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Hypoxic osteocytes recruit human MSCs through an OPN/CD44-mediated pathway.
Leah Forquer Raheja1, Damian C Genetos, Clare E Yellowley
1Department of Anatomy, Physiology & Cell Biology, School of Veterinary Medicine, University of California, 4206 VM3A, 1285 Veterinary Medicine Drive, Davis, CA 95616, USA.
Biochemical and Biophysical Research Communications
|December 25, 2007
Summary
Hypoxia at fracture sites stimulates osteocytes to release osteopontin (OPN), a signaling molecule that recruits mesenchymal stem cells (MSCs) for bone repair. This study identifies OPN as a key factor in fracture healing.
Area of Science:
- Bone biology
- Stem cell research
- Fracture healing mechanisms
Background:
- Osteocytes' role in recruiting mesenchymal stem cells (MSCs) to damaged bone matrix is poorly understood.
- Vascular disruption at fracture sites leads to hypoxia, known to increase cell migration genes like osteopontin (OPN).
Purpose of the Study:
- To investigate the effect of conditioned media from hypoxic osteocytes on MSC migration.
- To determine if OPN is involved in osteocyte-mediated MSC recruitment during fracture repair.
Main Methods:
- Cultured osteocytes under hypoxic conditions.
- Assessed MSC migration in response to osteocyte-conditioned media.
- Measured OPN expression in hypoxic osteocytes.
- Utilized OPN and CD44 neutralizing antibodies.
- Tested recombinant OPN's effect on MSC migration.
Main Results:
- Hypoxic osteocyte media significantly enhanced MSC migration.
- OPN expression was notably increased in hypoxic osteocytes.
- OPN and CD44 neutralizing antibodies substantially inhibited MSC migration.
- Recombinant OPN dose-dependently increased MSC migration.
Conclusions:
- Hypoxia stimulates osteocytes to release chemotactic factors, specifically OPN.
- OPN released by osteocytes plays a crucial role in recruiting MSCs to fracture sites.
- These findings suggest a novel mechanism for osteocyte and OPN involvement in fracture repair.
