Abstract
Deletion of connexin (Cx) 43 from osteoblasts and osteocytes (OCN-Cre;Cx43fl/− mice) or from osteocytes only (DMP1-8kb-Cre;Cx43fl/fl mice) results in increased cortical, but not cancellous, osteocyte apoptosis and widening of the femoral midshaft without changes in cortical thickness. Despite the consequent larger moment of inertia, stiffness and ultimate load, measures of mechanical strength assessed by three-point bending, are not higher in either model of Cx43 deficiency due to reduced Young’s modulus, a measure of the stiffness of the material per unit of area. In OCN-Cre;Cx43fl/− mice, this was accompanied by a reduced ratio of nonreducible/reducible collagen cross-links as assessed by Fourier transformed infrared imaging (FTIRI) in the femoral diaphysis. On the other hand, DMP1-8kb-Cre;Cx43fl/fl mice did not show a significant reduction in collagen maturation in the same skeletal site, but a small decrease in mineralization was detected by FTIRI. Remarkably, both osteoblastic and osteocytic cells lacking Cx43 expressed lower mRNA levels of lysyl oxidase, a crucial enzyme involved in collagen maturation. These findings suggest that Cx43 expression in osteoblasts is involved in maintaining the quality of the bone matrix in cortical bone through the maturation of collagen cross-links. Osteocytic Cx43 expression is important also to maintain the stiffness of the bone material, where Cx43 deficiency results in local reduction in mineralization, possibly due to osteocyte apoptosis.
Similar content being viewed by others
References
Goodenough DA, Paul DL (2009) Gap junctions. Cold Spring Harb Perspect Biol 1:a002576
Civitelli R (2008) Cell–cell communication in the osteoblast/osteocyte lineage. Arch Biochem Biophys 473:188–192
Cherian PP, Siller-Jackson AJ, Gu S, Wang X, Bonewald LF, Sprague E, Jiang JX (2005) Mechanical strain opens connexin 43 hemichannels in osteocytes: a novel mechanism for the release of prostaglandin. Mol Biol Cell 16:3100–3106
Genetos DC, Kephart CJ, Zhang Y, Yellowley CE, Donahue HJ (2007) Oscillating fluid flow activation of gap junction hemichannels induces ATP release from MLO-Y4 osteocytes. J Cell Physiol 212:207–214
Goodenough DA, Paul DL (2003) Beyond the gap: functions of unpaired connexon channels. Nat Rev Mol Cell Biol 4:285–294
Plotkin LI, Manolagas SC, Bellido T (2002) Transduction of cell survival signals by connexin-43 hemichannels. J Biol Chem 277:8648–8657
Decrock E, Vinken M, De Vuyst E, Krysko DV, D’ Herde K, Vanhaecke T, Vandenabeele P, Rogiers V, Leybaert L (2009) Connexin-related signaling in cell death: to live or let die? Cell Death Differ 16:524–536
Plotkin LI, Lezcano V, Thostenson J, Weinstein RS, Manolagas SC, Bellido T (2008) Connexin 43 is required for the anti-apoptotic effect of bisphosphonates on osteocytes and osteoblasts in vivo. J Bone Miner Res 23:1712–1721
Plotkin LI, Weinstein RS, Parfitt AM, Roberson PK, Manolagas SC, Bellido T (1999) Prevention of osteocyte and osteoblast apoptosis by bisphosphonates and calcitonin. J Clin Invest 104:1363–1374
Bivi N, Lezcano V, Romanello M, Bellido T, Plotkin LI (2011) Connexin43 interacts with βarrestin: a pre-requisite for osteoblast survival induced by parathyroid hormone. J Cell Biochem 112:2920–2930
Bivi N, Condon KW, Allen MR, Farlow N, Passeri G, Brun L, Rhee Y, Bellido T, Plotkin LI (2012) Cell autonomous requirement of connexin 43 for osteocyte survival: consequences for endocortical resorption and periosteal bone formation. J Bone Miner Res 27:374–389
Aguirre JI, Plotkin LI, Stewart SA, Weinstein RS, Parfitt AM, Manolagas SC, Bellido T (2006) Osteocyte apoptosis is induced by weightlessness in mice and precedes osteoclast recruitment and bone loss. J Bone Miner Res 21:605–615
Cardoso L, Herman BC, Verborgt O, Laudier D, Majeska RJ, Schaffler MB (2009) Osteocyte apoptosis controls activation of intracortical resorption in response to bone fatigue. J Bone Miner Res 24:597–605
Emerton KB, Hu B, Woo AA, Sinofsky A, Hernandez C, Majeska RJ, Jepsen KJ, Schaffler MB (2009) Osteocyte apoptosis and control of bone resorption following ovariectomy in mice. Bone 46:577–583
