Cryopreservation of dissociated human embryonic stem cells in the presence of ROCK inhibitor

Improving Cell Recovery: Freezing and Thawing Optimization of Induced Pluripotent Stem Cells

Achieving good cell recovery after cryopreservation is an essential process when working with induced pluripotent stem cells (iPSC). Optimized freezing and thawing methods are required for good cell attachment and survival. In this review, we concentrate on these two aspects, freezing and thawing, but also discuss further factors influencing cell recovery such as cell storage and transport. Whenever a problem occurs during the thawing process of iPSC, it is initially not clear what it is caused by, because there are many factors involved that can contribute to insufficient cell recovery. Thawing problems can usually be solved more quickly when a certain order of steps to be taken is followed. Under optimized conditions, iPSC should be ready for further experiments approximately 4-7 days after thawing and seeding. However, if the freezing and thawing protocols are not optimized, this time can increase up to 2-3 weeks, complicating any further experiments. Here, we suggest optimization steps and troubleshooting options for the freezing, thawing, and seeding of iPSC on feeder-free, Matrigel™-coated, cell culture plates whenever iPSC cannot be recovered in sufficient quality. This review applies to two-dimensional (2D) monolayer cell culture and to iPSC, passaged, frozen, and thawed as cell aggregates (clumps). Furthermore, we discuss usually less well-described factors such as the cell growth phase before freezing and the prevention of osmotic shock during thawing.

Zooming in on Cryopreservation of hiPSCs and Neural Derivatives: A Dual-Center Study Using Adherent Vitrification

Human induced pluripotent stem cells (hiPSCs) are an important tool for research and regenerative medicine, but their efficient cryopreservation remains a major challenge. The current gold standard is slow‐rate freezing of dissociated colonies in suspension, but low recovery rates limit immediate post‐thawing applicability. We tested whether ultrafast cooling by adherent vitrification improves post‐thawing survival in a selection of hiPSCs and small molecule neural precursor cells (smNPCs) from Parkinson's disease and controls. In a dual‐center study, we compared the results by immunocytochemistry (ICC), fluorescence‐activated cell sorting analysis, and RNA‐sequencing (RNA‐seq). Adherent vitrification was achieved in the so‐called TWIST substrate, a device combining cultivation, vitrification, storage, and post‐thawing cultivation. Adherent vitrification resulted in preserved confluency and significantly higher cell numbers, and viability at day 1 after thawing, while results were not significantly different at day 4 after thawing. RNA‐seq and ICC of hiPSCs revealed no change in gene expression and pluripotency markers, indicating that physical damage of slow‐rate freezing disrupts cellular membranes. Scanning electron microscopy showed preserved colony integrity by adherent vitrification. Experiments using smNPCs demonstrated that adherent vitrification is also applicable to neural derivatives of hiPSCs. Our data suggest that, compared to the state‐of‐the‐art slow‐rate freezing in suspension, adherent vitrification is an improved cryopreservation technique for hiPSCs and derivatives. stem cells translational medicine2019;8:247&259

Stem Cells of Dental Origin: Current Research Trends and Key Milestones towards Clinical Application

Dental Mesenchymal Stem Cells (MSCs), including Dental Pulp Stem Cells (DPSCs), Stem Cells from Human Exfoliated Deciduous teeth (SHED), and Stem Cells From Apical Papilla (SCAP), have been extensively studied using highly sophisticated in vitro and in vivo systems, yielding substantially improved understanding of their intriguing biological properties. Their capacity to reconstitute various dental and nondental tissues and the inherent angiogenic, neurogenic, and immunomodulatory properties of their secretome have been a subject of meticulous and costly research by various groups over the past decade. Key milestone achievements have exemplified their clinical utility in Regenerative Dentistry, as surrogate therapeutic modules for conventional biomaterial-based approaches, offering regeneration of damaged oral tissues instead of simply “filling the gaps.” Thus, the essential next step to validate these immense advances is the implementation of well-designed clinical trials paving the way for exploiting these fascinating research achievements for patient well-being: the ultimate aim of this ground breaking technology. This review paper presents a concise overview of the major biological properties of the human dental MSCs, critical for the translational pathway “from bench to clinic.”

