雷公藤多糖诱导胰腺干细胞成胰岛样细胞团

doi:10.3969/j.issn.2095-4344.0443

中国组织工程研究 ›› 2018, Vol. 22 ›› Issue (5): 729-735.doi: 10.3969/j.issn.2095-4344.0443

• 干细胞培养与分化 stem cell culture and differentiation • 上一篇下一篇

雷公藤多糖诱导胰腺干细胞成胰岛样细胞团

岑妍慧^1，2，李中华¹，贾微¹，杨瑞¹，包鹃¹，何国珍¹，吴晓君¹，钟静¹，邓慧枫¹，石磊¹

¹广西中医药大学，广西壮族自治区南宁市 530222：²广西壮族自治区中医药大学第一附属医院，广西壮族自治区南宁市 530023

修回日期:2017-09-09 出版日期:2018-02-18 发布日期:2018-02-18
通讯作者: 贾微，硕士，副教授。广西中医药大学，广西壮族自治区南宁市 530222;并列通讯作者：杨瑞，广西中医药大学，广西壮族自治区南宁市 530222
作者简介:岑妍慧，女，1980年生，汉族，2012年广西医科大学毕业，博士，副教授。并列第一作者：李中华，广西中医药大学，广西壮族自治区南宁市 530222
基金资助:
国家自然科学基金项目(81503406)；中国博士后科学基金(2017M6232)；广西壮族自治区卫生厅中医药科技专项课题(GZBZ16-07，GZLC16-23)；广西自然科学基金(2014GXNSFAA118177)

Tripterygium wilfordii polysaccharide induces differentiation of pancreatic stem cells into islet-like cell clusters

Cen Yan-hui^{1, 2}, Li Zhong-hua¹, Jia Wei¹, Yang Rui¹, Bao Juan¹, He Guo-zhen¹, Wu Xiao-jun¹, Zhong Jing¹, Deng Hui-feng¹, Shi Lei¹

¹Guangxi University of Chinese Medicine, Nanning 530222, Guangxi Zhuang Autonomous Region, China; ²First Affiliated Hospital of Guangxi University of Chinese Medicine, Nanning 530023, Guangxi Zhuang Autonomous Region, China

Revised:2017-09-09 Online:2018-02-18 Published:2018-02-18
Contact: Jia Wei, Master, Associate professor, Guangxi University of Chinese Medicine, Nanning 530222, Guangxi Zhuang Autonomous Region, China;Yang Rui, Guangxi University of Chinese Medicine, Nanning 530222, Guangxi Zhuang Autonomous Region, China
About author:Cen Yan-hui, M.D., Associate professor, Guangxi University of Chinese Medicine, Nanning 530222, Guangxi Zhuang Autonomous Region, China; First Affiliated Hospital of Guangxi University of Chinese Medicine, Nanning 530023, Guangxi Zhuang Autonomous Region, China. Li Zhong-hua, Guangxi University of Chinese Medicine, Nanning 530222, Guangxi Zhuang Autonomous Region, China. Cen Yan-hui and Li Zhong-hua contributed equally to this work.
Supported by:
the National Natural Science Foundation of China, No. 81503406; the China Postdoctoral Science Foundation, No. 2017M6232; the Special Fund for Traditional Chinese Medicine by the Health Department of Guangxi Zhuang Autonomous Region, No. GZBZ16-07, GZLC16-23; the Natural Science Foundation of Guangxi Zhuang Autonomous Region, No. 2014GXNSFAA118177

摘要/Abstract

摘要：

文章快速阅读：

文题释义：
诱导分化：是指通过物理或生物方法将目的基因导入到真核细胞的基因组中，使其调控靶细胞向特定的方向表达。
诱导分化的方法：常用的方法分非病毒方法和病毒载体方法，非病毒方法有微粒子轰击法、脂质体转染法、电穿孔法等，病毒方法有反转录病毒法、慢病毒法、腺病毒法及腺相关病毒法。

