A highly enriched niche of precursor cells with neuronal and glial potential within the hair follicle dermal papilla of adult skin

Skin-derived precursor cells (SKPs) are multipotent neural crest-related stem cells that grow as self-renewing spheres and are capable of generating neurons and myelinating glial cells. SKPs are of clinical interest because they are accessible and potentially autologous. However, although spheres can be readily isolated from embryonic and neonatal skin, SKP frequency falls away sharply in adulthood, and primary sphere generation from adult human skin is more problematic. In addition, the culture-initiating cell population is undefined and heterogeneous, limiting experimental studies addressing important aspects of these cells such as the behavior of endogenous precursors in vivo and the molecular mechanisms of neural generation. Using a combined fate-mapping and microdissection approach, we identified and characterized a highly enriched niche of neural crest-derived sphere-forming cells within the dermal papilla of the hair follicle of adult skin. We demonstrated that the dermal papilla of the rodent vibrissal follicle is 1,000-fold enriched for sphere-forming neural crest-derived cells compared with whole facial skin. These "papillaspheres" share a phenotypic and developmental profile similar to that of SKPs, can be readily expanded in vitro, and are able to generate both neuronal and glial cells in response to appropriate cues. We demonstrate that papillaspheres can be efficiently generated and expanded from adult human facial skin by microdissection of a single hair follicle. This strategy of targeting a highly enriched niche of sphere-forming cells provides a novel and efficient method for generating neuronal and glial cells from an accessible adult somatic source that is both defined and minimally invasive.     

Skin-derived precursors differentiate into skeletogenic cell types and contribute to bone repair

Skin-derived precursors (SKPs) are multipotent dermal precursors that share similarities with neural crest stem cells and that can give rise to peripheral neural and some mesodermal cell types, such as adipocytes. Here, we have asked whether rodent or human SKPs can generate other mesenchymally derived cell types, with a particular focus on osteocytes and chondrocytes. In culture, rodent and human foreskin-derived SKPs differentiated into alkaline-positive, collagen type-1-positive, mineralizing osteocytes, and into collagen type-II-positive chondrocytes that secreted chondrocyte-specific proteoglycans. Clonal analysis demonstrated that SKPs efficiently generated these skeletogenic cell types, and that they were multipotent with regard to the osteogenic and chondrogenic lineages. To ask if SKPs could generate these same lineages in vivo, genetically tagged, undifferentiated rat SKPs were transplanted into a tibial bone fracture model. Over the ensuing 6 weeks, many of the transplanted cells survived within the bone callus, where they were morphologically and phenotypically similar to the endogenous mesenchymal/osteogenic cells. Moreover, some transplanted cells adopted a mature osteocyte phenotype and integrated into the newly formed bone. Some transplanted cells also differentiated into chondrocytes and into smooth muscle cells and/or pericytes that were associated with blood vessels. Thus, both rodent and human SKPs generate skeletogenic cell types in culture, and the injured bone environment is sufficient to instruct SKPs to differentiate down an osteogenic lineage, in a fashion similar to the endogenous mesenchymal precursors.     

The in vivo developmental potential of porcine skin-derived progenitors and neural stem cells

Multipotent skin-derived progenitors (SKPs) can be traced back to embryonic neural crest cells and are able to differentiate into both neural and mesodermal progeny in vitro. Neural stem cells (NSCs) are capable of self-renewing and can contribute to neuron and glia in the nervous system. Recently, we derived porcine SKPs and NSCs from the same enhanced green fluorescent protein (EGFP) transgenic fetuses and demonstrated that SKPs could contribute to neural and mesodermal lineages in vivo. However, it remains unclear whether porcine SKPs and NSCs can generate ectoderm and mesoderm lineages or other germ layers in vivo. Embryonic chimeras are a well-established tool for investigating cell lineage determination and cell potency through normal embryonic development. Thus, the purpose of this study was to investigate the in vivo developmental potential of porcine SKPs and fetal brain-derived NSCs by chimera production. Porcine SKPs, NSCs, and fibroblasts were injected into precompact in vitro fertilized embryos (IVF) and then transferred into corresponding surrogates 24?h postinjection. We found that porcine SKPs could incorporate into the early embryos and contribute to various somatic tissues of the 3 germ layers in postnatal chimera, and especially have an endodermal potency. However, this developmental potential is compromised when they differentiate into fibroblasts. In addition, porcine NSCs fail to incorporate into host embryos and contribute to chimeric piglets. Therefore, neural crest-derived SKPs may represent a more primitive state than their counterpart neural stem cells in terms of their contributions to multiple cell lineages.     

