Wnt/beta-catenin signaling is a normal physiological response to mechanical loading in bone.
A preliminary expression profiling analysis of osteoblasts derived from tibia explants of the high bone mass LRP5 G171V transgenic mice demonstrated increased expression of canonical Wnt pathway and Wnt/beta-catenin target genes compared with non-transgenic explant derived osteoblasts. Therefore, expression of Wnt/beta-catenin target genes were monitored after in vivo loading of the tibia of LRP5 G171V transgenic mice compared with non-transgenic mice. Loading resulted in the increased expression of Wnt pathway and Wnt/beta-catenin target genes including Wnt10B, SFRP1, cyclin D1, FzD2, WISP2, and connexin 43 in both genotypes; however, there was a further increased in transcriptional response with the LRP5 G171V transgenic mice. Similar increases in the expression of these genes (except cyclin D1) were observed when non-transgenic mice were pharmacologically treated with a canonical Wnt pathway activator, glycogen synthase kinase 3beta inhibitor and then subjected to load. These in vivo results were further corroborated by in vitro mechanical loading experiments in which MC3T3-E1 osteoblastic cells were subjected to 3400 microstrain alone for 5 h, which increased the expression of Wnt10B, SFRP1, cyclin D1, FzD2, WISP2, and connexin 43. Furthermore, when MC3T3-E1 cells were treated with either glycogen synthase kinase 3beta inhibitor or Wnt3A to activate Wnt signaling and then subjected to load, a synergistic up-regulation of these genes was observed compared with vehicle-treated cells. Collectively, the in vivo and in vitro mechanical loading results support that Wnt/beta-catenin signaling is a normal physiological response to load and that activation of the Wnt/beta-catenin pathway enhances the sensitivity of osteoblasts/osteocytes to mechanical loading.
Robinson
John A
JA
Women's Health and Musculoskeletal Biology, Wyeth Research, Collegeville, Pennsylvania 19426, USA. robinsj@wyeth.com
Chatterjee-Kishore
Moitreyee
M
Yaworsky
Paul J
PJ
Cullen
Diane M
DM
Zhao
Weiguang
W
Li
Christine
C
Kharode
Yogendra
Y
Sauter
Linda
L
Babij
Philip
P
Brown
Eugene L
EL
Hill
Andrew A
AA
Akhter
Mohammed P
MP
Johnson
Mark L
ML
Recker
Robert R
RR
Komm
Barry S
BS
Bex
Frederick J
FJ
D000818:Animals; D001842:Bone and Bones / Q000378:metabolism*; D019938:Cyclin D1 / Q000378:metabolism; D017931:DNA Primers / Q000737:chemistry; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors; D000071679:Glycogen Synthase Kinase 3 beta; D051379:Mice; D008822:Mice, Transgenic; D010006:Osteoblasts / Q000378:metabolism; D010641:Phenotype; D012313:RNA / Q000378:metabolism; D015398:Signal Transduction; D013314:Stress, Mechanical; D014158:Transcription, Genetic; D051155:Wnt1 Protein / Q000378:metabolism; D051176:beta Catenin / Q000378:metabolism*
D017931:DNA Primers; D051155:Wnt1 Protein; D051176:beta Catenin; D019938:Cyclin D1; D012313:RNA; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D038362:Glycogen Synthase Kinase 3