Cationic surface charge combined with either vitronectin or laminin dictates the evolution of human embryonic stem cells/microcarrier aggregates and cell growth in agitated cultures

3D Microcapsules for Human Bone Marrow Derived Mesenchymal Stem Cell Biomanufacturing in a Vertical-Wheel Bioreactor

Microencapsulation of human mesenchymal stromal cells (MSCs) via electrospraying has been well documented in tissue engineering and regenerative medicine. Herein, we report the use of microencapsulation, via electrospraying, for MSC expansion using a commercially available hydrogel that is durable, optimized to MSC culture, and enzymatically degradable for cell recovery. Critical parameters of the electrospraying encapsulation process such as seeding density, correlation of microcapsule output with hydrogel volume, and applied voltage were characterized to consistently fabricate cell-laden microcapsules of uniform size. Upon encapsulation, we then verified ~ 10x expansion of encapsulated MSCs within a vertical-wheel bioreactor and the preservation of critical quality attributes such as immunophenotype and multipotency after expansion and cell recovery. Finally, we highlight the genetic manipulation of encapsulated MSCs as an example of incorporating bioactive agents in the capsule material to create new compositions of MSCs with altered phenotypes.

Surface grafting of sericin onto thermoplastic polyurethanes to improve cell adhesion and function

Thermoplastic polyurethane (TPU) membrane has super physical-mechanical properties and biocompatibility, but the surface is inert and lack of active groups which limit its application in cell culture. Silk sericin (SS) can improve cell adhesion, proliferation, growth and metabolism. In this paper, SS was grafted onto the surface of TPU membrane by -NH₂ bridge to build a high efficiency cell culture membrane. The FT-IR spectrum results indicated SS was grafted by chemical bond. According to the SEM and AFM results, we found that the grafting of SS reduced the water contact angle by 43.31% and increased the surface roughness by about four times. When TPU-SS was used for HepG2 cell culture, the cell adhesion rate of TPU-SS was significantly higher than that of the general TCPS cell culture plate, and the cell proliferation rate was close to that of TCPS. FDA/EB staining showed that HepG2 cells remained a better cellular growth behavior. HepG2 cells had higher cell vitality including the albumin secretion and the intracellular total protein synthesis. Grafting SS maintained the stability of cell and significantly decreased the cytotoxicity by decreased LDH release. In conclusion, SS grafting is beneficial to cell culture in vitro, and provides a key material for bioartificial liver culture system.

Scaffolding Biomaterials for 3D Cultivated Meat: Prospects and Challenges

Cultivating meat from stem cells rather than by raising animals is a promising solution to concerns about the negative externalities of meat production. For cultivated meat to fully mimic conventional meat's organoleptic and nutritional properties, innovations in scaffolding technology are required. Many scaffolding technologies are already developed for use in biomedical tissue engineering. However, cultivated meat production comes with a unique set of constraints related to the scale and cost of production as well as the necessary attributes of the final product, such as texture and food safety. This review discusses the properties of vertebrate skeletal muscle that will need to be replicated in a successful product and the current state of scaffolding innovation within the cultivated meat industry, highlighting promising scaffold materials and techniques that can be applied to cultivated meat development. Recommendations are provided for future research into scaffolds capable of supporting the growth of high-quality meat while minimizing production costs. Although the development of appropriate scaffolds for cultivated meat is challenging, it is also tractable and provides novel opportunities to customize meat properties.

Gellan gum-gelatin viscoelastic hydrogels as scaffolds to promote fibroblast differentiation

