Enzymatic detachment of therapeutic mesenchymal stromal cells grown on glass carriers in a bioreactor

ReBiA-Robotic Enabled Biological Automation: 3D Epithelial Tissue Production

The Food and Drug Administration's recent decision to eliminate mandatory animal testing for drug approval marks a significant shift to alternative methods. Similarly, the European Parliament is advocating for a faster transition, reflecting public preference for animal-free research practices. In vitro tissue models are increasingly recognized as valuable tools for regulatory assessments before clinical trials, in line with the 3R principles (Replace, Reduce, Refine). Despite their potential, barriers such as the need for standardization, availability, and cost hinder their widespread adoption. To address these challenges, the Robotic Enabled Biological Automation (ReBiA) system is developed. This system uses a dual-arm robot capable of standardizing laboratory processes within a closed automated environment, translating manual processes into automated ones. This reduces the need for process-specific developments, making in vitro tissue models more consistent and cost-effective. ReBiA's performance is demonstrated through producing human reconstructed epidermis, human airway epithelial models, and human intestinal organoids. Analyses confirm that these models match the morphology and protein expression of manually prepared and native tissues, with similar cell viability. These successes highlight ReBiA's potential to lower barriers to broader adoption of in vitro tissue models, supporting a shift toward more ethical and advanced research methods.

Scaling up human mesenchymal stem cell manufacturing using bioreactors for clinical uses

Human mesenchymal stem cells (hMSCs) are multipotent cells and an attractive therapeutic agent in regenerative medicine and intensive clinical research. Despite the great potential, the limitation that needs to be overcome is the necessity of ex vivo expansion because of insufficient number of hMSCs presented within adult organs and the high doses required for a transplantation. As a result, numerous research studies aim to provide novel expansion methods in order to achieve appropriate numbers of cells with preserved therapeutic quality. Bioreactor-based cell expansion provide high-level production of hMSCs in accordance with good manufacturing practice (GMP) and quality standards. This review summarizes current knowledge about the hMSCs manufacturing platforms with a main focus to the application of bioreactors for large-scale production of GMP-grade hMSCs.

Challenges and Opportunities in Downstream Separation Processes for Mesenchymal Stromal Cells Cultured in Microcarrier-based Stirred Suspension Bioreactors

Mesenchymal stromal cells (MSC) are a promising platform for regenerative medicine applications because of their multi-lineage differentiation abilities and ease of collection, isolation, and growth ex-vivo. To meet the demand for clinical applications, large scale manufacturing will be required using three-dimension culture platforms in vessels such as stirred suspension bioreactors. As MSCs are an adherent cell type, microcarriers are added to the culture to increase the available surface area for attachment and growth. Although extensive research has been performed on efficiently culturing MSCs using microcarriers, challenges persist in downstream processing including harvesting, filtration, and volume reduction which all play a critical role for the translation of cell therapies to the clinic. The objective of this review is to assess the current state of downstream technologies available for microcarrier-based MSC cultures. This includes a review of current research within the three stages: harvesting, filtration, and volume reduction. Using this information, a downstream process for MSCs is proposed which can be applied for a wide range of applications. This article is protected by copyright. All rights reserved.

PillarX: A Microfluidic Device to Profile Circulating Tumor Cell Clusters Based on Geometry, Deformability, and Epithelial State

Circulating tumor cell (CTC) clusters are associated with increased metastatic potential and worse patient prognosis, but are rare, difficult to count, and poorly characterized biophysically. The PillarX device described here is a bimodular microfluidic device (Pillar-device and an X-magnetic device) to profile single CTCs and clusters from whole blood based on their size, deformability, and epithelial marker expression. Larger, less deformable clusters and large single cells are captured in the Pillar-device and sorted according to pillar gap sizes. Smaller, deformable clusters and single cells are subsequently captured in the X-device and separated based on epithelial marker expression using functionalized magnetic nanoparticles. Clusters of established and primary breast cancer cells with variable degrees of cohesion driven by different cell-cell adhesion protein expression are profiled in the device. Cohesive clusters exhibit a lower deformability as they travel through the pillar array, relative to less cohesive clusters, and have greater collective invasive behavior. The ability of the PillarX device to capture clusters is validated in mouse models and patients of metastatic breast cancer. Thus, this device effectively enumerates and profiles CTC clusters based on their unique geometrical, physical, and biochemical properties, and could form the basis of a novel prognostic clinical tool.

