Activin A in iPSC differentiation protocols
Activin A is the single most important growth factor in iPSC differentiation toward endoderm-derived lineages, and one of the most widely used in cardiac mesoderm protocols as well. It sits at the centre of the TGF-β signalling axis that governs the earliest cell-fate decisions in human pluripotent stem cells, and it is the workhorse reagent of essentially every published protocol that aims to generate liver, pancreas, intestine, lung or thyroid cell types from iPSCs. It is also one of the most expensive reagents in those protocols, frequently dominating the cost of goods of a full differentiation run.
Despite this central role, Activin A is often used without a clear understanding of how concentration, timing and signalling context shape the outcome. The same molecule can maintain pluripotency, drive cells into mesoderm, specify definitive endoderm or push downstream toward foregut and pancreatic fates, depending entirely on dose, duration, co-factors and the state of the starting cell population. Lot-to-lot variability in commercial Activin A preparations is a documented source of failed differentiations, and the conventional soluble protein has a short functional half-life that contributes to the high concentrations typically required.
This article reviews the role of Activin A in iPSC differentiation: its signalling mechanism, the dose-dependent lineage outcomes that have been established across multiple laboratories, the concentrations and timings used in the most influential published protocols, and the practical issues of lot variability, cost and reproducibility. It also covers sustained-release Activin A as an emerging alternative to the conventional soluble format. The intended audience is researchers running or troubleshooting iPSC differentiation protocols where Activin A is a primary or secondary signalling input.
| Key Point |
| Activin A is dose-dependent and context-dependent. Low concentrations support pluripotency through SMAD2/3-NANOG signalling; intermediate concentrations drive mesoderm; concentrations of 30 to 100 ng/ml combined with Wnt activation specify definitive endoderm. Optimal concentration is iPSC line-dependent, requires empirical optimisation, and lot-to-lot variability in conventional soluble Activin A is a documented cause of protocol failure. |
Activin A Signalling: The Molecular Basis
Activin A is a homodimer of two activin βA chains and a member of the TGF-β superfamily. It signals through a heterodimeric receptor complex composed of type I (ALK4, also known as ACVR1B) and type II (ACVR2A or ACVR2B) serine/threonine kinase receptors. Ligand binding triggers phosphorylation of receptor-regulated SMAD proteins SMAD2 and SMAD3, which then complex with SMAD4 and translocate to the nucleus to regulate transcription of target genes. The pathway is closely related to that of Nodal, which signals through the same receptors and produces overlapping but not identical transcriptional outputs in vivo. In iPSC culture, recombinant Activin A is typically used as a more stable and economical surrogate for Nodal signalling [5].
The remarkable feature of Activin/Nodal signalling in human pluripotent stem cells is that it produces fundamentally different cellular outcomes depending on context. The same SMAD2/3 effector machinery that maintains pluripotency in self-renewing iPSCs also drives those cells into mesendoderm and definitive endoderm when other inputs are altered. This duality is now well understood at the molecular level: SMAD2/3 partners with NANOG to support the pluripotency network in self-renewing cells, and partners with EOMES and other developmental transcription factors during differentiation to activate lineage-specific programmes [6, 7]. Cross-talk with PI3K/AKT signalling appears to act as the master switch: when PI3K/AKT activity is high, Activin/SMAD2/3 signalling supports self-renewal through NANOG; when PI3K/AKT activity drops, the same SMAD2/3 input cooperates with Wnt to drive differentiation [8].
This context-dependence has direct practical consequences. Inhibition of PI3K signalling alongside Activin A treatment substantially improves definitive endoderm induction efficiency, because it removes the brake that would otherwise allow Activin A to support residual pluripotency rather than drive lineage commitment [9]. The presence of insulin and IGFs in serum or knockout serum replacement (KSR) is one of the main sources of unwanted PI3K activation during DE protocols, which is why most published DE protocols deliberately use low-serum or serum-free conditions during the Activin A induction window.
