Osteoclast-derived IGF1 is required for pagetic lesion formation in vivo
Kazuaki Miyagawa, … , G. David Roodman, Noriyoshi Kurihara
Kazuaki Miyagawa, … , G. David Roodman, Noriyoshi Kurihara
Published February 20, 2020
Citation Information: JCI Insight. 2020;5(6):e133113. https://doi.org/10.1172/jci.insight.133113.
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Research Article Bone biology Hematology

Osteoclast-derived IGF1 is required for pagetic lesion formation in vivo

Abstract

We report that transgenic mice expressing measles virus nucleocapsid protein (MVNP) in osteoclasts (OCLs) (MVNP mice) are Paget’s disease (PD) models and that OCLs from patients with PD and MVNP mice express high levels of OCL-derived IGF1 (OCL-IGF1). To determine OCL-IGF1’s role in PD and normal bone remodeling, we generated WT and MVNP mice with targeted deletion of Igf1 in OCLs (Igf1-cKO) and MVNP/Igf1-cKO mice, and we assessed OCL-IGF1’s effects on bone mass, bone formation rate, EphB2/EphB4 expression on OCLs and osteoblasts (OBs), and pagetic bone lesions (PDLs). A total of 40% of MVNP mice, but no MVNP/Igf1-cKO mice, had PDLs. Bone volume/tissue volume (BV/TV) was decreased by 60% in lumbar vertebrae and femurs of MVNP/Igf1-cKO versus MVNP mice with PDLs and by 45% versus all MVNP mice tested. Bone formation rates were decreased 50% in Igf1-cKO and MVNP/Igf1-cKO mice versus WT and MVNP mice. MVNP mice had increased EphB2 and EphB4 levels in OCLs/OBs versus WT and MVNP/Igf1-cKO, with none detectable in OCLs/OBs of Igf1-cKO mice. Mechanistically, IL-6 induced the increased OCL-IGF1 in MVNP mice. These results suggest that high OCL-IGF1 levels increase bone formation and PDLs in PD by enhancing EphB2/EphB4 expression in vivo and suggest OCL-IGF1 may contribute to normal bone remodeling.

Authors

Kazuaki Miyagawa, Yasuhisa Ohata, Jesus Delgado-Calle, Jumpei Teramachi, Hua Zhou, David D. Dempster, Mark A. Subler, Jolene J. Windle, John M. Chirgwin, G. David Roodman, Noriyoshi Kurihara

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Figure 5

Characterization of OCLs formed in marrow cultures of WT, Igf1-cKO, MVNP, and MVNP/Igf1-cKO mice.

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Characterization of OCLs formed in marrow cultures of WT, Igf1-cKO, MVNP...
All experiments used BM mononuclear cells from 12-month-old mice. (A) OCLs formation in 4 genotype mice. Results are expressed as the mean ± SEM from 4 technical replicates from 4 genotype mice. The data were analyzed using a 1-way ANOVA with Tukey test. *P < 0.05, **P < 0.01 with OCLs from 4 genotype mice. The results are representative of 4 biological replicates. (B) OCL morphology, photomicrographs of OCLs in marrow cultures treated with RANKL (50 ng/mL) and stained with TRACP. Scale bar: 50 μm. (C) Nuclear numbers per OCL. Results are expressed as the mean ± SEM of 25 randomly counted OCLs from 4 genotype mice. The data were analyzed using 1-way ANOVA with Tukey test, *P < 0.01 as compared with each indicated group. (D) Expression of cathepsin K and NFATc-1. The expression of cathepsin K and NFATc-1 were examined by Western blotting as described in Methods. GAPDH was used as the loading control. Protein expression levels were quantitated by ImageJ software (NIH). The basal ratio for each protein/loading control for OCLs from WT mice was set at 1.0. Results are representative of 3 biological replicates of 4 genotype mice. (E) Photomicrographs of bone resorption area. Bone slices were stained with hematoxylin. Scale bar: 50 μm. (F) Bone resorption capacity was assayed as described in Methods. Results are expressed as the mean ± SEM (representative of 3 biological replicated for 4 genotype mice). The data were analyzed using a 1-way ANOVA with Tukey test. *P < 0.01 as compared with each indicated group. The results are representative of 4 biological replicates.