摘要
背景：胰岛细胞来源不足说明胰岛细胞移植治疗糖尿病不能满足临床需要。因此，体外诱导胰腺干细胞分化为胰岛细胞成为研究的热点。
目的：观察雷公藤多糖对小鼠胰岛来源的胰腺干细胞的诱导分化作用，从而探索中药诱导胰腺干细胞分化为胰岛β细胞的作用。
方法：采用雷公藤多糖体外诱导经纯化的小鼠胰腺干细胞分化为胰岛细胞。胰岛样细胞团进行形态学观察，双硫腙染色和Western blot分析。
结果与结论：①细胞形态学、细胞生长特性及免疫细胞化学染色显示，实验不仅得到了纯度高的小鼠胰腺干细胞，而且该细胞经雷公藤多糖诱导后能形成球形的胰岛样结构，有细长的蒂与培养瓶底部相连，双硫腙染色呈铁红色；②Western-blot检测显示，胰岛样细胞团中有β细胞素蛋白的表达；③结果表明，小鼠胰腺干细胞可以体外经雷公藤多糖诱导分化为含有β细胞的胰岛样细胞团。

中国组织工程研究杂志出版内容重点：干细胞；骨髓干细胞；造血干细胞；脂肪干细胞；肿瘤干细胞；胚胎干细胞；脐带脐血干细胞；干细胞诱导；干细胞分化；组织工程
orcid: 0000-0001-8751-7245(Jia Wei)

关键词: 雷公藤多糖, 胰腺干细胞, 形态学, 生长特征, 诱导分化, 胰岛样细胞团, 免疫细胞化学染色, 双硫腙, Western-blot, β细胞素, 组织工程

Abstract:

BACKGROUND: Inadequate sources of islet cells mean that islet cell transplantation for diabetes cannot meet the clinical demand. Therefore, in vitro induction of pancreatic stem cells to differentiate into islets has become a focus of research.

OBJECTIVE: To study the effect of Tripterygium wilfordii polysaccharides on the differentiation of pancreatic stem cells from islets in mice, so as to explore the effect of traditional Chinese medicine on the differentiation of pancreatic stem cells into pancreatic beta cells.

METHODS: Tripterygium wilfordii polysaccharide was used to induce the differentiation of purified mouse pancreatic stem cells into islets in vitro. The islet-like cell clusters then underwent morphologic observation, dithizone (DTZ) staining, and western blot analysis.

RESULTS AND CONCLUSION: Cell morphology, cell growth characteristics and immunocytochemical staining showed that mouse pancreatic stem cells were obtained. They were induced by Tripterygium wilfordii polysaccharide into spherical islet-like structures, which had a spindly pedicle connected with the bottom of the culture flask, and were DTZ-stained to iron red. Western blot assay detected β-cytokine proteins in the islet-like cell clusters. These findings confirm that mouse pancreatic stem cells can be induced to differentiate into islet-like cell clusters containing β cells in vitro by Tripterygium wilfordii polysaccharide.

中国组织工程研究杂志出版内容重点：干细胞；骨髓干细胞；造血干细胞；脂肪干细胞；肿瘤干细胞；胚胎干细胞；脐带脐血干细胞；干细胞诱导；干细胞分化；组织工程

Key words: Stem Cells, Tissue Engineering, Islets of Langerhans

中图分类号:

R394.2

岑妍慧，李中华，贾微，杨瑞，包鹃，何国珍，吴晓君，钟静，邓慧枫，石磊. 雷公藤多糖诱导胰腺干细胞成胰岛样细胞团[J]. 中国组织工程研究, 2018, 22(5): 729-735.

Cen Yan-hui, Li Zhong-hua, Jia Wei, Yang Rui, Bao Juan, He Guo-zhen, Wu Xiao-jun, Zhong Jing, Deng Hui-feng, Shi Lei. Tripterygium wilfordii polysaccharide induces differentiation of pancreatic stem cells into islet-like cell clusters[J]. Chinese Journal of Tissue Engineering Research, 2018, 22(5): 729-735.

图/表（结果） 1

Stem cells derived from the endocrine pancreas were obtained by discontinuous density gradient centrifugation

After the discontinuous Percoll density gradient centrifugation, the pancreatic tissue cells were distributed into three different density interfaces. The DTZ staining showed that 80%–90% of the cells from the first and second density interfaces were red iron (Figure 1), indicating that those cells were derived from the endocrine pancreas. Therefore, cells from both density interfaces were collected for primary culture.

