SLE患者PBMC凋亡状态及相关基因表达的研究

探讨外周血单个核细胞(PBMC)凋亡及其基因调控在系统性红斑狼疮(systemic lupus erythematosus,SLE)发病机制中的作用.用流式细胞仪(FCM)检测PBMC凋亡百分率及T细胞亚群的凋亡状态;用RT-PCR检测PBMC bcl-2和bax的mRNA表达;用FCM检测凋亡相关基因bcl-2,bax,fas,p53和c-myc的蛋白表达.结果显示,SLE患者PBMC凋亡百分率明显高于正常人,且活动期患者高于非活动期患者.SLE活动期患者CD4+,CD8+T细胞数明显低于正常人;非活动期患者CD8+T细胞数明显低于正常人,而CD4+T细胞数与正常人比较无统计学差异;SLE患者PBMC bcl-2和bax mRNA表达与正常人比较无统计学差异;SLE患者PBMC bcl-2,bax和fas蛋白表达明显高于正常人,p53和c-myc蛋白表达在各组之间无统计学差异.SLE患者PBMC凋亡百分率增高、外周血T细胞亚群的异常及bcl-2,bax和fas蛋白表达增高,在SLE发病机制中可能起了一定的作用.     

子宫内膜异位症与子宫内膜息肉发病机制的相关性研究进展

子宫内膜异位症(endometriosis,EMT)和子宫内膜息肉(endometrial polyp,EP)是两类常见的良性妇科疾病，以子宫内膜组织的异常种植或增生为主要病理特征。流行病学数据显示，EMT患者的EP发生率攀升，EP患者合并EMT的风险也增加，提示二者可能存在密切关系与潜在的关联机制。尽管EMT和EP的发病机制尚未完全明确，但近年研究表明，EMT和EP的发生可能与长期高水平雌激素刺激、雌激素受体与孕激素受体表达失衡、细胞凋亡与增殖异常、细胞因子的表达、局部慢性炎症刺激、免疫系统失调、氧化应激、微生物群紊乱、代谢异常等因素有关。两者共有多种危险因素，可能参与彼此的疾病进程，从而在临床治疗上显示出消极的相互作用。本文通过对EMT和EP发病机制的相关性进行综述，为二者的基础研究和临床治疗提供更多理论依据。     

基质金属蛋白酶-2 在子宫内膜异位症中的表达及应用价值

目的:探讨粘附分子CD44拼构变异体6(CD44v6)和基质金属蛋白酶-2(MMP-2)在子宫内膜异位症(EMs)组织中的表达及相关性。方法:选取20例异位内膜组织标本、20例在位内膜组织标本及20例正常子宫内膜标本,用病理常规免疫组织化学方法检测MMP-2和CD44v6的表达,并分析其相关性。结果:CD44v6在异位内膜组的表达明显高于在位内膜组和对照组,且对照组明显高于在位内膜组,差异具有统计学意义(P0.05);CD44v6在在位内膜组和对照组中分泌期的表达明显高于同组增生期,差异具有统计学意义(P0.05)。MMP-2在异位内膜组和在位内膜组的表达明显高于对照组,差异具有统计学意义(P0.01);MMP-2在各组增生期和分泌期表达不规律。异位内膜组中,CD44v6和MMP-2在Ⅲ-Ⅳ期的表达明显高于Ⅰ-Ⅱ期,差异具有统计学意义(P0.01)。Spearman相关性分析结果显示:EMs组织中MMP-2和CD44v6之间呈现正相关性(r=0.724,P0.05);EMs不同分期组织中MMP-2和CD44v6之间亦呈现正相关性(r=0.623,P0.05)。结论:MMP-2和CD44v6在EMs异位内膜中高表达,且有正协同作用,二者可能与EMs的发生发展有关。     

