Influence of Microenvironment on Mesenchymal Stem Cell Therapeutic Potency: From Planar Culture to Microcarriers

Continuous collection of human mesenchymal-stromal-cell-derived extracellular vesicles from a stirred tank reactor operated under xenogeneic-free conditions for therapeutic applications

BACKGROUND

Mesenchymal-stromal-cell-derived extracellular vesicles (MSC-EVs) play a key role in the paracrine effects of MSC and have demonstrated therapeutic potential in various preclinical models. However, clinical translation is hindered by manufacturing practices relying on planar culture systems, fetal bovine serum (FBS)-supplemented media, and non-scalable, low-purity EV isolation methods that fail to meet dose and safety requirements, underscoring the need for innovative approaches. In this study, we developed a scalable platform to manufacture human MSC-EVs at clinically relevant numbers, integrating continuous collection of EV-enriched conditioned media (CM) using a stirred-tank reactor (STR) under xenogeneic-free conditions and a scalable downstream process.

METHODS

Wharton's jelly-derived MSC (MSC(WJ)) were expanded using microcarriers in a controlled STR using human platelet lysate (hPL)-supplemented medium. Then, a 3-day EV production stage, featuring continuous harvesting of the CM, was established using a novel serum-/xeno(geneic)-free exosome depleted-hPL supplement. For the isolation of MSC-EVs, a scalable process was implemented by pairing tangential flow filtration and anion exchange chromatography. Isolated MSC-EVs were characterised using nanoparticle tracking analysis, protein and zeta potential quantification, western blot analysis of EV protein markers, transmission electron microscopy and uptake studies of fluorescently labelled-EVs.

RESULTS

The system sustained the efficient expansion of MSC(WJ), reaching a total of (6.03 ± 0.181) x 107 cells after 7 days, which corresponds to a 30.1 ± 0.740-fold expansion. Upon a 3-day continuous CM harvesting, a total of (2.13 ± 0.301) x 1012 EVs were isolated corresponding to a particle yield factor of (1.26 ± 0.186) x 104 EVs/cell/day. MSC-EVs presented high purity levels ((5.53 ± 1.55) x 109 particles/µg), a homogeneous small size distribution (mean diameter of 115 ± 4.88 nm), a surface charge of -23.4 ± 6.23 mV, positive detection of tetraspanins CD9 and CD63 and syntenin-1 and displayed a typical cup-shaped morphology. MSC-EVs were readily incorporated by endothelial cells and two human breast cancer cell lines.

CONCLUSIONS

Overall, the scalable and Good Manufacturing Practices (GMP)-compliant platform established herein enabled the reproducible manufacturing of MSC-EVs with high purity and generally accepted characteristics concerning size, protein markers, surface charge, morphology, and cellular internalization, validating its potential for future clinical applications.

Preparation of Cell-Cultured Fish Fat via Adipogenic Transdifferentiation of Larimichthys crocea Muscle Satellite Cells

Cell-cultured fish fat (CCF) has the potential to enhance the flavor and texture of cell-cultured fish meat (CCM). Herein, CCF was developed through the adipogenic transdifferentiation of Larimichthys crocea muscle satellite cells (LCMSCs). A low-serum culture system and a large-scale culture system were established. A rapid transdifferentiation medium was also developed, and the mechanisms in promoting adipogenic transdifferentiation were preliminarily analyzed. The results indicated that the proliferation rate and morphology of cells were not significantly affected by serum reduction following domestication. These cells can be cultured in bioreactors, achieving a 10-fold increase in density. The combination of horse serum and oleic acid enabled adipogenic transdifferentiation within 8 days. Transcriptomic and metabolomic analyses revealed significant changes in gene expression and lipid metabolism, with enrichment of pathways related to fatty acid metabolism. Five inducers were quantified to assess the quality of CFF. This study provides a feasible method for CCF production and lays the theoretical basis for the development of CCM.

