Niche interactions in epidermal stem cells

Within the epidermis and dermis of the skin, cells secrete and are surrounded by the extracellular matrix(ECM), which provides structural and biochemical support. The ECM of the epidermis is the basement membrane, and collagen and other dermal components constitute the ECM of the dermis. There is significant variation in the composition of the ECM of the epidermis and dermis, which can affect "cell to cell" and "cell to ECM" interactions. These interactions, in turn, can influence biological responses, aging, and wound healing; abnormal ECM signaling likely contributes toskin diseases. Thus, strategies for manipulating cellECM interactions are critical for treating wounds and a variety of skin diseases. Many of these strategies focus on epidermal stem cells, which reside in a unique niche in which the ECM is the most important component; interactions between the ECM and epidermal stem cells play a major role in regulating stem cell fate. As they constitute a major portion of the ECM, it is likely that integrins and type Ⅳ collagens are important in stem cell regulation and maintenance. In this review, we highlight recent research-including our previous work-exploring the role that the ECM and its associated components play in shaping the epidermal stem cell niche.

Enrichment of putative human epidermal stem cells based on cell size and collagen type IV adhesiveness

The enrichment and identification of human epidermal stem cells （EpSCs） are of paramount importance for both basic research and clinical application. Although several approaches for the enrichment of EpSCs have been established, enriching a pure population of viable EpSCs is still a challenging task. An improved approach is worth developing to enhance the purity and viability of EpSCs. Here we report that cell size combined with collagen type IV adhesiveness can be used in an improved approach to enrich pure and viable human EpSCs. We separated the rap- idly adherent keratinocytes into three populations that range in size from 5-7 μm （population A）, to 7-9 μm （population B）, to ≥9μm （population C） in diameter, and found that human putative EpSCs could be further enriched in population A with the smallest size. Among the three populations, population A displayed the highest density of plintegrin receptor, contained the highest percentage of cells in G0/G1 phase, showed the highest nucleus to cytoplasm ratio, and possessed the highest colony formation efficiency （CFE）. When injected into murine blastocysts, these cells participated in multi-tissue formation. More significantly, compared with a previous approach that sorted putative EpSCs according to pl-integrin antibody staining, the viability of the EpSCs enriched by the improved approach was significantly enhanced. Our results provide a putative strategy for the enrichment of human EpSCs, and encourage further study into the role of cell size in stem cell biology.

Substance P combined with epidermal stem cells promotes wound healing and nerve regeneration in diabetes mellitus

Exogenous substance P accelerates wound healing in diabetes,but the mechanism remains poorly understood.Here,we established a rat model by intraperitoneally injecting streptozotocin.Four wounds（1.8 cm diameter） were drilled using a self-made punch onto the back,bilateral to the vertebral column,and then treated using amniotic membrane with epidermal stem cells and/or substance P around and in the middle of the wounds.With the combined treatment the wound-healing rate was 100% at 14 days.With prolonged time,type I collagen content gradually increased,yet type III collagen content gradually diminished.Abundant protein gene product 9.5-and substance P-immunoreactive nerve fibers regenerated.Partial nerve fiber endings extended to the epidermis.The therapeutic effects of combined substance P and epidermal stem cells were better than with amniotic membrane and either factor alone.Our results suggest that the combination of substance P and epidermal stem cells effectively contributes to nerve regeneration and wound healing in diabetic rats.

Feeder-free maintenance of hESCs in mesenchymal stem cell-conditioned media： distinct requirements for TGF-β and IGF-Ⅱ

