JNK/SAPK Signaling Is Essential for Efficient Reprogramming of Human Fibroblasts to Induced Pluripotent Stem Cells

Distinct molecular features of FLNC mutations, associated with different clinical phenotypes

Filamin С is a key an actin-binding protein of muscle cells playing a critical role in maintaining structural integrity and sarcomere organization. FLNC mutations contribute to various types of cardiomyopathies and myopathies through potentially different molecular mechanisms. Here, we described the impact of two clinically distinct FLNC variants (R1267Q associated with arrhythmogenic cardiomyopathy and V2264M associated with restrictive cardiomyopathy) on calcium homeostasis, electrophysiology, and gene expression profile of iPSC-derived patient-specific cardiomyocytes. We demonstrated that R1267Q FLNC variant leads to greater disturbances in calcium dynamics, Nav1.5 kinetics and action potentials compared to V2264M variant. These functional characteristics were accompanied by transcriptome changes in genes linked to action potential and sodium transport as well as structural cardiomyocyte genes. We suggest distinct molecular effects of two FLNC variants linked to different types of cardiomyopathies in terms of myofilament structure, electrophysiology, ion channel function and intracellular calcium homeostasis providing the molecular the bases for their different clinical phenotypes.

Metabolic control of induced pluripotency

Pluripotent stem cells of the mammalian epiblast and their cultured counterparts-embryonic stem cells (ESCs) and epiblast stem cells (EpiSCs)-have the capacity to differentiate in all cell types of adult organisms. An artificial process of reactivation of the pluripotency program in terminally differentiated cells was established in 2006, which allowed for the generation of induced pluripotent stem cells (iPSCs). This iPSC technology has become an invaluable tool in investigating the molecular mechanisms of human diseases and therapeutic drug development, and it also holds tremendous promise for iPSC applications in regenerative medicine. Since the process of induced reprogramming of differentiated cells to a pluripotent state was discovered, many questions about the molecular mechanisms involved in this process have been clarified. Studies conducted over the past 2 decades have established that metabolic pathways and retrograde mitochondrial signals are involved in the regulation of various aspects of stem cell biology, including differentiation, pluripotency acquisition, and maintenance. During the reprogramming process, cells undergo major transformations, progressing through three distinct stages that are regulated by different signaling pathways, transcription factor networks, and inputs from metabolic pathways. Among the main metabolic features of this process, representing a switch from the dominance of oxidative phosphorylation to aerobic glycolysis and anabolic processes, are many critical stage-specific metabolic signals that control the path of differentiated cells toward a pluripotent state. In this review, we discuss the achievements in the current understanding of the molecular mechanisms of processes controlled by metabolic pathways, and vice versa, during the reprogramming process.

Inactivation of Tumor Suppressor CYLD Inhibits Fibroblast Reprogramming to Pluripotency

CYLD is a tumor suppressor gene coding for a deubiquitinating enzyme that has a critical regulatory function in a variety of signaling pathways and biological processes involved in cancer development and progression, many of which are also key modulators of somatic cell reprogramming. Nevertheless, the potential role of CYLD in this process has not been studied. With the dual aim of investigating the involvement of CYLD in reprogramming and developing a better understanding of the intricate regulatory system governing this process, we reprogrammed control (CYLDWT/WT) and CYLD DUB-deficient (CYLDΔ9/Δ9) mouse embryonic fibroblasts (MEFs) into induced pluripotent stem cells (iPSCs) through ectopic overexpression of the Yamanaka factors (Oct3/4, Sox2, Klf4, c-myc). CYLD DUB deficiency led to significantly reduced reprogramming efficiency and slower early reprogramming kinetics. The introduction of WT CYLD to CYLDΔ9/Δ9 MEFs rescued the phenotype. Nevertheless, CYLD DUB-deficient cells were capable of establishing induced pluripotent colonies with full spontaneous differentiation potential of the three germ layers. Whole proteome analysis (Data are available via ProteomeXchange with identifier PXD044220) revealed that the mesenchymal-to-epithelial transition (MET) during the early reprogramming stages was disrupted in CYLDΔ9/Δ9 MEFs. Interestingly, differentially enriched pathways revealed that the primary processes affected by CYLD DUB deficiency were associated with the organization of the extracellular matrix and several metabolic pathways. Our findings not only establish for the first time CYLD's significance as a regulatory component of early reprogramming but also highlight its role as an extracellular matrix regulator, which has profound implications in cancer research.