CD44v6和MMP-2 在子宫内膜异位症组织中的表达及相关性

目的:探讨粘附分子CD44拼构变异体6(CD44v6)和基质金属蛋白酶-2(MMP-2)在子宫内膜异位症(EMs)组织中的表达及相关性。方法:选取40例异位内膜组织标本、40例在位内膜组织标本及40例正常子宫内膜标本,用免疫组织化学方法检测CD44v6和MMP-2的表达,并分析其相关性。结果:CD44v6在异位内膜组的表达明显高于在位内膜组和对照组,且对照组明显高于在位内膜组,差异具有统计学意义(P0.05);CD44v6在在位内膜组和对照组中分泌期的表达明显高于同组增生期,差异具有统计学意义(P0.05)。MMP-2在异位内膜组和在位内膜组的表达明显高于对照组,差异具有统计学意义(P0.01);MMP-2在各组增生期和分泌期表达不规律。异位内膜组中,CD44v6和MMP-2在Ⅲ-Ⅳ期的表达明显高于Ⅰ-Ⅱ期,差异具有统计学意义(P0.01)。Spearman相关性分析结果显示:EMs组织中CD44v6和MMP-2之间呈现正相关性(r=0.724,P0.05);EMs不同分期组织中CD44v6和MMP-2之间亦呈现正相关性(r=0.623,P0.05)。结论:CD44v6和MMP-2在EMs异位内膜中高表达,且有正协同作用,二者可能与EMs的发生发展有关。     

子宫内膜异位症患者凋亡相关基因TGF-β mRNA表达的研究

目的:探计TGF-β在子宫内膜异位症发病及发展中的分子生物学机制及与凋亡的相关性.方法:选取子宫内膜异位症患者12例为研究对象(EMS组),正常妇女正常子宫内膜12例(对照组),应用半定量逆转录-聚合酶链反应(RT-PCR)方法,测定TGF-β mRNA表达水平;运用western-blotting印迹法检测检测TGF-β蛋白的表达.同时用TUNEL染色对标本进行凋亡检测.结果:异位子宫内膜的凋亡率明显低于正常子宫内膜,且EMS组患者异位内膜的TGF-β mKNA和蛋白的表达水平上调.结论:患者子宫内膜中凋亡率的改变,在子宫内膜异位症的发生发展中起重要作用.异位的子宫内膜可能是由于TGF-β的表达上调增加了抗凋亡能力.     

KAI1/CD82 在早孕小鼠子宫内膜组织的表达研究

目的：观察KAI1／CD82 mRNA和蛋白在小鼠妊娠D1-D8子宫内膜组织的表达。方法：以胚胎与肿瘤同源性为理论基础,胚胎植入与肿瘤侵袭转移相似为切入点,采用免疫组化和RT-PCR技术。结果：KAI1／CD82 mRNA和蛋白在早孕子宫中,KAI1／CD82mRNA的表达渐增多,蛋白表达的量和范围也渐增强。结论：KAI1／CD82mRNA和蛋白在早孕子宫组织中的动态表达,提示它在胚胎精确侵袭子宫内膜的调节中发挥作用,是滋养层细胞精确侵袭调控的分子机制之一。     

神经细胞黏附因子在子宫腺肌病病灶中的表达及意义

目的:探究神经细胞黏附因子(NCAM)在子宫腺肌病病灶中的表达及意义。方法:将2016年6月~2017年6月在我院接受治疗的80例子宫腺肌病患者作为研究对象,包括分泌期与增生期各40例,采用免疫组化法检测,其在位内膜、异位内膜组织中NCAM表达情况,并以同期我院40例正常者子宫内膜标本作为对照。对子宫腺肌病患者痛经程度给予NRS疼痛评估,比较其NCAM的表达。结果:80例子宫腺肌病在位内膜、异位内膜均存在NCAM表达,40例正常内膜腺上皮有38例存在NCAM表达,2例正常内膜无表达。NCAM在异位内膜组织中的表达明显高于在位内膜及正常子宫内膜(P0.05),差异均有统计学意义。NCAM在在位内膜组织分泌期表达与增生期差异有统计学意义(P0.05);子宫腺肌病异位病灶NCAM表达与患者NRS评分呈现明显正相关(r=0.824,P0.05)。结论:NCAM在异位子宫内膜高表达,可能参与了子宫内膜异位症的发生和发展,并与患者痛经程度呈现出正相关。     

