Neural crest stem cells from dental tissues: a new hope for dental and neural regeneration

Abstract

Several stem cell sources persist in the adult human body, which opens the doors to both allogeneic and autologous cell therapies. Tooth tissues have proven to be a surprisingly rich and accessible source of neural crest-derived ectomesenchymal stem cells (EMSCs), which may be employed to repair disease-affected oral tissues in advanced regenerative dentistry. Additionally, one area of medicine that demands intensive research on new sources of stem cells is nervous system regeneration, since this constitutes a therapeutic hope for patients affected by highly invalidating conditions such as spinal cord injury, stroke, or neurodegenerative diseases. However, endogenous adult sources of neural stem cells present major drawbacks, such as their scarcity and complicated obtention. In this context, EMSCs from dental tissues emerge as good alternative candidates, since they are preserved in adult human individuals, and retain both high proliferation ability and a neural-like phenotype in vitro. In this paper, we discuss some important aspects of tissue regeneration by cell therapy and point out some advantages that EMSCs provide for dental and neural regeneration. We will finally review some of the latest research featuring experimental approaches and benefits of dental stem cell therapy.

Figure 1

Origin and differentiation potential of dental ectomesenchymal stem cells (EMSCs). (a) Origin of neural crest stem cells (NCSCs). The neural crest arises as a cell population belonging to the fusing edges of the neuroectoderm. After neural tube fusion, neural crest cells undergo an epithelial-mesenchymal transition (EMT), where they transform into EMSCs. EMSCs migrate to generate the majority of craniofacial tissues, including tooth tissues fat, muscle, bone, and cartilage tissues, as well as cranial peripheral ganglia and nerves, among others. (b) EMSCs are retained in the adult dental pulp and periodontal tissues. These cells keep the potential to differentiate to various cell lineages and thus regenerate different dental and connective tissues. Dental EMSCs appear to hold a particularly high neurogenic potential and may also be used to regenerate nerve tissue.

Figure 2

Dental EMSCs express neural differentiation and pluripotency markers and can acquire a prominent neural-like morphology in vitro. Dental EMSCs isolated from dental pulp (DPSCs) form clonogenic adherent colonies (a), which present Nestin+ immunoreactivity (b) and from which equally Nestin+ migrating cells spread to eventually bring the culture plate to full confluency (c). Dental EMSCs also express pluripotency markers such as Oct-4, in the absence of any genetic or pharmacological manipulation (d). The cellular morphology and proliferation rates of dental EMSCs vary depending on the presence of FBS in the culture medium. DPSCs proliferate slowly in the absence of serum. Cells cultured without serum are equally Nestin+ but display very variable morphologies, including the appearance of cells with striking neuron-like shape, that show very thin and long cytoplasmic processes, resembling dendrites and axons (f, g). When DPSC are expanded for 3 weeks with 10% FBS, following another 3 weeks of serum deprivation, a sheet of nerve-like tissue is formed (h). Times after seeding: (a) 1 week; (e) 3 weeks; (h) 6 weeks (3 + 3); (b–d; f–g) double merged images of Nestin (green) and Oct-4 (red) immunolabeled cells, with DAPI (blue) introduced as a nuclear counterstain. Scale bars: 50 μm.