Chemical reprogramming for cell fate manipulation: Methods, applications, and perspectives

Chemical reprogramming offers an unprecedented opportunity to control somatic cell fate and generate desired cell types including pluripotent stem cells for applications in biomedicine in a precise, flexible, and controllable manner. Recent success in the chemical reprogramming of human somatic cells by activating a regeneration-like program provides an alternative way of producing stem cells for clinical translation. Likewise, chemical manipulation enables the capture of multiple (stem) cell states, ranging from totipotency to the stabilization of somatic fates in vitro. Here, we review progress in using chemical approaches for cell fate manipulation in addition to future opportunities in this promising field.

Essential Role of Adhesion GPCR, GPR123, for Human Pluripotent Stem Cells and Reprogramming towards Pluripotency

G-protein-coupled receptors (GPCRs) are the largest family of cell surface receptors. They modulate key physiological functions and are required in diverse developmental processes including embryogenesis, but their role in pluripotency maintenance and acquisition during the reprogramming towards hiPSCs draws little attention. Meanwhile, it is known that more than 106 GPCRs are overexpressed in human pluripotent stem cells (hPSCs). Previously, to identify novel effectors of reprogramming, we performed a high-throughput RNA interference (RNAi) screening assay and identified adhesion GPCR, GPR123, as a potential reprogramming effector. Its role has not been explored before. Herein, by employing GPR123 RNAi we addressed the role of GPR123 for hPSCs. The suppression of GPR123 in hPSCs leads to the loss of pluripotency and differentiation, impacted colony morphology, accumulation of cells at the G2 phase of the cell cycle, and absence of the scratch closure. Application of the GPR123 RNAi at the initiation stage of reprogramming leads to a decrease in the percentage of the "true" hiPSC colonies, a drop in E-cadherin expression, a decrease in the percentage of NANOG+ nuclei, and the absence of actin cytoskeleton remodeling. Together this leads to the absence of the alkaline-phosphatase-positive hiPSCs colonies on the 18th day of the reprogramming process. Overall, these data indicate for the first time the essential role of GPR123 in the maintenance and acquisition of pluripotency.

LMNA mutation leads to cardiac sodium channel dysfunction in the Emery-Dreifuss muscular dystrophy patient

Pathogenic variants in the LMNA gene are known to cause laminopathies, a broad range of disorders with different clinical phenotypes. LMNA genetic variants lead to tissue-specific pathologies affecting various tissues and organs. Common manifestations of laminopathies include cardiovascular system abnormalities, in particular, cardiomyopathies and conduction disorders. In the present study, we used induced pluripotent stem cells from a patient carrying LMNA p.R249Q genetic variant to create an in vitro cardiac model of laminopathy. Induced pluripotent stem cell-derived cardiomyocytes with LMNA p.R249Q genetic variant showed a decreased sodium current density and an impaired sodium current kinetics alongside with changes in transcription levels of cardiac-specific genes. Thus, we obtained compelling in vitro evidence of an association between LMNA p.R249Q genetic variant and cardiac-related abnormalities.

Plant callus-derived shikimic acid regenerates human skin through converting human dermal fibroblasts into multipotent skin-derived precursor cells

Background

The human skin-derived precursors (SKPs) are a good cell source for regeneration. However, the isolation of SKP from human skin is limited. To overcome this drawback, we hypothesized that the component of plant stem cells could convert human fibroblasts to SKPs.

Methods

Human dermal fibroblasts were treated with shikimic acid, a major component of Sequoiadendron giganteum callus extract. The characteristics of these reprogrammed cells were analyzed by qPCR, western blot, colony-forming assay, and immunofluorescence staining. Artificial human skin was used for CO₂ laser-induced wound experiments. Human tissues were analyzed by immunohistochemistry.

Results

The reprogrammed cells expressed nestin (a neural precursor-specific protein), fibronectin, and vimentin and could differentiate into the ectodermal and mesodermal lineage. Nestin expression was induced by shikimic acid through the mannose receptor and subsequent MYD88 activation, leading to P38 phosphorylation and then CREB binding to the nestin gene promoter. Finally, we confirmed that shikimic acid facilitated the healing of cut injury and enhanced dermal reconstruction in a human artificial skin model. Moreover, in a clinical study with healthy volunteers, plant callus extracts increased the expression of stem cell markers in the basal layer of the epidermis and collagen deposit in the dermis.

