title: In vivo mechanical loading rapidly activates β-catenin signaling in osteocytes through a prostaglandin mediated mechanism.
abstract: The response of the skeleton to loading appears to be mediated through the activation of the Wnt/β-catenin signaling pathway and osteocytes have long been postulated to be the primary mechanosensory cells in bone. To examine the kinetics of the mechanoresponse of bone and cell types involved in vivo, we performed forearm loading of 17-week-old female TOPGAL mice. β-catenin signaling was observed only in embedded osteocytes, not osteoblasts, at 1h post-loading, spreading to additional osteocytes and finally to cells on the bone surface by 24h. This early activation at 1h appeared to be independent of receptor (Lrp5/6) mediated activation as it occurred in the presence of the inhibitors sclerostin and/or Dkk1. The COX-2 inhibitor, Carprofen, blocked the activation of β-catenin signaling and decline in sclerostin positive osteocytes post-loading implying an important role for prostaglandin. In vitro, PI3K/Akt activation was shown to be required for β-catenin nuclear translocation downstream from prostaglandin in MLO-Y4 osteocyte-like cells supporting this mechanism. Downstream targets of β-catenin signaling, sclerostin and Dkk1, were also examined and found to be significantly downregulated in osteocytes in vivo at 24h post-loading. The pattern of initially activated osteocytes appeared random and in order to understand this heterogeneous expression, a novel finite element model of the strain field in the ulna was developed, which predicts highly variable local magnitudes of strain experienced by osteocytes. In summary, both in vivo and in vitro models show the rapid activation of β-catenin in response to load through the early release of prostaglandin and that strain fields in the bone are extremely heterogeneous resulting in heterogeneous activation of the β-catenin pathway in osteocytes in vivo.
authors.affiliation: UMKC School of Dentistry, Department of Oral and Craniofacial Sciences, Kansas City, MO 64108, USA.
authors.forename: N
authors.initials: N
authors.lastname: Lara-Castillo
authors.affiliation: UMKC School of Dentistry, Department of Oral and Craniofacial Sciences, Kansas City, MO 64108, USA.
authors.forename: N A
authors.initials: NA
authors.lastname: Kim-Weroha
authors.affiliation: UMKC School of Dentistry, Department of Oral and Craniofacial Sciences, Kansas City, MO 64108, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Kamel
authors.affiliation: The Royal Veterinary College, Royal College Street, London, NW1 0TU, UK.
authors.forename: B
authors.initials: B
authors.lastname: Javaheri
authors.affiliation: OsteoGeneX Inc, Kansas City, KS 66103, USA.
authors.forename: D L
authors.initials: DL
authors.lastname: Ellies
authors.affiliation: UMKC School of Dentistry, Department of Oral and Craniofacial Sciences, Kansas City, MO 64108, USA; Stowers Institute for Medical Research, Kansas City, MO 64110, USA.
authors.forename: R E
authors.initials: RE
authors.lastname: Krumlauf
authors.affiliation: UMKC School of Computing and Engineering, Kansas City, MO 64110, USA.
authors.forename: G
authors.initials: G
authors.lastname: Thiagarajan
authors.affiliation: UMKC School of Dentistry, Department of Oral and Craniofacial Sciences, Kansas City, MO 64108, USA. Electronic address: johnsonmark@umkc.edu.
authors.forename: M L
authors.initials: ML
authors.lastname: Johnson
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002460:Cell Line; D005260:Female; D020342:Finite Element Analysis; D006023:Glycoproteins / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D007700:Kinetics; D051379:Mice; D010011:Osteocytes / Q000378:metabolism*; D011453:Prostaglandins / Q000378:metabolism*; D015398:Signal Transduction; D013314:Stress, Mechanical; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C501127:Dkk1 protein, mouse; D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; D011453:Prostaglandins; C486030:Sost protein, mouse; D051176:beta Catenin
keywords: Mechanical loading; Osteocyte; Prostaglandin; Wnt/β-catenin signaling
references.citation: Am J Hum Genet. 2002 Jan;70(1):11-9
references.pmid: 11741193
references.citation: J Biol Chem. 2008 Feb 29;283(9):5866-75
references.pmid: 18089564
references.citation: Connect Tissue Res. 2004;45(1):40-9
references.pmid: 15203939
references.citation: Metabolism. 1970 Dec;19(12):1071-84
references.pmid: 4321644
references.citation: J Bone Miner Res. 1989 Oct;4(5):783-8
references.pmid: 2816520
references.citation: J Cell Biochem. 1994 Jul;55(3):287-99
references.pmid: 7962159
references.citation: Bone. 2013 Jun;54(2):285-95
