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 2

Impaired osteogenic differentiation of PECs from MetΔJMD mice.

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Impaired osteogenic differentiation of PECs from MetΔJMD mice. (A and B)...
(A and B) Relative expression of the osteogenic genes Ibsp (A) and Dmp1 (B) in control (n = 4–9) and MetΔJMD (n = 4–9) PECs prior to (undifferentiated [Undiff.], black) and following osteogenic differentiation (Osteo., blue). Statistically significant differences were determined by 2-way ANOVA with Šidák’s multiple-test correction. (C and D) Representative alizarin red and crystal violet (CV) staining (C) and quantification (D) following osteogenic differentiation of control (Met+/+, n = 6) and MetΔJMD (n = 6) PECs. Statistically significant differences were determined by t test. (E–J) Quantification of cortical porosity (E) (Ct. Por.), cortical thickness (F) (Ct. Th.), pMOI (G), periosteal perimeter (H) (Ps. Pm), endosteal perimeter (I) (Es. Pm.), and stiffness (J) of femurs from 4-month-old male and female control (black; n = 15–49) and MetΔJMD (blue; n = 13–47) male and female mice. Statistically significant differences were determined by 2-way ANOVA with Šidák’s multiple-test correction. (K) Quantification of PYT of femurs from 4-month-old male control (n = 17) and MetΔJMD (n = 11) mice. Statistically significant differences were determined by t test. (L and M) Relative expression of the osteogenic genes Ibsp (L) and Dmp1 (M) prior to differentiation (Undiff., black) or following standard osteogenic differentiation (Osteo., blue) or osteogenic differentiation with BMP2 (Osteo.+BMP2, orange) in control (n = 5) and MetΔJMD (n = 5–6) PECs. Statistically significant differences were determined by 2-way ANOVA with Tukey’s multiple-test correction. (N and O) Representative alizarin red staining (N) and quantification (O) following osteogenic differentiation of MetΔJMD PECs. (D, K, and N) Statistically significant differences were determined by 2-tailed t test (n = 4 per group). RT-qPCR from cultured cells and other quantification data are presented as the mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001.