christopher R (2018) Primary cilia are necessary for Prx1-expressing cells to contribute to postnatal skeletogenesis. J Cell Sci 131:
Spasic, Milos; Jacobs, Christopher R (2017) Primary cilia: Cell and molecular mechanosensors directing whole tissue function. Semin Cell Dev Biol 71:42-52
Spasic, M; Jacobs, C R (2017) Lengthening primary cilia enhances cellular mechanosensitivity. Eur Cell Mater 33:158-168
Chen, Julia C; Hoey, David A; Chua, Mardonn et al. (2016) Mechanical signals promote osteogenic fate through a primary cilia-mediated mechanism. FASEB J 30:1504-11
Nguyen, An M; Young, Y-N; Jacobs, Christopher R (2015) The primary cilium is a self-adaptable, integrating nexus for mechanical stimuli and cellular signaling. Biol Open 4:1733-8
Lee, Kristen L; Guevarra, Marie D; Nguyen, An M et al. (2015) The primary cilium functions as a mechanical and calcium signaling nexus. Cilia 4:7
Chen, Julia C; Chua, Mardonn; Bellon, Raymond B et al. (2015) Epigenetic changes during mechanically induced osteogenic lineage commitment. J Biomech Eng 137:020902
Duffy, Michael P; Jacobs, Christopher R (2015) Seeing the unseen: cell strain and mechanosensing. Biophys J 108:1583-1584

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