Fabricating hydrogel scaffolds that are both bioreactive toward fibroblasts while still mechanically compatible with surrounding tissue is a major challenge in tissue engineering. This is because the outcome of scaffold implantation is largely determined by fibroblasts differentiating toward myofibroblasts, which is characterized by the expression of α-smooth muscle actin (α-SMA). Previous studies promoted fibroblasts differentiation by increasing scaffold substrate stiffness. However, the stiffness of scaffold has to be compatible with surrounding tissue, as mismatched stiffness may cause initial hyperplasia and inappropriate endothelial layer development. Therefore, we adjusted the hydrogel chemical component, and thus viscoelasticity to affect the mechano-signaling of fibroblasts and promote fibroblasts differentiation. Elastic gellan gum and viscoelastic gelatin were hybridized at different ratios to fabricate hydrogel scaffold with varied stress-relaxation. Vitronectin (VN) was used to further regulate the interaction between fibroblasts and the substrate. Fibroblast differentiation, characterized by α-SMA area per cell, increased from~3000-4000 μm²/cell on less viscoelastic gels to ~5000 μm²/cell on the most viscoelastic gel. Fibroblasts seeded on hydrogels had a slower migration rate on more viscoelastic hydrogels (slowest at 38 ± 14 μm/h) compared to the migration speed on less viscoelastic hydrogels (74 ± 20 μm/h). VN slowed the migration speed on all hydrogels. The organization of collagen deposited by fibroblasts cultured on the hydrogels was characterized by second harmonic generation (SHG), which showed that collagen was more organized (parallel) on more viscoelastic hydrogels. In summary, we provided a novel strategy to fabricate hydrogel scaffolds that can promote fibroblasts differentiation while keeping the stiffness compatible with blood vessels. The most viscoelastic hydrogel studied here meets these requirements best.

Industrially Compatible Transfusable iPSC-Derived RBCs: Progress, Challenges and Prospective Solutions

Amidst the global shortfalls in blood supply, storage limitations of donor blood and the availability of potential blood substitutes for transfusion applications, society has pivoted towards in vitro generation of red blood cells (RBCs) as a means to solve these issues. Many conventional research studies over the past few decades have found success in differentiating hematopoietic stem and progenitor cells (HSPCs) from cord blood, adult bone marrow and peripheral blood sources. More recently, techniques that involve immortalization of erythroblast sources have also gained traction in tackling this problem. However, the RBCs generated from human induced pluripotent stem cells (hiPSCs) still remain as the most favorable solution due to many of its added advantages. In this review, we focus on the breakthroughs for high-density cultures of hiPSC-derived RBCs, and highlight the major challenges and prospective solutions throughout the whole process of erythropoiesis for hiPSC-derived RBCs. Furthermore, we elaborate on the recent advances and techniques used to achieve cost-effective, high-density cultures of GMP-compliant RBCs, and on their relevant novel applications after downstream processing and purification.

Bioprocess Technologies that Preserve the Quality of iPSCs

Large-scale production of induced pluripotent stem cells (iPSCs) is essential for the treatment of a variety of clinical indications. However, culturing enough iPSCs for clinical applications is problematic due to their sensitive pluripotent state and dependence on a supporting matrix. Developing stem cell bioprocessing strategies that are scalable and meet clinical needs requires incorporating methods that measure and monitor intrinsic markers of cell differentiation state, developmental status, and viability in real time. In addition, proper cell culture modalities that nurture the growth of high-quality stem cells in suspension are critical for industrial scale-up. In this review, we present an overview of cell culture media, suspension modalities, and monitoring techniques that preserve the quality and pluripotency of iPSCs during initiation, expansion, and manufacturing.

Selection of human induced pluripotent stem cells lines optimization of cardiomyocytes differentiation in an integrated suspension microcarrier bioreactor

Background

The production of large quantities of cardiomyocyte is essential for the needs of cellular therapies. This study describes the selection of a human-induced pluripotent cell (hiPSC) line suitable for production of cardiomyocytes in a fully integrated bioprocess of stem cell expansion and differentiation in microcarrier stirred tank reactor.

Methods

Five hiPSC lines were evaluated first for their cardiac differentiation efficiency in monolayer cultures followed by their expansion and differentiation compatibility in microcarrier (MC) cultures under continuous stirring conditions.

Results

Three cell lines were highly cardiogenic but only one (FR202) of them was successfully expanded on continuous stirring MC cultures. FR202 was thus selected for cardiac differentiation in a 22-day integrated bioprocess under continuous stirring in a stirred tank bioreactor. In summary, we integrated a MC-based hiPSC expansion (phase 1), CHIR99021-induced cardiomyocyte differentiation step (phase 2), purification using the lactate-based treatment (phase 3) and cell recovery step (phase 4) into one process in one bioreactor, under restricted oxygen control (< 30% DO) and continuous stirring with periodic batch-type media exchanges. High density of undifferentiated hiPSC (2 ± 0.4 × 10⁶ cells/mL) was achieved in the expansion phase. By controlling the stirring speed and DO levels in the bioreactor cultures, 7.36 ± 1.2 × 10⁶ cells/mL cardiomyocytes with > 80% Troponin T were generated in the CHIR99021-induced differentiation phase. By adding lactate in glucose-free purification media, the purity of cardiomyocytes was enhanced (> 90% Troponin T), with minor cell loss as indicated by the increase in sub-G1 phase and the decrease of aggregate sizes. Lastly, we found that the recovery period is important for generating purer and functional cardiomyocytes (> 96% Troponin T). Three independent runs in a 300-ml working volume confirmed the robustness of this process.

