Increased autophagy in EphrinB2-deficient osteocytes is associated with elevated secondary mineralization and brittle bone

Christina Vrahnas; Martha Blank; Toby A. Dite; Liliana Tatarczuch; Niloufar Ansari; Blessing Crimeen-Irwin; Huynh Nguyen; Mark R. Forwood; Yifang Hu; Mika Ikegame; Keith R. Bambery; Cyril Petibois; Eleanor J. Mackie; Mark J. Tobin; Gordon K. Smyth; Jonathan S. Oakhill; T. John Martin; Natalie A. Sims

doi:10.1038/s41467-019-11373-9

Increased autophagy in EphrinB2-deficient osteocytes is associated with elevated secondary mineralization and brittle bone

Christina Vrahnas, Martha Blank, Toby A. Dite, Liliana Tatarczuch, Niloufar Ansari, Blessing Crimeen-Irwin, Huynh Nguyen, Mark R. Forwood, Yifang Hu, Mika Ikegame, Keith R. Bambery, Cyril Petibois, Eleanor J. Mackie, Mark J. Tobin, Gordon K. Smyth, Jonathan S. Oakhill, T. John Martin, Natalie A. Sims

Research output: Contribution to journal › Article › peer-review

23 Citations (Scopus)

Abstract

Mineralized bone forms when collagen-containing osteoid accrues mineral crystals. This is initiated rapidly (primary mineralization), and continues slowly (secondary mineralization) until bone is remodeled. The interconnected osteocyte network within the bone matrix differentiates from bone-forming osteoblasts; although osteoblast differentiation requires EphrinB2, osteocytes retain its expression. Here we report brittle bones in mice with osteocyte-targeted EphrinB2 deletion. This is not caused by low bone mass, but by defective bone material. While osteoid mineralization is initiated at normal rate, mineral accrual is accelerated, indicating that EphrinB2 in osteocytes limits mineral accumulation. No known regulators of mineralization are modified in the brittle cortical bone but a cluster of autophagy-associated genes are dysregulated. EphrinB2-deficient osteocytes displayed more autophagosomes in vivo and in vitro, and EphrinB2-Fc treatment suppresses autophagy in a RhoA-ROCK dependent manner. We conclude that secondary mineralization involves EphrinB2-RhoA-limited autophagy in osteocytes, and disruption leads to a bone fragility independent of bone mass.

Original language	English
Article number	3436
Journal	Nature communications
Volume	10
Issue number	1
DOIs	https://doi.org/10.1038/s41467-019-11373-9
Publication status	Published - Dec 1 2019

ASJC Scopus subject areas

Chemistry(all)
Biochemistry, Genetics and Molecular Biology(all)
Physics and Astronomy(all)

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10.1038/s41467-019-11373-9

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Vrahnas, C., Blank, M., Dite, T. A., Tatarczuch, L., Ansari, N., Crimeen-Irwin, B., Nguyen, H., Forwood, M. R., Hu, Y., Ikegame, M., Bambery, K. R., Petibois, C., Mackie, E. J., Tobin, M. J., Smyth, G. K., Oakhill, J. S., Martin, T. J., & Sims, N. A. (2019). Increased autophagy in EphrinB2-deficient osteocytes is associated with elevated secondary mineralization and brittle bone. Nature communications, 10(1), [3436]. https://doi.org/10.1038/s41467-019-11373-9

Increased autophagy in EphrinB2-deficient osteocytes is associated with elevated secondary mineralization and brittle bone. / Vrahnas, Christina; Blank, Martha; Dite, Toby A.; Tatarczuch, Liliana; Ansari, Niloufar; Crimeen-Irwin, Blessing; Nguyen, Huynh; Forwood, Mark R.; Hu, Yifang; Ikegame, Mika; Bambery, Keith R.; Petibois, Cyril; Mackie, Eleanor J.; Tobin, Mark J.; Smyth, Gordon K.; Oakhill, Jonathan S.; Martin, T. John; Sims, Natalie A.

In: Nature communications, Vol. 10, No. 1, 3436, 01.12.2019.

