骨靶向硼替佐米调控Prx1颅骨骼干细胞Sirt1表达促进骨缝牵张成骨的机制研究

骨缝牵张成骨(SDO)常用于颅颌面部发育畸形的正畸治疗，但极易复发。我们前期发现颅骨缝来源的Prx1+细胞是典型的颅骨骼干细胞；蛋白酶体抑制剂硼替佐米(Btz)促进Prx1+细胞成骨分化同时上调Sirt1表达；Prx1-Sirt1TG小鼠牙槽骨量增加；我们新合成的骨靶向Btz具有更强的成骨效应，更低的副作用。因此提出骨靶向Btz通过上调颅骨骼干细胞Sirt1表达促进骨缝牵张新骨形成。我们拟通过组织、细胞、分子生物学等方法，1）利用Prx1-CrenT/nG小鼠矢状缝牵张模型，研究颅骨骼干细胞在SDO中的时空表达规律；2）研究骨靶向Btz调控颅骨骼干细胞成骨分化促进SDO的作用；3）利用Prx1-Cre; Sirt1fl/fl和Prx1-Sirt1TG小鼠矢状缝牵张模型，研究骨靶向Btz抑制颅骨骼干细胞Sirt1降解促进SDO的作用机制。本研究将为使用骨靶向Btz提高SDO疗效提供理论依据。

Sutural distraction osteogenesis (SDO) is a preferred treatment to craniomaxillofacial congenital malformation in orthodontics. However, the patients after surgery still have a risk of recurrence, even after a retention phase. Our preliminary studies revealed that craniofacial suture-derived Prx1+ cells displayed typical characteristics of skeletal stem cells (SSCs). Proteasome inhibitor Bortezomib (Btz) could promote Prx1+ cells differentiation and up-regulate Sirt1. Overexpression of Sirt1 in Prx1+ cells increased the alveolar bone volume in Prx1-Sirt1TG mice. Our new synthetic bone-targeted Bortezomib has greater bone anabolic and less systemic adverse effects than regular Btz. Therefore, we hypothesize that BP-Btz is able to up-regulate Sirt1 expression in prx1 calvarial SSCs to promote SDO. We will test our hypotheses in 3 Specific Aims by using histological, cellular and molecular techniques. Aim 1, we will examine the spatiotemporal expression of prx1 calvarial SSCs and mechanotransduction related factors using Prx1-CrenT/nG murine sagittal suture distraction model. Aim 2, we will investigate the biological effects of BP-Btz on regulating prx1 calvarial SSCs in vivo and in vitro. Aim 3, we will study the molecular mechanism of BP-Btz inhibiting the degradation of Sirt1 in prx1 calvarial SSCs to enhance SDO, using Prx1-Cre; Sirt1fl/fl and Prx1-Sirt1TG murine SDO models. Thus, our study will provide theoretical evidences for using BP-Btz to improve the efficacy of SDO.