Stem cells derived from the endocrine pancreas had significant morphologic features

At 48 hours of primary culture, cells derived from the endocrine pancreas showed some big, round, mononuclear cells surrounding the islet-like cell clusters. These cells had strong refraction of cytoplasm and a high nuclear-cytoplasmic ratio, showing adherence growth (Figure 2). In addition, these cells reflected the morphologic properties of pancreatic stem cells, so we named them pancreatic stem-like cells. Continuous cell culture was conducted after 7 days in primary culture.

Islet-differentiated pancreatic stem cells were identified via a series of methods

Growth characteristics of pancreatic stem cells

Pancreatic stem-like cells began to obviously divide and grow during subculture, and soon formed a large colony (Figure 3). After passage at 96 hours, when these cells covered more than 80% of the orifice aperture area, and passage continued. In continuous passage, the cells remained large and round, with a single core, a high nuclear-cytoplasm ratio, a strong proliferative capacity, and other characteristics, at each passage (Figure 4).

Detection of pancreatic stem cell-specific molecular markers of PDX-1

Immunocytochemical staining detecting the expression of PDX-1 showed positive results; the claybank-stained cytoplasm confirmed that the products were endocrine pancreas-derived stem cells (Figure 5).

Pancreatic stem cells were induced into islet-like cell clusters by Tripterygium wilfordii polysaccharide

Cell morphology and DTZ staining after induction

After continuous induction and differentiation via Tripterygium wilfordii polysaccharide for 7 days, some of the cells began to gather, but there were no significant changes in cell morphology. These cells were divided and produced more budding cells to grow upward, forming a spherical islet-like cell structure after approximately 1 month, had spindly pedicles connected with the bottom of the culture flask, and floated in the culture medium as shown in Figure 6. The DTZ staining of the islet-like cell clusters was iron red, while the DTZ staining of the surrounding cells was negative (Figure 7).

Islet-like cell clusters formed by induction expressed β-cytokine protein

Western blot results revealed that the induced islet-like cell clusters expressed β-cytokine protein with a relative molecular mass of approximately 32 000, as shown in Figure 8. GAPDH was used as an internal control, and the emergence of a target band confirmed the high quality of the extracted total cellular protein.

参考文献

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引言

Diabetes is an important disease damaging human health^[1], which can only be cured by pancreas or islet transplantation. However, this method faces the challenges of a shortage of pancreas donors and post-transplant immune rejection^[2]. Therefore, it is necessary to find a new source of islet cells. With the deepening of research on pancreatic stem cells, we confirm the existence of pancreatic stem cells in pancreatic tissues, and also find that they can be differentiated into islet cells by proper induction, which undoubtedly opens up a new way for the treatment of diabetes^[3-4].

Although after years of research, a set of methods for ideal pancreatic stem cells separation, culture and identification have been built, we still faces pancreatic stem cell differentiation rate is not high, and it is necessary to explore new and effective pancreatic stem cell inducer and induction method. Tripterygium wilfordii, as a traditional Chinese medicine, has extensive medicinal values. In China's general survey of botanical medicine, it has been found that Tripterygium wilfordii has a good effect in preventing diabetes. Our team found that the effective part of Tripterygium wilfordii for decreasing blood glucose is its polysaccharide components, and found that the hypoglycemic effect of Tripterygium wilfordii polysaccharides is related to an increase in the number of islet beta cells as well as in the release of insulin function (the related research results have not yet been published). But recent studies have shown that polysaccharide components of Chinese herbal medicine can regulate the differentiation of stem cells^[5-6], and the induction rate is higher than the traditional method of Western medicine. But there is no research on the application of Tripterygium wilfordii polysaccharides to induce the differentiation of pancreatic stem cells into islet β cells. So we put forward the work hypothesis that Tripterygium wilfordii polysaccharide can induce islet-derived pancreatic stem cells to differentiate into islet beta cells under suitable conditions. Based on the hypothesis, we worked out the optimal concentration and induction time of Tripterygium wilfordii polysaccharide, and then the differentiation of pancreatic stem cells was induced by Tripterygium wilfordii polysaccharide. Histochemical staining and Western blot were consequently used to analyze the level of Tripterygium wilfordii polysaccharide that induced the differentiation of stem cells derived from the endocrine pancreas. More importantly, we explored the role of traditional Chinese medicine in inducing the differentiation of pancreatic stem cells into islet β cells, which is expected to be a new theoretical basis for the clinical application of Chinese medicine in the treatment of diabetes.