A paracrine regulation was recently proposed in human embryonic stem cells （hESCs） grown in mouse embryonic fibroblast （MEF）-conditioned media （MEF-CM）, where hESCs spontaneously differentiate into autologous fibroblastlike cells to maintain culture homeostasis by producing TGF-β and insulin-like growth factor-lI （IGF-Ⅱ） in response to basic fibroblast growth factor （bFGF）. Although the importance of TGF-β family members in the maintenance of pluripotency of hESCs is widely established, very little is known about the role of IGF-Ⅱ. In order to ease hESC cul- ture conditions and to reduce xenogenic components, we sought （i） to determine whether hESCs can be maintained stable and pluripotent using CM from human foreskin fibroblasts （HFFs） and human mesenchymal stem cells （hM- SCs） rather than MEF-CM, and （ii） to analyze whether the cooperation of bFGF with TGF-β and IGF-Ⅱ to maintain hESCs in MEF-CM may be extrapolated to hESCs maintained in allogeneic mesenchymal stem cell （MSC）-CM and HFF-CM. We found that MSCs and HFFs express all FGF receptors （FGFR1-4） and specifically produce TGF-β in response to bFGF. However, HFFs but not MSCs secrete IGF-Ⅱ. Despite the absence of IGF-Ⅱ in MSC-CM, hESC pluripotency and culture homeostasis were successfully maintained in MSC-CM for over 37 passages. Human ESCs derived on MSCs and hESCs maintained in MSC-CM retained hESC morphology, euploidy, expression of surface markers and transcription factors linked to pluripotency and displayed in vitro and in vivo multilineage developmental potential, suggesting that IGF-Ⅱ may be dispensable for hESC pluripotency. In fact, IGF-Ⅱ blocking had no effect on the homeostasis of hESC cultures maintained either on HFF-CM or on MSC-CM. These data indicate that hESCs are successfully maintained feeder-free with IGF-Ⅱ-lacking MSC-CM, and that the previously proposed paracrine mechanism by which bFGF cooperates with TGF-β and IGF-Ⅱ in the maintenance of hESCs in MEF-CM may not be fully extrapolated to hESCs maintained in CM from human MSCs.

Induced Pluripotent Stem Cells: Next Generation Cells for Tissue Regeneration

More than two decades of in vitro experimentation supported by the data from experimental animal studies in both small as well as large experimental animal models have culminated into multiple clinical studies worldwide to assess their regenerative potential. Although the data generated from these studies have only met with cautious response from the researchers, efforts are still underway with the hope to refine the different aspects of cell-based therapy approach to develop it into an effective routine therapeutic intervention. Besides others, search for a cell type with optimal characteristics remains an area of intense research. Pluripotent stem cells in general, and induced pluripotent stem cells in particular have gained special attention of researchers due to their ability to adopt a morphofuntionally competent phenotype. They are being considered as surrogate embryonic stem cells albeit without moral and ethical issues of availability and having better immunological acceptability. We provide a head-to-head comparison of ESCs and iPSCs and an overview of stem cell therapy approach converging on the observed advantages of pluripotent stem cells during pre-clinical and clinical studies.

Epithelial stem cell islands in the regenerated epidermis

Objective: The effects of growth factors on wound healing have been studied extensively, however, their molecular and genetic mechanisms that regulate epidermal regeneration are not fully understood. In this study, we explore the cell reversion characteristics and epithelial stem cell distribution in human regenerated epidermis treated with recombinant human epidermal growth factor (rhEGF). Methods:Tissue biospies from 8 regenerated skins treated with rhEGF were used to evaluate the cell reversion.

Perfluorinated iodine alkanes promote the differentiation of mouse embryonic stem cells by regulating estrogen receptor signaling

Investigating the development toxicity of perfuorinated iodine alkanes(PFIs)is critical,given their estrogenic effects through binding with estrogen receptors(ERs).In the present study,two PFIs,including dodecafuoro-1,6-diiodohexane(PFHx DI)and tridecafuorohexyl iodide(PFHx I),with binding preference to ERαand ERβ,respectively,were selected to evaluate their effects on proliferation and differentiation of the mouse embryonic stem cells(m ESCs).The results revealed that,similar to E_(2),50μmol/L PFHx DI accelerated the cell proliferation of the m ESCs.The PFI stimulation at the exposure concentrations of 2–50μmol/L promoted the differentiation of the m ESCs as characterized by the upregulation of differentiation-related biomarkers(i.e.,Otx2 and Dnmt3β)and downregulation of pluripotency genes(i.e.,Oct4,Nanog,Sox2,Prdm14 and Rex1).Comparatively,PFHx DI exhibited higher induction effect on the differentiation of the m ESCs than did PFHx I.The tests on ER signaling indicated that both PFI compounds induced exposure concentration-dependent expressions of ER signaling-related biomarkers(i.e.,ERα,ERβand Caveolin-1)in the m ESCs,and the downstream ER responsive genes(i.e.,c-fos,c-myc and c-jun)well responded to PFHx I stimulation.The role of ER in PFI-induced effects on the m ESCs was further validated by the antagonistic experiments using an ER inhibitor(ICI).The findings demonstrated that PFIs triggered ER signaling,and perturbed the differentiation program of the m ESCs,causing the potential health risk during early stage of development.