The potential of mouse skin-derived precursors to differentiate into mesenchymal and neural lineages and their application to osteogenic induction in vivo

Although previous studies indicate that skin-derived precursors (SKPs) are multipotent dermal precursors that share similarities with neural crest stem cells (NCSCs), a shared ability for multilineage differentiation toward neural crest lineages between SKPs and NCSCs has not been fully demonstrated. Here, we report the derivation of SKPs from adult mouse skin and their directed multilineage differentiation toward neural crest lineages. Under controlled in vitro conditions, mouse SKPs were propagated and directed toward peripheral nervous system lineages such as peripheral neurons and Schwann cells, and mesenchymal lineages, such as osteogenic, chondrogenic, adipogenic, and smooth muscle cells. To ask if SKPs could generate these same lineages in vivo, a mixture of SKP-derived mesenchymal stem cells and hydroxyapatite/tricalcium phosphate was transplanted into the rat calvarial defects. Over the ensuing 4 weeks, we observed formation of osteogenic structure in the calvarial defect without any evidence of teratomas. These findings demonstrate the multipotency of adult mouse SKPs to differentiate into neural crest lineages. In addition, SKP-derived mesenchymal stem cells represent an accessible, potentially autologous source of precursor cells for tissue-engineered bone repair.     

Neural crest-derived multipotent cells in the adult mouse iris stroma

The purpose of this study was to characterize neural crest-derived cells within the adult murine iris. The iris was isolated from P0-Cre/Floxed-EGFP transgenic (TG) mice. The isolated iris cells formed EGFP-positive spheres on non-adhesive culture plates. Immunostaining showed that these EGFP-positive spheres expressed neural crest markers including Sox10 and p75NTR, and these cells showing in vitro sphere-forming ability were originally resided in the iris stroma (IS), in vivo. Real-time RT-PCR showed that the EGFP-positive spheres expressed significantly higher levels of the neural crest markers than EGFP-negative spheres and bone marrow-derived mesenchymal stem cells. Furthermore, the iris stromal sphere had capability to differentiate into various cell lineages including smooth muscle and cartilage. These data indicate that neural crest-derived multipotent cells can be isolated from the murine IS and expanded in sphere culture.     

Adult human dental pulp stem cells differentiate toward functionally active neurons under appropriate environmental cues

Human adult dental pulp stem cells (DPSCs) reside within the perivascular niche of dental pulp and are thought to originate from migrating cranial neural crest (CNC) cells. During embryonic development, CNC cells differentiate into a wide variety of cell types, including neurons of the peripheral nervous system. Previously, we have demonstrated that DPSCs derived from adult human third molar teeth differentiate into cell types reminiscent of CNC embryonic ontology. We hypothesized that DPSCs exposed to the appropriate environmental cues would differentiate into functionally active neurons. The data demonstrated that ex vivo-expanded human adult DPSCs responded to neuronal inductive conditions both in vitro and in vivo. Human adult DPSCs, but not human foreskin fibroblasts (HFFs), acquired a neuronal morphology, and expressed neuronal-specific markers at both the gene and protein levels. Culture-expanded DPSCs also exhibited the capacity to produce a sodium current consistent with functional neuronal cells when exposed to neuronal inductive media. Furthermore, the response of human DPSCs and HFFs to endogenous neuronal environmental cues was determined in vivo using an avian xenotransplantation assay. DPSCs expressed neuronal markers and acquired a neuronal morphology following transplantation into the mesencephalon of embryonic day-2 chicken embryo, whereas HFFs maintained a thin spindle fibroblastic morphology. We propose that adult human DPSCs provide a readily accessible source of exogenous stem/precursor cells that have the potential for use in cell-therapeutic paradigms to treat neurological disease.     

Three-dimensional hydrogel scaffolds facilitate in vitro self-renewal of human skin-derived precursors

Skin-derived precursors (SKPs) are multipotent cells with dermal stem cell properties. These easily available cells possess the capacity to reconstitute the skin in vivo, as well as a broader differentiation potential in vitro, which endows them with great prospects in regenerative medicine. However, the present authors’ group and others previously found that adult human SKPs (hSKPs) expanded deficiently in vitro, which largely counteracted their research and practical values. Taking the physiological micro-environment of hSKPs into consideration, the authors sought to establish a hydrogel scaffold-based three-dimensional (3-D) culture system for hSKPs in the present study. After comparing their morphology, growth characteristics, signature gene expression and differentiation potential in different hydrogels, the present authors found that a chemically defined hyaluronic acid and denatured collagen-based hydrogel system that mimicked the natural niche of hSKPs in the dermis could alleviate hSKP senescence, support hSKP proliferation as spheres, while largely retaining their properties and potential. This study suggested that recapitulating the in vivo stem cell niche by providing them with 3-D extracellular matrix environments could help them achieve better self-renewal in vitro. In addition, the animal-origin-free and biocompatible 3-D hydrogel system will certainly benefit fundamental research and clinical applications of hSKPs in the near future.     