Cryopreservation of human pluripotent stem cells in defined medium

This unit describes a cryopreservation procedure using an enzyme-free dissociation method to harvest cells and preserve cells in albumin-free chemically defined E8 medium for human pluripotent stem cells (hPSCs). The dissociation by EDTA/PBS produces small cell aggregates that allow high survival efficiency in passaging and cryopreservation. Cryopreservation in E8 medium eliminates serum and other animal products, and is suitable for dealing with the increasing demand for high-quality hPSCs in translational research. In combination with the special feature of EDTA/PBS dissociation, the protocols in this unit allow for efficient cryopreservation in a more time-saving manner.

Stem cells in neuroinjury and neurodegenerative disorders: challenges and future neurotherapeutic prospects

The prevalence of neurodegenerative diseases and neural injury disorders is increasing worldwide. Research is now focusing on improving current neurogenesis techniques including neural stem cell therapy and other biochemical drug-based approaches to ameliorate these disorders. Unfortunately, we are still facing many obstacles that are rendering current neurotherapies ineffective in clinical trials for reasons that are yet to be discovered. That is why we should start by fully understanding the complex mechanisms of neurogenesis and the factors that affect it, or else, all our suggested therapies would fail since they would not be targeting the essence of the neurological disorder but rather the symptoms. One possible paradigm shift is to switch from neuroprotectant therapies towards neurodegeneration/neurorestorative approaches. In addition, other and our laboratories are increasingly focusing on combining the use of pharmacological agents (such as Rho-associated kinase (ROCK) inhibitors or other growth factors (such as brain-derived neurotrophic factor (BDNF)) and stem cell treatment to enhance the survivability and/or differentiation capacity of transplanted stem cells in neurotrauma or other neurodegeneration animal models. Ongoing stem cell research is surely on the verge of a breakthrough of multiple effective therapeutic options for neurodegenerative disorders. Once, we fully comprehend the process of neurogenesis and its components, we will fully be capable of manipulating and utilizing it. In this work, we discuss the current knowledge of neuroregenerative therapies and their associated challenges.

Technological progress and challenges towards cGMP manufacturing of human pluripotent stem cells based therapeutic products for allogeneic and autologous cell therapies

Recent technological advances in the generation, characterization, and bioprocessing of human pluripotent stem cells (hPSCs) have created new hope for their use as a source for production of cell-based therapeutic products. To date, a few clinical trials that have used therapeutic cells derived from hESCs have been approved by the Food and Drug Administration (FDA), but numerous new hPSC-based cell therapy products are under various stages of development in cell therapy-specialized companies and their future market is estimated to be very promising. However, the multitude of critical challenges regarding different aspects of hPSC-based therapeutic product manufacturing and their therapies have made progress for the introduction of new products and clinical applications very slow. These challenges include scientific, technological, clinical, policy, and financial aspects. The technological aspects of manufacturing hPSC-based therapeutic products for allogeneic and autologous cell therapies according to good manufacturing practice (cGMP) quality requirements is one of the most important challenging and emerging topics in the development of new hPSCs for clinical use. In this review, we describe main critical challenges and highlight a series of technological advances in all aspects of hPSC-based therapeutic product manufacturing including clinical grade cell line development, large-scale banking, upstream processing, downstream processing, and quality assessment of final cell therapeutic products that have brought hPSCs closer to clinical application and commercial cGMP manufacturing.