Conclusions

These results indicate that shikimic acid is an effective agent for tissue regeneration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02409-3.

Unlocking the Recovery Potential: JMJD3 Inhibition-Mediated SAPK/JNK Signaling Inactivation Supports Endogenous Oligodendrocyte-Lineage Commitment Post Mammalian Spinal Cord Injury

Spinal cord injury (SCI) induced catastrophic neurological disability is often incurable at present. The injury triggered immediately oligodendrocytes loss and overwhelming demyelination are regarded as an insurmountable barrier to SCI recovery. To date, effective strategy to promote the endogenous oligodendrocytes replacement post SCI remains elusive. Epigenetic modifications are emerging as critical molecular switches of gene expression in CNS. However, the epigenetic mechanisms underlying oligodendrogenesis post SCI yet to be discovered. In this study, we report that H3K27me3 demethylase JMJD3 exists as a pivotal epigenetic regulator which manipulates the endogenous oligodendrogenesis post SCI. We found that JMJD3 inhibition promotes the oligodendrocyte linage commitment of neural stem/progenitor cells (NPCs) in vitro and in vivo. Moreover, we demonstrated that JMJD3 inhibition mediated SAPK/JNK signaling inactivation is functionally necessary for endogenous oligodendrocyte-lineage commitment post SCI. Our results also suggested that JMJD3 is downstream of SAPK/JNK pathway, and capable of translates SCI induced SAPK/JNK signaling into epigenetic codes readable by spinal cord endogenous NPCs. Taken together, our findings provide novel evidence of JMJD3 mediated oligodendrocyte-lineage commitment orchestration post SCI, which would be a potential epigenetic approach to induce the mature mammalian endogenous recovery.

Effect of low oxygen tension on transcriptional factor OCT4 and SOX2 expression in New Zealand rabbit bone marrow-derived mesenchymal stem cells

Background and Aim:

Octamer-binding transcription factor 4 (OCT4) and sex-determining region Y-box 2 (SOX2) are transcription factors whose functions are essential to maintain the pluripotency of embryonic stem cells. The purpose of this study was to derive stem cells for in vitro culture and to maintain their viability and pluripotency, with the goal to obtain a cell line for transplantation in patients with degenerative diseases or injuries. This research focused on examining the effect of low oxygen tension on the ability of bone marrow-derived mesenchymal stem cells (BM-MSCs) to express OCT4 and SOX2 in vitro.

Materials and Methods:

BM-MSCs were obtained from femurs of 2000 to 3000 g New Zealand male rabbits. BM-MSCs were divided into three groups to test different culture conditions: A control group under hyperoxia condition (21% O₂) and two treatment groups with low oxygen tension (1% and 3% O₂). We characterized the BM-MSCs using flow cytometric measurement of cluster differentiation 44 (CD44) and cluster differentiation 90 (CD90) expression. The expression of OCT4 and SOX2 was measured by immunofluorescence staining after 48 h of incubation in chambers with normal or low oxygen tension with controlled internal atmosphere consisting of 95% N₂, 5% CO₂, and 1% O₂ (T1) and 3% O₂ (T2). We considered OCT4 and SOX2 as two markers of pluripotency induction. All immunofluorescence data were subjected to a post hoc normality Tukey’s honestly significant difference test; all differences with p<5% were considered significant.

Results:

BM-MSCs were positive for CD44 and CD90 expression after isolation. Oxygen tension culture conditions of 1% and 3% O₂ led to OCT4 and SOX2 expression on culture days 2 and 4 (p<0.05), respectively, as compared to the hyperoxia condition (21% O₂).

Conclusion:

Based on the OCT4 and SOX2 immunofluorescence data, we conclude that the stem cells were pluripotent at low O₂ tension (at 1% O₂ on day 2 and at 3% O₂ on day 4), whereas under 21% O₂ the OCT4 and SOX2 were not expressed.