Serial imaging of human embryonic stem-cell engraftment and teratoma formation in live mouse models

Two new types of lentiviral vectors expressing a reporter transgene encoding either firefly luciferase （fLuc） for bioluminescence imaging or the HSV1 thymidine kinase （HSV1-TK） for radiopharmaceutical-based imaging were constructed to monitor human embryonic stem cell （hESC） engraftment and proliferation in live mice after trans- plantation. The constitutive expression of either transgene did not alter the properties of hESCs in the culture. We next monitored the formation of teratomas in SCID mice to test （1） whether the gene-modified hESCs maintain their developmental pluripotency, and （2） whether sustained reporter gene expression allows noninvasive, whole-body imaging of hESC derivatives in a live mouse model. We observed teratoma formation from both types of gene-modified cells as well as wild-type hESCs 2-4 months after inoculation. Using an optical imaging system, bioluminescence from the fLuc-transduced hESCs was easily detected in mice bearing teratomas long before palpable tumors could be detected. To develop a noninvasive imaging method more readily translatable to the clinic, we also utilized HSV1-TK and its specific substrate, 1-（2＇-deoxy-2＇-fluoro-β-D-arabinofuranosyl）-5-[^125I]iodouracil（[^125I]FIAU）, as a reporter/ probe pair. After systemic administration, [^125I]FIAU is phosphorylated only by the transgene-encoded HSV1-TK enzyme and retained within transduced （and transplanted） cells, allowing sensitive and quantitative imaging by single-photon emission computed tomography. Noninvasive imaging methods such as these may enable us to monitor the presence and distribution of transplanted human stem cells repetitively within live recipients over a long term through the expression of a reporter gene.

哌唑嗪(PRA)拮抗去甲肾上腺素(NE)诱导人类胚胎干细胞来源的心肌细胞(hESCs-CMs)肥大

目的在人类胚胎干细胞来源的心肌细胞(human embryonic stem cells-cardiomyocytes,hESCs-CMs)上,研究α受体拮抗剂-哌唑嗪(prazosin,PRA)对去甲肾上腺素(norepinephrine,NE)诱导的心肌肥大效果的影响。方法通过体外二维培养分化的方法将hESCs-H7细胞系定向诱导分化为CMs,并通过imageJ软件计算免疫荧光染色图片来检测CMs面积的改变,qRT-PCR方法检测CMs肥大相关基因mRNA表达的改变,通过Leica显微镜FelixGX细胞动缘检测系统来测定CM收缩力及跳动情况的改变。结果20 μmol/L NE处理可使hESCs-CMs面积明显增大,肥大相关基因mRNA水平表达上调,收缩力及跳动频率增加;15 μmol/L PRA处理后hESCs-CMs面积相较NE组有所降低,肥大相关基因 BNP、TNNT2 mRNA表达明显降低,CM收缩力及跳动频率明显减弱。结论α受体拮抗剂PRA在hESCs-CMs上通过抑制NE诱导的细胞面积增大、肥大相关基因表达上调、收缩力增强以及跳动频率增加,从而改善NE诱导的心肌肥大。

Effect of combination therapy with alginate dressing and mouse epidermal growth factor on epidermal stem cells in patients with refractory wounds