Silk Fibroin-Laponite Porous Microspheres as Cell Microcarriers for Osteogenic Differentiation

Silk fibroin (SF) has garnered significant attention as a natural polymer for fabricating porous scaffolds in various engineering applications. However, the limited osteoinductive property of SF has hindered its efficacy in bone repair applications. In this study, we constructed an SF-based injectable porous microcarrier that is doped with laponite (LAP), containing magnesium ions (Mg2+). The influence of freezing temperatures and concentrations of SF and LAP on the structural parameters of SF-LAP microcarriers was investigated. The SF-LAP microcarrier exhibited a porosity of 76.7 ± 1.2% and a controlled pore size of 24.6 ± 4.0 μm. At the 6 weeks of in vitro degradation test, a mild alkaline level in culture medium containing SF-LAP microcarriers was detected. The release of Mg2+ from the SF-LAP microcarrier was maintained at a concentration within the range of 1.2-2.3 mM during the 6 weeks. The seeded human adipose-derived stem cells in the SF-LAP microcarrier demonstrated a significant enhancement in osteogenic differentiation compared with cells seeded in the pure SF microcarrier, as evidenced by quantitative alkaline phosphatase activity and the expression of osteogenic marker genes. These findings underscore the potential of the SF-LAP microcarrier as an ideal cell carrier in the treatment of bone defects.

Evaluation of Biocompatible Materials for Enhanced Mesenchymal Stem Cell Expansion: Collagen-Coated Alginate Microcarriers and PLGA Nanofibers

Mesenchymal stem cells (MSCs) hold significant potential in regenerative medicine, tissue engineering, and cultivated meat production. However, large-scale MSC production is limited by their need for surface adherence during growth. This study evaluates two biocompatible materials-collagen-coated alginate microcarriers and polylactic-co-glycolic acid (PLGA) nanofibers-as novel growth substrates to enhance MSC proliferation. Physicochemical characterization confirmed successful collagen integration on both materials. In vitro, bone marrow-derived MSCs (bmMSCs) cultured on collagen-coated alginate microcarriers exhibited significantly enhanced growth compared to commercial microcarriers, while PLGA nanofibers supported bmMSC growth comparable to traditional growth surfaces. Scanning Electron Microscopy (SEM) revealed that bmMSCs adhered not only to the surface but also grew within the porous structure of the alginate microcarriers. Mycoplasma testing confirmed that the bmMSCs were free from contamination. Both materials were assessed for biocompatibility using ISO-10993 guidelines, demonstrating no skin or ocular irritation, supporting their potential for in situ applications in clinical and therapeutic settings. This study highlights the promise of collagen-coated alginate microcarriers and PLGA nanofibers for scalable MSC production, offering efficient, biocompatible alternatives to traditional growth surfaces in regenerative medicine and cultivated meat manufacturing. Future research should focus on optimizing these materials for larger-scale production and exploring specific applications in therapeutic and food sectors.

Nicotinamide adenine dinucleotide rejuvenates septic bone marrow mesenchymal stem cells

BACKGROUND

Sepsis is a severe illness characterized by systemic and multiorgan reactive responses and damage. However, the impact of sepsis on the bone marrow, particularly on bone marrow mesenchymal stem cells (BMSCs), is less reported. BMSCs are critical stromal cells in the bone marrow microenvironment that maintain bone stability and hematopoietic homeostasis; however, the impairment caused by sepsis remains unknown.

AIM

To investigate the effects of sepsis on BMSCs and the underlying mechanisms.

METHODS

BMSCs were obtained from healthy donors and patients with sepsis. We compared the self-renewal capacity, differentiation potential, and hematopoietic supportive ability in vitro. Senescence of septic BMSCs was assessed using β-galactosidase staining, senescence-associated secretory phenotype, intracellular reactive oxygen species levels, and the expression of P16 and P21. Finally, the changes in septic BMSCs after nicotinamide adenine dinucleotide (NAD) treatment were evaluated.

RESULTS

Septic BMSCs showed decreased proliferation and self-renewal, bias towards adipogenic differentiation, and weakened osteogenic differentiation. Additionally, hematopoietic supportive capacity declines in sepsis. The levels of aging markers were significantly higher in the septic BMSCs. After NAD treatment, the proliferation capacity of septic BMSCs showed a recovery trend, with increased osteogenic and hematopoietic supportive capacities. Sepsis resulted in decreased expression of sirtuin 3 (SIRT3) in BMSCs, whereas NAD treatment restored SIRT3 expression, enhanced superoxide dismutase enzyme activity, reduced intracellular reactive oxygen species levels, maintained mitochondrial stability and function, and ultimately rejuvenated septic BMSCs.

CONCLUSION

Sepsis accelerates the aging of BMSCs, as evidenced by a decline in self-renewal and osteogenic capabilities, as well as weakened hematopoietic support functions. These deficiencies can be effectively reversed via the NAD/SIRT3/superoxide dismutase pathway.

