TY - JOUR
T1 - Interleukin-6 (IL-6) deficiency enhances intramembranous osteogenesis following stress fracture in mice
AU - Coates, Brandon A.
AU - McKenzie, Jennifer A.
AU - Yoneda, Susumu
AU - Silva, Matthew J.
N1 - Funding Information:
This work was supported by funding from NIAMS ( R01 AR050211 , P30 AR057235 , P30 AR074992 ) and NIBIB ( T32 EB018266 ). The authors would like to thank the cores and staff of the Washington University Musculoskeletal Research Center for their assistance. Specifically, thanks to Crystal Idleburg and Samantha Coleman for histological processing and sectioning and Dan Leib for assistance in microCT acquisition. Histology slides were imaged at the Alafi Neuroimaging Core (S10 RR027552). RNA sequencing was performed by the Genome Technology Access Center in the Department of Genetics at Washington University School of Medicine which is partially supported by NCI ( P30 CA91842 ) and NCRR ( UL1 TR000448 ).
Funding Information:
The authors would like to disclose that Matthew Silva has past research grant support from Merck Co. (2014–2017) and occasional royalty income from Springer.
Funding Information:
This work was supported by funding from NIAMS (R01 AR050211, P30 AR057235, P30 AR074992) and NIBIB (T32 EB018266). The authors would like to thank the cores and staff of the Washington University Musculoskeletal Research Center for their assistance. Specifically, thanks to Crystal Idleburg and Samantha Coleman for histological processing and sectioning and Dan Leib for assistance in microCT acquisition. Histology slides were imaged at the Alafi Neuroimaging Core (S10 RR027552). RNA sequencing was performed by the Genome Technology Access Center in the Department of Genetics at Washington University School of Medicine which is partially supported by NCI (P30 CA91842) and NCRR (UL1 TR000448). The authors would like to disclose that Matthew Silva has past research grant support from Merck Co. (2014?2017) and occasional royalty income from Springer. All other authors have no financial conflicts of interest with the submission of this manuscript.
Publisher Copyright:
© 2020 Elsevier Inc.
PY - 2021/2
Y1 - 2021/2
N2 - Interleukin-6 (IL-6) is highly upregulated in response to skeletal injury, suggesting it plays a role in the inflammatory phase of fracture repair. However, the impact of IL-6 on successful repair remains incompletely defined. Therefore, we investigated the role of IL-6 in two models of fracture repair (full fracture and stress fracture) using 12-week old IL-6 global knockout mice (IL-6 KO) and wild type (WT) littermate controls. Callus morphology and mineral density 14 days after full femur fracture did not differ between IL-6 knockout mice and controls. In contrast, IL-6 KO mice had an enhanced bone response 7 days after ulnar stress fracture compared to WT, with increased total callus volume (p = 0.020) and callus bone volume (p = 0.045). IL-6 KO did not alter the recruitment of immune cells (Gr-1 or F4/80 positive) to the stress fracture callus. IL-6 KO also did not alter the number of osteoclasts in the stress fracture callus. Using RNA-seq, we identified differentially expressed genes in stress fracture vs. contralateral control ulnae, and observed that IL-6 KO resulted in only modest alterations to the gene expression response to stress fracture (SFx). Wnt1 was more highly upregulated in IL-6 KO SFx callus at both day 1 (fold change 12.5 in KO vs. 5.7 in WT) and day 3 (fold change 4.7 in KO vs. 1.9 in WT). Finally, using tibial compression to induce bone formation without bone injury, we found that IL-6 KO directly impacted osteoblast function, increasing the propensity for woven bone formation. In summary, we report that IL-6 knockout enhanced formation of callus and bone following stress fracture injury, likely through direct action on the osteoblast's ability to produce woven bone. This suggests a novel role of IL-6 as a suppressor of intramembranous bone formation.
AB - Interleukin-6 (IL-6) is highly upregulated in response to skeletal injury, suggesting it plays a role in the inflammatory phase of fracture repair. However, the impact of IL-6 on successful repair remains incompletely defined. Therefore, we investigated the role of IL-6 in two models of fracture repair (full fracture and stress fracture) using 12-week old IL-6 global knockout mice (IL-6 KO) and wild type (WT) littermate controls. Callus morphology and mineral density 14 days after full femur fracture did not differ between IL-6 knockout mice and controls. In contrast, IL-6 KO mice had an enhanced bone response 7 days after ulnar stress fracture compared to WT, with increased total callus volume (p = 0.020) and callus bone volume (p = 0.045). IL-6 KO did not alter the recruitment of immune cells (Gr-1 or F4/80 positive) to the stress fracture callus. IL-6 KO also did not alter the number of osteoclasts in the stress fracture callus. Using RNA-seq, we identified differentially expressed genes in stress fracture vs. contralateral control ulnae, and observed that IL-6 KO resulted in only modest alterations to the gene expression response to stress fracture (SFx). Wnt1 was more highly upregulated in IL-6 KO SFx callus at both day 1 (fold change 12.5 in KO vs. 5.7 in WT) and day 3 (fold change 4.7 in KO vs. 1.9 in WT). Finally, using tibial compression to induce bone formation without bone injury, we found that IL-6 KO directly impacted osteoblast function, increasing the propensity for woven bone formation. In summary, we report that IL-6 knockout enhanced formation of callus and bone following stress fracture injury, likely through direct action on the osteoblast's ability to produce woven bone. This suggests a novel role of IL-6 as a suppressor of intramembranous bone formation.
KW - Interleukin-6
KW - Intramembranous ossification
KW - Stress fracture
KW - Tibial loading
UR - http://www.scopus.com/inward/record.url?scp=85096820708&partnerID=8YFLogxK
U2 - 10.1016/j.bone.2020.115737
DO - 10.1016/j.bone.2020.115737
M3 - Article
C2 - 33181349
AN - SCOPUS:85096820708
SN - 8756-3282
VL - 143
JO - Bone
JF - Bone
M1 - 115737
ER -