An Insight into Reprogramming Barriers to iPSC Generation

Derivation of induced Pluripotent Stem Cells (iPSCs) by reprogramming somatic cells to a pluripotent state has revolutionized stem cell research. Ensuing this, various groups have used genetic and non-genetic approaches to generate iPSCs from numerous cell types. However, achieving a pluripotent state in most of the reprogramming studies is marred by serious limitations such as low reprogramming efficiency and slow kinetics. These limitations are mainly due to the presence of potent barriers that exist during reprogramming when a mature cell is coaxed to achieve a pluripotent state. Several studies have revealed that intrinsic factors such as non-optimal stoichiometry of reprogramming factors, specific signaling pathways, cellular senescence, pluripotency-inhibiting transcription factors and microRNAs act as a roadblock. In addition, the epigenetic state of somatic cells and specific epigenetic modifications that occur during reprogramming also remarkably impede the generation of iPSCs. In this review, we present a comprehensive overview of the barriers that inhibit reprogramming and the understanding of which will pave the way to develop safe strategies for efficient reprogramming.

JNK Signaling in Stem Cell Self-Renewal and Differentiation

C-JUN N-terminal kinases (JNKs), which belong to the mitogen-activated protein kinase (MAPK) family, are evolutionarily conserved kinases that mediate cell responses to various types of extracellular stress insults. They regulate physiological processes such as embryonic development and tissue regeneration, playing roles in cell proliferation and programmed cell death. JNK signaling is also involved in tumorigenesis and progression of several types of malignancies. Recent studies have shown that JNK signaling has crucial roles in regulating the traits of cancer stem cells (CSCs). Here we describe the functions of the JNK signaling pathway in self-renewal and differentiation, which are essential features of various types of stem cells, such as embryonic, induced pluripotent, and adult tissue-specific stem cells. We also review current knowledge of JNK signaling in CSCs and discuss its role in maintaining the CSC phenotype. A better understanding of JNK signaling as an essential regulator of stemness may provide a basis for the development of regenerative medicine and new therapeutic strategies against malignant tumors.

MOP-dependent enhancement of methadone on the effectiveness of ALA-PDT for A172 cells by upregulating phosphorylated JNK and BCL2

BACKGROUND

Methadone, as a long-acting opioid analgesic, shows an ability to sensitize the treatment of ALA-PDT for glioblastoma cells (A172) in vitro by promoting apoptosis. However, the mechanisms how methadone enhances the effectiveness of ALA-PDT for tumor cells remains to be clarified.

METHODS

The expression of mu opioid receptor (MOP), apoptosis, phosphorylated c-Jun N-terminal kinase (JNK) and phosphorylated apoptosis regulator B cell lymphoma 2 (BCL2) were measured by flow cytometry. Cytotoxicity was determined using Cell Counting Kit-8 (CCK-8). A MOP antagonist, naloxone, was used to evaluate the role of MOP in the above process.

RESULTS

It was found that A172 cells show the expression of MOP and that naloxone inhibits the enhancement of the methadone effect on apoptosis following ALA-PDT (p < 0.05). Phosphorylated JNK and BCL2 induced by ALA-PDT were promoted in the presence of methadone (p < 0.05). These methadone effects were also inhibited by naloxone (p < 0.05).

CONCLUSIONS

The results suggest that apoptosis induced by ALA-PDT is enhanced by methadone, mostly MOP-mediated, through the upregulation of accumulation of phosphorylated JNK and BCL2, leading to a promotion of cytotoxicity of ALA-PDT for A172 cells.

Yorkie and JNK revert syncytial muscles into myoblasts during Org-1-dependent lineage reprogramming

The formation and differentiation of syncytial muscles is typically considered an irreversible developmental process. Schaub et al. describe molecular events that dedifferentiate syncytial muscle into mononucleate myoblasts during a naturally occurring lineage reprogramming process.

Lineage reprogramming has received increased research attention since it was demonstrated that lineage-restricted transcription factors can be used in vitro for direct reprogramming. Recently, we reported that the ventral longitudinal musculature of the adult Drosophila heart arises in vivo by direct lineage reprogramming from larval alary muscles, a process that starts with the dedifferentiation and fragmentation of syncytial muscle cells into mononucleate myoblasts and depends on Org-1 (Drosophila Tbx1). Here, we shed light on the events occurring downstream of Org-1 in this first step of transdifferentiation and show that alary muscle lineage-specific activation of Yorkie plays a key role in initiating the dedifferentiation and fragmentation of these muscles. An additional necessary input comes from active dJNK signaling, which contributes to the activation of Yorkie and furthermore activates dJun. The synergistic activities of the Yorkie/Scalloped and dJun/dFos transcriptional activators subsequently initiate alary muscle fragmentation as well as up-regulation of Myc and piwi, both crucial for lineage reprogramming.