Background The aim of this research was to determine the efficacy of combination therapy using an alginate dressing and mouse epidermal growth factor （mEGF） on proliferation and differentiation of epidermal stem cells （ESCs） in patients with refractory wounds.Methods Eighteen patients （12 males and 6 females,aged from 18 to 61 years （mean 36.4 years）） with various skin wounds,were treated by dressing changing for one month.The wounds were located in the foot （11）,calf （3）,thigh （2）and forearm （2）.The patients were randomly divided into 3 groups：alginate dressing and mEGF （group A; n=6）,mEGF （group B; n=6） and control （group C; n=6）.Wound closure indexes were measured at 7,14,21 and 28 days.Samples were harvested for pathologic examination,at 7 and 14 days following treatment.Cytokeratin 10 （CK10） and cytokeratin 15 （CK15） positive cells were evaluated using the super-sensitivity （SP） immunohistochemical staining technique.Results Wound healing was promoted in groups A and B.In group A,the wound closure index was increased significantly （P 〈0.05）,and in one case the maximum cure area reached 102 cm2.Pathological examination identified a thicker epidermis,active angiogenesis and enhanced granulation in group A compared with groups B and C.Using the SP immunohistochemical staining technique,we showed that ESCs in group A were bigger in size and larger in number than in groups B and C.Overall,there was a significant difference in ESCs proliferation and differentiation between group A and group B （or C）.Conclusions Combination therapy using an alginate dressing and mEGF shows increased proliferation and differentiation of ESCs in patients with refractory wounds compared with those treated with mEGF alone.

增生性瘢痕差异表达基因及小分子药物预测的生物信息学分析与验证

背景:增生性瘢痕是以成纤维细胞过度增殖、表皮增厚和角质层功能不良为特征的皮肤纤维化疾病,目前其具体发病机制仍不清楚。目的:基于生物信息学筛选增生性瘢痕相关数据集的核心(Hub)基因及重要信号通路,再用细胞实验加以验证,预测对其可能有治疗作用的小分子药物。方法:从基因表达综合数据库搜索增生性瘢痕相关的数据集,通过R软件筛选差异表达基因,对差异表达基因进行基因本体论和京都基因与基因组百科全书(Kyoto Encyclopedia of Genes and Gnomes,KEGG)富集分析,使用String在线平台构建差异表达基因的蛋白质相互作用网络,然后分别利用Cytoscape软件中的Cytohubba和MCODE插件筛选出蛋白质相互作用网络中的关键基因和核心模块,进一步将上述关键基因和构成核心模块的基因求交集得到Hub基因,通过荧光定量PCR验证Hub基因mRNA在人增生性瘢痕与正常皮肤表皮干细胞中的表达差异,并利用人类蛋白图谱中组织学数据验证Hub基因编码蛋白在2种组织中表达量和分布的差异,最后用connectivity map数据库预测针对增生性瘢痕的潜在作用药物。结果与结论:①筛选出的差异表达基因中上调基因102个、下调基因702个,基因本体论和KEGG分析结果显示,富集的信号通路及生物学过程主要涉及紧密连接、花生四烯酸代谢、细胞外基质受体交互、表皮发育和角质化等;②取交集得到8个Hub基因与调控胆固醇代谢的甲羟戊酸途径密切相关,分别是HMGCS1、DHCR7、MSMO1、FDPS、MVK、HMGCR、MVD和ACAT2;③荧光定量PCR结果显示,相比正常皮肤组,增生性瘢痕组HMGCS1、DHCR7、MSMO1、FDPS、HMGCR、MVD和ACAT2 mRNA的表达均显著下降(P<0.05),而MVK mRNA的表达无明显变化(P>0.05);④除MVK外,其余Hub基因编码蛋白在正常皮肤组织中表达水平均高于增生性瘢痕组织(P<0.05);⑤评分排列前10的候选药物包括蛋白激酶A抑制剂(H-89)、丝氨酸蛋白酶抑制剂(Dabigatran-Etexilate)、FLT3抑制剂(舒尼替尼)等,其中白藜芦醇和β-谷甾醇均为植物来源;⑥提示与甲羟戊酸代谢途径密切相关的Hub基因可能通过调控脂质代谢影响表皮结构与功能,这可能是增生性瘢痕的重要发病机制之一,此次研究筛选的小分子化合物可作为治疗增生性瘢痕的候选药物。