中国组织工程研究杂志出版内容重点：干细胞；骨髓干细胞；造血干细胞；脂肪干细胞；肿瘤干细胞；胚胎干细胞；脐带脐血干细胞；干细胞诱导；干细胞分化；组织工程

材料方法

Design

A cytological experiment.

Time and setting

The experiment was initialized in January 2016 and ended until July 2017 at the comprehensive laboratory of medical innovation in the Basic Medical College of Guangxi University of traditional Chinese medicine, China.

Experimental animals

An unlimited number of healthy, newborn (within 24 hours) specific-pathogen-free Kunming mice, unlimited sex [License No. SCXK (Hu) 2007-2005], were purchased from the Experimental Animal Center of Guangxi University of Chinese Medicine (animal license number: Guangxi medical animal No. 11004). The experimental treatment of the animals was in accordance with the Guidance Suggestions for the Care and Use of Laboratory Animals issued by the Ministry of Science and Technology of China^[7].

Reagents and cell culture

Tripterygium wilfordii polysaccharide was extracted. The powder was dissolved in phosphate buffered saline (PBS), and added to the medium at the time of use to give an inducing solution with a final concentration of 5%.

Anti-PDX antibody was purchased from BD Biosciences (China), trypsin and fetal bovine serum were from Gibco (China). The cells were maintained in L-DMEM supplemented with 10% fetal bovine serum, 100 U/mL penicillin, and 100 μg/mL streptomycin, and incubated in a 5% CO₂ humidified condition at 37 ℃.

Discontinuous density gradient centrifugation to identify the source of pancreas stem cells

As the cells of the endocrine and exocrine pancreas have different densities, the discontinuous density gradient centrifugation method was used to separate the pancreatic stem cells. In accordance with the literature^[8-9], our previous studies explored effective cell separation using the discontinuous Percoll density gradient centrifugation to centrifuge pancreatic cells. This allowed the separation of pancreatic secretory cells into different density interfaces. The cells from different density interfaces were collected, and the cell source was identified using dithizone (DTZ) staining tests^[10]. DTZ is a complex that can specifically bind with Zn²⁺ to form a red complex, and islet β cells are rich in Zn²⁺. Thus islet β cells can be combined with DTZ and dyed to create a red color. Cells from the exocrine pancreas are generally not colored; therefore the source of islet cells can be identified on the basis of the staining.

Primary culture of pancreatic stem cells following determination of the islet source

Serum-free low glucose DMEM medium was used in the primary culture of pancreatic stem cells after the islet source was determined. This medium can reduce the stimulation of pancreatic stem cells^[11], and is conducive to their maintenance with undifferentiated characteristics. A commonly used two-step process was used in the culture method: first, the islets were separated, the suspension was cultured for 2-3 days, and the islets were picked out; second, pancreatic stem cells were adherently cultured^[12].

Purification of primary pancreatic stem cells by subculture using the differential adhesion method

When the amplified pancreatic stem cells covered approximately 60% of the bottom area of a culture flask as a single layer, according to the different sensitivities to trypsin of fibroblast-like cells and epithelial cells, and the difference in their adherence (differential adhesion), the fibroblast-like cells and other miscellaneous cell types were removed to purify the pancreatic stem cells. The subculture medium remained serum-free low-glucose DMEM.

Morphologic and growth characteristics of pancreatic stem cells

An inverted microscope was usually used to observe the shape, size, growth pattern, and characteristics of the cells.

Identification of pancreatic stem cell expression and characterization

Immunocytochemical staining was used to identify the pancreatic stem cell-specific molecular marker, PDX-1. PDX-1 is an important transcription factor in regulating insulin expression. In mammalian pancreatic tissue, it is an insulin and somatostatin transcription factor and is responsible for mature pancreatic β cells and maintaining function. PDX-1 is therefore considered to be a marker of islet-differentiation of pancreatic stem cells^{[13, 14]} and immunohistochemical staining can be used to detect its expression.

Induction of endocrine pancreas stem cells in culture

The method described previously was used for culture, counting cells in each hole of well plate before induction.

Preparation of Tripterygium wilfordii polysaccharide inducing liquid

Early through the orthogonal experiment optimized the extraction and purification methods of the optimal Tripterygium wilfordii polysaccharide, the weight was 0.856 g, and then the UV spectrophotometer was used to measure the effective composition that was 0.445 12 g. The polysaccharide was added into 10 mL of PBS buffer to make the inducing liquid.