Conclusion

A streamlined and controllable platform for large quantity manufacturing of pure functional atrial, ventricular and nodal cardiomyocytes on MCs in conventional-type stirred tank bioreactors was established, which can be further scaled up and translated to a good manufacturing practice-compliant production process, to fulfill the quantity requirements of the cellular therapeutic industry.

Supplementary information

The online version of this article (10.1186/s13287-020-01618-6) contains supplementary material, which is available to authorized users.

Drug-Mimicking Nanofibrous Peptide Hydrogel for Inhibition of Inducible Nitric Oxide Synthase

In this work, we develop a drug-mimicking nanofibrous peptide hydrogel that shows long-term bioactivity comparable to a small-molecule inhibitor of inducible nitric oxide synthase (iNOS). The iNOS inhibitor, N ⁶-(1-iminoethyl)-l-lysine (l-NIL), is a positively charged amino acid whose structure could be readily integrated into the framework of a positively charged multidomain peptide (MDP) through the modification of lysine side chains. This new l-NIL-MDP maintains the self-assembling properties of the base peptide, forming β-sheet nanofibers, which entangle into a thixotropic hydrogel. The l-NIL-MDP hydrogel supports cell growth in vitro and allows syringe-directed delivery that persists in a targeted location in vivo for several weeks. Multiple characterization assays demonstrate the bioactivity of the l-NIL-MDP hydrogel to be comparable to the l-NIL small molecule. This includes iNOS inhibition of macrophages in vitro, reduced nitrotyrosine immunostaining in murine subcutaneous histology, and reduced serum levels of vascular endothelial growth factor in vivo. This study expands the toolbox of available peptide hydrogel scaffold designs that can modify biological activity without the need for any additional small-molecule drugs, proteins, or cells.

Mechanism of anchorage-independency and tumor formation of cancer cells: possible involvement of cell membrane-bound laminin-332

Cancer cells are characterized by anchorage-independency and tumor formation. Involvement of laminin-332 in the pathogenesis of cancer has also been reported. I present a theory that can explain these characteristics together. Proliferating keratinocytes in wound healing produce and deposit laminin-332, which is shown in the provisional basement membrane of a wound. In association with wound closure, expression of LG4/5 domain on the α3 chain of laminin-332 disappears, implicating cleavage of LG4/5 domain. LG4/5 domain expression indicates that laminin-332 prior to the cleavage is bound to the cell membrane, because LG4/5 domain is a cell binding site. In this binding, heparan sulfate proteoglycan on the cell surface seems to be the acceptor for LG4/5 domain. I named this laminin "cell membrane-bound laminin-332" (ML332). ML332 would then bind to integrin α3β1 via LG1-3 domain, the integrin binding site, and activate FAK and the following Ras/MAPK pathway. Therefore, ML332 eliminates the need for proliferating keratinocytes to bind to processed laminin-332 secreted and deposited into the basement membrane for their proliferation (anchorage-independency). This may hold true of every proliferating epithelial cell, either benign or malignant. Whereas wound closure deprives keratinocytes of anchorage-independency, such events do not occur in cancer cells, and cancer cells maintain anchorage-independency. In the basement membrane formation by epithelial cells, short arms of laminin-332 anchored to the cell membrane bind each other and generate a meshwork polymer. This is the three-arm interaction model. In a similar manner, short-arm interactions between adjacent cancer cells may occur and induce tumor formation.