Scalable production of muscle and adipose cell-laden microtissues using edible macroporous microcarriers for 3D printing of cultured fish fillets

Cellular agriculture is a novel platform for addressing the issues of protein scarcity, environmental pressures, and food safety. However, expanding seed cells at a large scale remains a prerequisite for achieving industrial cultured meat production. We here propose the production of large-pore-sized edible porous microcarriers (EPMs) by using NaCl to precisely control ice crystal growth during cryogenic crosslinking. Muscle satellite cells (SCs) and adipose-derived stem cells (ASCs) from large yellow croakers exhibit remarkable adhesion, proliferation, and differentiation on gelatin-based EPMs. Following consecutive expansion, SCs and ASCs densities reach 6.25 × 105 and 5.77 × 105 cells/mL, leading to a 499-fold and 461-fold increase in cell numbers, respectively. Subsequently, the mature microtissues are incorporated into a bioink, thereby enabling successful three-dimensional printing of cultured fish fillets with sensory properties similar to native fish fillets. EPM-based cell expansion and food structuring techniques are promising in facilitating large-scale cultured fish meat production.

Hybrid hydrogels containing gradients in gold nanoparticles for localized delivery of mesenchymal stem cells and enhanced nerve tissues remodeling in vivo

Currently, most peripheral nerve injuries are incurable mainly due to excessive reactive oxygen species (ROS) generation in inflammatory tissues, which can further exacerbate localized tissue injury and cause chronic diseases. Although promising for promoting nerve regeneration, stem cell therapy still suffers from abundant intrinsic limitations, mainly including excessive ROS in lesions and inefficient production of growth factors (GFs). Biomaterials that scavenge endogenous ROS and promote GFs secretion might overcome such limitations and thus are being increasingly investigated. Herein, firstly reported as specific ROS scavenging agents and paracrine stimulators, gold nanoparticles (GNPs) were incorporated in the chitosan/polyvinyl alcohol hydrogel networks. The GNPs/hydrogel composite can support the survival of mesenchymal stem cells (MSCs) with excellent expansion efficiency and protect MSCs in a simulated ROS microenvironment, decreasing the intracellular ROS levels and simultaneously enhancing cell viability. Moreover, biodegradable scaffolds, along with MSCs, were implanted into sciatic nerve defects in a rat model to show good application value in vivo. Our work demonstrated that the GNPs/hydrogel shows great promise in MSCs therapy for peripheral nerve injury with convincing biological evidence.

A Simple, Cost-Effective Microfluidic Device Using a 3D Cross-Flow T-Junction for Producing Decellularized Extracellular Matrix-Derived Microcarriers

Cell therapies using human mesenchymal stromal cells (MSCs) are promising for a wide variety of clinical applications. However, broad-scale clinical translation is limited by conventional culture methods for MSC expansion within 2D tissue-culture flasks. MSC expansion on ECM-derived microcarriers within stirred bioreactor systems offers a promising approach to support MSC growth. Previously, our team established methods for fabricating ECM-derived microcarriers from a variety of decellularized tissue sources using electrospraying techniques. However, these microcarriers are relatively large and have a broad size distribution, which may limit their utility. Smaller and more uniform microcarriers may be favorable for MSC growth within bioreactors and have greater potential to serve as a minimally invasive injectable cell delivery platform. To address these limitations, the current project focused on the development of a new microfluidic-based approach enabling both uniform and small microcarrier production. Using a novel, modified 3D T-junction design, we successfully generated microcarriers using human decellularized adipose tissue (DAT) as the ECM source. Our new cost-effective device produced microbeads that were small and monodisperse, at a range of flow rate combinations and with high production rates. Photo-crosslinking using rose bengal allowed for the generation of microcarriers that retained their shape and could withstand rehydration, with a mean diameter of 196 ± 47 μm. Following methods optimization and microcarrier characterization, in vitro studies confirmed that the new microcarriers supported human adipose-derived stromal cell (hASC) attachment and growth, as well as ECM production, across 14 days within spinner flask bioreactors. Overall, this study demonstrates the feasibility of using our novel, cost-effective, and reusable microfluidics device to generate cell-supportive microcarriers comprised exclusively of ECM that show promise as an MSC expansion platform.