补益营卫方对衰老小鼠表皮干细胞Wnt/β-catenin信号通路相关蛋白表达的影响

目的探究补益营卫方对衰老小鼠表皮干细胞经Dickkopf-1(DKK1)阻断后Wnt/β-catenin信号通路中的原癌基因转录因子(C-myc)、轴抑制因子2(axis inhibitor2,Axin2)、基质金属蛋白酶-7(matrix metalloproteinase-7,MMP-7)、散乱蛋白1(dishevelled1,Dsh1)、淋巴增强因子-1(lymphoid enhancer factor-1,LEF-1)蛋白和mRNA表达水平的影响及其延缓皮肤衰老的作用。方法选取3月龄SPF级SAMR1雄性小鼠3只,作为年轻常规组;8月龄SPF级SAMP8雄性小鼠9只,随机分成衰老常规组、衰老阻断剂组和衰老药物干预组,每组3只,剪取各组小鼠的背部皮肤,分离得到表皮干细胞,并传代培养至融合。年轻常规组小鼠表皮干细胞用常规培养基培养,衰老常规组用常规培养基培养,衰老阻断剂组用含160 ng·mL^(-1)DKK1的完全培养基培养,衰老药物干预组用含160 ng·mL^(-1)DKK1+2.5%药物血清浓度的完全培养基培养(药物为补益营卫方,其组成为人参5 g、生黄芪15 g和炙甘草7 g,其浓度为0.5 g·mL^(-1))。使用Western blot法检测小鼠表皮干细胞中C-myc、Axin2、MMP-7、Dsh1、LEF-1蛋白的表达水平,RT-qPCR法检测小鼠表皮干细胞中C-myc、Axin2、MMP-7、Dsh1、LEF-1 mRNA的表达水平。结果与年轻常规组相比,衰老常规组小鼠表皮干细胞中的Cmyc、Axin2、MMP-7、Dsh1、LEF-1蛋白表达水平均升高(P均<0.01);与衰老常规组相比,衰老阻断剂组小鼠表皮干细胞中的上述5种蛋白的表达水平均降低(P均<0.01);与衰老常规组和衰老阻断剂组相比,衰老药物干预组5种蛋白表达水平均降低(P均<0.01)。与年轻常规组相比,衰老常规组小鼠表皮干细胞中的C-myc、Axin2、MMP-7、Dsh1、LEF-1的mRNA表达水平均升高(P<0.05或P<0.01);与衰老常规组相比,衰老阻断剂组小鼠表皮干细胞中的C-myc、Axin2、LEF-1 mRNA表达水平均降低(P<0.05或P<0.01),但MMP-7、Dsh1 mRNA表达差异均无统计学意义(P均>0.05);与衰老常规组相比,衰老药物干预组小鼠表皮干细胞中的C-myc、Axin2、MMP-7、Dsh1、LEF-1 mRNA的表达水平均降低(P<0.05或P<0.01);与衰老阻断剂组相比,衰老药物干预组表皮干细胞中C-myc、Axin2、Dsh1、LEF-1 mRNA水平均降低(P<0.05或P<0.01),但MMP-7 mRNA表达差异无统计学意义(P>0.05)。结论补益营卫方能降低衰老小鼠表皮干细胞Wnt/β-catenin信号通路中C-myc、Axin2、MMP-7、Dsh1、LEF-1蛋白和C-myc、Axin2、Dsh1、LEF-1 mRNA的表达,并与其阻断剂DKK1协同降低衰老小鼠表皮干细胞Wnt/β-catenin信号通路的活性,以延缓皮肤的衰老。