Activin A in Pluripotency Maintenance
Although this article focuses on differentiation, the role of Activin A in maintaining the iPSC starting population is worth noting because it directly affects differentiation efficiency. Most defined iPSC culture media (mTeSR1, Essential 8, StemPro and similar formulations) contain Activin A or rely on endogenous Nodal production for SMAD2/3 activation. Activin/Nodal signalling directly maintains NANOG expression by SMAD2/3 binding to the NANOG promoter, and inhibition of Activin/Nodal signalling causes loss of NANOG and progression toward neuroectoderm differentiation [6, 10].
The practical implication is that the state of Activin/Nodal signalling in the iPSC population at the start of a differentiation protocol affects how cleanly the cells will respond to the differentiation stimulus. iPSCs that have been allowed to drift toward spontaneous differentiation, or that have experienced disruption of their pluripotency culture, will respond less consistently to Activin A-based DE protocols. This is one reason why high-quality iPSC maintenance with stable NANOG expression is a prerequisite for reproducible differentiation, and why measuring pluripotency markers immediately before initiating differentiation is good practice.
Dose-Dependent Lineage Choice
The single most important parameter governing the outcome of Activin A treatment in iPSC differentiation is dose. The dose-response is non-monotonic and depends on the presence of co-signals (particularly Wnt activators and BMP), but a consistent picture emerges across multiple studies.
At very low concentrations (around 5 ng/ml or below), Activin A has no measurable effect on definitive endoderm marker expression and cells continue to express pluripotency markers [11]. This is below the threshold for productive lineage induction.
At low to intermediate concentrations (below approximately 30 ng/ml), Activin A supports pluripotency in undifferentiated cultures but, when combined with appropriate co-signals, can also bias cells toward mesoderm rather than endoderm. Concentrations below 30 ng/ml have been shown to favour mesoderm specification over endoderm in iPSC cultures [12].
At intermediate to high concentrations (30 to 100 ng/ml), combined with Wnt activation through CHIR99021 or WNT3A, Activin A drives definitive endoderm specification. Within this range, the optimal concentration is line-dependent. The original D'Amour protocol used 100 ng/ml Activin A with low serum and reported up to 80% DE induction efficiency [1]. However, subsequent optimisation studies have shown that lower concentrations can be equally effective for specific iPSC lines: 30 ng/ml was identified as optimal for the R1-hiPSC1 line in a systematic dose-response study [12], and a 50% reduction from 100 ng/ml to 50 ng/ml gave equivalent definitive endoderm and downstream beta cell marker expression in stem cell-derived islet-like cell protocols [13].
For cardiac mesoderm specification, the optimal Activin A concentration is much lower than for endoderm and the dose is critical. Stage-specific optimisation studies in human pluripotent stem cells found that small changes in Activin A concentration dramatically alter the proportion of KDR+/PDGFRα+ cardiac mesoderm that develops, with optimised conditions in the range of 6 ng/ml Activin A combined with 10 ng/ml BMP4 producing more than 50% KDR+/PDGFRα+ cells in human PSCs [3]. Dose optimisation between Activin A and BMP4 was shown to be necessary on a line-by-line basis for efficient cardiac differentiation.
This dose-dependent bifurcation, with high doses favouring endoderm and low doses favouring mesoderm, reflects the role of Activin/Nodal as a morphogen during gastrulation, where graded signalling specifies different positions along the anterior-posterior axis of the primitive streak [14].
| Activin A Concentration and Lineage Outcome in iPSC Differentiation | ||
| Concentration range | Typical co-factors | Predominant outcome |
| Below 5 ng/ml | N/A | No measurable effect on differentiation; cells retain pluripotency markers |
| Approximately 5 ng/ml in maintenance media | FGF2, IGF-1 or insulin (via PI3K) | Pluripotency maintenance through SMAD2/3-NANOG axis |
| Approximately 6 ng/ml | BMP4 (5 to 10 ng/ml) | Cardiac mesoderm (KDR+/PDGFRα+); line-dependent optimisation required |
| Below 30 ng/ml | Wnt activator | Mesoderm specification favoured over endoderm |
| 30 to 100 ng/ml | CHIR99021 (3 µM) or WNT3A (25 ng/ml); low serum or serum-free | Definitive endoderm (SOX17+ FOXA2+ CXCR4+); 70 to 95% efficiency reported |
| 100 ng/ml | CHIR99021 day 1 only, then Activin A alone | Standard high-efficiency DE induction (D'Amour protocol and derivatives) |
Definitive Endoderm: The Foundational Protocol
Differentiation toward definitive endoderm is the most established Activin A-based protocol and the entry point for liver, pancreas, intestinal, lung and thyroid differentiations. The protocol established by D'Amour and colleagues in 2005 used 100 ng/ml Activin A with low serum (0.2 to 2% FBS) over three days and achieved up to 80% DE induction in human ES cells [1]. The follow-up D'Amour protocol added WNT3A at 25 ng/ml on day 1 to further enhance efficiency [15].