O’Brien CA, Jia D, Plotkin LI, Bellido T, Powers CC, Stewart SA, Manolagas SC, Weinstein RS (2004) Glucocorticoids act directly on osteoblasts and osteocytes to induce their apoptosis and reduce bone formation and strength. Endocrinology 145:1835–1841
Watkins M, Grimston SK, Norris JY, Guillotin B, Shaw A, Beniash E, Civitelli R (2011) Osteoblast connexin43 modulates skeletal architecture by regulating both arms of bone remodeling. Mol Biol Cell 22:1240–1251
Zhang Y, Paul EM, Sathyendra V, Davidson A, Bronson S, Srinivasan S, Gross TS, Donahue HJ (2011) Enhanced osteoclastic resorption and responsiveness to mechanical load in gap junction deficient bone. PLoS One 6:e23516
Lakso M, Sauer B, Mosinger B Jr, Lee EJ, Manning RW, Yu SH, Mulder KL, Westphal H (1992) Targeted oncogene activation by site-specific recombination in transgenic mice. Proc Natl Acad Sci USA 89:6232–6236
Orban PC, Chui D, Marth JD (1992) Tissue- and site-specific DNA recombination in transgenic mice. Proc Natl Acad Sci USA 89:6861–6865
Theis M, de Wit C, Schlaeger TM, Eckardt D, Kruger O, Doring B, Risau W, Deutsch U, Pohl U, Willecke K (2001) Endothelium-specific replacement of the connexin43 coding region by a lacZ reporter gene. Genesis 29:1–13
Reaume AG, de Sousa PA, Kulkarni S, Langille BL, Zhu D, Davies TC, Juneja SC, Kidder GM, Rossant J (1995) Cardiac malformation in neonatal mice lacking connexin43. Science 267:1831–1834
Zhang M, Xuan S, Bouxsein ML, Von Stechow D, Akeno N, Faugere MC, Malluche H, Zhao G, Rosen CJ, Efstratiadis A, Clemens TL (2002) Osteoblast-specific knockout of the insulin-like growth factor (IGF) receptor gene reveals an essential role of IGF signaling in bone matrix mineralization. J Biol Chem 277:44005–44012
Hilton MJ, Tu X, Wu X, Bai S, Zhao H, Kobayashi T, Kronenberg HM, Teitelbaum SL, Ross FP, Kopan R, Long F (2008) Notch signaling maintains bone marrow mesenchymal progenitors by suppressing osteoblast differentiation. Nat Med 14:306–314
Silverstein DM, Urban M, Gao Y, Mattoo TK, Spray DC, Rozental R (2001) Renal morphology in connexin43 knockout mice. Pediatr Nephrol 16:467–471
Kalajzic I, Braut A, Guo D, Jiang X, Kronenberg MS, Mina M, Harris MA, Harris SE, Rowe DW (2004) Dentin matrix protein 1 expression during osteoblastic differentiation, generation of an osteocyte GFP-transgene. Bone 35:74–82
Almeida M, Han L, Martin-Millan M, Plotkin LI, Stewart SA, Roberson PK, Kousteni S, O’Brien CA, Bellido T, Parfitt AM, Weinstein RS, Jilka RL, Manolagas SC (2007) Skeletal involution by age-associated oxidative stress and its acceleration by loss of sex steroids. J Biol Chem 282:27285–27297
Plotkin LI, Bivi N, Bellido T (2011) A bisphosphonate that does not affect osteoclasts prevents osteoblast and osteocyte apoptosis and the loss of bone strength induced by glucocorticoids in mice. Bone 49:122–127
Allen MR, Reinwald S, Burr DB (2008) Alendronate reduces bone toughness of ribs without significantly increasing microdamage accumulation in dogs following 3 years of daily treatment. Calcif Tissue Int 82:354–360
Gadaleta SJ, Paschalis EP, Betts F, Mendelsohn R, Boskey AL (1996) Fourier transform infrared spectroscopy of the solution-mediated conversion of amorphous calcium phosphate to hydroxyapatite: new correlations between X-ray diffraction and infrared data. Calcif Tissue Int 58:9–16
Paschalis EP, Verdelis K, Doty SB, Boskey AL, Mendelsohn R, Yamauchi M (2001) Spectroscopic characterization of collagen cross-links in bone. J Bone Miner Res 16:1821–1828
Miller LM, Vairavamurthy V, Chance MR, Mendelsohn R, Paschalis EP, Betts F, Boskey AL (2001) In situ analysis of mineral content and crystallinity in bone using infrared micro-spectroscopy of the nu(4) PO(4)(3-) vibration. Biochim Biophys Acta 1527:11–19
Bouxsein ML, Boyd SK, Christiansen BA, Guldberg RE, Jepsen KJ, Muller R (2010) Guidelines for assessment of bone microstructure in rodents using micro-computed tomography. J Bone Miner Res 25:1468–1486