旋转细胞培养系统对老年人表皮干细胞增殖和干性维持的影响

背景:由于人口老龄化和老年疾病的增加,对老年人表皮干细胞的研究和利用变得越来越重要。但由于老年人表皮干细胞的增殖和干性能力较弱,限制了其在生物医学和临床研究的应用。目的:探讨旋转细胞培养系统培养的老年人表皮干细胞的增殖和干性维持能力。方法:采用传统平面培养方法获取儿童(7-12岁)和老年人(60岁以上)表皮干细胞,经细胞形态学和细胞免疫荧光鉴定后,通过流式细胞术、CCK-8、细胞克隆形成实验分析儿童和老年人表皮干细胞增殖能力的差异;采用旋转细胞培养系统和3D TableTrix®微载体培养儿童和老年人表皮干细胞,通过活/死染色、细胞倍增效率、细胞倍增时间以及实时定量聚合酶链反应检测细胞增殖情况以及干性标志物的表达。结果与结论:①在平面培养条件下,儿童组表皮干细胞较老年组具有更强的增殖能力;②与平面培养相比,经旋转细胞培养系统动态培养的老年人表皮干细胞的细胞倍增效率更高(P<0.01),细胞倍增时间更短(P<0.01);③旋转细胞培养系统动态培养促使老年人表皮干细胞自组装形成基于微载体支架的三维细胞球,具有和儿童组表皮干细胞相似的增殖情况;④动态培养后的老年人表皮干细胞在干性标记物基因(ITGA6和ITGB1)、基底细胞标记物基因(K5)和分化标记物基因(K10和K1)表达上可达到和儿童组相近的表达水平。结果表明:旋转细胞培养系统动态培养不仅可以提高老年人表皮干细胞的培养效率,促进细胞增殖和自组装成三维细胞球,而且可维持老年人表皮干细胞一定的干性,未发生完全终末分化。

Yes相关蛋白在电离辐射后表皮干细胞分化中的作用

目的探讨Yes相关蛋白(YAP)在电离辐射(IR)后表皮干细胞(EPSC)分化中的作用。方法①利用打孔器建立小鼠背部皮肤损伤,随后分为IR组(给予^(60)Coγ射线局部照射),对照组(不照射);照射后0,1,3,6,9和12 d收集创面皮肤组织提取RNA和蛋白,Western印迹法检测创面愈合过程中YAP蛋白变化;实时荧光定量PCR(RT-qPCR)检测创面愈合过程中Yap及其下游靶基因结缔组织生长因子(Ctgf)和富含半胱氨酸蛋白61(Cyr61)的mRNA变化。②将EPSC给予60Coγ射线照射,细胞对照组不照射;4或8 Gy剂量照射后4,12,24和36 h收集细胞提取RNA,RT-qPCR检测YAP mRNA变化。4或8 Gy剂量照射36 h收集细胞提取蛋白,Western印迹法检测YAP蛋白水平;③短发夹RNA(shRNA)构建稳定的YAP基因敲低细胞,Western印迹法验证shYAP的敲低效率;RT-qPCR检测IR后YAP敲低对K1和K10 mRNA的影响。结果①与对照组相比,IR组小鼠在创面愈合过程中YAP蛋白水平显著降低(P<0.05,P<0.01),Yap及其下游靶基因Ctgf和Cyr61的mRNA水平显著降低(P<0.05,P<0.01)。②与细胞对照组相比,IR组细胞YAP mRNA和蛋白水平显著降低(P<0.01)。③在shYAP稳转细胞中,YAP蛋白水平显著降低(P<0.01);shYAP在IR后EPSC分化标志物K1和K10的mRNA水平明显降低(P<0.01)。结论YAP调控IR后创面愈合过程中EPSC的分化。

FOXC1人表皮干细胞向汗腺细胞分化的影响

目的探究叉头框C1(FOXC1)对人表皮干细胞向汗腺细胞分化的影响及可能机制。方法收集2021年1月至2022年6月行包皮环切术7例的患者正常包皮组织,分离培养得到表皮干细胞,采用慢病毒介导FOXC1基因进行转染,并为过表达组、干扰组和对照组,RT-PCR及Western blot检测细胞FOXC1 mRNA及蛋白表达,MTT实验及吉姆萨染色检测细胞增殖水平、克隆形成率,ELISA检测培养基中基质金属蛋白酶-2(MMP-2)、MMP-9表达,激光共聚焦显微镜检测Ca^(2+)荧光强度,Western blot检测细胞角蛋白(CK19)、CK18、癌胚抗原(CEA)、β1整合素(ITGB1)表达。结果与对照组比较,过表达组细胞中FOXC1 mRNA及蛋白相对表达量、细胞增殖水平、细胞克隆形成率、Ca^(2+)荧光强度、MMP-2、MMP-9、表皮干细胞标记物CK18、CEA蛋白表达量升高(P<0.05),ITGB1、CK19蛋白表达量降低(P<0.05);与对照组比较,干扰组中FOXC1 mRNA及蛋白相对表达量、细胞增殖水平、细胞克隆形成率、Ca^(2+)荧光强度、MMP-2、MMP-9、表皮干细胞标记物CK18、CEA蛋白表达量降低(P<0.05),ITGB1、CK19蛋白表达量升高(P<0.05)。结论FOXC1可促进表皮干细胞向汗腺细胞分化的表型改变,其作用可能与其能促进表皮干细胞增殖及上调Ca^(2+)、MMP-2、MMP-9表达有关。