Subsequent protocols replaced WNT3A with the GSK-3 inhibitor CHIR99021, which is more cost-effective and produces comparable or superior DE induction. A typical modern protocol combines 100 ng/ml Activin A with 3 µM CHIR99021 on day 1, followed by Activin A alone (with or without low FBS) on days 2 and 3 [16]. Comparative analysis confirmed that CHIR99021 outperforms WNT3A as the Wnt input for DE specification, primarily because it more effectively suppresses E-CADHERIN/CDH1 and pluripotency factor expression to drive complete commitment [2].
Definitive endoderm cells produced by these protocols are identified by co-expression of SOX17, FOXA2 (HNF3β), CXCR4 (CD184), C-KIT (CD117) and GATA4, and absence of OCT4 and other pluripotency markers. CXCR4 and CD117 double-positive populations are commonly used as a flow cytometry readout, with well-optimised protocols achieving over 95% double-positive cells [17]. Critically, DE rather than extraembryonic endoderm is confirmed by absence of SOX7 and PDGFRα.
Timing matters as well as concentration. Comparison of 72-hour versus 168-hour Activin A treatment showed that the longer exposure produced higher endodermal gene expression and more efficient DE induction in feeder-free iPSC cultures [17]. However, extended Activin A treatment also exposes cells to longer windows of cellular toxicity that has been documented during the first days of DE induction, with some iPSC lines showing notable cell loss before proliferation resumes on days 3 to 4 [4]. Cell density at the start of DE induction (typically 90 to 95% confluence) is therefore an important determinant of final yield.
Activin A in Hepatocyte Differentiation
Hepatocyte differentiation from iPSCs proceeds through DE as an obligate intermediate, then through hepatic specification of the foregut endoderm. Activin A is used in both stages, although in different ways. The DE induction stage uses the standard 100 ng/ml Activin A regimen described above. Hepatic specification then continues with Activin A, often at the same concentration, for an additional 2 to 3 days, sometimes combined with BMP4 and FGF2 or FGF10 [4].
Continued Activin A treatment after DE specification has been shown to bias cells toward the ventral foregut and liver bud fate, with upregulation of HEX, SOX17, HNF4A, FOXA1, FOXA2 and TBX3 [18]. Conversely, inhibition of Activin/Nodal signalling using SB431542 at this stage decreases liver bud gene expression and is required for pancreatic specification, illustrating the crucial role of timed Activin A withdrawal in lineage divergence.
The full Activin A regimen for hepatocyte protocols is therefore typically 5 to 7 days at 100 ng/ml, with co-factors changing across the period: CHIR99021 or WNT3A for the first 24 hours, then Activin A alone, then Activin A combined with BMP4/FGF for hepatic specification, before the cells are switched to hepatic maturation media containing HGF, oncostatin M and dexamethasone.
Activin A in Pancreatic and Intestinal Differentiation
Pancreatic differentiation also begins with Activin A-driven DE induction, but Activin/Nodal signalling must then be actively suppressed to allow pancreatic specification. Inhibition of Activin/Nodal signalling using SB431542 is necessary for pancreatic differentiation of human pluripotent stem cells, demonstrating that the same pathway that initiates the protocol must subsequently be turned off for the desired outcome [18]. This switch typically occurs at the transition from DE to primitive gut tube and posterior foregut, around days 4 to 6 of a six-stage pancreatic protocol.