Expression of serine/threonine protein kinase SGK1F promotes an hepatoblast state in stem cells directed to differentiate into hepatocytes

The rat pancreatic AR42J-B13 (B-13) cell line differentiates into non-replicative hepatocyte-like (B-13/H) cells in response to glucocorticoid. Since this response is dependent on an induction of serine/threonine protein kinase 1 (SGK1), this may suggest that a general pivotal role for SGK1 in hepatocyte maturation. To test this hypothesis, the effects of expressing adenoviral-encoded flag tagged human SGK1F (AdV-SGK1F) was examined at 3 stages of human induced pluripotent stem cell (iPSC) differentiation to hepatocytes. B-13 cells infected with AdV-SGK1F in the absence of glucocorticoid resulted in expression of flag tagged SGK1F protein; increases in β-catenin phosphorylation; decreases in Tcf/Lef transcriptional activity; expression of hepatocyte marker genes and conversion of B-13 cells to a cell phenotype near-similar to B-13/H cells. Given this demonstration of functionality, iPSCs directed to differentiate towards hepatocyte-like cells using a standard protocol of chemical inhibitors and mixtures of growth factors were additionally infected with AdV-SGK1F, either at an early time point during differentiation to endoderm; during endoderm differentiation to anterior definitive endoderm and hepatoblasts and once converted to hepatocyte-like cells. SGK1F expression had no effect on differentiation to endoderm, likely due to low levels of expression. However, expression of SGK1F in both iPSCs-derived endoderm and hepatocyte-like cells both resulted in promotion of cells to an hepatoblast phenotype. These data demonstrate that SGK1 expression promotes an hepatoblast phenotype rather than maturation of human iPSC towards a mature hepatocyte phenotype and suggest a transient role for Sgk1 in promoting an hepatoblast state in B-13 trans-differentiation to B-13/H cells.

Endothelial Differentiation G Protein-Coupled Receptor 5 Plays an Important Role in Induction and Maintenance of Pluripotency

Direct reprogramming of human somatic cells toward induced pluripotent stem cells holds great promise for regenerative medicine and basic biology. We used a high-throughput small interfering RNA screening assay in the initiation phase of reprogramming for 784 genes belonging to kinase and phosphatase families and identified 68 repressors and 22 effectors. Six new candidates belonging to the family of the G protein-coupled receptors (GPCRs) were identified, suggesting an important role for this key signaling pathway during somatic cell-induced reprogramming. Downregulation of one of the key GPCR effectors, endothelial differentiation GPCR5 (EDG5), impacted the maintenance of pluripotency, actin cytoskeleton organization, colony integrity, and focal adhesions in human embryonic stem cells, which were associated with the alteration in the RhoA-ROCK-Cofilin-PAXILLIN-actin signaling pathway. Similarly, downregulation of EDG5 during the initiation stage of somatic cell-induced reprogramming resulted in alteration of cytoskeleton, loss of human-induced pluripotent stem cell colony integrity, and a significant reduction in partially and fully reprogrammed cells as well as the number of alkaline phosphatase positive colonies at the end of the reprogramming process. Together, these data point to an important role of EDG5 in the maintenance and acquisition of pluripotency. Stem Cells 2019;37:318-331.

bFGF-mediated pluripotency maintenance in human induced pluripotent stem cells is associated with NRAS-MAPK signaling

BACKGROUND

Human pluripotent stem cells (PSCs) open new windows for basic research and regenerative medicine due to their remarkable properties, i.e. their ability to self-renew indefinitely and being pluripotent. There are different, conflicting data related to the role of basic fibroblast growth factor (bFGF) in intracellular signal transduction and the regulation of pluripotency of PSCs. Here, we investigated the effect of bFGF and its downstream pathways in pluripotent vs. differentiated human induced (hi) PSCs.

METHODS

bFGF downstream signaling pathways were investigated in long-term culture of hiPSCs from pluripotent to differentiated state (withdrawing bFGF) using immunoblotting, immunocytochemistry and qPCR. Subcellular distribution of signaling components were investigated by simple fractionation and immunoblotting upon bFGF stimulation. Finally, RAS activity and RAS isoforms were studied using RAS assays both after short- and long-term culture in response to bFGF stimulation.