Microparticles in Contact with Cells: From Carriers to Multifunctional Tissue Modulators

For several decades microparticles have been exclusively and extensively explored as spherical drug delivery vehicles and large-scale cell expansion carriers. More recently, microparticulate structures gained interest in broader bioengineering fields, integrating myriad strategies that include bottom-up tissue engineering, 3D bioprinting, and the development of tissue/disease models. The concept of bulk spherical micrometric particles as adequate supports for cell cultivation has been challenged, and systems with finely tuned geometric designs and (bio)chemical/physical features are current key players in impacting technologies. Herein, we critically review the state of the art and future trends of biomaterial microparticles in contact with cells and tissues, excluding internalization studies, and with emphasis on innovative particle design and applications.

Large-scale production of megakaryocytes in microcarrier-supported stirred suspension bioreactors

Megakaryocytes (MKs) are the precursors of platelets (PLTs) and may be used for PLT production in vivo or in vitro, as well as a source for PLT-derived growth factors. Induced pluripotent stem cells represent an unlimited cell source for the in vitro production of MKs. This study aimed at developing an effective, xeno-free and scalable system to produce high numbers of MKs. In particular, microcarrier beads-assisted stirred bioreactors were evaluated as a means of improving MK yields. This method resulted in the production of 18.7 × 10⁷ MKs per 50 ml medium. Laminin-coated microcarriers increased MK production per iPSC by up to 10-fold. MKs obtained in this system showed typical features of mature MKs and were able to produce PLTs in vitro and in vivo. To increase safety, MKs produced in the bioreactors were irradiated; a procedure that did not affect their capability to form proPLTs and PTLs after transfusion. In vitro generated MKs represent a promising alternative to donor PLTs and open the possibility for the development of innovative MK-based cell therapies.

The influence of surface modified poly(l-lactic acid) films on the differentiation of human monocytes into macrophages

Macrophages play a crucial role in the biological performance of biomaterials, as key factors in defining the optimal inflammation-healing balance towards tissue regeneration and implant integration. Here, we investigate how different surface modifications performed on poly(l-lactic acid) (PLLA) films would influence the differentiation of human monocytes into macrophages. We tested PLLA films without modification, surface-modified by plasma treatment (pPLLA) or by combining plasma treatment with different coating materials, namely poly(l-lysine) and a series of proteins from the extracellular matrix: collagen I, fibronectin, vitronectin, laminin and albumin. While all the tested films are non-cytotoxic, differences in cell adhesion and morphology are observed. Monocyte-derived macrophages (MDM) present a more rounded shape in non-modified films, while a more elongated phenotype is observed containing filopodia-like and podosome-like structures in all modified films. No major differences are found for the expression of HLA-DR⁺/CD80⁺ and CD206⁺/CD163⁺ surface markers, as well as for the ability of MDM to phagocytize. Interestingly, MDM differentiated on pPLLA present the highest expression of MMP9. Upon differentiation, MDM in all surface modified films present lower amounts of IL-6 and IL-10 compared to non-modified films. After stimulating MDM with the potent pro-inflammatory agent LPS, pPLLA and poly(l-lysine) and fibronectin-modified films reveal a significant reduction in IL-6 secretion, while the opposite effect is observed with IL-10. Of note, in comparison to non-modified films, all surface modified films induce a significant reduction of the IL-6/IL-10 ratio, a valuable prognosticator of the pro- versus anti-inflammatory balance. These findings provide important insights into MDM-biomaterial interactions, while strengthening the need for designing immune-informed biomaterials.

Efficient Large-Scale 2D Culture System for Human Induced Pluripotent Stem Cells and Differentiated Cardiomyocytes

Cardiac regenerative therapies utilizing human induced pluripotent stem cells (hiPSCs) are hampered by ineffective large-scale culture. hiPSCs were cultured in multilayer culture plates (CPs) with active gas ventilation (AGV), resulting in stable proliferation and pluripotency. Seeding of 1 × 10⁶ hiPSCs per layer yielded 7.2 × 10⁸ hiPSCs in 4-layer CPs and 1.7 × 10⁹ hiPSCs in 10-layer CPs with pluripotency. hiPSCs were sequentially differentiated into cardiomyocytes (CMs) in a two-dimensional (2D) differentiation protocol. The efficiency of cardiac differentiation using 10-layer CPs with AGV was 66%–87%. Approximately 6.2–7.0 × 10⁸ cells (4-layer) and 1.5–2.8 × 10⁹ cells (10-layer) were obtained with AGV. After metabolic purification with glucose- and glutamine-depleted and lactate-supplemented media, a massive amount of purified CMs was prepared. Here, we present a scalable 2D culture system using multilayer CPs with AGV for hiPSC-derived CMs, which will facilitate clinical applications for severe heart failure in the near future.