For pancreatic beta cell production from iPSCs, the standard six-stage protocol uses 100 ng/ml Activin A with 3 µM CHIR99021 on day 1 of stage 1 (DE induction), then Activin A alone for two additional days [13]. As discussed above, this concentration can be reduced to 50 ng/ml without compromising downstream beta cell marker expression, providing significant cost savings for therapeutic-scale manufacturing [13].
For intestinal differentiation, DMSO co-treatment has been shown to substantially reduce the Activin A requirement. In the presence of 0.8% DMSO, intestinal DE differentiation can be achieved at 6.25 ng/ml Activin A with similar efficiency to the standard 100 ng/ml protocol, representing a 16-fold reduction in Activin A use [19]. After DE induction, the BIO/DAPT combination drives posterior DE specification toward CDX2-expressing intestinal progenitors.
Lot-to-Lot Variability and Quality Control
Lot-to-lot variability in commercial Activin A preparations is one of the most consistently reported sources of failed iPSC differentiations. High variability of Activin A activity from lot to lot has been documented and is sufficient to drive laboratories to switch from individually purchased Activin A to pre-formulated commercial DE induction kits to obtain reproducible results [4]. The variability typically manifests as inconsistent DE induction efficiency between runs that are otherwise identical, and as cell line-by-cell line differences in the same lot performing well on one line and poorly on another.
Several factors contribute to this variability. Activin A is produced in heterologous expression systems (commonly E. coli, CHO or HEK293 cells) and the post-translational processing, glycosylation status and folding can differ between batches and between manufacturers. Bioactivity is typically assessed by an ED50 measurement in a defined cellular assay, but the same ED50 in a proliferation assay does not guarantee equivalent activity in DE induction or other complex differentiation outcomes. Endotoxin levels also vary between preparations and can affect iPSC differentiation independently of Activin A activity.
For laboratories running production differentiations, the practical responses to lot variability are: (1) test each new lot against the previous reference lot before adopting it, (2) request a certificate of analysis with lot-specific ED50 and bioactivity data rather than pass/fail certification, (3) buy enough of a validated lot to cover an entire experimental campaign, and (4) where possible, request lot-specific samples for testing before committing to bulk purchase. Cell Guidance Systems provides certificates of analysis with specific ED50 values for each growth factor lot, including all Activin A products, allowing direct comparison between batches.
| Activin A Quality Control: Specifications to Verify Before Use | |
| Specification | Why it matters |
| Lot-specific ED50 in defined bioactivity assay | Quantitative comparison between lots; pass/fail certification is insufficient for differentiation work |
| Endotoxin level (typically below 0.1 EU/µg) | Endotoxin contamination affects iPSC behaviour independently of Activin A activity |
| Purity by SDS-PAGE (typically above 95%) | Co-purifying proteins or aggregates can affect signalling kinetics |
| Expression system (E. coli vs mammalian) | Affects glycosylation status; switching expression system mid-project may require re-optimisation of dose |
| Animal-component-free production | Required for any work moving toward clinical translation |
The Stability Problem and Sustained-Release Activin A
Conventional soluble Activin A has a relatively short functional half-life in cell culture media. Like most recombinant growth factors, it is subject to proteolytic degradation by proteases present in serum and secreted by the cells, and its bioactive concentration declines significantly between media changes. The standard practice of daily media changes during DE induction is partly a consequence of this instability: each change replenishes the Activin A signal but also exposes cells to a transient concentration spike followed by gradual decline, rather than a steady signal.
This instability contributes to the high concentrations typically required (100 ng/ml is far higher than the affinity of Activin A for its receptor would suggest is necessary at steady state), and to the cost dominance of Activin A in DE protocols. Cost of goods analyses for iPSC-derived islet-like cell manufacturing have identified Activin A as the single most expensive reagent in the differentiation protocol [13].
Sustained-release formulations address this directly. PODS® Human Activin A is a co-crystalline formulation in which Activin A is captured within a protective polyhedrin protein lattice and released gradually as proteases secreted by the cells degrade the scaffold. The release kinetics produce near zero-order availability of Activin A over 1 to 3 weeks, in contrast to the spike-and-decay profile of soluble Activin A. The crystals also provide remarkable thermal stability, with the polyhedrin lattice having a low solvent content of 19% that protects cargo proteins even at elevated temperatures.