Research output: Contribution to journal › Article › peer-review

Vrahnas, C, Blank, M, Dite, TA, Tatarczuch, L, Ansari, N, Crimeen-Irwin, B, Nguyen, H, Forwood, MR, Hu, Y, Ikegame, M, Bambery, KR, Petibois, C, Mackie, EJ, Tobin, MJ, Smyth, GK, Oakhill, JS, Martin, TJ & Sims, NA 2019, 'Increased autophagy in EphrinB2-deficient osteocytes is associated with elevated secondary mineralization and brittle bone', Nature communications, vol. 10, no. 1, 3436. https://doi.org/10.1038/s41467-019-11373-9

Vrahnas, Christina ; Blank, Martha ; Dite, Toby A. ; Tatarczuch, Liliana ; Ansari, Niloufar ; Crimeen-Irwin, Blessing ; Nguyen, Huynh ; Forwood, Mark R. ; Hu, Yifang ; Ikegame, Mika ; Bambery, Keith R. ; Petibois, Cyril ; Mackie, Eleanor J. ; Tobin, Mark J. ; Smyth, Gordon K. ; Oakhill, Jonathan S. ; Martin, T. John ; Sims, Natalie A. / Increased autophagy in EphrinB2-deficient osteocytes is associated with elevated secondary mineralization and brittle bone. In: Nature communications. 2019 ; Vol. 10, No. 1.

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title = "Increased autophagy in EphrinB2-deficient osteocytes is associated with elevated secondary mineralization and brittle bone",

abstract = "Mineralized bone forms when collagen-containing osteoid accrues mineral crystals. This is initiated rapidly (primary mineralization), and continues slowly (secondary mineralization) until bone is remodeled. The interconnected osteocyte network within the bone matrix differentiates from bone-forming osteoblasts; although osteoblast differentiation requires EphrinB2, osteocytes retain its expression. Here we report brittle bones in mice with osteocyte-targeted EphrinB2 deletion. This is not caused by low bone mass, but by defective bone material. While osteoid mineralization is initiated at normal rate, mineral accrual is accelerated, indicating that EphrinB2 in osteocytes limits mineral accumulation. No known regulators of mineralization are modified in the brittle cortical bone but a cluster of autophagy-associated genes are dysregulated. EphrinB2-deficient osteocytes displayed more autophagosomes in vivo and in vitro, and EphrinB2-Fc treatment suppresses autophagy in a RhoA-ROCK dependent manner. We conclude that secondary mineralization involves EphrinB2-RhoA-limited autophagy in osteocytes, and disruption leads to a bone fragility independent of bone mass.",

author = "Christina Vrahnas and Martha Blank and Dite, {Toby A.} and Liliana Tatarczuch and Niloufar Ansari and Blessing Crimeen-Irwin and Huynh Nguyen and Forwood, {Mark R.} and Yifang Hu and Mika Ikegame and Bambery, {Keith R.} and Cyril Petibois and Mackie, {Eleanor J.} and Tobin, {Mark J.} and Smyth, {Gordon K.} and Oakhill, {Jonathan S.} and Martin, {T. John} and Sims, {Natalie A.}",

note = "Funding Information: We thank the staff of the St. Vincent{\textquoteright}s Health Bioresources Center for excellent animal care and assistance, Mr Joshua Johnson and Mrs Ingrid Poulton for technical assistance with histology, Dr. Roger Curtain (Bio21) for technical assistance with BSEM, Dr. Paul Roschger for advice on BSEM analysis, Dr. Eleftherios Paschalis for advice on collagen crosslinking analysis, and Dr. Elizabeth Allan for work on the Kusa 4b10 cells. This work was supported by NHMRC Grants 1042129 and 1081242 to N.A.S. and T.J.M., Program Grant 1054618 to G.K.S., and a Brockhoff Foundation Grant to C.V. J.S.O. was supported by an ARC Future Fellowship. N.A.S. was supported by an NHMRC Senior Research Fellowship and by the SVI Brenda Shanahan Fellowship. Part of this work was untaken at the Infrared Microspectroscopy Beamline at the Australian Synchrotron, part of ANSTO. C.V. also thanks the Australia and New Zealand Bone and Mineral Society for the award of the Christine & T.J. Martin Travel Award, which allowed the laboratory visit to C.P. St. Vincent{\textquoteright}s Institute acknowledges the support of the Victorian State Government OIS program. Publisher Copyright: {\textcopyright} 2019, The Author(s).",

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doi = "10.1038/s41467-019-11373-9",

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T1 - Increased autophagy in EphrinB2-deficient osteocytes is associated with elevated secondary mineralization and brittle bone

AU - Vrahnas, Christina

AU - Blank, Martha

AU - Dite, Toby A.