•

Efficient mass production of hiPSCs by multilayer culture plates with AGV

•

Efficient mass production of hiPSC-CMs using a massive 2D culture system with AGV

•

Mass production of pure hiPSC-CMs via metabolic selection

Immobilization of vitronectin-binding heparan sulfates onto surfaces to support human pluripotent stem cells

Functionalizing medical devices with polypeptides to enhance their performance has become important for improved clinical success. The extracellular matrix (ECM) adhesion protein vitronectin (VN) is an effective coating, although the chemistry used to attach VN often reduces its bioactivity. In vivo, VN binds the ECM in a sequence-dependent manner with heparan sulfate (HS) glycosaminoglycans. We reasoned therefore that sequence-based affinity chromatography could be used to isolate a VN-binding HS fraction (HS9) for use as a coating material to capture VN onto implant surfaces. Binding avidity and specificity of HS9 were confirmed by enzyme-linked immunosorbent assay (ELISA) and surface plasmon resonance (SPR)-based assays. Plasma polymerization of allylamine (AA) to tissue culture-treated polystyrene (TCPS) was then used to capture and present HS9 as determined by radiolabeling and ELISA. HS9-coated TCPS avidly bound VN, and this layered surface supported the robust attachment, expansion, and maintenance of human pluripotent stem cells. Compositional analysis demonstrated that 6-O- and N-sulfation, as well as lengths greater than three disaccharide units (dp6) are critical for VN binding to HS-coated surfaces. Importantly, HS9 coating reduced the threshold concentration of VN required to create an optimally bioactive surface for pluripotent stem cells. We conclude that affinity-purified heparan sugars are able to coat materials to efficiently bind adhesive factors for biomedical applications. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1887-1896, 2018.

Tunable Volumetric Density and Porous Structure of Spherical Poly-ε-caprolactone Microcarriers, as Applied in Human Mesenchymal Stem Cell Expansion

Polymeric microspheres may serve as microcarrier (MC) matrices, for the expansion of anchorage-dependent stem cells. They require surface properties that promote both initial cell adhesion and the subsequent spreading of cells, which is a prerequisite for successful expansion. When implemented in a three-dimensional culture environment, under agitation, their suspension under low shear rates depends on the MCs having a modest negative buoyancy, with a density of 1.02-1.05 g/cm³. Bioresorbable poly-ε-caprolactone (PCL), with a density of 1.14 g/cm³, requires a reduction in volumetric density, for the microspheres to achieve high cell viability and yields. Uniform-sized droplets, from solutions of PCL dissolved in dichloromethane (DCM), were generated by coaxial microfluidic geometry. Subsequent exposure to ethanol rapidly extracted the DCM solvent, solidifying the droplets and yielding monodisperse microspheres with a porous structure, which was demonstrated to have tunable porosity and a hollow inner core. The variation in process parameters, including the molecular weight of PCL, its concentration in DCM, and the ethanol concentration, served to effectively alter the diffusion flux between ethanol and DCM, resulting in a broad spectrum of volumetric densities of 1.04-1.11 g/cm³. The solidified microspheres are generally covered by a smooth thin skin, which provides a uniform cell culture surface and masks their internal porous structure. When coated with a cationic polyelectrolyte and extracellular matrix protein, monodisperse microspheres with a diameter of approximately 150 μm and densities ranging from 1.05-1.11 g/cm³ are capable of supporting the expansion of human mesenchymal stem cells (hMSCs). Validation of hMSC expansion was carried out with a positive control of commercial Cytodex 3 MCs and a negative control of uncoated low-density PCL MCs. Static culture conditions generated more than 70% cell attachment and similar yields of sixfold cell expansion on all coated MCs, with poor cell attachment and growth on the negative control. Under agitation, coated porous microspheres, with a low density of 1.05 g/cm³, achieved robust cell attachment and resulted in high cell yields of ninefold cell expansion, comparable with those generated by commercial Cytodex 3 MCs.