Lecka-Czernik B, Gubrij I, Moerman EA, Kajkenova O, Lipschitz DA, Manolagas SC, Jilka RL (1999) Inhibition of Osf2/Cbfa1 expression and terminal osteoblast differentiation by PPAR-gamma 2. J Cell Biochem 74:357–371
Livak KJ, Schmittgen TD (2001) Analysis of relative gene expression data using real-time quantitative PCR and the 2−ΔΔCT method. Methods 25:402–408
Turner CH (2006) Bone strength: current concepts. Ann N Y Acad Sci 1068:429–446
Turner CH, Burr DB (1993) Basic biomechanical measurements of bone: a tutorial. Bone 14:595–608
Burr DB (2002) The contribution of the organic matrix to bone’s material properties. Bone 31:8–11
Saito M, Marumo K (2010) Collagen cross-links as a determinant of bone quality: a possible explanation for bone fragility in aging, osteoporosis, and diabetes mellitus. Osteoporos Int 21:195–214
Viguet-Carrin S, Garnero P, Delmas PD (2006) The role of collagen in bone strength. Osteoporos Int 17:319–336
Pischon N, Maki JM, Weisshaupt P, Heng N, Palamakumbura AH, N’Guessan P, Ding A, Radlanski R, Renz H, Bronckers TA, Myllyharju J, Kielbassa AM, Kleber BM, Bernimoulin JP, Trackman PC (2009) Lysyl oxidase (lox) gene deficiency affects osteoblastic phenotype. Calcif Tissue Int 85:119–126
Qing H, Ardeshirpour L, Pajevic PD, Dusevich V, Jahn K, Kato S, Wysolmerski J, Bonewald LF (2012) Demonstration of osteocytic perilacunar/canalicular remodeling in mice during lactation. J Bone Miner Res 27:1018–1029
Currey JD (1969) The mechanical consequences of variation in the mineral content of bone. J Biomech 2:1–11
Currey JD (1969) The relationship between the stiffness and the mineral content of bone. J Biomech 2:477–480
Miller LM, Little W, Schirmer A, Sheik F, Busa B, Judex S (2007) Accretion of bone quantity and quality in the developing mouse skeleton. J Bone Miner Res 22:1037–1045
Paschalis EP, Tatakis DN, Robins S, Fratzl P, Manjubala I, Zoehrer R, Gamsjaeger S, Buchinger B, Roschger A, Phipps R, Boskey AL, Dall’Ara E, Varga P, Zysset P, Klaushofer K, Roschger P (2011) Lathyrism-induced alterations in collagen cross-links influence the mechanical properties of bone material without affecting the mineral. Bone 49:1232–1241
Chavassieux P, Seeman E, Delmas PD (2007) Insights into material and structural basis of bone fragility from diseases associated with fractures: how determinants of the biomechanical properties of bone are compromised by disease. Endocr Rev 28:151–164
Davison KS, Siminoski K, Adachi JD, Hanley DA, Goltzman D, Hodsman AB, Josse R, Kaiser S, Olszynski WP, Papaioannou A, Ste-Marie LG, Kendler DL, Tenenhouse A, Brown JP (2006) Bone strength: the whole is greater than the sum of its parts. Semin Arthritis Rheum 36:22–31
Sanada H, Shikata J, Hamamoto H, Ueba Y, Yamamuro T, Takeda T (1978) Changes in collagen cross-linking and lysyl oxidase by estrogen. Biochim Biophys Acta 541:408–413
Nyman JS, Roy A, Acuna RL, Gayle HJ, Reyes MJ, Tyler JH, Dean DD, Wang X (2006) Age-related effect on the concentration of collagen crosslinks in human osteonal and interstitial bone tissue. Bone 39:1210–1217
Acknowledgments
The authors thank Kanan Vyas, Drs. Keith Condon and Ignacio Aguirre for technical assistance, and Drs. Charles Tuner, David Burr, and Matthew Allen for insightful suggestions. This research was supported by the National Institutes of Health (R01-AR053643). μCT studies were performed using equipment obtained with NIH grant S10-RR023710 (PI: James Williams, Department of Anatomy and Cell Biology, Indiana University School of Medicine).
Author information
Authors and Affiliations
Corresponding author
Additional information
The authors have stated that they have no conflict of interest.
Rights and permissions
About this article
Cite this article
Bivi, N., Nelson, M.T., Faillace, M.E. et al. Deletion of Cx43 from Osteocytes Results in Defective Bone Material Properties but Does Not Decrease Extrinsic Strength in Cortical Bone. Calcif Tissue Int 91, 215–224 (2012). https://doi.org/10.1007/s00223-012-9628-z
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00223-012-9628-z