Photothermal release and recovery of mesenchymal stem cells from substrates functionalized with gold nanorods

Mesenchymal stem cell therapies show great promise in regenerative medicine. However, to generate clinically relevant numbers of these stem cells, significant in vitro expansion of the cells is required before transplantation into the affected wound or defect. The current gold standard protocol for recovering in vitro cultured cells involves treatment with enzymes such as trypsin which can affect the cell phenotype and ability to interact with the environment. Alternative enzyme free methods of adherent cell recovery have been investigated, but none match the convenience and performance of enzymatic detachment. In this work we have developed a synthetically simple, low cost cell culture substrate functionalized with gold nanorods that can support cell proliferation and detachment. When these nanorods are irradiated with biocompatible low intensity near infrared radiation (785 nm, 560 mWcm^-2) they generate localized surface plasmon resonance induced nanoscale heating effects which trigger detachment of adherent mesenchymal stem cells. Through simulations and thermometry experiments we show that this localized heating is concentrated at the cell-nanorod interface, and that the stem cells detached using this technique show either similar or improved multipotency, viability and ability to differentiate into clinically desirable osteo and adipocytes, compared to enzymatically harvested cells. This proof-of-principle work shows that photothermally mediated cell detachment is a promising method for recovering mesenchymal stem cells from in vitro culture substrates, and paves the way for further studies to scale up this process and facilitate its clinical translation. STATEMENT OF SIGNIFICANCE: New non-enzymatic methods of harvesting adherent cells without damaging or killing them are highly desirable in fields such as regenerative medicine. Here, we present a synthetically simple, non-toxic, infra-red induced method of harvesting mesenchymal stem cells from gold nanorod functionalized substrates. The detached cells retain their ability to differentiate into therapeutically valuable osteo and adipocytes. This work represents a significant improvement on similar cell harvesting studies due to: its simplicity; the use of clinically valuable stem cells as oppose to immortalized cell lines; and the extensive cellular characterization performed. Understanding, not just if cells live or die but how they proliferate and differentiate after photothermal detachment will be essential for the translation of this and similar techniques into commercial devices.

Facile bead-to-bead cell-transfer method for serial subculture and large-scale expansion of human mesenchymal stem cells in bioreactors

The conventional planar culture of adherent cells is inefficient for large‐scale manufacturing of cell and gene therapy products. We developed a facile and efficient bead‐to‐bead cell‐transfer method for serial subculture and large‐scale expansion of human mesenchymal stem cells (hMSCs) with microcarriers in bioreactors. We first compared culture medium with and without nucleosides and found the former maintained the expression of surface markers of hMSCs during their prolonged culture and enabled faster cell proliferation. Subsequently, we developed our bead‐to‐bead cell transfer method to subculture hMSCs and found that intermittent agitation after adding fresh microcarriers to cell‐populated microcarriers could promote spontaneous cell migration to fresh microcarriers, reduce microcarrier aggregation, and improve cell yield. This method enabled serial subculture of hMSCs in spinner flasks from passage 4 to passage 9 without using proteolytic enzymes, which showed faster cell proliferation than the serial planar cultures undergoing multiple enzyme treatment. Finally, we used the medium containing nucleosides and our bead‐to‐bead cell transfer method for cell culture scale‐up from 4‐ to 50‐L cultures in single‐use bioreactors. We achieved a 242‐fold increase in the number of cells to 1.45 × 10¹⁰ after 27‐day culture and found that the cells harvested from the bioreactors maintained proliferation ability, expression of their surface markers, tri‐lineage differentiation potential and immunomodulatory property. This study shows the promotive effect of nucleosides on hMSC expansion and the potential of using our bead‐to‐bead transfer method for larger‐scale manufacturing of hMSCs for cell therapy.

