Dental pulp stem cells and regeneration

Dental pulp‐derived stem cells (DPSCs) are considered to be of great promise for use in tissue repair and regenerative medicine. DPSCs can easily be collected from discarded teeth with little ethical concerns and harvested in a minimally invasive and safe manner. However, unfractionated clonogenic DPSCs are heterogenous and have variations in their phenotype. In this review paper, we summarize further isolation methods of DPSC subpopulations including immunoselection methods and a granulocyte colony‐stimulating factor (G‐CSF) gradient mobilization method for therapeutic clinical applications. The fractionated DPSC subpopulations exhibit stem cell properties in vitro: (i) high expression of pluripotency markers, Oct3/4, Nanog, and Sox2; (ii) high stability in long‐term expansion; (iii) multi‐lineage differentiation capacity; (iv) high migratory activity; and (v) high expression of trophic factors to enhance proliferation, migration, and anti‐apoptotic and immunomodulatory effects as well as angiogenesis and neurite extension. DPSC subpopulations have higher angiogenic, neurogenic, and regenerative potential compared with bone marrow stem cells and adipose stem cells, presenting an alternate versatile stem cell source for cellular therapies. Preclinical efficacy of DPSC subpopulations has also been investigated in various tissue/organ disease models including pulpitis, and currently a few clinical trials are underway to determine their safety and efficacy. Therefore, the major aim of this review is to highlight the recent progress in DPSC biology, trends in preclinical regenerative studies, and future perspectives.     

Dental pulp stem cells in regenerative dentistry

Stem cells constitute the source of differentiated cells for the generation of tissues during development, and for regeneration of tissues that are diseased or injured postnatally. In recent years, stem cell research has grown exponentially owing to the recognition that stem cell-based therapies have the potential to improve the life of patients with conditions that span from Alzheimer’s disease to cardiac ischemia to bone or tooth loss. Growing evidence demonstrates that stem cells are primarily found in niches and that certain tissues contain more stem cells than others. Among these tissues, the dental pulp is considered a rich source of mesenchymal stem cells that are suitable for tissue engineering applications. It is known that dental pulp stem cells have the potential to differentiate into several cell types, including odontoblasts, neural progenitors, osteoblasts, chondrocytes, and adipocytes. The dental pulp stem cells are highly proliferative. This characteristic facilitates ex vivo expansion and enhances the translational potential of these cells. Notably, the dental pulp is arguably the most accessible source of postnatal stem cells. Collectively, the multipotency, high proliferation rates, and accessibility make the dental pulp an attractive source of mesenchymal stem cells for tissue regeneration. This review discusses fundamental concepts of stem cell biology and tissue engineering within the context of regenerative dentistry.     

Dental pulp neuropathophysiology

Mechanisms of pulpal pathophysiology are complex and the low compliance environment in which the dental pulp is allocated, further enhances the complexity of this process. Although it is known that it involves the interaction of the immune cells, pulpal cells, cytokines, chemokines and multiple neuropeptides but still there are many gaps in our current knowledge. The understanding of the biochemical and molecular pathways involved in the pulpal inflammation is important so that it can be used clinically to keep the dental pulp vital and healthy. It may thus provide an opportunity to develop potentially new treatment modalities for the inflamed dental pulp in future.     

牙髓干细胞及其表面特异标志物

牙髓干细胞是位于牙髓组织中的一种成体干细胞,具有高度增殖与多向分化的能力。牙髓干细胞的出现,为牙髓病的治疗提供了新的治疗途径。下面就牙髓干细胞及其表面特异性标志物的研究进展作一综述。     

牙髓干细胞修复即刻种植周围骨缺损

目的：建立兔下颌骨前牙区即刻种植种植体周围骨缺损的动物实验模型,并观察牙髓干细胞在种植体周围骨缺损中骨再生能力。方法：将实验兔分为2组,分别拔除兔双侧下颌前牙,并在拔牙窝颊侧建立2 mm ×3 mm大小骨缺损区,即刻植入种植体。对照组植入Bio-oss骨粉,实验组植入Bio-oss骨粉与牙髓干细胞（ Dental Pulp Stem Cells,DPSCs）,通过扫描电镜和HE染色观察评价植入后4周种植体-骨结合状况。结果：扫描电镜观察见实验组种植体周围骨缺损处可见编织骨及骨小梁形成,种植体与牙槽窝间隙基本消失且与龈方间隙减小,周围松质骨密度增高。实验组HE染色切片见种植体周围骨缺损处牙槽骨部分胞质呈空泡状,成骨细胞与破骨细胞分布于骨小梁上,骨小梁致密且排列规则。结论：建立的兔下颌骨前牙区即刻种植的种植体周围骨缺损动物实验模型,可为即刻种植方向的相关研究提供重要参考。     

Dental pulp evoked potentials

The purpose of this work was to explore the possibilities of dental pulp evoked potential registration and to standardize the mean values of peak latencies and amplitudes recorded from the vertex in both sexes. The long latency evoked potentials of the brain cortex were obtained by electrostimulation with the corresponding parameters. The peak latencies recorded in the female group N 40, P 80 and N 140 were significantly shorter than peak latencies N 50, P 90 and N 150 in the male group. Peak amplitudes recorded in the female group were higher than in the male group, but statistically they were not significant.     