For iPSC differentiation applications, the practical implications are: (1) the same nominal mass of Activin A can be used in PODS form as in soluble form, but with sustained availability over the differentiation window, (2) media change frequency can be reduced, (3) the steady-state concentration of available Activin A is more uniform, which may improve protocol reproducibility, and (4) PODS can be immobilised to surfaces to create localised concentration gradients, opening possibilities for more sophisticated patterning protocols. PODS® Mouse Activin A and PODS® Rat Activin A are also available, although mature Activin A protein sequence is 100% conserved across human, mouse, rat, porcine, bovine and feline species, so cross-species use is possible.
The optimal PODS dose for any specific differentiation protocol must be empirically determined. As a starting point, the same nominal cargo mass as the conventional soluble Activin A protocol is a reasonable first approximation, with refinement based on differentiation marker readouts.
Cellular Toxicity and Recovery
A frequently overlooked aspect of Activin A treatment is the cellular toxicity observed during the first days of DE induction. Cell loss in the first 24 to 48 hours of Activin A treatment has been documented across multiple iPSC lines, with cell numbers declining before recovering on days 3 and 4 as the surviving DE population proliferates [4]. This is not solely a consequence of the differentiation stimulus itself: Activin A has documented apoptotic activity through caspase activation in a dose- and time-dependent manner, and the Smad pathway is an important mediator of this effect [12].
The practical consequences are that initial seeding density needs to account for some cell loss during induction, that ROCK inhibitor (Y-27632) at 10 µM is commonly used in the first 24 hours to improve survival of single-cell-passaged iPSCs, and that some iPSC lines exhibit higher Activin A sensitivity than others. Lines that show poor cell number recovery by day 3 or 4 are unlikely to produce acceptable yields and may benefit from reduced Activin A concentration (down to 30 to 50 ng/ml) or alternative protocols.
Practical Protocol Reference
| Activin A Use in Established iPSC Differentiation Protocols | ||
| Target lineage | Activin A regimen | Key co-factors and notes |
| Definitive endoderm (general) | 100 ng/ml for 3 days | CHIR99021 (3 µM) day 1; low serum or serum-free; 30 to 50 ng/ml may be sufficient on a line-specific basis |
| Hepatocyte | 100 ng/ml for 5 to 7 days | CHIR99021 day 1; BMP4 (10 to 20 ng/ml) and FGF2 (10 ng/ml) added from day 4 onward for hepatic specification |
| Pancreatic beta cell | 50 to 100 ng/ml for 3 days | CHIR99021 (3 µM) day 1; Activin/Nodal must be suppressed (SB431542) at stage 2 onward for pancreatic specification |
| Intestinal (with DMSO) | 6.25 to 100 ng/ml for 4 days | 0.8% DMSO reduces Activin A requirement; BIO and DAPT added at posterior DE specification stage |
| Cardiac mesoderm | Approximately 6 ng/ml for 1 day | BMP4 (10 ng/ml); line-specific optimisation required; very different dose regime from endoderm protocols |
| iPSC pluripotency maintenance | Approximately 5 ng/ml continuous | Component of mTeSR1, Essential 8, StemPro and similar defined media; works through SMAD2/3-NANOG axis |
Troubleshooting Common Activin A-Related Problems
| Activin A Differentiation Troubleshooting | ||
| Symptom | Likely cause(s) | Corrective action |
| Low SOX17/FOXA2 expression at end of DE induction | Activin A lot of low activity; PI3K signalling not suppressed; serum/insulin too high; iPSC starting population not fully pluripotent | Test new lot against reference lot; reduce serum to 0.2%; consider PI3K inhibitor; verify NANOG/OCT4 in starting population |
| High mesodermal marker expression (TBXT, MIXL1) at end of DE induction | Activin A concentration too low; CHIR99021 concentration too high (above 3 µM); Wnt signalling overdriving toward mesoderm | Increase Activin A toward 100 ng/ml; reduce CHIR99021 to 3 µM or lower; limit CHIR99021 exposure to day 1 only |
