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High–efficiency generation of induced pluripotent stem cells from human foreskin fibroblast cells using the Sagunja-tang herbal formula
© The Author(s). 2017
Received: 12 April 2017
Accepted: 5 December 2017
Published: 11 December 2017
Sagunja-Tang (SGT-4) is a traditional herbal formula in Korean medicine that is used to treat anti-metabolic syndrome, and has antioxidant activity. In this study, we evaluated the effects of SGT-4 on the formation efficiency of induced pluripotent stem cells (iPSCs) from human foreskin fibroblasts (HFFs) by four reprogramming transcription factors: Oct4, Sox2, KIf4, and c-Myc (OSKM).
SGT-4 contained four different herbal medicines that are composed of Ginseng Radix, Glycyrrhizae Radix et Rhizoma, Atractylodis Rhizoma Alba, and Poria Sclerotium. The composition of SGT-4 was analyzed by high-performance liquid chromatography (HPLC). HFFs were transfected with episomal vectors contained by four OSKM. Western blotting, RT-PCR, immunofluroescence, and in vitro differentiation were used to assess the pluripotency of the iPSC cells.
SGT-4 exhibited antioxidant activity against the generation of intracellular reactive oxygen species (ROS) as well as promoted the activation of superoxide dismutase 1 (SOD1), catalase, gluthathione peroxidase 1 (GPX1), and glutathione (GSH). Moreover, the ATP level was not significantly fluctuated depending on the concentration of SGT-4 in the hiPSCs.
Our results indicate that the SGT-4, herbal formula significantly increases the efficiency of human iPSC generation via the transcription factors (Oct4, Sox2, KIf4, and c-Myc).
Induced pluripotent stem cells (iPSCs) are an attractive potential resource for autologous cell replacement therapy. Thus, it is necessary to still improve the efficiency of cellular reprogramming, which is currently one of the major issues in iPSC field. Because of the infinite proliferative abilities and self-renewal capacity of iPSCs, these cells cannot only provide limitless amounts of cellular therapeutic materials, but also potentially differentiate toward any cell types within our bodies.
According to previous studies, the p53 protein has a negatively affects reprogramming efficiency by intrinsically inducing either apoptosis or cell cycle arrest. Thus, only temporary knockdown of p53 function can effectively improve the reprogramming efficiency . In addition to genetic factors, several chemicals that can influence on chromatic structure, can also affect the reprogramming process positively. Most reported chemicals often modulate the chromatin structure and gene activity in the entire genome [2, 3]. For example, recent studies have demonstrated that valproic acid (VPA), a histone deacetylase inhibitor, has been shown to improve both the kinetics and efficiency of mouse and human iPSC generation . In addition, BIX-01294, an inhibitor of histone methyltransferase G9a, and RG108, a DNA methyltransferase inhibitor, have been reported to enhance the efficiency of iPSC generation [4, 5].
Recently, butyrate, a naturally occurring short chain fatty acid and histone deacetylase inhibitor, has been shown to support the self-renewal of both human and mouse embryonic stem (ES) cells within a range of low concentrations relatively , whereas higher concentration of butyrate have also been reported to induce differentiation . In addition, efforts to improve iPSCs safety have focused on using fewer factors and non-vital methods. For example, it was reported that Oct4 alone could reprogram human epidermal keratinocytes into human iPSCs (hiPSCs) .
Sagunja-Tang (SGT-4), a traditional Korean herbal decoction, comprises four oriental herbs.
(Ginseng Radix, Glycyrrhizae Radix et Rhizoma, Atractylodis Rhizoma Alba, Poria Sclerotium) and has been medicinally used in Asian countries to enhance vital energy and tonify spleen and stomach function. SGT-4 is applied to patients with reduced physical strength, weakened immune system, and gastrointestinal diseases . Recent studies have shown that SGT-4 exhibits several effects, including immune stimulatory activity, a radioprotective effect and a soothing effect [10–12]. Like the mechanism by which vitamin C effectively promotes iPSC production, SGT-4, an antioxidant, can be a potential candidate to promote cell reprogramming by reducing the production of reactive oxygen species (ROS) during reprogramming . In this study, we examined whether SGT-4 exert any effect on iPSC generation, identifying that ROS level is decreased during reprogramming process.
