Downregulation of ROR2 promotes dental pulp stem cell senescence by inhibiting STK4‐FOXO1/SMS1 axis in sphingomyelin biosynthesis

Abstract

Dental pulp stem cells (DPSCs) play a vital role in tooth restoration, regeneration, and homeostasis. The link between DPSC senescence and tooth aging has been well‐recognized. ROR2 plays an important role in aging‐related gene expression. However, the expression and function of ROR2 in DPSC aging remain largely unknown. In this study, we found that ROR2 expression was significantly decreased in aged pulp tissues and DPSCs. The depletion of ROR2 in young DPSCs inhibits their self‐renewal capacity, while its overexpression in aged DPSCs restores their self‐renewal capacity. Interestingly, we found that sphingomyelin (SM) is involved in the senescence of DPSCs regulated by ROR2. Mechanistically, we confirmed that ROR2 inhibited the phosphorylation of STK4, which promoted the translocation of Forkhead Box O1 (FOXO1) to the nucleus. STK4 inhibition or knockdown of FOXO1 markedly increased the proliferation of DPSCs and upregulated the expression of SMS1, which catalyzed SM biogenesis. Moreover, FOXO1 directly bound to the SMS1 promoter, repressing its transcription. Our findings demonstrated the critical role of the ROR2/STK4‐FOXO1/SMS1 axis in the regulation of SM biogenesis and DPSC senescence, providing a novel target for antagonizing tooth aging.

Cellular senescence: the good, the bad and the unknown

“…Several transcription factors also regulate SCS of different origins. NANOG delays senescence in hair follicle-derived MSCs 89 , GATA6 and SOX11 regulate bone-marrow SCS 90 , MDM2–p53 signalling has a vital role in epidermal SCS 91 and the ROR2–STK4–FOXO1–SMS1 pathway regulates dental pulp SCS 92 . Endometrial SCS, which is associated with recurrent pregnancy loss, may be mediated by SERPINB2–sonic hedgehog signalling 93 .…”

Disturbing NLRP3 acetylation and inflammasome assembly inhibits androgen receptor‐promoted inflammatory responses and prostate cancer progression

“…Total RNA was extracted from the cells or ground tissues using the miRNeasy Mini Kit (217004; Qiagen) according to the manufacturer's instructions 22,23 . The RNA concentrations were assayed using NanoDrop 2000.…”

“…Total RNA was extracted from the cells or ground tissues using the miRNeasy Mini Kit (217004; Qiagen) according to the manufacturer's instructions. 22,23 The RNA concentrations were assayed using NanoDrop 2000. The RNA was reverse transcribed to cDNA using the Reverse Transcription Kit (MR05201M; Monad), and real-time quantitative PCR (qRT-PCR) was then performed using the ChemoHS qPCR Mix (MQ00401S; Monad).…”

The Ror-Family Receptors in Development, Tissue Regeneration and Age-Related Disease

“…They can be isolated from human dental pulp tissues and expanded in culture, but gradually lose their proliferative ability and multipotent differentiation potential during the expansion because of entering cellular senescence. In cultured human DPSCs, Ror2 is expressed highly at earlier passages, but its expression is decreased in senescent DPSCs ( Dong et al, 2021 ). Consistently, decreased expression of Ror2 is also detected in DPSCs isolated from elderly donors compared to those from young donors.…”

“…Consistently, decreased expression of Ror2 is also detected in DPSCs isolated from elderly donors compared to those from young donors. Furthermore, Ror2 can inhibit induction of cellular senescence in cultured DPSCs by inhibiting STK4-Foxo1 pathway in a Wnt5a-independent manner ( Dong et al, 2021 ). Therefore, supplementing expression of Ror2 or inhibiting decreased expression of Ror2 in DPSCs might lead to the maintenance of their stemness, which might be useful for the clinical use of DPSCs.…”