Transcriptional profiling of cortical versus cancellous bone from mechanically-loaded murine tibiae reveals differential gene expression

Kelly, Natalie H.; Schimenti, John C.; Ross, F. Patrick; Meulen, Marjolein C. H. van der

doi:10.1016/j.bone.2016.02.007

Cited by 62 publications

(91 citation statements)

References 58 publications

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“…5 E ). These findings are consistent with Kelly and colleagues, (46) who performed RNA-Seq on tibias of 10-week-old mice after one bout of tibial compression. They reported increased Wnt1 expression in cortical bone at 3 hours (6.2-fold) and 24 hours (6.1-fold) after loading, and increased Wnt7b (3.2-fold) at 3 hours.…”

Section: Discussionsupporting

confidence: 91%

“…First, we did not find a significant change in Wnt10b expression after one bout of loading, whereas others have reported increased Wnt10b at 3 to 4 hours and 24 hours after loading. (45,46) One possible reason for the difference is that we used a less stimulating protocol. We applied 7 to 8 N peak force to engender −2200 με peak compressive strain at the diaphyseal site of interest, a protocol we have shown stimulates lamellar bone formation with little to no woven bone.…”

Section: Discussionmentioning

confidence: 99%

“…We applied 7 to 8 N peak force to engender −2200 με peak compressive strain at the diaphyseal site of interest, a protocol we have shown stimulates lamellar bone formation with little to no woven bone. (9) Kelly and colleagues (46) applied a slightly higher peak force (9 N) using an otherwise identical protocol, whereas Robinson and colleagues (45) used a tibial four-point bending protocol that has been shown to induce woven bone. (50) Another finding at odds with some previous reports is the downregulation of osteoblast/bone formation genes early after initial loading.…”

Section: Discussionmentioning

confidence: 99%

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Activation of Wnt Signaling by Mechanical Loading Is Impaired in the Bone of Old Mice

Holguin

Brodt

Silva³

2016

Journal of Bone and Mineral Research

127

137

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Aging diminishes bone formation engendered by mechanical loads, but the mechanism for this impairment remains unclear. Because Wnt signaling is required for optimal loading-induced bone formation, we hypothesized that aging impairs the load-induced activation of Wnt signaling. We analyzed dynamic histomorphometry of 5-month-old, 12-month-old, and 22-month-old C57Bl/6JN mice subjected to multiple days of tibial compression and corroborated an age-related decline in the periosteal loading response on day 5. Similarly, 1 day of loading increased periosteal and endocortical bone formation in young-adult (5-month-old) mice, but old (22-month-old) mice were unresponsive. These findings corroborated mRNA expression of genes related to bone formation and the Wnt pathway in tibias after loading. Multiple bouts (3 to 5 days) of loading upregulated bone formation–related genes, e.g., Osx and Col1a1, but older mice were significantly less responsive. Expression of Wnt negative regulators, Sost and Dkk1, was suppressed with a single day of loading in all mice, but suppression was sustained only in young-adult mice. Moreover, multiple days of loading repeatedly suppressed Sost and Dkk1 in young-adult, but not in old tibias. The age-dependent response to loading was further assessed by osteocyte staining for Sclerostin and LacZ in tibia of TOPGAL mice. After 1 day of loading, fewer osteocytes were Sclerostin-positive and, corroboratively, more osteocytes were LacZ-positive (Wnt active) in both 5-month-old and 12-month-old mice. However, although these changes were sustained after multiple days of loading in 5-month-old mice, they were not sustained in 12-month-old mice. Last, Wnt1 and Wnt7b were the most load-responsive of the 19 Wnt ligands. However, 4 hours after a single bout of loading, although their expression was upregulated threefold to 10-fold in young-adult mice, it was not altered in old mice. In conclusion, the reduced bone formation response of aged mice to loading may be due to failure to sustain Wnt activity with repeated loading.