The four medicinal components of SGT-4 were purchased from Omniherb (Yeongcheon, Korea) and HMAX (Jecheon, Korea) in February 2008. The origin of each component was confirmed by Prof. Je Hyun Lee, (College of Oriental Medicine, Dongguk University Gyeongju, Korea) and Prof. Young-Bae Seo, (College of Oriental Medicine, Daejeon University, Daejeon, Korea). A voucher specimen (2008-KE24–1 ~ KE24–4) has been deposited at the K-herb Research Center (Korea Institute of Oriental Medicine).
Preparation of SGT-4
The four medicinal herbs (Ginseng Radix, Glycyrrhizae Radix et Rhizoma, Atractylodis Rhizoma Alba, and Poria Sclerotium) were combined in equal amounts to produce SGT-4. The mixture was then extracted in a 10-fold volume of distilled water at 100 °C for 2 h using an electric extractor (COSMOS-660; Kyungseo Machine Co., Incheon, Korea). The solution was filtered using a standard sieve (No. 270, 53 μm; Chung Gye Sang Gong Sa, Seoul, Korea), evaporated to dryness at 40 °C under a vacuum (Eyela N-11, Tokyo, Japan), and then freeze-dried (PVT100, IlShin Bio Base, Yangju, Korea). The amount of water extract was 446.0 g (yield: 22.3%).
High-performance liquid chromatography (HPLC) analysis of SGT-4
HPLC analysis of the extract was performed using a Shimadzu Prominence LC-20A series (Kyoto, Japan) coupled with a photodiode array (PDA) detector. The data were acquired and processed using LabSolution software (version 5.54 SP3). Seven analytes were separated on a Waters SunFire C18 column (250 × 4.6 mm, 5 μm, Milford, MA, USA) at an oven temperature of 40 °C. The mobile phases consisted of 0.1% (v/v) TFA in distilled water (A) and acetonitrile (B). The gradient flow was as follows: 10–60% B for 0–30 min, 60–100% B for 30–40 min, 100% B for 40–45 min, 100–10% B for 45–50 min, and 10% B for 50–60 min, with a flow-rate of 1.0 mL/min and an injection volume of 10 μL. For the simultaneous HPLC analysis of the seven primary biomarker compounds in SGT-4 sample, 200 mg of lyophilized SGT-4 extract was dissolved in 20 mL of 70% methanol and then extracted using an ultrasonicator for 20 min. The extracted solution was filtered through a 0.2 μm syringe filter (PALL Life Sciences, Ann Arbor, MI, USA) prior to HPLC analysis.
Human foreskin fibroblast (HFFs) were obtained from System Biosciences (Mountain View, CA, USA) and maintained in DMEM supplemented with 10% FBS. The human dermal fibroblast (HDF) cell line was obtained from ScienCell (Carlsbad, CA, USA). HDFs were propagated in fibroblast medium supplemented with 5% FBS, 1% fibroblast growth supplement, and 1% penicillin and streptomycin (P/S). In addition, the established hiPSCs, were maintained in mTeSR 1 basal medium containing supplements on Matrigel-coating plates purchased form STEMCELL Technologies (Vancouver, BA, Canada). To maintain the hiPSCs in an undifferentiated state, the medium was refreshed daily, and the cells were passaged once a week. The cells were maintained at 37 °C in a humidified environment containing 5% CO2.
Cells were preincubated with the indicated concentration pre-incubated with SGT-4 for 24 h, washed with PBS and exposed to a UVB (100 mJ/cm2) light source for 20 min (VL-6.LM, Viber Loumat, France). Afterwards, the cells were washed with PBS, and DMEM was added for 60 min.
Derivation of hiPSCs
pMX-based retroviral vectors containing the genes for human Oct4, Sox2, Klf4, and cMyc (Addgene Inc., Cambridge, MA, USA) were transfected into HFF cells using the Neon® Transfection System (Invitrogen, Carlsbad, CA, USA). Beginning either 48 or 72 h after transfection, the medium was changed daily until hESC-like colonies emerged. To establish hiPSC cells, the colonies were treated with ReLeSR to detach the cells and transferred onto Matrigel-coated plates. Each colony was further maintained and expanded for subsequent experiments.