Putative epidermal stem cell convert into corneal epithelium-like cell under corneal tissue in vitro

Rhesus putative epidermal stem cells are being investigated for their potential use in regenerative corneal epithelium-like cells, which may provide a practical source of autologous seed cells for the construction of bioengineered corneas. The goal of this study was to investigate the potential of epi-dermal stem cells for trans-differentiation into corneal epithelium-like cells. Rhesus putative epidermal stem cells were isolated by type IV collagen attachment method. Flow cytometry analysis, immuno-histology and RT-PCR were conducted to identify the expression of specific markers (β1, α6 integrin, K15, K1/K10, K3/K12 and CD71) on the isolated rapid attaching cells. The isolated cells were cocultured with human corneal limbal stroma and corneal epithelial cells. After coculture, the expression of the same specific markers was evaluated in order to identify expression difference caused by the coculture conditions. K3/K12 expression was analyzed in coculture cells on day 2, 4, 6, 8 and 10. Putative epi-dermal stem cells in conditioned culture media were used as control. Putative epidermal stem cells were predominant in rapid attaching cells by type IV collagen attachment isolation. Before being co-cultured, the rhesus putative epidermal stem cells expressed K15, α6 and β1 integrin, but no CD71, K1/K10 and K3/K12. After coculture, these cells expressed K3/K12 (a marker of corneal epithelial cells), K15 and β 1 integrin, but no K1/K10. Cells being not coculture converted into terminally differentiated cells expressing K1/K10. These results indicate that rhesus putative epidermal stem cells can trans-differentiate into corneal epithelium-like cells and, therefore, may have potential therapeutic application as autologous seed cells for the construction of bioengineered corneas.

Transfection of the glial cell line-derived neurotrophic factor gene promotes neuronal differentiation

Glial cell line-derived neurotrophic factor recombinant adenovirus vector-transfected bone marrow mesenchymal stem cells were induced to differentiate into neuron-like cells using inductive medium containing retinoic acid and epidermal growth factor. Cell viability, micro- tubule-associated protein 2-positive cell ratio, and the expression levels of glial cell line-derived neurotrophic factor, nerve growth factor and growth-associated protein-43 protein in the su- pernatant were significantly higher in glial cell line-derived neurotrophic factor/bone marrow mesenchymal stem cells compared with empty virus plasmid-transfected bone marrow mes- enchymal stem cells. Furthermore, microtubule-associated protein 2, glial cell line-derived neurotrophic factor, nerve growth factor and growth-associated protein743 mRNA levels in cell pellets were statistically higher in glial cell line-derived neurotrophic factor/bone marrow mesen- chymal stem cells compared with empty virus plasmid-transfected bone marrow mesenchymal stem cells. These results suggest that glial cell line-derived neurotrophic factor/bone marrow mesenchymal stem cells have a higher rate of induction into neuron-like cells, and this enhanced differentiation into neuron-like cells may be associated with up-regulated expression of glial cell line-derived neurotrophic factor, nerve growth factor and growth-associated protein-43.

