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In This Article

  • Summary
  • Abstract
  • Introduction
  • Protocol
  • Representative Results
  • Discussion
  • Acknowledgements
  • Materials
  • References
  • Reprints and Permissions

Summary

We here present a method that combines the use of chemical epigenetic erasing with mechanosensing-related cues to efficiently generate mammalian pluripotent cells, without the need of gene transfection or retroviral vectors. This strategy is, therefore, promising for translational medicine and represents a notable advancement in stem cell organoid technology.

Abstract

Cell phenotype can be reversed or modified with different methods, with advantages and limitations that are specific for each technique. Here we describe a new strategy that combines the use of chemical epigenetic erasing with mechanosensing-related cues, to generate mammalian pluripotent cells. Two main steps are required. In the first step, adult mature (terminally differentiated) cells are exposed to the epigenetic eraser 5-aza-cytidine to drive them into a pluripotent state. This part of the protocol was developed, based on the increasing understanding of the epigenetic mechanisms controlling cell fate and differentiation, and involves the use of the epigenetic modifier to erase cell differentiated state and then drive into a transient high plasticity window.

In the second step, erased cells are encapsulated in polytetrafluoroethylene (PTFE) micro-bioreactors, also known as Liquid Marbles, to promote 3D cell rearrangement to extend and stably maintain the acquired high plasticity. PTFE is a non-reactive hydrophobic synthetic compound and its use permits the creation of a cellular microenvironment, which cannot be achieved in traditional 2D culture systems. This system encourages and boosts the maintenance of pluripotency though bio-mechanosensing-related cues.

The technical procedures described here are simple strategies to allow for the induction and maintenance of a high plasticity state in adult somatic cells. The protocol allowed the derivation of high plasticity cells in all mammalian species tested. Since it does not involve the use of gene transfection and is free of viral vectors, it may represent a notable technological advance for translational medicine applications. Furthermore, the micro-bioreactor system provides a notable advancement in stem cell organoid technology by in vitro re-creating a specific micro-environment that allows for the long-term culture of high plasticity cells, namely as ESCs, iPSCs, epigenetically erased cells and MSCs.

Introduction

During the last decades, the widely accepted concept of unidirectional progression towards cell commitment and differentiation was completely revised. It has been demonstrated that cell specification can be reversed, and a terminally differentiated cell can be pushed towards a less committed and higher permissive state, using different methods.

Among the several methods proposed, one of the most promising method involves the use of chemical compounds to induce cells into a so called chemically induced pluripotency. The small molecules used in this approach are able to interact and modify the epigenetic signature of an adult mature cell, avo....

Protocol

All studies were reviewed and approved by the Ethical Committee of the University of Milan. All animal experiments were performed in accordance with the Guide for the Care and Use of Laboratory Animals, published by the US National Institutes of Health (NIH). Human cells isolation from healthy adult individuals was approved by the Ethical Committee of the Ospedale Maggiore Policlinico, Milano. All the methods in our study were carried out in accordance with the approved guidelines.

1. Skin fibro.......

Representative Results

The present protocol describes all the steps to be performed to generate and stably maintain mammalian pluripotent cells from adult somatic cells. This method has been successful with fibroblasts isolated from different mammalian species, namely mouse, porcine and human. The representative results here reported are obtained from all cell lines, irrespectively of the species of origin.

Morphological analyses show that, after 18 h incubation with the demethylating agent 5-aza-CR, fibroblasts enc.......

Discussion

During the last decades, several studies focused on the development of strategies to revert a terminally differentiated cell towards a less committed and higher permissive state. The protocol here described allow the generation and long-term maintenance of pluripotent cells starting from adult mature terminally differentiated cells. The method combines two independent steps that involve the induction of a high permissive state which is achieved through chemical epigenetic erasing and its subsequent maintenance ensured us.......

Acknowledgements

This work was funded by Carraresi Foundation and MiND FoodS Hub ID: 1176436. All the authors are members of the COST Action CA16119 In vitro 3-D total cell guidance and fitness (CellFit).

....