新生大鼠海马源性神经干细胞的分离培养及其向胆碱能神经元定向诱导分化研究

本研究目的是从新生SD大鼠海马分离、培养神经干细胞并诱导其向胆碱能神经元方向分化。利用含b FGF(20ng/ml)和B27的无血清DMEM/F12培养基培养新生SD大鼠海马分离的具有自我更新和多向分化能力的细胞群,用免疫细胞化学技术检测巢蛋白(nestin),并于分化后分别检查特异性成熟神经细胞、星形胶质细胞、少突胶质细胞的标记抗原β微管蛋白(Tuj1 )、胶质纤维酸性蛋白(GFAP)和半乳糖脑苷脂(Galc)的表达;用鸡胚骨骼肌提取液,诱导神经干细胞向胆碱能神经元方向分化。结果显示:从海马分离的细胞群具有自我更新能力,表达nestin,分化成熟后的细胞表达神经元、星形胶质细胞和少突胶质细胞的特异性抗原;与对照组3. 9%相比,鸡胚骨骼肌提取液可以诱导这些细胞中的9. 6%分化成为胆碱能神经元。提示分离的细胞具有自我更新能力和多向分化潜能,是中枢神经系统的干细胞;在加有鸡胚骨骼肌提取液的培养基诱导下,能向胆碱能神经元方向分化。     

Neural crest as the source of adult stem cells

Recent studies suggest that adult stem cells can cross germ layer boundaries. For example, bone marrow-derived stem cells appear to differentiate into neurons and glial cells, as well as other types of cells. How can stem cells from bone marrow, pancreas, skin, or fat become neurons and glia; in other words, what molecular and cellular events direct mesodermal cells to a neural fate? Transdifferentiation, dediffereniation, and fusion of donor adult stem cells with fully differentiated host cells have been proposed to explain the plasticity of adult stem cells. Here we review the origin of select adult stem cell populations and propose a unifying hypothesis to explain adult stem cell plasticity. In addition, we outline specific experiments to test our hypothesis. We propose that peripheral, tissue-derived, or adult stem cells are all progeny of the neural crest.     

脊髓神经管神经上皮干细胞的分离培养和诱导分化

目的：从胚胎大鼠脊髓神经管中分离神经上皮干细胞并诱导其向多巴胺能神经元方向分化。方法：利用无血清悬浮培养、单细胞克隆技术分离神经上皮干细胞；采用5－溴－2－脱氧尿苷（BrdU）标记新生细胞，免疫细胞化学单标或双标染色技术，检测神经上皮干细胞蛋白（nestin）和分化后特异性神经细胞抗原的表达；用纹状体组织提取液，诱导神经上皮干细胞向多巴胺能神经元方向分化。结果：从胚胎大鼠脊髓神经管 中分离的细胞可以连续传代，表达nestin，它们分化后可以表达神经元、星形胶质细胞和少突胶质细胞的特异性抗原；与对照组3％相比，纹状体组织提取液可以诱导这些细胞中的12％分化成为多巴胺能神经元。结论：分离自脊髓神经管的细胞具有自我更新能力和多分化潜能（multipotent)，是增殖能力很强的神经干细胞；这些干细胞在一定的体外环境中能被诱导成为特定的神经元，提示其可以为神经移植提供材料。     

Isolation of novel multipotent neural crest-derived stem cells from adult human inferior turbinate

