Follistatin-like 3 is a mediator of exercise-driven bone formation and strengthening.
Exercise is vital for maintaining bone strength and architecture. Follistatin-like 3 (FSTL3), a member of follistatin family, is a mechanosensitive protein upregulated in response to exercise and is involved in regulating musculoskeletal health. Here, we investigated the potential role of FSTL3 in exercise-driven bone remodeling. Exercise-dependent regulation of bone structure and functions was compared in mice with global Fstl3 gene deletion (Fstl3-/-) and their age-matched Fstl3+/+ littermates. Mice were exercised by low-intensity treadmill walking. The mechanical properties and mineralization were determined by μCT, three-point bending test and sequential incorporation of calcein and alizarin complexone. ELISA, Western-blot analysis and qRT-PCR were used to analyze the regulation of FSTL3 and associated molecules in the serum specimens and tissues. Daily exercise significantly increased circulating FSTL3 levels in mice, rats and humans. Compared to age-matched littermates, Fstl3-/- mice exhibited significantly lower fracture tolerance, having greater stiffness, but lower strain at fracture and yield energy. Furthermore, increased levels of circulating FSTL3 in young mice paralleled greater strain at fracture compared to the lower levels of FSTL3 in older mice. More significantly, Fstl3-/- mice exhibited loss of mechanosensitivity and irresponsiveness to exercise-dependent bone formation as compared to their Fstl3+/+ littermates. In addition, FSTL3 gene deletion resulted in loss of exercise-dependent sclerostin regulation in osteocytes and osteoblasts, as compared to Fstl3+/+ osteocytes and osteoblasts, in vivo and in vitro. The data identify FSTL3 as a critical mediator of exercise-dependent bone formation and strengthening and point to its potential role in bone health and in musculoskeletal diseases.
Department of Bioengineering, University of California, Riverside, CA 92507, USA. Electronic address: jnam@engr.ucr.edu.
J
J
Nam
Division of Biosciences, The Ohio State University College of Dentistry, Columbus, OH 43210, USA.
P
P
Perera
Division of Biosciences, The Ohio State University College of Dentistry, Columbus, OH 43210, USA.
R
R
Gordon
Division of Orthodontics, The Ohio State University College of Dentistry, Columbus, OH 43210, USA.
Y H
YH
Jeong
Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH 43210, USA.
A D
AD
Blazek
Division of Orthodontics, The Ohio State University College of Dentistry, Columbus, OH 43210, USA.
D G
DG
Kim
Division of Orthodontics, The Ohio State University College of Dentistry, Columbus, OH 43210, USA.
B C
BC
Tee
Division of Orthodontics, The Ohio State University College of Dentistry, Columbus, OH 43210, USA.
Z
Z
Sun
Department of Internal Medicine, The Ohio State University College of Medicine, Columbus, OH 43210, USA.
T D
TD
Eubank
Department of Biomedical Engineering, The Ohio State University, Columbus, OH 43210, USA.
Y
Y
Zhao
Division of Periodontics, The Ohio State University College of Dentistry, Columbus, OH 43210, USA.
B
B
Lablebecioglu
Hormel Institute, University of Minnesota, MN 55901, USA.
S
S
Liu
Department of Biomedical Engineering, The Ohio State University, Columbus, OH 43210, USA; Department of Orthopedics, The Ohio State University College of Medicine, Columbus, OH 43210, USA.
A
A
Litsky
Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH 43210, USA.
N L
NL
Weisleder
Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH 43210, USA.
B S
BS
Lee
Department of Physiology, University of Kentucky, Lexington, KY 40536, USA.
T
T
Butterfield
Department of Veterinary and Animal Science, University of Massachusetts-Amherst, MA 01003, USA.
A L
AL
Schneyer
Division of Biosciences, The Ohio State University College of Dentistry, Columbus, OH 43210, USA; Department of Orthopedics, The Ohio State University College of Medicine, Columbus, OH 43210, USA.
S
S
Agarwal
D000328:Adult; D000368:Aged; D000818:Animals; D000880:Anthraquinones / Q000737:chemistry; D016723:Bone Remodeling; D001842:Bone and Bones / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005080:Exercise Test; D005260:Female; D005452:Fluoresceins / Q000737:chemistry; D038702:Follistatin-Related Proteins / Q000502:physiology*; D017353:Gene Deletion; D005786:Gene Expression Regulation; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010006:Osteoblasts / Q000166:cytology*; D010011:Osteocytes / Q000166:cytology*; D010805:Physical Conditioning, Animal; D051381:Rats; D017207:Rats, Sprague-Dawley; D013314:Stress, Mechanical; D013997:Time Factors; D015854:Up-Regulation; D016138:Walking; D055114:X-Ray Microtomography; D055815:Young Adult
D000880:Anthraquinones; D005452:Fluoresceins; D038702:Follistatin-Related Proteins; C000606403:Fstl3 protein, human; C498620:Fstl3 protein, mouse; C000606404:Fstl3 protein, rat; C070804:alizarin complexone; C007740:fluorexon
Bone remodeling; Exercise; Follistatin-like 3; Osteoblast; Osteocyte