| Severe cell loss in first 48 hours of induction | Activin A toxicity (line-dependent); single-cell passaging without ROCK inhibitor; suboptimal seeding density | Add Y-27632 at 10 µM for first 24 hours; increase seeding density; reduce Activin A to 50 ng/ml on sensitive lines |
| Run-to-run variability in DE induction efficiency | Activin A lot variability; variable iPSC starting population; inconsistent confluence at induction start | Standardise to one Activin A lot per campaign; standardise iPSC density and pluripotency check at induction start; consider sustained-release PODS Activin A for more uniform availability |
| Persistent OCT4/NANOG expression after DE induction | Insufficient Activin A duration; PI3K not suppressed; Activin A potentiating residual self-renewal rather than driving differentiation | Extend Activin A treatment to 4 to 5 days; reduce insulin/IGF in media; verify CHIR99021 activity |
| Strong PDGFRα or SOX7 expression in DE population | Extraembryonic endoderm contamination rather than definitive endoderm | Verify Activin A activity; consider switching to a more recent protocol incorporating BMP and Wnt timing controls (Loh et al. 2014) |
| Cardiac differentiation with low KDR+/PDGFRα+ population | Activin A concentration too high for cardiac (over 10 ng/ml); BMP4 dose not optimised; line-specific optimisation not done | Titrate Activin A in 2 to 10 ng/ml range; titrate BMP4 in 5 to 20 ng/ml range; optimise per cell line |
Cell Guidance Systems Activin A Products
Conventional Activin A. Cell Guidance Systems supplies recombinant human and rodent growth factors with lot-specific certificates of analysis providing ED50 values rather than pass/fail bioactivity certification. All growth factors are produced in animal-component-free conditions.
PODS® sustained-release Activin A. The PODS® Human Activin A formulation provides sustained release of Activin A over 1 to 3 weeks in cell culture, with steady-state availability driven by protease activity from the cultured cells. PODS® Mouse Activin A and PODS® Rat Activin A are also available; the mature Activin A protein sequence is 100% conserved across these species. PODS formulations can be used in solution or immobilised to surfaces for localised delivery in patterning applications.
PODS® Human Activin B. PODS® Human Activin B is also available for protocols requiring Activin B specifically, including some mesoderm induction and bone remodelling applications.
PODS® Human Follistatin. PODS® Human Follistatin provides sustained-release follistatin for protocols requiring controlled Activin A inhibition, including cardiac differentiation contexts where follistatin has been shown to enhance endoderm-to-cardiac fate transitions in some experimental systems.
| Activin A Product Selection Guide | |
| Application | Recommended product |
| Standard 3-day DE induction with daily media changes | Conventional recombinant human Activin A |
| Extended DE/hepatic induction (5+ days) or reduced media-change protocols | PODS® Human Activin A for sustained release |
| Immobilised growth factor patterning or 3D scaffold work | PODS® Human Activin A for surface immobilisation |
| Mouse or rat iPSC/ESC work | PODS® Mouse Activin A or PODS® Rat Activin A |
| Activin A pathway inhibition (e.g. cardiac protocols) | PODS® Human Follistatin |
| Practical Guidance |
| Activin A is dose-, time- and context-dependent. The same molecule maintains pluripotency at 5 ng/ml, drives cardiac mesoderm at 6 ng/ml with BMP4, and specifies definitive endoderm at 30 to 100 ng/ml with Wnt activation. There is no single "correct" Activin A concentration, only a correct concentration for a specific lineage target on a specific iPSC line in a specific signalling context. Empirical optimisation, careful lot management, and consideration of sustained-release alternatives are the most reliable route to reproducible differentiation. |
References
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[2] Teo AKK, Valdez IA, Dirice E, Kulkarni RN. Comparable generation of activin-induced definitive endoderm via additive Wnt or BMP signaling in absence of serum. Stem Cell Reports. 2014;3(1):5-14.