Towards Physiologic Culture Approaches to Improve Standard Cultivation of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are of great interest for their use in cell-based therapies due to their multipotent differentiation and immunomodulatory capacities. In consequence of limited numbers following their isolation from the donor tissue, MSCs require extensive expansion performed in traditional 2D cell culture setups to reach adequate amounts for therapeutic use. However, prolonged culture of MSCs in vitro has been shown to decrease their differentiation potential and alter their immunomodulatory properties. For that reason, preservation of these physiological characteristics of MSCs throughout their in vitro culture is essential for improving the efficiency of therapeutic and in vitro modeling applications. With this objective in mind, many studies already investigated certain parameters for enhancing current standard MSC culture protocols with regard to the effects of specific culture media components or culture conditions. Although there is a lot of diversity in the final therapeutic uses of the cells, the primary stage of standard isolation and expansion is imperative. Therefore, we want to review on approaches for optimizing standard MSC culture protocols during this essential primary step of in vitro expansion. The reviewed studies investigate and suggest improvements focused on culture media components (amino acids, ascorbic acid, glucose level, growth factors, lipids, platelet lysate, trace elements, serum, and xenogeneic components) as well as culture conditions and processes (hypoxia, cell seeding, and dissociation during passaging), in order to preserve the MSC phenotype and functionality during the primary phase of in vitro culture.

Development of pH-Responsive Polymer Coating as an Alternative to Enzyme-Based Stem Cell Dissociation for Cell Therapy

Cell therapy usually accompanies cell detachment as an essential process in cell culture and cell collection for transplantation. However, conventional methods based on enzymatic cell detachment can cause cellular damage including cell death and senescence during the routine cell detaching step due to an inappropriate handing. The aim of the current study is to apply the pH-responsive degradation property of poly (amino ester) to the surface of a cell culture dish to provide a simple and easy alternative method for cell detachment that can substitute the conventional enzyme treatment. In this study, poly (amino ester) was modified (cell detachable polymer, CDP) to show appropriate pH-responsive degradation under mild acidic conditions (0.05% (w/v) CDP, pH 6.0) to detach stem cells (human adipose tissue-derived stem cells (hADSCs)) perfectly within a short period (less than 10 min). Compared to conventional enzymatic cell detachment, hADSCs cultured on and detached from a CDP-coated cell culture dish showed similar cellular properties. We further performed in vivo experiments on a mouse hindlimb ischemia model (1.0 × 106 cells per limb). The in vivo results indicated that hADSCs retrieved from normal cell culture dishes and CDP-coated cell culture dishes showed analogous therapeutic angiogenesis. In conclusion, CDP could be applied to a pH-responsive cell detachment system as a simple and easy nonenzymatic method for stem cell culture and various cell therapies.

Magnetically Assisted Control of Stem Cells Applied in 2D, 3D and In Situ Models of Cell Migration

The success of cell therapy approaches is greatly dependent on the ability to precisely deliver and monitor transplanted stem cell grafts at treated sites. Iron oxide particles, traditionally used in vivo for magnetic resonance imaging (MRI), have been shown to also represent a safe and efficient in vitro labelling agent for mesenchymal stem cells (MSCs). Here, stem cells were labelled with magnetic particles, and their resulting response to magnetic forces was studied using 2D and 3D models. Labelled cells exhibited magnetic responsiveness, which promoted localised retention and patterned cell seeding when exposed to magnet arrangements in vitro. Directed migration was observed in 2D culture when adherent cells were exposed to a magnetic field, and also when cells were seeded into a 3D gel. Finally, a model of cell injection into the rodent leg was used to test the enhanced localised retention of labelled stem cells when applying magnetic forces, using whole body imaging to confirm the potential use of magnetic particles in strategies seeking to better control cell distribution for in vivo cell delivery.

The Evolution of Polystyrene as a Cell Culture Material

Polystyrene (PS) has brought in vitro cell culture from its humble beginnings to the modern era, propelling dozens of research fields along the way. This review discusses the development of the material, fabrication, and treatment approaches to create the culture material. However, native PS surfaces poorly facilitate cell adhesion and growth in vitro. To overcome this, liquid surface deposition, energetic plasma activation, and emerging functionalization methods transform the surface chemistry. This review seeks to highlight the many potential applications of the first widely accepted polymer growth surface. Although the majority of in vitro research occurs on two-dimensional surfaces, the importance of three-dimensional (3D) culture models cannot be overlooked. The methods to transition PS to specialized 3D culture surfaces are also reviewed. Specifically, casting, electrospinning, 3D printing, and microcarrier approaches to shift PS to a 3D culture surface are highlighted. The breadth of applications of the material makes it impossible to highlight every use, but the aim remains to demonstrate the versatility and potential as both a general and custom cell culture surface. The review concludes with emerging scaffolding approaches and, based on the findings, presents our insights on the future steps for PS as a tissue culture platform.