MDM2基因和TBX2在子宫内膜样腺癌中的表达及临床意义

目的:探讨MDM2和TBX2基因在正常增殖期子宫内膜、子宫内膜增殖症和子宫内膜样腺癌组织中的表达和临床意义。方法:采用免疫组织化学链菌素亲生物素基因过氧化物酶连接法(SP法)和组织芯片技术检测20例增殖期子宫内膜、41例子宫内膜增生性病变和45例子宫内膜样腺癌中MDM2和TBX2基因的表达情况。结果:MDM2在增殖期子宫内膜和单纯性增生子宫内膜中均无强阳性表达,复杂性增生子宫内膜和子宫内膜样腺癌中MDM2强阳性表达率分别为23.81%和51.11,明显高于增殖期子宫内膜和单纯性增生子宫内膜(P<0.05)。子宫内膜样腺癌中MDM2的强阳性表达率为51.11%(23/45),明显高于复杂性增生子宫内膜和复杂性非典型增生中的子宫内膜(P<0.05)。子宫内膜样腺癌中MDM2强阳性表达与肿瘤分化程度和TNM分期密切相关,Ⅱ、Ⅲ级子宫内膜样腺癌的强阳性表达率明显高于I级(72.41%vs 13.33%,P<0.05),而与淋巴结转移无相关性(P>0.05)。TBX2在增殖期子宫内膜,单纯性增生子宫内膜,复杂性增生子宫内膜,子宫内膜样腺癌中的阳性表达率分别为30%,35%,45%和72.7%。子宫内膜样腺癌中TBX2基因的阳性表达明显高于其它各组(P<0.05)。TBX2与子宫内膜样腺癌分化程度、TNM分期均有相关性(P<0.05),与有无淋巴结转移均无相关性(P>0.05)。结论:MDM2、TBX2基因在复杂性增生宫内膜和子宫内膜样腺癌中表达明显增强,提示两者在子宫内膜样腺癌发生中起到一定作用。     

西酞普兰对慢性应激大鼠额叶皮质神经细胞bax mRNA、bcl-2 mRNA表达及凋亡的影响

目的:探讨西酞普兰对慢性应激大鼠的额叶皮质神经细胞bax、bcl-2 mRNA表达的影响。方法:取24只雄性SD大鼠随机分为对照组(不进行任何处理)、应激组(应激+生理盐水灌胃)、实验组(应激+西酞普兰灌胃),采用强迫游泳制造慢性应激模型(15 min/d,共4周),用原位杂交技术检测bax、bcl-2 mRNA表达情况,TUNEL法检测细胞凋亡,尼康图像分析(NIS DR)软件测量各指标阳性细胞数量。结果:应激组较对照组,大鼠额叶皮质bax mRNA阳性表达细胞明显增多(P0.01)、染色加深;bcl-2 mRNA阳性表达细胞明显减少(P0.01)且染色变浅,且TUNEL阳性细胞数量增多(P0.01),染色增强。而实验组较应激组大鼠,额叶皮质bax mRNA阳性表达细胞减少(P0.01)、染色变浅,bcl-2 mRNA阳性表达细胞明显增多(P0.05),染色加深,且TUNEL阳性细胞数量减少(P0.01),染色减弱。结论:大鼠额叶皮质神经细胞bax mRNA和bcl-2 mRNA的表达水平受到慢性应激的影响,导致细胞凋亡加剧,西酞普兰能够有效调控额叶皮质神经细胞bax和bcl-2 mRNA的表达水平,拮抗细胞凋亡,这可能是西酞普兰防治慢性应激引起的神经精神疾病的相关机制之一。     

miRNA的重要调节者Dicer和Drosha与子宫内膜异位症的相关性研究

利用荧光定量PCR和Western blot检测证实,在异位的子宫内膜组织中Dicer和Drosha的表达低于在位子宫内膜组织,随后体外培养在位子宫内膜组织,采用siRNA干扰Dicer和Drosha,发现与干扰对照组相比,子宫内膜细胞的增殖加快而凋亡减少;同时ELISA检测显示转化生长因子-β1(transforming growth factor-beta 1, TGF-β1)的表达上调;Western blot检测显示凋亡抑制蛋白Bcl2表达增加而促凋亡蛋白Bax的表达减少．结果表明,miRNA的重要调节者Dicer和Drosha可以影响TGF-β1及Bcl2/Bax的表达进而影响细胞的增殖和凋亡,从而参与了子宫内膜异位症的形成．     

Expression, regulation and function of AC133, a putative cell surface marker of primitive human haematopoietic cells