Materials

NameCompanyCatalog NumberComments
2-MercaptoethanolSigma-AldrichM7522Component of ESC medium
5-AzacytidineSigma-AldrichA23855-aza-CR, for fibroblast epigenetic erasing
AdenosineSigma-AldrichA4036Component of nucleoside mix for ESC medium
Antibiotic Antimycotic Solution (100×)Sigma-AldrichA5955Component of fibroblast and ESC media
CFX96 Real-Time PCRBio-Rad LaboratoriesNAThermal cycler for quantitative PCR
CytidineSigma-AldrichC4654Component of nucleoside mix for ESC medium
DMEM, high glucose, pyruvateThermo Fisher Scientific41966052For fibroblast isolation and culture medium
DMEM, low glucose, pyruvateThermo Fisher Scientific31885023For ESC medium
Dulbecco’s Phosphate Buffered SalineSigma-AldrichD5652PBS; for biopsy and cell wash and for solution preparation
Dynabeads mRNA DIRECT Micro Purification KitThermo Fisher Scientific61021mRNA estraction
ESGRO Recombinant Mouse LIF ProteinSigma-AldrichESG1106Component of ESC medium
Fetal Bovine Serum, qualified, heat inactivatedThermo Fisher Scientific10500064Component of fibroblast and ESC media
FGF-Basic (AA10-155) Recombinant Human ProteinThermo Fisher ScientificPHG0024Component of ESC medium
Gelatin from porcine skinSigma-AldrichG1890For dish coating
GeneAmp PCR System 2700Applied BiosystemsNAThermal cycler for qualitative PCR
Global DNA Methylation ELISA KitCELL BIOLABSSTA-380Methylation study
GoTaq G2 Flexi DNA PolymerasePromegaM7801Qualitative PCR
GuanosineSigma-AldrichG6264Component of nucleoside mix for ESC medium
Ham's F-10 Nutrient MixThermo Fisher Scientific31550031For ESC medium
KnockOut Serum ReplacementThermo Fisher Scientific10828028Component of ESC medium
KOVA glasstic slide 10 with gridsHycor Biomedical87144For cell counting
Leica MZ APO Stereo MicroscopeLeicaNAFor organoid observation
L-Glutamine solutionSigma-AldrichG7513Component of fibroblast and ESC media
MEM Non-Essential Amino Acids Solution (100X)Thermo Fisher Scientific11140035Component of ESC medium
Millex-GS 0.22 µm pore filtersMilliporeSLGS033SBFor solution sterilization
M-MLV Reverse Transcriptase, RNase H Minus, Point MutantPromegaM3681mRNA reverse transcription
Multiskan FC Microplate PhotometerThermo Fisher Scientific51119000For ELISA plate reading
Nikon Eclipse TE300 Inverted Phase Contrast MicroscopeNikonNAFor cell observation
Perkin Elmer Thermal Cycler 480Perkin ElmerNAThermal cycler for reverse transcription
Poly(tetrafluoroethylene) 1 μm particle sizeSigma-Aldrich430935For generating micro-bioreactor
PureLink Genomic DNA Mini KitThermo Fisher ScientificK182001Genomic DNA estraction
TaqMan Gene Expression Cells-to-CT KitThermo Fisher ScientificAM1728Quantitative PCR
ThymidineSigma-AldrichT1895Component of nucleoside mix for ESC medium
Tissue Culture Dish 100X20 mm, StandardSarstedt833902For fibroblast isolation
Tissue Culture Dish 35X10 mm, StandardSarstedt833900For Fibroblast isolation
Tissue Culture Dish 35X10 mm, SuspensionSarstedt833900500Bacteriology petri dish for liquid marble culture
Tissue Culture Plate 96 Well,Standard,FSarstedt833924005For liquid marble culture
Trypsin-EDTA solutionSigma-AldrichT3924For fibroblast dissociation
Tube 15ml, 120x17mm, PSSarstedt62553041For cell suspension centrifugation
UridineSigma-AldrichU3003Component of nucleoside mix for ESC medium

References

  1. Pennarossa, G., et al. Brief demethylation step allows the conversion of adult human skin fibroblasts into insulin-secreting cells. Proceedings of the National Academy of Sciences of the United States of America. 110 (22), 8948-8953 (2013).
  2. Pennarossa, G., et al.

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