Mesenchymal Stromal Cells: From Discovery to Manufacturing and Commercialization

Over the last decades, mesenchymal stromal cells (MSC) have been the focus of intense research by academia and industry due to their unique features. MSC can be easily isolated and expanded through in vitro culture by taking full advantage of their self-renewing capacity. In addition, MSC exert immunomodulatory effects and can be differentiated into various lineages, which makes them highly attractive for clinical applications in cell-based therapies. In this review, we attempt to provide a brief historical overview of MSC discovery, characterization, and the first clinical studies conducted. The current MSC manufacturing platforms are reviewed with special attention regarding the use of bioreactors for the production of GMP-compliant clinically relevant cell numbers. The first commercial MSC-based products are also addressed, as well as the remaining challenges to the widespread use of MSC-derived products.

Three-Dimensional Bioreactor Technologies for the Cocultivation of Human Mesenchymal Stem/Stromal Cells and Beta Cells

Diabetes is a prominent health problem caused by the failure of pancreatic beta cells. One therapeutic approach is the transplantation of functional beta cells, but it is difficult to generate sufficient beta cells in vitro and to ensure these cells remain viable at the transplantation site. Beta cells suffer from hypoxia, undergo apoptosis, or are attacked by the host immune system. Human mesenchymal stem/stromal cells (hMSCs) can improve the functionality and survival of beta cells in vivo and in vitro due to direct cell contact or the secretion of trophic factors. Current cocultivation concepts with beta cells are simple and cannot exploit the favorable properties of hMSCs. Beta cells need a three-dimensional (3D) environment to function correctly, and the cocultivation setup is therefore more complex. This review discusses 3D cultivation forms (aggregates, capsules, and carriers) for hMSCs and beta cells and strategies for large-scale cultivation. We have determined process parameters that must be balanced and considered for the cocultivation of hMSCs and beta cells, and we present several bioreactor setups that are suitable for such an innovative cocultivation approach. Bioprocess engineering of the cocultivation processes is necessary to achieve successful beta cell therapy.

Attachment, Growth, and Detachment of Human Mesenchymal Stem Cells in a Chemically Defined Medium

The manufacture of human mesenchymal stem cells (hMSCs) for clinical applications requires an appropriate growth surface and an optimized, preferably chemically defined medium (CDM) for expansion. We investigated a new protein/peptide-free CDM that supports the adhesion, growth, and detachment of an immortalized hMSC line (hMSC-TERT) as well as primary cells derived from bone marrow (bm-hMSCs) and adipose tissue (ad-hMSCs). We observed the rapid attachment and spreading of hMSC-TERT cells and ad-hMSCs in CDM concomitant with the expression of integrin and actin fibers. Cell spreading was promoted by coating the growth surface with collagen type IV and fibronectin. The growth of hMSC-TERT cells was similar in CDM and serum-containing medium whereas the lag phase of bm-hMSCs was prolonged in CDM. FGF-2 or surface coating with collagen type IV promoted the growth of bm-hMSCs, but laminin had no effect. All three cell types retained their trilineage differentiation capability in CDM and were detached by several enzymes (but not collagenase in the case of hMSC-TERT cells). The medium and coating did not affect detachment efficiency but influenced cell survival after detachment. CDM combined with cell-specific surface coatings and/or FGF-2 supplements is therefore as effective as serum-containing medium for the manufacture of different hMSC types.

Bioreactor expansion of human mesenchymal stem cells according to GMP requirements

In cell therapy, the use of autologous and allogenic human mesenchymal stem cells is rising. Accordingly, the supply of cells for clinical applications in highest quality is required. As hMSCs are considered as an advanced therapy medicinal products (ATMP), they underlie the requirements of GMP and PAT according to the authorities (FDA and EMA). The production process of these cells must therefore be documented according to GMP, which is usually performed via a GMP protocol based on standard operating procedures. This chapter provides an example of such a GMP protocol for hMSC, here a genetically modified allogenic cell line, based on a production process in a microcarrier-based stirred tank reactor including process monitoring according to PAT and final product quality assurance.