To explore the physiological significance of AC133 expression on human haematopoietic cells, we phenotyped normal and malignant human haematopoietic cells for AC133 expression, evaluated the utility of AC133 for isolating human stem/progenitor cells in comparison to other known early haematopoietic cell markers, investigated the role of AC133 in regulating hematopoiesis, and evaluated the possibility that MYB might regulate AC133. We found that while human CD34+ progenitor cells expressed AC133, expression was rapidly downregulated during differentiation. In apparent contrast, AC133 mRNA was detectable in cells isolated from CFU-Mix, BFU-E, CFU-GM and CFU-Meg colonies. Human cord blood CD34+ cells expressed AC133 at higher levels than their normal bone marrow counterparts. In apparent contrast to normal primitive haematopoietic cells, the AC133 protein was undetectable on cells from 24 different human haematopoietic cells lines, even though the majority of these cells expressed AC133 mRNA. Since CD34, AC133 and the c-kit (KIT) receptor are all co-expressed on human stem/progenitor cells, we compared the ability of monoclonal antibodies directed against each of these proteins to isolate early progenitor cells. Using these antibodies and magnetized particles in a standard immunoaffinity isolation protocol, we found that anti-CD34 and anti-KIT MoAbs could isolate > 80-90% of the clonogeneic cell population present in a given marrow sample. Anti-AC133 MoAbs recovered approximately 75-80% of CFU-GM and CFU-Meg, but only about 30% of CFU-Mix and BFU-E. Perturbation of AC133 expression with antisense oligodeoxynucleotides (AS ODN) resulted in transient downregulation of AC133 protein on human CD34+ cells but no apparent effect on cell survival or cloning efficiency ex vivo. Finally, downregulation of MYB expression with AS ODN had no effect on the AC133 expression at either the mRNA or protein level. Based on these results, we conclude that AC133 offers no distinct advantage over CD34 or c-kit as a target for immunoaffinity based isolation of primitive hematopoietic cells, that AC133 expression is not required for normal hematopoietic progenitor cell development in vitro, and finally that AC133 expression may not be MYB-dependent.     

Epigenetic modification involved in benzene-induced apoptosis through regulating apoptosis-related genes expression

Benzene is an established haematotoxic and genotoxic carcinogen. DNA methyltransferase inhibitor, 5-aza (5-aza-2'-eoxycytidine) and histone deacetylase inhibitor, TSA (trichostatin A) are two kinds of key epigenetic modification reagents. Although apoptosis has been considered as the key cytotoxicity mechanism, the effects of these epigenetic reagents on benzene-induced apoptosis have not been reported. In this study, BMCs (bone marrow cells) from rats were incubated with benzene and then with either 5-aza, TSA alone or the combination of the two drugs. Apoptosis and mRNA expression were detected by annexin V/PI (propidium iodide) staining assay and real-time PCR, respectively. Results showed that benzene caused cell apoptosis accompanied with bcl-2 mRNA decrease, caspase-3 and bax mRNA increase. Moreover, benzene-induced apoptosis and the decrease of bcl-2 mRNA were both reversed by both 5-aza and TSA, but the role of TSA was significantly larger than 5-aza. More interestingly, these increases in benzene-induced caspase-3 and bax mRNA expression were obviously suppressed by 5-aza but not by TSA. In conclusion, 5-aza inhibited benzene-induced apoptosis through down-regulating of caspase-3 and bax and up-regulating bcl-2 mRNA expression, whereas the effect of TSA on apoptosis dominatingly affected bcl-2 mRNA expression, and 5-aza together with TSA had no synergic effect on benzene-induced apoptosis.     

Analyses to clarify rich fractions in hepatic progenitor cells from human umbilical cord blood and cell fusion