Analysis of hiPSCs by flow cytometry
pMX-based retroviral vectors containing the genes for human Oct4, Sox2, Klf4, and cMyc were transfected into HFF cells. And then 48 h after transfection, the medium was changed daily until hESC-like colonies emerged. To establish hiPSC cells, we harvested differentiated from hiPSCs using 0.25% trypsin/EDTA for 2–3 min at 37 °C and resuspended in PBS/1% FBS at 1 × 106 cells per 500 μl. The cells were labeled with antibodies against SSEA1-FITC, SSEA3-FITC, and SSEA4-FITC (all from Santa Cruz Biotechnology), at 4 °C for 30 min, washed twice with PBS/1% FBS, and analyzed using a FACSCanto™II flow cytometer (BD Biosciences, Bedford, MA, USA) according to the manufacturer’s instructions. The data were analyzed using BD FACSDiva (BD Biosciences).
hiPSCs were treated with different concentrations (0.25,0.5, 1, and 2 μg/ml) in a 96-well white plate for 24 h, and then total intracellular ATP content was determined using an ATP luminescent detection kit (PerkinElmer, Waltham, MA, USA) and a luminometer (Berthold Technologies, Bad Wildbad, Germany). The ATP content was determined by running an internal standard and is expressed as a percentage of the ATP content in untreated cells.
Determination of GSH
HFFs were treated with different concentrations (0.25,0.5, 1, and 2 μg/ml) in a 6-well plate for 24 h, and then total intracellular glutathione (GSH) content was determined using a chemical assay kit (Cayman Chemical, Ann Arbor, MI, USA) following the manufacturer’s instructions.
Measurement of ROS generation
After the UVB-irradiated cells rested for 30 min in DMEM, they were washed with PBS and incubated with a DCF-DA (10 μM) staining solution for 10 min at 37 °C in the dark. as previously described .
To quantify gene expression in hiPSCS, RT-PCR analysis was performed (ABI QuantStudio™ 6 Flex Real-Time PCR system, Applied Biosystems, Waltham, MA, USA) using a TaqMan universal PCR Master Mix (Applied Biosystems, USA). The relative mRNA expression levels of Nanog, Sox2, Oct4, c-Myc and KIf4 were normalized to those of GAPDH . The PCR protocol comprised of 40 cycles of 95 °C for 15 s and 60 °C for 1 min. Each sample was assayed in triplicate and the relative mRNA expression levels were calculated using the ΔΔCt method.
Cell lysates from HFFs (5 × 106) in 1× Laemmli lysis buffer (2.4 M glycerol, 0.14 M Tris (pH 6.8), 0.21 M sodium dodecyl sulfate, and 0.3 mM bromophenol blue), and boiled for 10 min. The protein content was measured using the BCA protein assay reagent (Pierce, Waltham, MA, USA). Protein samples (20 μg) were diluted in 1× lysis buffer, separated by electrophoresis (4.5%–15% gradient), and transferred onto polyvinylidene fluoride membranes (PVDF). The membranes were then incubated with primary antibodies against SOD1 (1:1000), catalase (1:1000), GPX1 (1:1000), and β-actin (1:1000) overnight followed by incubation with horseradish peroxide-conjugated secondary antibodies, Bound antibodies were detected using an enhanced chemiluminescence detection system from Amersham Bioscience (Buckinghamshire, UK). The protein expression levels were determined by analyzing the captured signals on an image analyzer (Las-3000, Fujifilm, Tokyo, Japan).
The iPSCs generated from HFFs were washed with PBS and fixed in 4% formaldehyde at room temperature (RT) for 15 min. The cells were permeablized in 0.1% Triton X-100 in PBS and blocked with a blocking solution (4% bovine serum albumin (BSA) for 1 h at RT. Primary antibodies against Oct4, Nanog, Sox2, and β-actin (Abcam, all 1:500) were diluted in blocking solution and incubated with the prepared cells overnight at 4 °C. After washing the cells with phosphate-buffered saline containing 0.01% Tween-20 (PBST), the cells were incubated with the Alexa Fluor 488- or Alexa Fluor 594-congugated secondary antibodies for 45 min at RT in the dark. The cells were washed three times with PBST, and incubated with DAPI (300 ng/ml) for 10 min to counterstain the cells nuclei. The samples were analyzed using a FluroView confocal microscopes (Olympus, Tokyo, Japan).
The data are presented as the mean ± standard deviation (SD) of at least three separate experiments. Comparisons between two groups were made using the Student’s t-test in Graph Pad software (San Diego, CA, USA); and statistical significance was established at P < 0.05.