Induction grouping and induction scheme

Cells were divided into two groups: a control group, which was cultured in only basic culture medium, and a Tripterygium wilfordii polysaccharide group in which Tripterygium wilfordii polysaccharide was used to induce differentiation of pancreatic stem cells, with the induction medium being changed every 24 hours. Induction time and concentration depended on the best induction time and concentration calculated in a pre-experiment (the final induction concentration was 5% every 2 days, for 2 continuous weeks).

DTZ staining after cell induction

The DTZ staining method was used as described previously. Positive staining indicates that pancreatic stem cells have been induced to differentiate into islet β cells in vitro, to allow determination of the initial rate of induction of differentiation.

Western blot assessment of the expression of induced β-cytokine

Total proteins were extracted after islet-like cell clusters were obtained. Quantitative analysis was carried out using the Bradford method: 100 μg of proteins were mixed with buffer, degenerated at 100 ℃ for 5 minutes, separated by 12% SDS-PAGE gel electrophoresis, and then electro-transferred to nitrocellulose membranes. These membranes were then incubated with rat anti-mouse polyclonal insulin antibodies (1:200) overnight at 4 ℃, and 0.05% PBS Tween-20 (PBST) was added to wash the membrane at room temperature. Finally, the membrane was incubated with horseradish peroxidase-labeled goat anti-rat IgG (H+L) secondary antibody (1:5 000) and placed on a rocker at room temperature for 2 hours. The membrane was washed three times with 0.05% PBST, and incubated with ECL X-ray exposure for 1–5 minutes to create a luminescent signal. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) was used as an internal control.

Main outcome measure

Morphology of pancreatic stem cells and expression of β-cytokine proteins in the islet-like cell clusters were detected in this study.

中国组织工程研究杂志出版内容重点：干细胞；骨髓干细胞；造血干细胞；脂肪干细胞；肿瘤干细胞；胚胎干细胞；脐带脐血干细胞；干细胞诱导；干细胞分化；组织工程

讨论

In this study, we successfully obtained pancreas stem cells from the endocrine pancreas through the discontinuous Percoll density gradient centrifugation, and found that stem cells from the endocrine pancreas expressed the pancreatic stem cells marker PDX-1, showing differentiation potential toward β cells (i.e., islets)^[14]. PDX-1, also known as an insulin promoter factor-1 and somatostatin transcription factor-1, is considered important in the regulation of pancreatic development and is responsible for maintaining pancreas β cell maturation and function^[14-16]. Therefore, if pancreatic stem cells express PDX-1, it indicates that a particular gene is activated to induce these cells to differentiate into insulin-secreting cells (i.e., Β cells). Thus, we believe that obtaining pure exocrine pancreas stem cells and inducing them to differentiate into β cells is more straightforward, compared with other sources of stem cells (including pancreatic stem cells derived from the exocrine pancreas), as it has a natural differentiation potential, which can more significantly improve the rate of differentiation of pancreatic stem cells into β cells.

Tripterygium wilfordii, also known as yellow vine, thunder god vine, yellow wax vine, vegetable insecticide, red medicine, and water mangcao, is a member of the Celastraceae Tripterygium species. Primarily produced in Fujian, Zhejiang, Anhui, and Henan provinces in China, it tastes bitter, pungent, and cool, and pharmacological studies have shown that it has anti-tumor, anti-inflammatory, anti-fertility, and immunomodulatory effects^[17].Tripterygium wilfordii has a complex composition; to date, almost 70 types of elements have been extracted from the Tripterygium genus, mainly including alkaloids, diterpenoids, triterpenoids, sesquiterpenoids, and polysaccharides. Studies on the chemical composition of Tripterygium wilfordii have focused on alkaloids, diterpenoids, triterpenoids, and sesquiterpenoids.

In addition to the above-mentioned pharmacological effects, an herbal census carried out in China found that Tripterygium wilfordii has been used in Chinese folk medicine for the prevention and alleviation of diabetes, producing good results. However, the hypoglycemic effect of Tripterygium wilfordii has been little reported, to date, with the exception of Zhang et al.^[18], who treated alloxan diabetic mice with Tripterygium wilfordii decoction and found that it significantly reduced alloxan-induced hyperglycemia of diabetes, and Ouyang et al.^[19], who used Tripterygium glycosides to treat adults with early latent autoimmune diabetes and found that they not only inhibited the patient's own immune response, but also improved islet β-cell function and reduced blood glucose.