Umbilical cord blood (UCB) is a source of hematopoietic stem cells and other stem cells, and human UCB cells have been reported to contain transplantable hepatic progenitor cells. However, the fractions of UCB cells in which hepatic progenitor cells are rich remain to be clarified. In the present study, first, the fractionated cells by CD34, CD38, and c-kit were transplanted via portal vein of NOD/SCID mice, and albumin mRNA expression was examined in livers at 1 and 3 months posttransplantation. At 1 and 3 months, albumin mRNA expression in CD34+UCB cells-transplanted livers was higher than that in CD34- cells-transplanted livers. Albumin mRNA expression in CD34+CD38+ cells-transplanted livers was higher than that in CD34+CD38- cells-transplanted [corrected] liver at 1 month. However, it was much higher [corrected] in CD34+CD38- cell-transplanted livers at 3 months. Similar expression of albumin mRNA was obtained between CD34+CD38+c-kit+ cells- and CD34+CD38-c-kit- cells-transplanted livers, and between CD34+CD38-c-kit+ cells- and CD34+CD38-c-kit- cells-transplanted livers, respectively. Second, fluorescence in situ hybridization and immunohistochemistry were performed to examine whether UCB cells really transdifferentiated into hepatocytes or they only fused with mouse hepatocytes. In mouse liver sections, of 1.2% cells which had human chromosomes, 0.9% cells were due to cell fusion, whereas 0.3% cells were transdifferentiated into human hepatocytes. These results suggest that CD34+UCB cells are rich fractions in hepatic progenitor cells, and that transdifferentiation from UCB cells into hepatocytes as well as cell fusion simultaneously occur in this situation.     

Expression of p53, p21/waf, bcl-2, bax, Rb and Ki67 proteins in colorectal adenocarcinomas

This study investigated the combined immunoexpression of p53, p21, bcl-2, bax, Rb and Ki67 proteins in colorectal adenocarcinomas and correlated expression patterns with tumour stage and grade. Paraffin sections from 98 cases of colorectal adenocarcinomas were stained by immunohistochemistry for p53, p21, bcl-2, bax, Rb and MIB-1 (Ki67) proteins. In addition, 12 cases of colorectal adenomas and normal colorectal mucosa were studied in parallel. P53, p21, bcl-2, bax, Rb and Ki67 proteins were detected in at least 5% of tumour cells in 63/98, 72/98, 52/98, 96/98 and 98/98 adenocarcinomas, respectively. Comparative study of the normal-adenoma-carcinoma tissues revealed abrogation of the normal immunotopography in adenomas and adenocarcinomas, and considerable modifications, increase or reduction, of the expression of p53, p21, bcl-2, bax, Rb and Ki67 proteins in adenocarcinomas when compared with normal mucosa and adenomas. Statistically significant correlations were found between low bax expression and Dukes C stage of carcinomas, Ki67 expression and carcinoma grade, and Ki67 and Rb expression. P53, p21, bcl-2 and Rb immunoexpression did not correlate with tumour stage or grade. Our findings show that low bax immunoexpression is frequently related to colorectal adenocarcinomas with lymph node metastases suggesting that low levels of bax expression play a role in late stage colorectal cancer. The correlation between Ki67 and Rb expression, in view of previous data that the hyperphosphorylated inactive Rb protein is frequently increased in colorectal adenocarcinomas, suggests that Rb protein is somewhat ineffective in inhibiting the cell-cycle progression in these malignancies. Furthermore, our findings provide immunohistochemical evidence that the abrogation of the normal immunotopography and the modifications of the expression of p53, p21, bcl-2, bax, Rb and Ki67 proteins reflect important events in colorectal oncogenesis.     

Sodium fluoride induces apoptosis and alters bcl-2 family protein expression in MC3T3-E1 osteoblastic cells

Chronic excessive fluoride intake is known to be toxic and can lead to fluorosis and bone pathologies. However, the cellular mechanisms underlying NaF-induced cytotoxicity in osteoblasts are not well understood. The objectives of this study were to determine the effects of fluoride treatment on MC3T3-E1 osteoblastic cell viability, cell cycle analysis, apoptosis and the expression levels of bcl-2 family members: bcl-2 and bax. MC3T3-E1 cells were treated with 10⁻⁵; 5 × 10⁻⁵; 10⁻⁴; 5 × 10⁻⁴ and 10⁻³ M NaF for up to 48 h. NaF was found to reduce cell viability in a temporal and concentration dependent manner and promote apoptosis even at low concentrations (10⁻⁵ M). This increased apoptosis was due to alterations in the expression of both pro-apoptotic bax and anti-apoptotic bcl-2. The net result was a decrease in the bcl-2/bax ratio which was found at both the mRNA and protein levels. Furthermore, we also noted that NaF-induced S-phase arrest during the cell cycle of MC3T3-E1 cells. These data suggest that fluoride-induced osteoblast apoptosis is mediated by direct effects of fluoride on the expression of bcl-2 family members.     

