title: Low-intensity pulsed ultrasound promotes chondrogenic progenitor cell migration via focal adhesion kinase pathway.
abstract: Low-intensity pulsed ultrasound (LIPUS) has been studied frequently for its beneficial effects on the repair of injured articular cartilage. We hypothesized that these effects are due to stimulation of chondrogenic progenitor cell (CPC) migration toward injured areas of cartilage through focal adhesion kinase (FAK) activation. CPC chemotaxis in bluntly injured osteochondral explants was examined by confocal microscopy, and migratory activity of cultured CPCs was measured in transwell and monolayer scratch assays. FAK activation by LIPUS was analyzed in cultured CPCs by Western blot. LIPUS effects were compared with the effects of two known chemotactic factors: N-formyl-methionyl-leucyl-phenylalanine (fMLF) and high-mobility group box 1 (HMGB1) protein. LIPUS significantly enhanced CPC migration on explants and in cell culture assays. Phosphorylation of FAK at the kinase domain (Tyr 576/577) was maximized by 5 min of exposure to LIPUS at a dose of 27.5 mW/cm(2) and frequency of 3.5 MHz. Treatment with fMLF, but not HMBG1, enhanced FAK activation to a degree similar to that of LIPUS, but neither fMLF nor HMGB1 enhanced the LIPUS effect. LIPUS-induced CPC migration was blocked by suppressing FAK phosphorylation with a Src family kinase inhibitor that blocks FAK phosphorylation. Our results imply that LIPUS might be used to promote cartilage healing by inducing the migration of CPCs to injured sites, which could delay or prevent the onset of post-traumatic osteoarthritis.
authors.affiliation: Department of Orthopaedics and Rehabilitation, University of Iowa, Iowa City, Iowa, USA; Department of Biomedical Engineering, University of Iowa, Iowa City, Iowa, USA.
authors.forename: Kee W
authors.initials: KW
authors.lastname: Jang
authors.affiliation: Department of Orthopaedics and Rehabilitation, University of Iowa, Iowa City, Iowa, USA.
authors.forename: Lei
authors.initials: L
authors.lastname: Ding
authors.affiliation: Department of Orthopaedics and Rehabilitation, University of Iowa, Iowa City, Iowa, USA.
authors.forename: Dongrim
authors.initials: D
authors.lastname: Seol
authors.affiliation: Department of Biomedical Engineering, University of Iowa, Iowa City, Iowa, USA.
authors.forename: Tae-Hong
authors.initials: TH
authors.lastname: Lim
authors.affiliation: Department of Orthopaedics and Rehabilitation, University of Iowa, Iowa City, Iowa, USA; Veterans Affairs Medical Center, Iowa City, Iowa, USA.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Buckwalter
authors.affiliation: Department of Orthopaedics and Rehabilitation, University of Iowa, Iowa City, Iowa, USA. Electronic address: james-martin@uiowa.edu.
authors.forename: James A
authors.initials: JA
authors.lastname: Martin
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002358:Cartilage, Articular / Q000378:metabolism*; D002417:Cattle; D002465:Cell Movement; D019902:Chondrocytes / Q000166:cytology / Q000378:metabolism*; D051417:Focal Adhesion Kinase 1 / Q000378:metabolism*; D018613:Microscopy, Confocal; D010003:Osteoarthritis / Q000517:prevention & control; D010766:Phosphorylation; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism*; D014464:Ultrasonic Therapy; D014945:Wound Healing
chemical_list: D051417:Focal Adhesion Kinase 1
keywords: Articular cartilage; Cell migration; Focal adhesion kinase; Low-intensity pulsed ultrasound; Post-traumatic osteoarthritis