In order to further understand the hypoglycemic effect of Tripterygium wilfordii, an active tracking method was used by our group, and we found that the effective hypoglycemic component of Tripterygium wilfordii was its polysaccharide. This ingredient has previously been ignored by researchers, and we have not found any reports describing its pharmacological effects. Therefore, we used the orthogonal experiment, chromatography and thin layer chromatography, and other methods to extract, isolate, and purify Tripterygium wilfordii polysaccharide. In addition, the effects of pancreatic cell function and glucose metabolism-related enzyme activities were observed via in vitro and in vivo experiments to understand its role in lowering blood glucose in diabetic animal models. The results showed that polysaccharides from Tripterygium wilfordii effectively reduced blood glucose in a diabetic rat model, increased its number of islet β cells and enhanced cell release of insulin (the results are unpublished as yet).

Although the research on polysaccharide-induced stem cells began only latterly, many studies conducted in recent years have shown that polysaccharide plays a regulatory role in directing differentiation of stem cells in Chinese medicine^{[5-6, 20-23]}, and induction rates are higher than in traditional Western medicine. Polysaccharide has been successfully used to induce marrow mesenchymal stem cells to differentiate into neural cells, cardiomyocytes, adipocytes, and osteoblasts in Chinese medicine^{[5-6, 20-23]}. However, there are no published reports to date, either from China or elsewhere, on whether applications of polysaccharide from Tripterygium wilfordii can induce pancreatic stem cells to differentiate into islet β cells. Therefore, a series of preliminary studies: 1) islet-derived pancreatic stem cells showed the potential to naturally differentiate into islet β cells; 2) polysaccharide from Tripterygium wilfordii has a significant hypoglycemic effect;previous usage of polysaccharide induction of stem cells in Chinese medicine. So we obtained pure endocrine pancreas stem cells by discontinuous density gradient centrifugation, and carried out their amplified culture, subculture, and identification.

After exploring the optimal induction time and concentration of polysaccharide from Tripterygium wilfordii, it was then used to continuously induce pancreatic stem cells. As a result, the obtained pancreatic stem cells were induced to differentiate into islet-like cell clusters, and DTZ staining showed an iron red color. Since DTZ specifically chelates with zinc within β cell insulin particles to make them appear iron red, the cell mass contained β cells. Western blot results via β-cytokine confirmed this, because β-cytokine was mainly expressed in the pancreas and small intestine. In addition, in fetal pancreatic endocrine precursor cells and in patients with islet metrocyte hyperplasia, β-cytokine has previously been found in insulin-secreting cells^[24]. β-cytokine can transform pancreatic amylase-secreting cells AR42J into insulin-secreting cells^[25], and also has mitogenic effects in undifferentiated human pancreatic epithelial cells^[26].

These results indicate that β-cytokine plays an important role in the growth and/or differentiation of pancreatic endocrine progenitor cells. Therefore, we believe that polysaccharide from Tripterygium wilfordii can induce the formation of cell clusters expressing β-cytokine, showing that the cells can be induced to differentiate toward insulin-secreting cells, that is, β cells.

In conclusion, the present study showed that polysaccharide from Tripterygium wilfordii can induce pancreatic stem cells differentiation into islet-like cell clusters under suitable conditions in vitro. It is expected that this will provide experimental evidence to assist in solving problems in clinical islet transplantation in the treatment of diabetes, for example, donor shortage. Future studies should further improve detection of related indicators, such as transmission electron microscopy, to observe the internal structure of the cell following induction, and conduct glucose stimulus experiments to understand insulin release after induction. In addition, further examination of how to promote maturation of induced cells to differentiate into islet-like cell clusters in vitro is also required.

中国组织工程研究杂志出版内容重点：干细胞；骨髓干细胞；造血干细胞；脂肪干细胞；肿瘤干细胞；胚胎干细胞；脐带脐血干细胞；干细胞诱导；干细胞分化；组织工程

雷公藤多糖诱导胰腺干细胞成胰岛样细胞团

Tripterygium wilfordii polysaccharide induces differentiation of pancreatic stem cells into islet-like cell clusters

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