Adult human neural crest-derived stem cells (NCSCs) are of extraordinary high plasticity and promising candidates for the use in regenerative medicine. Here we describe for the first time a novel neural crest-derived stem cell population within the respiratory epithelium of human adult inferior turbinate. In contrast to superior and middle turbinates, high amounts of source material could be isolated from human inferior turbinates. Using minimally-invasive surgery methods isolation is efficient even in older patients. Within their endogenous niche, inferior turbinate stem cells (ITSCs) expressed high levels of nestin, p75(NTR), and S100. Immunoelectron microscopy using anti-p75 antibodies displayed that ITSCs are of glial origin and closely related to nonmyelinating Schwann cells. Cultivated ITSCs were positive for nestin and S100 and the neural crest markers Slug and SOX10. Whole genome microarray analysis showed pronounced differences to human ES cells in respect to pluripotency markers OCT4, SOX2, LIN28, and NANOG, whereas expression of WDR5, KLF4, and c-MYC was nearly similar. ITSCs were able to differentiate into cells with neuro-ectodermal and mesodermal phenotype. Additionally ITSCs are able to survive and perform neural crest typical chain migration in vivo when transplanted into chicken embryos. However ITSCs do not form teratomas in severe combined immunodeficient mice. Finally, we developed a separation strategy based on magnetic cell sorting of p75(NTR) positive ITSCs that formed larger neurospheres and proliferated faster than p75(NTR) negative ITSCs. Taken together our study describes a novel, readily accessible source of multipotent human NCSCs for potential cell-replacement therapy.     

人骨髓间充质干细胞的生物学特性及向神经前体细胞分化的实验研究

目的 观察体外培养的人骨髓间充质干细胞(hMSCs)的生物学特性,并探讨使其转分化为神经前体细胞(NPCs)的方法.方法以密度梯度离心和贴壁法相结合分离成人骨髓间充质干细胞,并观察细胞形态、生长、表面标记以及成骨和成软骨及成脂肪能力的情况.选用第3代细胞进行诱导,先经胚胎干细胞培养液扩增,再用加有5-氮胞苷和曲古菌素A的神经诱导液诱导,7d后,一部分样本进行Nestin、Sox2免疫荧光染色和RT-PCR检测;另一部分样本在含有B27的神经培养液中继续培养7d,然后进行NF-L的免疫荧光检测.结果分离培养的hMSCs纯度较高,CD29、CD44的阳性率均在90%以上;具有明显的成骨、成软骨和成脂肪能力;经5-氮杂胞苷和曲古菌素A作用后能向神经前体细胞分化,免疫荧光染色及RT-PCR结果显示,诱导后的细胞能特异性表达神经前体细胞标志物Nestin和Sox2;在神经培养液中继续培养后检测神经细胞标记物NF-L,可见较多阳性细胞.结论 hMSCs可在体外进行分离培养扩增,经药物修饰后具有向神经前体细胞分化的潜能.     

Stage-specific conditional mutagenesis in mouse embryonic stem cell-derived neural cells and postmitotic neurons by direct delivery of biologically active Cre recombinase

Conditional mutagenesis using Cre/loxP recombination is a powerful tool to investigate genes involved in neural development and function. However, the efficient delivery of biologically active Cre recombinase to neural cells, particularly to postmitotic neurons, represents a limiting factor. In this study, we devised a protocol enabling highly efficient conditional mutagenesis in ESC-derived neural progeny. Using a stepwise in vitro differentiation paradigm, we demonstrate that recombinant cell-permeable Cre protein can be used to efficiently induce recombination at defined stages of neural differentiation. Recombination rates of more than 90% were achieved in multipotent pan-neural and glial precursors derived from the Z/EG reporter mouse ESC line, in which Cre recombination activates enhanced green fluorescent proteinexpression. Recombined precursor cells displayed a normal phenotype and were able to differentiate into neurons and/or glial cells, indicating that Cre treatment has no overt side effects on proliferation and neural differentiation. Our data further demonstrate that recombination via Cre protein transduction is not restricted to dividing cells but can even be applied to postmitotic neurons. The ability to conduct Cre/loxP recombination at defined stages of stem cell differentiation in an expression-independent manner provides new prospects for studying the role of individual genes under stringent temporal control.     

Isolation of multipotent neural crest-derived stem cells from the adult mouse cornea

We report the presence of neural crest-derived corneal precursors (COPs) that initiate spheres by clonal expansion from a single cell. COPs expressed the stem cell markers nestin, Notch1, Musashi-1, and ABCG2 and showed the side population cell phenotype. COPs were multipotent with the ability to differentiate into adipocytes, chondrocytes, as well as neural cells, as shown by the expression of beta-III-tubulin, glial fibrillary acidic protein, and neurofilament-M. COP spheres prepared from E/nestin-enhanced green fluorescent protein (EGFP) mice showed induction of EGFP expression that was not originally observed in the cornea, indicating activation of the neural-specific nestin second intronic enhancer in culture. COPs were Sca-1(+), CD34(+), CD45(-), and c-kit(-). Numerous GFP(+) cells were observed in the corneas of mice transplanted with whole bone marrow of transgenic mice ubiquitously expressing GFP; however, no GFP(+) COP spheres were initiated from these mice. On the other hand, COP spheres from transgenic mice encoding P0-Cre/Floxed-EGFP as well as Wnt1-Cre/Floxed-EGFP were GFP(+), indicating the neural crest origin of COPs, which was confirmed by the expression of the embryonic neural crest markers Twist, Snail, Slug, and Sox9. Taken together, these data indicate the existence of neural crest-derived, multipotent stem cells in the adult cornea.     