Fabrication of uniform-sized poly-ɛ-caprolactone microspheres and their applications in human embryonic stem cell culture

The generation of liquefied poly-ɛ-caprolactone (PCL) droplets by means of a microfluidic device results in uniform-sized microspheres, which are validated as microcarriers for human embryonic stem cell culture. Formed droplet size and size distribution, as well as the resulting PCL microsphere size, are correlated with the viscosity and flow rate ratio of the dispersed (Q d) and continuous (Q c) phases. PCL in dichloromethane increases its viscosity with concentration and molecular weight. Higher viscosity and Q d/Q c lead to the formation of larger droplets, within two observed formation modes: dripping and jetting. At low viscosity of dispersed phase and Q d/Q c, the microfluidic device is operated in dripping mode, which generates droplets and microspheres with greater size uniformity. Solutions with lower molecular weight PCL have lower viscosity, resulting in a wider concentration range for the dripping mode. When coated with extracellular matrix (ECM) proteins, the fabricated PCL microspheres are demonstrated capable of supporting the expansion of human embryonic stem cells.

Serum-free media formulations are cell line-specific and require optimization for microcarrier culture

BACKGROUND AIMS

Mesenchymal stromal cells (MSCs) are being investigated as potential cell therapies for many different indications. Current methods of production rely on traditional monolayer culture on tissue-culture plastic, usually with the use of serum-supplemented growth media. However, the monolayer culturing system has scale-up limitations and may not meet the projected hundreds of billions to trillions batches of cells needed for therapy. Furthermore, serum-free medium offers several advantages over serum-supplemented medium, which may have supply and contaminant issues, leading to many serum-free medium formulations being developed.

METHODS

We cultured seven MSC lines in six different serum-free media and compared their growth between monolayer and microcarrier culture.

RESULTS

We show that (i) expansion levels of MSCs in serum-free monolayer cultures may not correlate with expansion in serum-containing media; (ii) optimal culture conditions (serum-free media for monolayer or microcarrier culture) differ for each cell line; (iii) growth in static microcarrier culture does not correlate with growth in stirred spinner culture; (iv) and that early cell attachment and spreading onto microcarriers does not necessarily predict efficiency of cell expansion in agitated microcarrier culture.

CONCLUSIONS

Current serum-free media developed for monolayer cultures of MSCs may not support MSC proliferation in microcarrier cultures. Further optimization in medium composition will be required for microcarrier suspension culture for each cell line.

Integrated processes for expansion and differentiation of human pluripotent stem cells in suspended microcarriers cultures

Current methods for human pluripotent stem cells (hPSC) expansion and differentiation can be limited in scalability and costly (due to their labor intensive nature). This can limit their use in cell therapy, drug screening and toxicity assays. One of the approaches that can overcome these limitations is microcarrier (MC) based cultures in which cells are expanded as cell/MC aggregates and then directly differentiated as embryoid bodies (EBs) in the same agitated reactor. This integrated process can be scaled up and eliminate the need for some culture manipulation used in common monolayer and EBs cultures. This review describes the principles of such microcarriers based integrated hPSC expansion and differentiation process, and parameters that can affect its efficiency (such as MC type and extracellular matrix proteins coatings, cell/MC aggregates size, and agitation). Finally examples of integrated process for generation cardiomyocytes (CM) and neural progenitor cells (NPC) as well as challenges to be solved are described.

Improved Human Pluripotent Stem Cell Attachment and Spreading on Xeno-Free Laminin-521-Coated Microcarriers Results in Efficient Growth in Agitated Cultures

Human pluripotent stem cells (hPSC) are self-renewing cells having the potential of differentiation into the three lineages of somatic cells and thus can be medically used in diverse cellular therapies. One of the requirements for achieving these clinical applications is development of completely defined xeno-free systems for large-scale cell expansion and differentiation. Previously, we demonstrated that microcarriers (MCs) coated with mouse laminin-111 (LN111) and positively charged poly-l-lysine (PLL) critically enable the formation and evolution of cells/MC aggregates with high cell yields obtained under agitated conditions. In this article, we further improved the MC system into a defined xeno-free MC one in which the MCs are coated with recombinant human laminin-521 (LN521) alone without additional positive charge. The high binding affinity of the LN521 to cell integrins enables efficient initial HES-3 cell attachment (87%) and spreading (85%), which leads to generation of cells/MC aggregates (400 μm in size) and high cell yields (2.4–3.5×10⁶ cells/mL) within 7 days in agitated plate and scalable spinner cultures. The universality of the system was demonstrated by propagation of an induced pluripotent cells line in this defined MC system. Long-term pluripotent (>90% expression Tra-1-60) cell expansion and maintenance of normal karyotype was demonstrated after 10 cell passages. Moreover, tri-lineage differentiation as well as directed differentiation into cardiomyocytes was achieved. The new LN521-based MC system offers a defined, xeno-free, GMP-compatible, and scalable bioprocessing platform for the production of hPSC with the quantity and quality compliant for clinical applications. Use of LN521 on MCs enabled a 34% savings in matrix and media costs over monolayer cultures to produce 10⁸ cells.