DMSO-Free Programmed Cryopreservation of Fully Dissociated and Adherent Human Induced Pluripotent Stem Cells

Three modes for cryopreservation (CP) of human iPSC cells have been compared: STD: standard CP of small clumps with 10% of CPA in cryovials, ACC: dissociation of the cells with Accutase and freezing in cryovials, and PLT: programmed freezing of adherent cells in plastic multiwell dishes in a programmable freezer using one- and multistep cooling protocols. Four CPAs were tesetd: dimethyl sulfoxide (DMSO), ethylene glycol (EG), propylene glycol (PG), and glycerol (GLY). The cells in ACC and PLT were frozen and recovered after thawing in the presence of a ROCK inhibitor Y-27632 (RI). EG was less toxic w/o CP cryopreservation than DMSO and allowed much better maintenance of pluripotency after CP than PG or GLY. The cells were cryopreserved very efficiently as adherent cultures (+RI) in plates (5-6-fold higher than STD) using EG and a 6-step freezing protocol. Recovery under these conditions is comparable or even higher than ACC+RI. Conclusions. Maintenance of cell-substratum adherence is a favorable environment that mitigates freezing and thawing stresses (ComfortFreeze^® concept developed by CELLTRONIX). CP of cells directly in plates in ready-to-go after thawing format for HT/HC screening can be beneficial in many SC-related scientific and commercial applications such as drug discovery and toxicity tests.

Cryopreservation of Human Stem Cells for Clinical Application: A Review

SUMMARY: Stem cells have been used in a clinical setting for many years. Haematopoietic stem cells have been used for the treatment of both haematological and non-haematological disease; while more recently mesenchymal stem cells derived from bone marrow have been the subject of both laboratory and early clinical studies. Whilst these cells show both multipotency and expansion potential, they nonetheless do not form stable cell lines in culture which is likely to limit the breadth of their application in the field of regenerative medicine. Human embryonic stem cells are pluripotent cells, capable of forming stable cell lines which retain the capacity to differentiate into cells from all three germ layers. This makes them of special significance in both regenerative medicine and toxicology. Induced pluripotent stem (iPS) cells may also provide a similar breadth of utility without some of the confounding ethical issues surrounding embryonic stem cells. An essential pre-requisite to the commercial and clinical application of stem cells are suitable cryopreservation protocols for long-term storage. Whilst effective methods for cryopreservation and storage have been developed for haematopoietic and mesenchymal stem cells, embryonic cells and iPS cells have proved more refractory. This paper reviews the current state of cryopreservation as it pertains to stem cells and in particular the embryonic and iPS cell.

Human endometrial cells express elevated levels of pluripotent factors and are more amenable to reprogramming into induced pluripotent stem cells

The human endometrium is a tissue with remarkable plasticity and regenerative capacity. Additionally, endometrial cells can be retrieved using minimally invasive procedures, which makes them an ideal source for reprogramming into a pluripotent state. Endometrial cells were obtained from donors in their fifth decade and reprogrammed into induced pluripotent stem (iPS) cells using retroviral transduction with SOX2, OCT4, KLF4, and MYC. The human endometrial cells displayed accelerated expression of endogenous NANOG and OCT4 during reprogramming compared with neonatal skin fibroblasts. As a result, iPS cell colonies that could be subcultured and propagated were established as early as 12 d after transduction rather than the usually reported 3-4 wk for other cell types. After 3 wk of reprogramming, the human endometrial cells also yielded significantly higher numbers of iPS colonies in comparison with the neonatal skin fibroblasts. Although the efficiency of iPS colony formation varied depending on the donor, the basal level of endogenous expression of the defined factors was positively correlated with reprogramming efficiency. The reprogramming resulted in an average colony-forming efficiency of 0.49 ± 0.10%, with a range from 0.31-0.66%, compared with the neonatal skin fibroblasts, resulting in an average efficiency of 0.03 ± 0.00% per transduction, with a range from 0.02-0.03%. Our studies show that the human endometrium expresses elevated levels of pluripotent factors, which with additional defined factors, results in significantly more efficient and accelerated generation of induced pluripotent stem cells compared with conventional somatic cells.

Improved viability of freeze-thawed embryonic stem cells after exposure to glutathione

Adding a potent antioxidant, glutathione (GSH), to a cryoprotective solution consisting of dimethyl sulfoxide and ethylene glycol and/or postthaw culture medium significantly improved the postthaw viability of mouse embryonic stem cells. This effect, which was caused by a decrease in reactive oxygen species, was only induced by exposure of embryonic stem cells during cryopreservation.