Phlpp protein phosphatases are abnormally abundant within human osteoarthritic articular chondrocytes and may contribute to the development of osteoarthritis. Mice lacking Phlpp1 were previously shown to be resistant to post-traumatic osteoarthritis. Here a small molecule with therapeutic properties that inhibits Phlpp1 and Phlpp2 was tested for its ability to slow post-traumatic OA in mice and to stimulate anabolic pathways in human articular cartilage from OA joints. PTOA was induced in male C57Bl/6 mice by surgically destabilizing the meniscus. Seven weeks after surgery, mice received a single intra-articular injection of the Phlpp inhibitor NSC117079 or saline. Mechanical allodynia was measured with von Frey assays, mobility was tracked in an open field system, and cartilage damage was assessed histologically. A single intra-articular injection of the Phlpp inhibitor NSC117079 attenuated mechanical allodynia and slowed articular cartilage degradation in joints with a destabilized meniscus. Animals treated with the Phlpp inhibitor 7 weeks after injury maintained normal activity levels, while those in the control group traveled shorter distances and were less active 3 months after the joint injury. NSC117079 also increased production of cartilage extracellular matrix components (glycosaminoglycans and aggrecan) in over 90% of human articular cartilage explants from OA patients and increased phosphorylation of Phlpp1 substrates (AKT2, ERK1/2, and PKC) in human articular chondrocytes. Our results indicate that Phlpp inhibitor NSC117079 is a novel osteoarthritis disease modifying drug candidate that may have palliative affects.
Bibliographical noteFunding Information:
Conflict of interest: None. Grant sponsor: National Institutes of Health; Grant numbers: R01 AR68103, T32 AR56950, K01 AR65397; Grant sponsor: Regenerative Medicine Minnesota; Grant number: 20156272; Grant sponsor: Orthopedic Research and Education Foundation; Grant sponsor: Howard Hughes Medical Institute. Correspondence to: Elizabeth W. Bradley (T: +1-507-293-0105; F: +1-507-284-5075; E-mail: email@example.com) and Jennifer J. Westendorf (T: +1-507-538-5651; F: +1-507-284-5075; E-mail: firstname.lastname@example.org)
The authors would like to thank Dr. David Razidlo and Mr. Xiaodong Li for technical assistance. We are grateful to Mr. Dirk Larson for statistical support, Dr. Alexandra C. Newton for helpful discussions, and Drs. Daniel Berry and Michael Stuart for providing surgical specimens. This work was supported by research and training grants from the National Institutes of Health (R01 AR68103, T32 AR56950, K01 AR65397), Regenerative Medicine Minnesota 2015 6272, and the Orthopedic Research and Education Foundation in collaboration with the Howard Hughes Medical Institute.
- DMM surgery
- post-traumatic osteoarthritis
PubMed: MeSH publication types
- Journal Article
- Research Support, N.I.H., Extramural
- Research Support, Non-U.S. Gov't