Inhibition of apoptosis signal-regulating kinase 1 enhances endochondral bone formation by increasing chondrocyte survival.
Endochondral ossification is the result of chondrocyte differentiation, hypertrophy, death and replacement by bone. The careful timing and progression of this process is important for normal skeletal bone growth and development, as well as fracture repair. Apoptosis Signal-Regulating Kinase 1 (ASK1) is a mitogen-activated protein kinase (MAPK), which is activated by reactive oxygen species and other cellular stress events. Activation of ASK1 initiates a signaling cascade known to regulate diverse cellular events including cytokine and growth factor signaling, cell cycle regulation, cellular differentiation, hypertrophy, survival and apoptosis. ASK1 is highly expressed in hypertrophic chondrocytes, but the role of ASK1 in skeletal tissues has not been investigated. Herein, we report that ASK1 knockout (KO) mice display alterations in normal growth plate morphology, which include a shorter proliferative zone and a lengthened hypertrophic zone. These changes in growth plate dynamics result in accelerated long bone mineralization and an increased formation of trabecular bone, which can be attributed to an increased resistance of terminally differentiated chondrocytes to undergo cell death. Interestingly, under normal cell culture conditions, mouse embryonic fibroblasts (MEFs) derived from ASK1 KO mice show no differences in either MAPK signaling or osteogenic or chondrogenic differentiation when compared with wild-type (WT) MEFs. However, when cultured with stress activators, H2O2 or staurosporine, the KO cells show enhanced survival, an associated decrease in the activation of proteins involved in death signaling pathways and a reduction in markers of terminal differentiation. Furthermore, in both WT mice treated with the ASK1 inhibitor, NQDI-1, and ASK1 KO mice endochondral bone formation was increased in an ectopic ossification model. These findings highlight a previously unrealized role for ASK1 in regulating endochondral bone formation. Inhibition of ASK1 has clinical potential to treat fractures or to slow osteoarthritic progression by enhancing chondrocyte survival and slowing hypertrophy.
Department of Orthopaedic Surgery, Thomas Jefferson University, Philadelphia, PA 19107, USA.
G J
GJ
Eaton
1] Department of Orthopaedic Surgery, Thomas Jefferson University, Philadelphia, PA 19107, USA [2] Department of Spine Surgery, The Second Xiangya Hospital of Central South University, Changsha, Hunan 410011, PR China.
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QS
Zhang
Department of Orthopaedic Surgery, Thomas Jefferson University, Philadelphia, PA 19107, USA.
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C
Diallo
Laboratory of Cell Signaling, University of Tokyo, Tokyo 113-0033, Japan.
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A
Matsuzawa
Open Innovation Center for Drug Discovery, University of Tokyo, Tokyo 113-0033, Japan.
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Ichijo
School of Biomedical Engineering, Science & Health Systems, Drexel University, Philadelphia, PA 19104, USA.
M J
MJ
Steinbeck
Department of Orthopaedic Surgery, Thomas Jefferson University, Philadelphia, PA 19107, USA.
T A
TA
Freeman
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001060:Aporphines / Q000494:pharmacology*; D001842:Bone and Bones / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D002113:Calcification, Physiologic / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D019902:Chondrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D020219:Chondrogenesis / Q000187:drug effects / Q000235:genetics; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006861:Hydrogen Peroxide / Q000037:antagonists & inhibitors / Q000494:pharmacology; D048848:MAP Kinase Kinase Kinase 5 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D010012:Osteogenesis / Q000187:drug effects / Q000235:genetics; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D011804:Quinolines / Q000494:pharmacology*; D015398:Signal Transduction; D019311:Staurosporine / Q000037:antagonists & inhibitors / Q000494:pharmacology
C000592751:2,7-dioxo-2,7-dihydro-3H-naphtho(1,2,3-de)quinoline-1-carboxylate; D001060:Aporphines; D047428:Protein Kinase Inhibitors; D011804:Quinolines; D006861:Hydrogen Peroxide; D048848:MAP Kinase Kinase Kinase 5; C482859:Map3k5 protein, mouse; D019311:Staurosporine