AU - Tatarczuch, Liliana

AU - Ansari, Niloufar

AU - Crimeen-Irwin, Blessing

AU - Nguyen, Huynh

AU - Forwood, Mark R.

AU - Hu, Yifang

AU - Ikegame, Mika

AU - Bambery, Keith R.

AU - Petibois, Cyril

AU - Mackie, Eleanor J.

AU - Tobin, Mark J.

AU - Smyth, Gordon K.

AU - Oakhill, Jonathan S.

AU - Martin, T. John

AU - Sims, Natalie A.

N1 - Funding Information: We thank the staff of the St. Vincent’s Health Bioresources Center for excellent animal care and assistance, Mr Joshua Johnson and Mrs Ingrid Poulton for technical assistance with histology, Dr. Roger Curtain (Bio21) for technical assistance with BSEM, Dr. Paul Roschger for advice on BSEM analysis, Dr. Eleftherios Paschalis for advice on collagen crosslinking analysis, and Dr. Elizabeth Allan for work on the Kusa 4b10 cells. This work was supported by NHMRC Grants 1042129 and 1081242 to N.A.S. and T.J.M., Program Grant 1054618 to G.K.S., and a Brockhoff Foundation Grant to C.V. J.S.O. was supported by an ARC Future Fellowship. N.A.S. was supported by an NHMRC Senior Research Fellowship and by the SVI Brenda Shanahan Fellowship. Part of this work was untaken at the Infrared Microspectroscopy Beamline at the Australian Synchrotron, part of ANSTO. C.V. also thanks the Australia and New Zealand Bone and Mineral Society for the award of the Christine & T.J. Martin Travel Award, which allowed the laboratory visit to C.P. St. Vincent’s Institute acknowledges the support of the Victorian State Government OIS program. Publisher Copyright: © 2019, The Author(s).

PY - 2019/12/1

Y1 - 2019/12/1

N2 - Mineralized bone forms when collagen-containing osteoid accrues mineral crystals. This is initiated rapidly (primary mineralization), and continues slowly (secondary mineralization) until bone is remodeled. The interconnected osteocyte network within the bone matrix differentiates from bone-forming osteoblasts; although osteoblast differentiation requires EphrinB2, osteocytes retain its expression. Here we report brittle bones in mice with osteocyte-targeted EphrinB2 deletion. This is not caused by low bone mass, but by defective bone material. While osteoid mineralization is initiated at normal rate, mineral accrual is accelerated, indicating that EphrinB2 in osteocytes limits mineral accumulation. No known regulators of mineralization are modified in the brittle cortical bone but a cluster of autophagy-associated genes are dysregulated. EphrinB2-deficient osteocytes displayed more autophagosomes in vivo and in vitro, and EphrinB2-Fc treatment suppresses autophagy in a RhoA-ROCK dependent manner. We conclude that secondary mineralization involves EphrinB2-RhoA-limited autophagy in osteocytes, and disruption leads to a bone fragility independent of bone mass.

AB - Mineralized bone forms when collagen-containing osteoid accrues mineral crystals. This is initiated rapidly (primary mineralization), and continues slowly (secondary mineralization) until bone is remodeled. The interconnected osteocyte network within the bone matrix differentiates from bone-forming osteoblasts; although osteoblast differentiation requires EphrinB2, osteocytes retain its expression. Here we report brittle bones in mice with osteocyte-targeted EphrinB2 deletion. This is not caused by low bone mass, but by defective bone material. While osteoid mineralization is initiated at normal rate, mineral accrual is accelerated, indicating that EphrinB2 in osteocytes limits mineral accumulation. No known regulators of mineralization are modified in the brittle cortical bone but a cluster of autophagy-associated genes are dysregulated. EphrinB2-deficient osteocytes displayed more autophagosomes in vivo and in vitro, and EphrinB2-Fc treatment suppresses autophagy in a RhoA-ROCK dependent manner. We conclude that secondary mineralization involves EphrinB2-RhoA-limited autophagy in osteocytes, and disruption leads to a bone fragility independent of bone mass.

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Increased autophagy in EphrinB2-deficient osteocytes is associated with elevated secondary mineralization and brittle bone

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