牙髓再生中促进血管化策略的新进展

Advances focusing on strategies of promoting vascularization in dental pulp regeneration

背景:再血管化在组织再生中起着决定性作用。由于牙髓有其独有的结构特点,其四周为坚硬的牙本质包裹,仅从狭小的根尖开口获得血供,因此再血管化在牙髓再生中难度增加。目的:从信号因子、支架和细胞的设计3个角度出发,阐述牙髓再生中促进血管化策略的研究进展。方法:检索PubMed数据库及中国知网数据库收录的相关文献。英文检索词为“dental pulp regeneration,revascularization,growth factor,material,scaffold,dental pulp stem cell,prevascularization,coculture”,中文检索词为“牙髓再生、血管再生、生长因子、材料、支架、牙髓干细胞、预血管化、共培养”,最终纳入69篇文献进行归纳总结。结果与结论:①促血管生成因子主要包括血管内皮生长因子、血小板来源生长因子和成纤维细胞生长因子等,通过促进内皮细胞和血管周细胞的增殖、迁移,促进干细胞的募集和向内皮细胞的分化来促进血管的生成和稳定。②为了维持微环境中适宜的促血管生成因子浓度,向支架上添加肝素、硅酸锂镁和纤维素纳米晶等化学材料,可以溶解包裹、吸附、共价交联信号因子,模拟体内信号因子储存、释放机制,而天然材料包括脱细胞牙髓基质、富血小板血浆和富血小板纤维蛋白等本身富含多种生物活性分子,且自身结构可保护并控释这些信号因子。③牙髓干细胞中不同细胞亚群有不同的成血管潜能,而通过生物、化学等载体可以转染干细胞以提高细胞分泌信号因子的能力,也可以促进干细胞向内皮细胞转化,转染后的细胞成血管能力显著提升,而将干细胞和内皮细胞共同植入体内也可以提升成血管能力。④预血管化或可成为促进牙髓再生快速血管化最有力的手段,在体外将内皮细胞和干细胞以一定比例共培养可以制备出含血管结构的微组织,也可以通过酶消化脂肪组织得到微血管碎片,其中的管状结构和功能细胞能促进植入体内后新生血管的发育,并和宿主血管的吻合。⑤目前针对牙髓再生血管化的临床研究仅限于牙髓血运重建术,即在刺激根管内血凝块形成的同时加入特定种类的信号因子并观察其效果,而其他研究方向主要涉及的是小型、大型动物体内实验,未来仍需进一步进行临床试验以观察再生效果、减轻副反应,并优化制备流程。

BACKGROUND:Revascularization plays an important role in tissue engineering.Dental pulp chamber has its unique anatomy structure,which is surrounded by hard dentin.The blood supply of dental pulp only comes from the narrow apical opening,which makes revascularization more difficult in dental pulp regeneration.OBJECTIVE:To conclude the research advances focusing on the designs of signal molecules,scaffolds and cells in promoting vascularization in dental pulp regeneration.METHODS:We searched the articles on PubMed and CNKI databases with the keywords of“dental pulp regeneration,revascularization,growth factor,material,scaffold,dental pulp stem cell,prevascularization,coculture”in Chinese and English,respectively.Finally,69 articles met the criteria for review.RESULTS AND CONCLUSION:(1)Vascular endothelial growth factor,platelet-derived growth factor and fibroblast growth factor are the most studied pro-angiogenic factors,which promote angiogenesis by promoting the proliferation and migration of endothelial and perivascular cells,the recruitment of stem cells and their differentiation to endothelial cells.(2)To maintain the appropriate concentration of pro-angiogenic factors in the microenvironment,the addition of heparin,laponite and cellulose nanocrystals to the scaffolds can solubilize,encapsulate,adsorb,and covalently cross-link signal molecules,which mimic in vivo storage and release mechanisms.Natural materials including decellularized dental pulp matrix,platelet-rich plasma,and platelet-rich fibrin are rich in bio-active molecules and their structures can protect and control the release of these signal molecules.(3)Different cell sub-populations of dental pulp stem cells have different angiogenic potentials.Moreover,stem cells can be transfected by biological and chemical vectors to improve the cells’ability to secrete signal molecules and to promote the transformation of stem cells to endothelial cells.Therefore,the angiogenic capacity of transfected cells is significantly enhanced.Co-implantation of stem cells and endothelial cells can also enhance angiogenic capacity.(4)Prevascularization may be the most powerful means to promote rapid vascularization of dental pulp regeneration.In vitro co-culture of endothelial cells and stem cells with a certain ratio can form microtissues containing vascular structures.Microvascular fragments can be obtained by enzymatic digestion of adipose tissue,in which tubular structures and functional cells can promote the development of new blood vessels and anastomosis with host vessels.(5)Current clinical studies on revascularization of dental pulp are limited to dental pulprevascularization,where signal molecules are added while stimulating the formation of blood clots in the root canal and the effects are observed.While other research directions mainly involve in vivo trials in small and large animals,and further clinical trials are still needed to observe regenerative effects,mitigate side effects,and optimize the preparation process.