[3] Kattman SJ, Witty AD, Gagliardi M, et al. Stage-specific optimization of activin/nodal and BMP signaling promotes cardiac differentiation of mouse and human pluripotent stem cell lines. Cell Stem Cell. 2011;8(2):228-240.
[4] Carpentier A, Nimgaonkar I, Chu V, Xia Y, Hu Z, Liang TJ. Hepatic differentiation of human pluripotent stem cells in miniaturized format suitable for high-throughput screen. Stem Cell Res. 2016;16(3):640-650.
[5] Pauklin S, Vallier L. Activin/Nodal signalling in stem cells. Development. 2015;142(4):607-619.
[6] Vallier L, Mendjan S, Brown S, et al. Activin/Nodal signalling maintains pluripotency by controlling Nanog expression. Development. 2009;136(8):1339-1349.
[7] Brown S, Teo A, Pauklin S, et al. Activin/Nodal signaling controls divergent transcriptional networks in human embryonic stem cells and in endoderm progenitors. Stem Cells. 2011;29(8):1176-1185.
[8] Singh AM, Reynolds D, Cliff T, et al. Signaling network crosstalk in human pluripotent cells: a Smad2/3-regulated switch that controls the balance between self-renewal and differentiation. Cell Stem Cell. 2012;10(3):312-326.
[9] McLean AB, D'Amour KA, Jones KL, et al. Activin A efficiently specifies definitive endoderm from human embryonic stem cells only when phosphatidylinositol 3-kinase signaling is suppressed. Stem Cells. 2007;25(1):29-38.
[10] James D, Levine AJ, Besser D, Hemmati-Brivanlou A. TGFβ/activin/nodal signaling is necessary for the maintenance of pluripotency in human embryonic stem cells. Development. 2005;132(6):1273-1282.
[11] Hao J, Zhu W, Sheng C, Yu Y, Zhou Q. Activin A can induce definitive endoderm differentiation from human parthenogenetic embryonic stem cells. Biotechnol Lett. 2015;37(8):1711-1717.
[12] Ghorbani-Dalini S, Azarpira N, Sangtarash MH, et al. Optimization of activin-A: a breakthrough in differentiation of human induced pluripotent stem cell into definitive endoderm. 3 Biotech. 2020;10(5):215.
[13] Castro-Gutierrez R, Aasmul-Olsen K, Crook K, et al. Reduction of activin A gives rise to comparable expression of key definitive endoderm and mature beta cell markers. Regen Med. 2024.
[14] Loh KM, Ang LT, Zhang J, et al. Efficient endoderm induction from human pluripotent stem cells by logically directing signals controlling lineage bifurcations. Cell Stem Cell. 2014;14(2):237-252.
[15] D'Amour KA, Bang AG, Eliazer S, et al. Production of pancreatic hormone-expressing endocrine cells from human embryonic stem cells. Nat Biotechnol. 2006;24(11):1392-1401.
[16] Sulzbacher S, Schroeder IS, Truong TT, Wobus AM. Activin A-induced differentiation of embryonic stem cells into endoderm and pancreatic progenitors-the influence of differentiation factors and culture conditions. Stem Cell Rev Rep. 2009;5(2):159-173.
[17] Kondo Y, Iwao T, Yoshihashi S, et al. An efficient method for the differentiation of human iPSC-derived endoderm toward enterocytes and hepatocytes. Cells. 2021;10(4):812.
[18] Cho CH, Hannan NR, Docherty FM, et al. Inhibition of activin/nodal signalling is necessary for pancreatic differentiation of human pluripotent stem cells. Diabetologia. 2012;55(12):3284-3295.
[19] Kawatani T, Endo H, Tsukada T, Kiyono T, Kitagawa M. A cost-effective system for differentiation of intestinal epithelium from human induced pluripotent stem cells. Sci Rep. 2015;5:17297.
Related Cell Guidance Systems Products
- PODS® Human Activin A
- PODS® Mouse Activin A
- PODS® Rat Activin A
- PODS® Human Activin B
- PODS® Human Follistatin
- PODS® Sustained-Release Growth Factors
- Conventional Recombinant Growth Factors
IMAGE iPSC differentiation. Credit Gabsoucisse (cc4.0)