Identification and quantification of the primary components of SGT-4
Optimization and characterization of hiPSCs from HFFs
SGT-4 promotes iPSC generation
SGT-4 accelerates iPSC generation
SGT-4 blocks UVB-induced ROS generation by antioxidant enzymes expression
SGT-4, a traditional herbal formula comprising four different herbal medicines, (Ginseng Radix, Glycyrrhizae Radix et Rhizoma, Atractylodis Rhizoma Alba, and Poria Sclerotium) has been used in Korea and China to treat diabetes, and metabolic syndrome. In addition, it has antioxidant properties . These four herbal medicines exhibit a reproductive effect in mice , a stimulatory effects on splenocytes , anti-melanogenesis activity against melanoma cells , and the ability to extend the lifespan of C. elegans . In the present study, we analyzed 7 marker compounds found in an SGT-4 ginsenoside Rg1, ginsenoside Rb1, atractylenolide III, liquiritigenin, liquiritin apioside, liquiritin, and glycyrrhizin using HPLC analysis (Fig. 1b). Ginsenosides Rb1 and Rg1 promote the proliferation of primary neuron cells . Atractylenolide III, and liquiritigenin have been shown to exert anti-inflammatory effects [22, 23], and glycyrrhizin attenuates stem cells- like phenotypes in papilla cells . Additionally, SGT-4 is used to treat patients with reduced physical strength, a weakened immune system or gastrointestinal diseases .
Reprogramming of adult somatic cells into pluripotent stem cells is considered as an attractive source of stem cells for basic biological studies and regenerative medicine. The generation of hiPSCs from somatic cells with specific transcription factors allows for the possibility to produce patient-specific ES-like stem cells for therapeutic purposes [25, 26]. Consistent with these studies, our data showed that iPSCs can be generated from adult HFFs or other somatic cells by retroviral transduction of the same four transcription factors commonly expressed in ES cells: KIf-4, c-Myc, Oct4, Sox2, and we also established HFFs-derived iPSCs. The human iPSCs are similar to human embryonic stem cells in many aspects, including morphology, proliferation, self-renewal, differentiation and gene expression profile.
SGT-4 treatment facilitates iPSCs generation, enhancing the generation of AP+ iPSCs by 3-fold when all four factors were used for reprogramming (Fig. 4a). A recent study by Chiou et al. demonstrated that hiPSCs present low levels of cellular ROS and elevated expression of antioxidant genes such as MnSOD, Cu/ZnSOD, catalase, and GPX . Our results showed that SGT-4 markedly reduced ROS generation and increased protein levels of SOD1, catalase, GPX1, and GSH activity (Fig. 5), which is consistent with the earlier finding by Chiou. Low ROS levels are necessary for the maintenance of self-renewal in several types of stem cells, including hematopoietic stem cells . Similarly to the many kinds of herbal medicine have the antioxidant property, the most reason that SGT-4 markedly decrease the ROS production, would result from the seven primary compounds of SGT-4, such as ginsenoside Rg1, ginsenoside Rb1, atractylenolide III, liquiritigenin, liquiritin apioside, liquiritin, and glycyrrhizin. These major agents commonly have the antioxidant property. Thus, as some antioxidant material, for instance Vitamin C, promotes somatic cell programming in general [29–34]. For this reason, we could predict that SGT-4 additionally supports the hiPSCs generation via ROS reduction, which is essentially required for cellular reprogramming. However, we did not measure ROS levels or the changes in the expression of antioxidant proteins required to modulate stem cells fates still need to be defined during the time of SGT-4 treatment, and did not reported the mechanism by which SGT-4 exerts its activity. According to previous report, vitamin C remarkably accelerates the reprogramming efficiency as an antioxidant, not less than 100-fold, inhibiting p53 activity as reprogramming key mechanism . In this context, we assume that SGT-4 may also contribute to hiPSCs generation through p53 pathway inhibition. More research to explore the effect of SGT-4 on the early reprogramming process at the molecular level as well as to better understand the technical aspects of this mechanism is required. Together, our findings indicate that the SGT-4 herbal formula facilitates the reprogramming of HFFs by antioxidant mechanism into hiPSCs in the presence of four exogenous reprogramming factors.
In conclusion, our results showed that SGT-4, herbal formula facilitates the reprogramming of HFFs by antioxidant property in the presence of four exogenous reprogramming factors.
We thank K-herb Research Center, KIOM providing for SGT-4 herbal formula.
This study was supported by the grants from Korea Institute of Oriental Medicine (KIOM) (K17131, C13040).
Availability of data and materials
Data and materials sharing is available upon reasonable request from the corresponding author.
KMK performed the experiments and wrote the manuscript; DRH performed the experiment; JYL performed the revision experiments; CSS performed the SGT-4 extract and HPLC analysis; SKC participated in protocol design and discussion. All authors have reviewed and approved the final manuscript.
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