RESULTS

Our results revealed that hiPSCs were differentiated into the ectoderm lineage upon withdrawing bFGF as an essential pluripotency mediator. Pluripotency markers OCT4, SOX2 and NANOG were downregulated, following a drastic decrease in MAPK pathway activity levels. Notably, a remarkable increase in phosphorylation levels of p38 and JAK/STAT3 was observed in differentiated hiPSCs, while the PI3K/AKT and JNK pathways remained active during differentiation. Our data further indicate that among the RAS paralogs, NRAS predominantly activates the MAPK pathway in hiPSCs.

CONCLUSION

Collectively, the MAPK pathway appears to be the prime signaling pathway downstream of bFGF for maintaining pluripotency in hiPSCs and among the MAPK pathways, the activity of NRAS-RAF-MEK-ERK is decreased during differentiation, whereas p38 is activated and JNK remains constant.

Role of Jnk1 in development of neural precursors revealed by iPSC modeling

Jnk1-deficient mice manifest disrupted anterior commissure formation and loss of axonal and dendritic microtubule integrity. However, the mechanisms and the specific stages underlying the developmental defects remain to be elucidated. Here, we report the generation of Jnk1-deficient (Jnk1 KO) iPSCs from Jnk1 KO mouse tail-tip fibroblasts (TTFs) for modeling the neural disease development. The efficiency in the early induction of iPSCs was higher from Jnk1 KO fibroblasts than that of wild-type (WT) fibroblasts. These Jnk1 KO iPSCs exhibited pluripotent stem cell properties and had the ability of differentiation into general three embryonic germ layers in vitro and in vivo. However, Jnk1 KO iPSCs showed reduced capacity in neural differentiation in the spontaneous differentiation by embryoid body (EB) formation. Notably, by directed lineage differentiation, Jnk1 KO iPSCs specifically exhibited an impaired ability to differentiate into early stage neural precursors. Furthermore, the neuroepitheliums generated from Jnk1 KO iPSCs appeared smaller, indicative of neural stem cell developmental defects, as demonstrated by teratoma tests in vivo. These data suggest that Jnk1 deficiency inhibits the development of neural stem cells/precursors and provide insights to further understanding the complex pathogenic mechanisms of JNK1-related neural diseases.

A critical role for p38MAPK signalling pathway during reprogramming of human fibroblasts to iPSCs

Reprogramming of somatic cells to induced pluripotent stem cells (iPSCs) holds enormous promise for regenerative medicine. Reprogramming is a stepwise process with well-defined stages of initiation, maturation and stabilisation which are critically dependent on interactions between key pluripotency transcription factors, epigenetic regulators and signalling pathways. In this manuscript we have investigated the role of p38 MAPK signalling pathway and have shown a subpopulation- and phase-specific pattern of activation occurring during the initiation and maturation stage of reprogramming in partially and fully reprogrammed cells respectively. Downregulation of p38 MAPK activity via RNA interference or small molecule inhibitor led to cell accumulation in G1 phase of the cell cycle and reduced expression of cell cycle regulators during the initiation stage of reprogramming. This was associated with a significant downregulation of key pluripotency marker expression, disruption of mesenchymal to epithelial transition (MET), increased expression of differentiation markers and presence of partially reprogrammed cells which retained a typical gene expression profile of mesendodermal cells and were unable to progress to fully reprogrammed phenotype. Together our data indicate an important role for p38 MAPK activity in proliferation, MET progression and establishment of pluripotent phenotype, which are necessary steps for the development of human iPSCs.

The Stagnant Adaptation of Defined and Xeno-Free Culture of iPSCs in Academia

Pluripotent Stem Cells were originally derived and cultured using a feeder layer of cells. Movements have been undertaken to transition from this method to one more defined, high-throughput, and without xenogenic factors. Tremendous research has been done in this area and many products have been developed, however, based on our analysis of recent publications in stem cell related journals many in academia are still using older methods like a feeder layer. In this short communication, we discuss the feasibility of transitioning to defined, xeno-free methods, how a standardized method could improve the field and industry, and that a study bringing together multiple institutions comparing culture methods could be done to evaluate the efficacy of these new methods.