Growth factor-and cytokine-driven pathways governing liver stemness and differentiation

Liver is unique in its capacity to regenerate in response to injury or tissue loss. Hepatocytes and other liver cells are able to proliferate and repopulate the liver. However, when this response is impaired, the contribution of hepatic progenitors becomes very relevant. Here, we present an update of recent studies on growth factors and cytokine-driven intracellular pathways that govern liver stem/pro-genitor cell expansion and differentiation, and the rel-evance of these signals in liver development, regeneration and carcinogenesis. Tyrosine kinase receptor signaling, in particular, c-Met, epidermal growth factor receptors or fibroblast growth factor receptors, contribute to prolifera-tion, survival and differentiation of liver stem/progenitor cells. Different evidence suggests a dual role for the trans-forming growth factor (TGF)-β signaling pathway in liver stemness and differentiation. On the one hand, TGF-βmediates progression of differentiation from a progenitor stage, but on the other hand, it contributes to the expan-sion of liver stem cells. Hedgehog family ligands are nec-essary to promote hepatoblast proliferation but need to be shut off to permit subsequent hepatoblast differentiation. In the same line, the Wnt family and β-catenin/T-cell fac-tor pathway is clearly involved in the maintenance of liver stemness phenotype, and its repression is necessary for liver differentiation during development. Collectively, data indicate that liver stem/progenitor cells follow their own rules and regulations. The same signals that are essential for their activation, expansion and differentiation are good candidates to contribute, under adequate conditions, to the paradigm of transformation from a pro-regenerative to a pro-tumorigenic role. From a clinical perspective, this is a fundamental issue for liver stem/progenitor cell-based therapies.

Calcium silicate accelerates cutaneous wound healing with enhanced re-epithelialization through EGF/EGFR/ERK-mediated promotion of epidermal stem cell functions

Background:Human epidermal stem cells(hESCs)play an important role in re-epithelialization and thereby in facilitating wound healing,while an effective way to activate hESCs remains to be explored.Calcium silicate(CS)is a form of bioceramic that can alter cell behavior and promote tissue regeneration.Here,we have observed the effect of CS on hESCs and investigated its possible mechanism.Methods:Using a mouse full-thickness skin excision model,we explored the therapeutic effect of CS on wound healing and re-epithelialization.In vitro,hESCs were cultured with diluted CS ion extracts(CSIEs),and the proliferation,migration ability and stemness of hESCs were evaluated.The effects of CS on the epidermal growth factor(EGF),epidermal growth factor receptor(EGFR)and extracellular signal-related kinase(ERK)signaling pathway were also explored.Results:In vivo,CS accelerated wound healing and re-epithelialization.Immunohistochemistry demonstrated that CS upregulated cytokeratin 19 and integrinβ1 expression,indicating that CS improved hESCs stemness.In vitro studies confirmed that CS improved the biological function of hESCs.And the possible mechanism could be due to the activation of the EGF/EGFR/ERK signaling pathway.Conclusion:CS can promote re-epithelialization and improve the biological functions of hESCs via activating the EGF/EGFR/ERK signaling pathway.

Novel nervous and multi-system regenerative therapeutic strategies for diabetes mellitus with mTOR

Throughout the globe,diabetes mellitus（DM） is increasing in incidence with limited therapies presently available to prevent or resolve the significant complications of this disorder.DM impacts multiple organs and affects all components of the central and peripheral nervous systems that can range from dementia to diabetic neuropathy.The mechanistic target of rapamycin（m TOR） is a promising agent for the development of novel regenerative strategies for the treatment of DM.m TOR and its related signaling pathways impact multiple metabolic parameters that include cellular metabolic homeostasis,insulin resistance,insulin secretion,stem cell proliferation and differentiation,pancreatic β-cell function,and programmed cell death with apoptosis and autophagy.m TOR is central element for the protein complexes m TOR Complex 1（m TORC1） and m TOR Complex 2（m TORC2） and is a critical component for a number of signaling pathways that involve phosphoinositide 3-kinase（PI 3-K）,protein kinase B（Akt）,AMP activated protein kinase（AMPK）,silent mating type information regulation 2 homolog 1（Saccharomyces cerevisiae）（SIRT1）,Wnt1 inducible signaling pathway protein 1（WISP1）,and growth factors.As a result,m TOR represents an exciting target to offer new clinical avenues for the treatment of DM and the complications of this disease.Future studies directed to elucidate the delicate balance m TOR holds over cellular metabolism and the impact of its broad signaling pathways should foster the translation of these targets into effective clinical regimens for DM.