皮肤间充质干细胞的体外培养和分化

从小鼠的皮肤组织中原代分离间充质干细胞,采用无血清培养基培养,经过2次传代后改为有血清培养,多次传代的细胞进行免疫细胞化学鉴定和诱导分化实验。结果表明:小鼠皮肤组织中的间充质干细胞体外可以长期培养,多次传代的细胞仍具有干细胞的特征,形态均一,体外增殖迅速,保持了向成骨细胞、脂肪细胞和神经元样细胞分化的潜能。体外长期传代培养小鼠皮肤间充质干细胞仍保持良好的干细胞特性,这为皮肤间充质干细胞的深入研究与中枢神经系统细胞移植提供了新的细胞来源。     

Expansion of mesenchymal stem cells from human pancreatic ductal epithelium

Fibroblast-like cells emerging from cultured human pancreatic endocrine and exocrine tissue have been reported. Although a thorough phenotypic characterization of these cells has not yet been carried out, these cells have been hypothesized to be contaminating fibroblasts, mesenchyme and/or possibly beta-cell progenitors. In this study, we expanded fibroblast-like cells from adult human exocrine pancreas following islet isolation and characterized these cells as mesenchymal stem cells (MSCs) based on their cell surface antigen expression and ability to differentiate into mesoderm. Analysis by flow cytometry demonstrated that pancreatic MSCs express cell surface antigens used to define MSCs isolated from bone marrow such as CD13, CD29, CD44, CD49b, CD54, CD90 and CD105. In addition, utilizing protocols used to differentiate MSCs isolated from other somatic tissues, we successfully differentiated pancreatic MSCs into: (1) osteocytes that stained positive for alkaline phosphatase, collagen, mineralization (calcification) and expressed osteocalcin, (2) adipocytes that contained lipid inclusions and expressed fatty acid binding protein 4 and (3) chondrocytes that expressed aggrecan. We also demonstrated that pancreatic MSCs are multipotent and capable of deriving cells of endodermal origin. Pancreatic MSCs were differentiated into hepatocytes that stained positive for human serum albumin and expressed endoderm and liver-specific genes such as GATA 4 and tyrosine aminotransferase. In addition, preliminary protocols used to differentiate these cells into insulin-producing cells resulted in the expression of genes necessary for islet and beta-cell development such as Pax4 and neurogenin 3. Therefore, multipotent MSCs residing within the adult exocrine pancreas could represent a progenitor cell, which when further manipulated could result in the production of functional islet beta-cells.     

Potential therapeutic clue of skin-derived progenitor cells following cytokine-mediated signal overexpressed in injured spinal cord

Recent evidence indicates that neural progenitor cell characters can be found in the population of adult skin-derived progenitor cells (SPCs). They have the ability to proliferate actively in vitro as spheres in suspension and they contain neural stem cells and several chemokines. Spheres derived from adult skin tissues have a higher capacity to differentiate into neurons in vitro. We report here that intravenous infusion of SPCs from adult skin ameliorated spinal cord lesions and improved motor function in laboratory mice with a spinal cord injury (SCI). After 4-5 weeks, transplanted SPCs survived and migrated into the injured region of the SCI very efficiently, and migrated cells were partially differentiated into neurons and glial cells. Behavioral and ultrastructural tissue analysis revealed that locomotor functions and remyelinated tissue lesions of SPCs engrafted onto SCI mice were restored significantly compared to those of the control group. Efficient migration of SPCs into SCI lesions suggests that SCI-induced chemotaxic factors facilitate the migration of SPCs. Also, we verified that SCI-induced chemotaxic factors play an important role in proliferation, migration, and differentiation of engrafted SPCs. In transplantation paradigms, the interaction between the SCI microenvironment and engrafted cells will be very important in promoting host injury repair through the induction of cell migration, proliferation, and differentiation. Finally, adult SPCs can behave as a multipotent population, suggesting potential clinical applications for SCI therapy.