Dental pulp tissue engineering

Dental pulp is a highly specialized mesenchymal tissue that has a limited regeneration capacity due to anatomical arrangement and post-mitotic nature of odontoblastic cells. Entire pulp amputation followed by pulp space disinfection and filling with an artificial material cause loss of a significant amount of dentin leaving as life-lasting sequelae a non-vital and weakened tooth. However, regenerative endodontics is an emerging field of modern tissue engineering that has demonstrated promising results using stem cells associated with scaffolds and responsive molecules. Thereby, this article reviews the most recent endeavors to regenerate pulp tissue based on tissue engineering principles and provides insightful information to readers about the different aspects involved in tissue engineering. Here, we speculate that the search for the ideal combination of cells, scaffolds, and morphogenic factors for dental pulp tissue engineering may be extended over future years and result in significant advances in other areas of dental and craniofacial research. The findings collected in this literature review show that we are now at a stage in which engineering a complex tissue, such as the dental pulp, is no longer an unachievable goal and the next decade will certainly be an exciting time for dental and craniofacial research.     

牙髓干细胞对皮肤成纤维细胞衰老及增殖能力的影响

目的：研究牙髓干细胞对皮肤成纤维细胞衰老及增殖能力的影响,并初步探讨其机制。方法：从人牙髓中提取,培养牙髓干细胞,与皮肤成纤维细胞分组共培养,分为3组：对照组（单纯皮肤成纤维细胞培养）、条件培养基组（利用牙髓干细胞条件培养基培养成纤维细胞）、直接共培养组（采用Transwell共培养小室）。共培养后,进行 β半乳糖苷酶（SA-β-gal）染色,检测成纤维细胞的衰老情况;利用 CCK-8 法检测各组成纤维细胞的活性;流式细胞仪分析成纤维细胞的细胞周期变化;采用RT-PCR和 Western免疫印迹检测各组成纤维细胞衰老相关蛋白 p21、p53以及pRb 的mRNA和蛋白表达水平。采用SPSS 13.0软件包对数据进行统计学分析。结果：与空白组相比,后2组的皮肤成纤维细胞表达β半乳糖苷酶降低、增殖能力增强、G1期细胞减少而S期和G2期增多, p53、p21 mRNA和蛋白表达水平降低而PRb表达升高。结论：牙髓干细胞及其条件培养基具有抗皮肤成纤维细胞衰老的作用,为牙髓干细胞在抗皮肤衰老方面的临床应用提供了依据。     

Dental pulp tissue engineering with stem cells from exfoliated deciduous teeth

Stem cells from human exfoliated deciduous teeth (SHED) have been isolated and characterized as multipotent cells. However, it is not known whether SHED can generate a dental pulp-like tissue in vivo. The purpose of this study was to evaluate morphologic characteristics of the tissue formed when SHED seeded in biodegradable scaffolds prepared within human tooth slices are transplanted into immunodeficient mice. We observed that the resulting tissue presented architecture and cellularity that closely resemble those of a physiologic dental pulp. Ultrastructural analysis with transmission electron microscopy and immunohistochemistry for dentin sialoprotein suggested that SHED differentiated into odontoblast-like cells in vivo. Notably, SHED also differentiated into endothelial-like cells, as demonstrated by B-galactosidase staining of cells lining the walls of blood-containing vessels in tissues engineered with SHED stably transduced with LacZ. This work suggests that exfoliated deciduous teeth constitute a viable source of stem cells for dental pulp tissue engineering.     

Dental pulp stem cells: characteristics, cryopreservation and therapeutic potentialities

Stem cells discovery and their potential have led to the emergence of new forms of therapy with the development of bio-engineering cell and tissue methods underlying future medicine. The availability of stem cells and their preservation thus become an issue for everyone's health. Among the different sources of stem cells, those in the dental pulp have the advantage of being pluripotent, they can be cryopreserved and stored for long periods without losing their multiplication and differentiation capacities and finally they are easily accessible. The wisdom or natal teeth extracted for medical reasons are an opportunity for everyone to preserve stem cells for an autologous use. Biobanks authorized and specialized in the preparation and storage of pulp stem cells provide access to autologous regenerative medicine of tomorrow.     

Dental pulp stem cells in chitosan/gelatin scaffolds for enhanced orofacial bone regeneration

Objective

Biomimetic chitosan/gelatin (CS/Gel) scaffolds have attracted great interest in tissue engineering of several tissues. However, limited information exists regarding the potential of combining CS/Gel scaffolds with oral cells, such as dental pulp stem cells (DPSCs), to produce customized constructs targeting alveolar/orofacial bone reconstruction, which has been the aim of the present study.

Dental pulp stem cells: Novel cell-based and cell-free therapy for peripheral nerve repair

The regeneration of peripheral nerves comprises complicated steps involving a set of cellular and molecular events in distal nerve stumps with axonal sprouting and remyelination. Stem cell isolation and expansion for peripheral nerve repair(PNR) can be achieved using a wide diversity of prenatal and adult tissues, such as bone marrow or brain tissues. The ability to obtain stem cells for cell-based therapy(CBT) is limited due to donor site morbidity and the invasive nature of the harvesting process. Dental pulp stem cells(DPSCs) can be relatively and simply isolated from the dental pulps of permanent teeth, extracted for surgical or orthodontic reasons. DPSCs are of neural crest origin with an outstanding ability to differentiate into multiple cell lineages. They have better potential to differentiate into neural and glial cells than other stem cell sources through the expression and secretion of certain markers and a range of neurotropic factors;thus, they should be considered a good choice for PNR using CBT. In addition,these cells have paracrine effects through the secretion of neurotrophic growth factors and extracellular vesicles, which can enhance axonal growth and remyelination by decreasing the number of dying cells and activating local inhabitant stem cell populations, thereby revitalizing dormant or blocked cells,modulating the immune system and regulating inflammatory responses. The use of DPSC-derived secretomes holds great promise for controllable and manageable therapy for peripheral nerve injury. In this review, up-to-date information about the neurotrophic and neurogenic properties of DPSCs and their secretomes is provided.