MEK inhibitor mirdametinib promotes fracture healing in osteofibrous dysplasia RASopathy
Aysha B. Khalid, Kristin Denton, Nandina Paria, Ila Oxendine, Meghan Wassell, Reuel Cornelia, Sasidhar Uppuganti, Jeffry S. Nyman, G. Jayashree Jagadeesh, Carlos R. Ferreira, Simon J. Conway, Robert E. Hammer, John Ritter, Mylinh Nguyen, David A. Podeszwa, Laura J. Klesse, Carol A. Wise, Jonathan J. Rios
Aysha B. Khalid, Kristin Denton, Nandina Paria, Ila Oxendine, Meghan Wassell, Reuel Cornelia, Sasidhar Uppuganti, Jeffry S. Nyman, G. Jayashree Jagadeesh, Carlos R. Ferreira, Simon J. Conway, Robert E. Hammer, John Ritter, Mylinh Nguyen, David A. Podeszwa, Laura J. Klesse, Carol A. Wise, Jonathan J. Rios
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Research Article Bone biology Clinical Research Genetics

MEK inhibitor mirdametinib promotes fracture healing in osteofibrous dysplasia RASopathy

Abstract

Osteofibrous dysplasia (OFD) is a skeletal RASopathy presenting with periosteal bone lesions that may progress to fracture and delayed healing (pseudarthrosis). MET gene mutations reducing ubiquitin-mediated protein degradation via loss of the juxtamembrane domain (METΔJMD) were previously identified in patients with OFD, resulting in ligand-dependent gain of function. The effect of METΔJMD expression on skeletal progenitor cell differentiation and the potential efficacy of targeted therapies remain unclear. We engineered MetΔJMD mice and showed that MetΔJMD expression inhibited osteogenic differentiation of skeletal progenitor cells in vitro and impaired cortical bone development and reduced bone stiffness in vivo. In contrast, conditional deletion of Met enhanced osteogenic differentiation of periosteal progenitor cells. Inhibition of MAPK signaling with MEK inhibitors restored osteogenic differentiation of mouse MetΔJMD skeletal progenitor cells and promoted the activation of transcriptional signatures associated with skeletal development and osteoblast differentiation in pseudarthrosis-derived primary cells from patients with OFD. With this preclinical support, we treated with the MEK inhibitor mirdametinib a pediatric patient with OFD who had a 3-year history of persistent pseudarthrosis, resulting in fracture union. Our findings demonstrate a bidirectional role for MET in regulating osteogenic differentiation of skeletal progenitor cells and a therapeutic avenue to improve clinical outcomes for this and potentially other skeletal RASopathies.

Authors

Aysha B. Khalid, Kristin Denton, Nandina Paria, Ila Oxendine, Meghan Wassell, Reuel Cornelia, Sasidhar Uppuganti, Jeffry S. Nyman, G. Jayashree Jagadeesh, Carlos R. Ferreira, Simon J. Conway, Robert E. Hammer, John Ritter, Mylinh Nguyen, David A. Podeszwa, Laura J. Klesse, Carol A. Wise, Jonathan J. Rios

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Figure 4

MEK inhibition rescues osteogenic differentiation of MetΔJMD PECs.

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MEK inhibition rescues osteogenic differentiation of MetΔJMD PECs. (A) S...
(A) Schematic of the MET receptor (blue) bound by HGF (yellow) to activate the downstream MEK/ERK signaling cascade, resulting in the regulation of osteogenic differentiation of skeletal progenitor cells. Pharmacologic inhibitors of MET (capmatinib) and MEK (mirdametinib, selumetinib) are shown in red. (B and C) Representative Western blot (B) and quantification (C) of ERK pathway activation in MetΔJMD PECs treated with vehicle (n = 8) or mirdametinib (mirda.) (n = 8). Statistically significant differences were determined by t test. (D) Cell counts of PECs from control (n = 14) and MetΔJMD (n = 14) mice. Statistically significant differences were determined by 1-way ANOVA with Tukey’s multiple-test correction. (E and F) Relative expression of the cell adhesion genes Ncad (E) and Vim (F) in control (Met+/+; n = 9–10) and MetΔJMD (n = 7–10) PECs treated with vehicle (Veh.) or mirdametinib. Statistically significant differences were determined by 1-way ANOVA with Tukey’s multiple-test correction. (G–I) Relative expression of the osteogenic genes Alpl (G), Ibsp (H), and Dmp1 (I) in MetΔJMD PECs prior to (Undiff., black) or following osteogenic differentiation in the presence of vehicle (Osteo.+vehicle, blue) or mirdametinib (Osteo.+mirda., orange) (n = 3–8 per group). Statistically significant differences were determined by 1-way ANOVA with Tukey’s multiple-test correction. (J and K) Representative alizarin red staining (J) and quantification (K) of MetΔJMD PECs following osteogenic differentiation in the presence of vehicle (blue, n = 6) or mirdametinib (orange, n = 6). Statistically significant differences were determined by t test. RT-qPCR from cultured cells and other quantification data are presented as the mean ± SEM. **P < 0.01, ***P < 0.001, and ****P < 0.0001.