references.pmid: 23318973
references.citation: Cell Tissue Res. 2013 May;352(2):191-8
references.pmid: 23329124
references.citation: Bone. 2013 Aug;55(2):335-46
references.pmid: 23643681
references.citation: Endocr Rev. 2013 Oct;34(5):658-90
references.pmid: 23612223
references.citation: Calcif Tissue Int. 2014 Jan;94(1):5-24
references.pmid: 24042263
references.citation: J Bone Miner Res. 2014 Mar;29(3):705-15
references.pmid: 23929793
references.citation: FASEB J. 2014 Apr;28(4):1582-92
references.pmid: 24347610
references.citation: Bone. 2014 Sep;66:131-9
references.pmid: 24925445
references.citation: J Orthop Res. 2014 Dec;32(12):1580-8
references.pmid: 25196694
references.citation: J Biomech. 2014 Jan 22;47(2):451-7
references.pmid: 24268312
references.citation: J Biol Chem. 2001 Apr 20;276(16):13365-71
references.pmid: 11278573
references.citation: Cell. 2001 Nov 16;107(4):513-23
references.pmid: 11719191
references.citation: N Engl J Med. 2002 May 16;346(20):1513-21
references.pmid: 12015390
references.citation: Calcif Tissue Int. 2002 Apr;70(4):320-9
references.pmid: 12004337
references.citation: Bone. 2008 Apr;42(4):606-15
references.pmid: 18280232
references.citation: J Bone Miner Res. 2008 Sep;23(9):1372-81
references.pmid: 18410233
references.citation: J Biol Chem. 2008 Oct 24;283(43):29196-205
references.pmid: 18723514
references.citation: J Bone Miner Res. 2011 Feb;26(2):229-38
references.pmid: 21254230
references.citation: PLoS One. 2011;6(3):e17772
references.pmid: 21436889
references.citation: Bone. 2011 Aug;49(2):184-93
references.pmid: 21419885
references.citation: J Bone Miner Res. 2011 Aug;26(8):1759-66
references.pmid: 21491486
references.citation: FEBS Lett. 2011 Aug 4;585(15):2450-4
references.pmid: 21723865
references.citation: J Biol Chem. 2011 Nov 11;286(45):39450-6
references.pmid: 21956113
references.citation: Bone. 2012 Jan;50(1):209-17
references.pmid: 22075208
references.citation: Med Eng Phys. 2012 Apr;34(3):350-6
references.pmid: 21903442
references.citation: Osteoporos Int. 2012 Apr;23(4):1225-34
references.pmid: 21573880
references.citation: Bone. 2013 Jun;54(2):205-12
references.pmid: 23069374
references.citation: Bone. 2013 Jun;54(2):296-306
references.pmid: 23072918
references.citation: Bone. 2013 Jun;54(2):182-90
references.pmid: 23085083
references.citation: FASEB J. 1995 Mar;9(5):441-5
references.pmid: 7896017
references.citation: Biochem Biophys Res Commun. 1995 Dec 14;217(2):640-8
references.pmid: 7503746
references.citation: Am J Physiol. 1996 Jul;271(1 Pt 1):E205-8
references.pmid: 8760099
references.citation: Biochem Biophys Res Commun. 1996 Aug 5;225(1):62-8
references.pmid: 8769095
references.citation: J Cell Biol. 1997 Oct 20;139(2):497-506
references.pmid: 9334351
references.citation: J Bone Miner Res. 1997 Dec;12(12):2014-23
references.pmid: 9421234
references.citation: Am J Physiol. 1999 Jan;276(1 Pt 1):E171-8
references.pmid: 9886964
references.citation: Development. 1999 Oct;126(20):4557-68
references.pmid: 10498690
references.citation: J Bone Miner Res. 2005 Jan;20(1):41-9
references.pmid: 15619668
references.citation: Science. 2005 Dec 2;310(5753):1504-10
references.pmid: 16293724
references.citation: J Biol Chem. 2005 Dec 16;280(50):41342-51
references.pmid: 16251184
references.citation: Gene. 2006 Feb 15;367:1-16
references.pmid: 16361069
references.citation: J Biol Chem. 2006 Apr 7;281(14):9576-88
references.pmid: 16461770
references.citation: J Biomech. 2006;39(9):1735-43
references.pmid: 15993413
references.citation: Biochem Biophys Res Commun. 2010 Jan 1;391(1):364-9
references.pmid: 19913504
references.citation: J Biol Chem. 2010 Mar 19;285(12):8743-58
references.pmid: 20042609
references.citation: Ann Biomed Eng. 2010 Mar;38(3):594-604
references.pmid: 20013156
references.citation: Bone. 2010 Nov;47(5):872-81
references.pmid: 20713195
references.citation: J Bone Miner Res. 2010 Dec;25(12):2657-68
references.pmid: 20578217
references.citation: J Bone Miner Res. 2011 Jan;26(1):100-12
references.pmid: 20658561
references.citation: J Biol Chem. 2006 Aug 18;281(33):23698-711
references.pmid: 16790443
references.citation: J Biol Chem. 2006 Oct 20;281(42):31720-8
references.pmid: 16908522
references.citation: J Biomech. 2007;40(10):2199-206
references.pmid: 17196968
references.citation: J Biol Chem. 2007 Jul 13;282(28):20715-27
references.pmid: 17491024
references.citation: J Immunol Methods. 2008 Jan 1;329(1-2):194-200
references.pmid: 18036607
references.citation: J Musculoskelet Neuronal Interact. 2007 Oct-Dec;7(4):313-5
references.pmid: 18094489
references.citation: J Biol Chem. 2003 Oct 31;278(44):43146-56
references.pmid: 12939279