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Section: Discussionsupporting

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Activation of Wnt Signaling by Mechanical Loading Is Impaired in the Bone of Old Mice

Holguin

Brodt

Silva³

2016

Journal of Bone and Mineral Research

127

137

View full text Add to dashboard Cite

show abstract

“…Differences between the studies, potentially due to differences in the loading protocols used and time points assayed, include differences in the Wnt ligands found to be regulated by loading. Holguin et al (2016) did not observe changes in the canonical Wnt ligand Wnt10b within the first day following loading, whereas enhanced Wnt10b levels were observed acutely following loading in the current study, as well as in previous studies (Johnson et al, 2006, Kelly et al, 2016). …”

Section: Discussionsupporting

confidence: 84%

Old age and the associated impairment of bones' adaptation to loading are associated with transcriptomic changes in cellular metabolism, cell-matrix interactions and the cell cycle

Galea

Meakin

Harris

et al. 2017

Gene

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In old animals, bone's ability to adapt its mass and architecture to functional load-bearing requirements is diminished, resulting in bone loss characteristic of osteoporosis. Here we investigate transcriptomic changes associated with this impaired adaptive response. Young adult (19-week-old) and aged (19-month-old) female mice were subjected to unilateral axial tibial loading and their cortical shells harvested for microarray analysis between 1 h and 24 h following loading (36 mice per age group, 6 mice per loading group at 6 time points). In non-loaded aged bones, down-regulated genes are enriched for MAPK, Wnt and cell cycle components, including E2F1. E2F1 is the transcription factor most closely associated with genes down-regulated by ageing and is down-regulated at the protein level in osteocytes. Genes up-regulated in aged bone are enriched for carbohydrate metabolism, TNFα and TGFβ superfamily components. Loading stimulates rapid and sustained transcriptional responses in both age groups. However, genes related to proliferation are predominantly up-regulated in the young and down-regulated in the aged following loading, whereas those implicated in bioenergetics are down-regulated in the young and up-regulated in the aged. Networks of inter-related transcription factors regulated by E2F1 are loading-responsive in both age groups. Loading regulates genes involved in similar signalling cascades in both age groups, but these responses are more sustained in the young than aged. From this we conclude that cells in aged bone retain the capability to sense and transduce loading-related stimuli, but their ability to translate acute responses into functionally relevant outcomes is diminished.

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“…This would further suggest that the load duration-related response could be strain magnitude dependent, with bone tissues that are subjected to lower peak strains reaching a load duration saturation at fewer load cycles than tissues subjected to greater strain magnitudes. It is also possible that the cellular mechanisms of the cancellous and cortical bone tissues’ responses to mechanical loading could be different [38] due to differences in their biological microenvironment [39, 40]. Another possibility is that longer loading durations (e.g.…”

Section: Discussionmentioning

confidence: 99%

Effects of Loading Duration and Short Rest Insertion on Cancellous and Cortical Bone Adaptation in the Mouse Tibia

2017

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The skeleton’s osteogenic response to mechanical loading can be affected by loading duration and rest insertion during a series of loading events. Prior animal loading studies have shown that the cortical bone response saturates quickly and short rest insertions between load cycles can enhance cortical bone formation. However, it remains unknown how loading duration and short rest insertion affect load-induced osteogenesis in the mouse tibial compressive loading model, and particularly in cancellous bone. To address this issue, we applied cyclic loading (-9 N peak load; 4 Hz) to the tibiae of three groups of 16 week-old female C57BL/6 mice for two weeks, with a different number of continuous load cycles applied daily to each group (36, 216 and 1200). A fourth group was loaded under 216 daily load cycles with a 10 s rest insertion after every fourth cycle. We found that as few as 36 load cycles per day were able to induce osteogenic responses in both cancellous and cortical bone. Furthermore, while cortical bone area and thickness continued to increase through 1200 cycles, the incremental increase in the osteogenic response decreased as load number increased, indicating a reduced benefit of the increasing number of load cycles. In the proximal metaphyseal cancellous bone, trabecular thickness increased with load up to 216 cycles. We also found that insertion of a 10 s rest between load cycles did not improve the osteogenic response of the cortical or cancellous tissues compared to continuous loading in this model given the age and sex of the mice and the loading parameters used here. These results suggest that relatively few load cycles (e.g. 36) are sufficient to induce osteogenic responses in both cortical and cancellous bone in the mouse tibial loading model. Mechanistic studies using the mouse tibial loading model to examine bone formation and skeletal mechanobiology could be accomplished with relatively few load cycles.

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Transcriptional profiling of cortical versus cancellous bone from mechanically-loaded murine tibiae reveals differential gene expression

Cited by 62 publications

References 58 publications

Activation of Wnt Signaling by Mechanical Loading Is Impaired in the Bone of Old Mice

Activation of Wnt Signaling by Mechanical Loading Is Impaired in the Bone of Old Mice

Old age and the associated impairment of bones' adaptation to loading are associated with transcriptomic changes in cellular metabolism, cell-matrix interactions and the cell cycle

Effects of Loading Duration and Short Rest Insertion on Cancellous and Cortical Bone Adaptation in the Mouse Tibia

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