鼻息肉患者前列腺素E2受体的表达及意义

摘要 目的：研究EP受体在慢性鼻-鼻窦炎伴鼻息肉（chronic rhinosinusitis with nasal polyps, CRSwNP）中的表达及意义。方法：收集20例嗜酸粒细胞性CRSwNP(eosinophilic CRSwNP,ECRSwNP )、20例非嗜酸粒细胞性CRSwNP（noneosinophilic CRSwNP,non-ECRSwNP)患者息肉和14例正常对照组鼻腔钩突黏膜。免疫组织化学和Western blot技术检测各组鼻组织中四种EP受体亚型蛋白的表达;对连续切片行免疫组化染色,检测EP受体与活化的嗜酸粒细胞之间的关系;用Real-time PCR检测各组EP受体和IL-5/IL-13 mRNA的表达水平。结果：EP受体主要表达于鼻黏膜上皮、腺体和上皮下炎症细胞,EP1受体选择性表达于上皮下炎症细胞。与对照组和non-ECRSwNP相比较,ECRSwNP组中EP1 mRNA和蛋白表达均上调,而三组间EP2、EP3和EP4受体的表达无明显差异。连续切片免疫组化染色示,EP1阳性的嗜酸粒细胞占EP1阳性总细胞数的50%。息肉组织EP1 mRNA与IL-5（r=0.55; P <0.001）、IL-13（r=0.69; P<0.001）mRNA的表达水平呈正相关。结论：ECRSwNP中EP1的表达上调与大量的嗜酸粒细胞等浸润有关。EP1受体可能通过趋化和活化嗜酸粒细胞参与ECRSwNP组织炎症的发生和发展。     

P2Y receptors activate neuroprotective mechanisms in astrocytic cells

Mechanical or ischemic trauma to the CNS causes the release of nucleotides and other neurotransmitters into the extracellular space. Nucleotides can activate nucleotide receptors that modulate the expression of genes implicated in cellular adaptive responses. In this investigation, we used human 1321N1 astrocytoma cells expressing a recombinant P2Y2 receptor to assess the role of this receptor in the regulation of anti-apoptotic (bcl-2 and bcl-xl) and pro-apoptotic (bax) gene expression. Acute treatment with the P2Y2 receptor agonist UTP up-regulated bcl-2 and bcl-xl, and down-regulated bax, gene expression. Activation of P2Y2 receptors was also coupled to the phosphorylation of cyclic AMP responsive element binding protein that positively regulates bcl-2 and bcl-xl gene expression. Cyclic AMP responsive element decoy oligonucleotides markedly attenuated the UTP-induced increase in bcl-2 and bcl-xl mRNA levels. Activation of P2Y2 receptors induced the phosphorylation of the pro-apoptotic factor Bad and caused a reduction in bax/bcl-2 mRNA expression ratio. All these signaling pathways are known to be involved in cell survival mechanisms. Using cDNA microarray analysis and RT-PCR, P2Y2 receptors were found to up-regulate the expression of genes for neurotrophins, neuropeptides and growth factors including nerve growth factor 2; neurotrophin 3; glia-derived neurite-promoting factor, as well as extracellular matrix proteins CD44 and fibronectin precursor--genes known to regulate neuroprotection. Consistent with this observation, conditioned media from UTP-treated 1321N1 cells expressing P2Y2 receptors stimulated the outgrowth of neurites in PC-12 cells. Taken together, our results suggest an important novel role for the P2Y2 receptor in survival and neuroprotective mechanisms under pathological conditions.     

Islet-derived stem cells from adult rats participate in the repair of islet damage

This study investigated the role of adult islet-derived stem cells in repairing islet damage. Using intraperitoneal injection of cerulein, a rat model of acute pancreatitis was induced in an experimental group. The expression of the protein c-kit, a pancreatic stem cell marker, was observed using immunohistochemistry at set intervals following successful model preparation. Pathological changes in pancreatic tissues were also observed using routine hematoxylin and eosin staining. Cells with positive c-kit staining were rarely observed in normal tissues. At all observation intervals after the induction of acute pancreatitis, c-kit staining was restricted to the islets. Over the course of observations, staining changed from low to high intensity, and then back to low intensity again. The primary pathological manifestation in the experimental group was edematous pancreatic tissues with local necrotic lesions. These findings suggested that c-kit positive cells are likely to be a type of pancreatic progenitor cell that is involved only in the self-repair of islet damage and does not migrate.