Upregulation of FOXD1 by YAP alleviates senescence and osteoarthritis

Cell senescence is a driver of various aging-associated disorders including osteoarthritis. Here, we identified a critical role for Yes-associated protein (YAP), a major effector of Hippo signaling, in maintaining a younger state of human mesenchymal stem cells (MSCs) and ameliorating osteoarthritis in mice. Targeted knockout of YAP in hMSCs resulted in premature cellular senescence. Mechanistically, YAP interacted with TEA domain transcriptional factor (TEAD) to activate forkhead box D1 (FOXD1) expression. YAP deficiency led to the downregulation of FOXD1, a geroprotective protein. In turn, overexpression of YAP or FOXD1 rejuvenated aged hMSCs. Moreover, intra-articular administration of lentiviral vectors encoding YAP or FOXD1 attenuated the development of osteoarthritis in mice. Collectively, our findings reveal YAP-FOXD1, a novel aging-associated regulatory axis, as a potential therapeutic target for gene therapy to alleviate osteoarthritis. Here, we generated isogenic YAP knockout and TAZ knockout human embryonic stem cells (hESCs) by CRISPR/Cas9-mediated gene editing. RNA sequencing and copy number variation (CNV) analyses demonstrated YAP-/- and TAZ-/- hESCs had similar transcriptomes with wild-type (WT) hESCs and maintained genomic stability. Three replicates per samples were sequenced for RNA analyses, and WT was the control. One repeat per samples were sequenced for CNV. Through directed differentiation, we then generated YAP-/- and TAZ-/- human mesenchymal stem cells (hMSCs) and performed RNA sequencing. Three replicates per samples were sequenced for RNA analyses, and WT was the control. We identified FOXD1, as a novel target of YAP, mediated the senescent phenotypes. Therefore, we knocked out FOXD1 in hMSCs using a lentivirus mediated CRISPR/Cas9 system. NTC was the control, FOXD1 represents FOXD1 knockout hMSCs. Three replicates per samples were sequenced for RNA analyses. Finally, we injected the lentiviruses encoding luciferase, YAP or FOXD1 into the osteoarthritic joint of mice and examined the transcriptional profiles. Mouse_joint_mControl represents the joints did not undergo surgery; Mouse_joint_mLuc represents the joints received anterior cruciate ligament transection (ACLT) followed by administration of lentivirus expressing luciferse; Mouse_joint_mYAP represents the joints received ACLT followed by administration of lentivirus expressing YAP; Mouse_joint_mFOXD1 represents the joints received ACLT followed by administration of lentivirus expressing FOXD1. Three replicates per samples were sequenced for RNA analyses.