Advances in cell culture: anchorage dependence

Anchorage-dependent cells are of great interest for various biotechnological applications. (i) They represent a formidable production means of viruses for vaccination purposes at very large scales (in 1000-6000 l reactors) using microcarriers, and in the last decade many more novel viral vaccines have been developed using this production technology. (ii) With the advent of stem cells and their use/potential use in clinics for cell therapy and regenerative medicine purposes, the development of novel culture devices and technologies for adherent cells has accelerated greatly with a view to the large-scale expansion of these cells. Presently, the really scalable systems--microcarrier/microcarrier-clump cultures using stirred-tank reactors--for the expansion of stem cells are still in their infancy. Only laboratory scale reactors of maximally 2.5 l working volume have been evaluated because thorough knowledge and basic understanding of critical issues with respect to cell expansion while retaining pluripotency and differentiation potential, and the impact of the culture environment on stem cell fate, etc., are still lacking and require further studies. This article gives an overview on critical issues common to all cell culture systems for adherent cells as well as specifics for different types of stem cells in view of small- and large-scale cell expansion and production processes.

Conjoint propagation and differentiation of human embryonic stem cells to cardiomyocytes in a defined microcarrier spinner culture

Introduction

Myocardial infarction is accompanied by a significant loss of cardiomyocytes (CMs). Functional CMs, differentiated from human embryonic stem cells (hESCs), offer a potentially unlimited cell source for cardiac disease therapies and regenerative cardiovascular medicine. However, conventional production methods on monolayer culture surfaces cannot adequately supply the large numbers of cells required for such treatments. To this end, an integrated microcarrier (MC) bioprocessing system for hESC propagation and subsequent CM differentiation was developed.

Methods

Production of hESC-derived CMs was initially established in monolayer cultures. This control condition was compared against hESC expansion on laminin-coated MC with cationic surface charge, in a stirred serum-free defined culture. Following expansion, the hESC/MC aggregates were placed in a CM differentiation medium, using Wnt signalling modulators in four different culture conditions. This process eliminated the need for manual colony cutting. The final optimized protocol was tested in stirred spinner flasks, combining expansion and differentiation on the same MC, with only media changes during the culture process.

Results

In the propagation phase, a 15-fold expansion of viable pluripotent HES-3 was achieved, with homogeneous sized aggregates of 316 ± 11 μm. Of the four differentiation conditions, stirred spinner flask cultures (MC-Sp) provided the best controlled aggregate sizes and yielded 1.9 × 10⁶ CM/ml, as compared to 0.5 × 10⁶ CM/ml using the monolayer cultures method: a four-fold increase in CM/ml. Similar results (1.3 × 10⁶ CM/ml) were obtained with an alternative hESC H7 line. The hESC/MC-derived CM expressed cardiac-specific transcription factors, structural, ion channel genes, and exhibited cross-striations of sarcomeric proteins, thus confirming their cardiac ontogeny. Moreover, E-4031 (0.3 μM) prolonged the QT-interval duration by 40% and verapamil (3 μM) reduced it by 45%, illustrating the suitability of these CM for pharmacological assays.

Conclusions

We have demonstrated a robust and scalable microcarrier system for generating hESC-derived CM. This platform is enabled by defined microcarrier matrices and it integrates cell propagation and differentiation within a continuous process, in serum-free culture media. It can generate significant numbers of CM, which are potentially suitable for future clinical therapies.

Electronic supplementary material

The online version of this article (doi:10.1186/scrt498) contains supplementary material, which is available to authorized users.