Cell Adhesion and Local Cytokine Control on Protein-Functionalized PNIPAM-co-AAc Hydrogel Microcarriers

Achieving adequate cell densities remains a major challenge in establishing economic biotechnological and biomedical processes. A possible remedy is microcarrier-based cultivation in stirred-tank bioreactors (STBR), which offers a high surface-to-volume ratio, appropriate process control, and scalability. However, despite their potential, commercial microcarriers are currently limited to material systems featuring unnatural mechanical properties and low adaptability. Because matrix stiffness and ligand presentation impact phenotypical attributes, differentiation potential, and genetic stability, biotechnological processes can significantly benefit from microcarrier systems tailorable toward cell-type specific requirements. This study introduces hydrogel particles co-polymerized from poly(N-isopropylacrylamide) (PNIPAM) and acrylic acid (AAc) as a platform technology for cell expansion. The resulting microcarriers exhibit an adjustable extracellular matrix-like softness, an adaptable gel charge, and functional carboxyl groups, allowing electrostatic and covalent coupling of cell adhesive and cell fate-modulating proteins. These features enable the attachment and growth of L929 mouse fibroblast cells in static microtiter plates and dynamic STBR cultivations while also providing vital growth factors, such as interleukin-3, to myeloblast-like 32D cells over 20 days of cultivation. The study explores the effects of different educt compositions on cell-particle interactions and reveals that PNIPAM-co-AAc microcarriers can provide both covalently coupled and diffusively released cytokine to adjacent cells.

Dual production of human mesenchymal stromal cells and derived extracellular vesicles in a dissolvable microcarrier-based stirred culture system

BACKGROUND & AIMS

Cell therapies based on mesenchymal stromal cells (MSCs) have gained an increasing therapeutic interest in the context of multiple disorders. Nonetheless, this field still faces important challenges, particularly concerning suitable manufacturing platforms. Here, we aimed at establishing a scalable culture system to expand umbilical cord-derived Wharton's jelly MSC (MSC(WJ)) and their derived extracellular vesicles (EVs) by using dissolvable microcarriers combined with xeno(geneic)-free culture medium.

METHODS

MSC(WJ) isolated from three donors were cultured at a starting density of 1 × 106 cells per spinner flask, i.e., 2.8 × 103 cells per cm2 of dissolvable microcarrier surface area. After a 6-day expansion period of MSC(WJ), extracellular vesicles (EVs) were produced for 24 h.

RESULTS

Taking advantage of an intermittent agitation regimen, we observed high adhesion rates to the microcarriers (over 90% at 24 h) and achieved 15.8 ± 0.7-fold expansion after 6 days of culture. Notably, dissolution of the microcarriers was achieved through a pectinase-based solution to recover the cell product, reducing the hurdles of downstream processing. MSC identity was validated by detecting the characteristic MSC immunophenotype and by multilineage differentiation assays. Considering the growing interest in MSC-derived EVs, which are known to be mediators of the therapeutic features of MSC, this platform also was evaluated for EV production. Upon a 24-h period of conditioning, secreted EVs were isolated by ultrafiltration followed by anion-exchange chromatography and exhibited the typical cup-shaped morphology, small size distribution (162.6 ± 30.2 nm) and expressed EV markers (CD63, CD9 and syntenin-1).

CONCLUSIONS

Taken together, we established a time-effective and robust scalable platform that complies with clinical-grade standards for the dual production of MSC(WJ) and their derived EV.

High throughput screening of mesenchymal stromal cell morphological response to inflammatory signals for bioreactor-based manufacturing of extracellular vesicles that modulate microglia

Due to their immunomodulatory function, mesenchymal stromal cells (MSCs) are a promising therapeutic with the potential to treat neuroinflammation associated with neurodegenerative diseases. This function is mediated by secreted extracellular vesicles (MSC-EVs). Despite established safety, MSC clinical translation has been unsuccessful due to inconsistent clinical outcomes resulting from functional heterogeneity. Current approaches to mitigate functional heterogeneity include 'priming' MSCs with inflammatory signals to enhance function. However, comprehensive evaluation of priming and its effects on MSC-EV function has not been performed. Furthermore, clinical translation of MSC-EV therapies requires significant manufacturing scale-up, yet few studies have investigated the effects of priming in bioreactors. As MSC morphology has been shown to predict their immunomodulatory function, we screened MSC morphological response to an array of priming signals and evaluated MSC-EV identity and potency in response to priming in flasks and bioreactors. We identified unique priming conditions corresponding to distinct morphologies. These conditions demonstrated a range of MSC-EV preparation quality and lipidome, allowing us to discover a novel MSC-EV manufacturing condition, as well as gain insight into potential mechanisms of MSC-EV microglia modulation. Our novel screening approach and application of priming to MSC-EV bioreactor manufacturing informs refinement of larger-scale manufacturing and enhancement of MSC-EV function.

Microenvironmental interference with intra-articular stem cell regeneration influences the onset and progression of arthritis

Studies have indicated that the preservation of joint health and the facilitation of damage recovery are predominantly contingent upon the joint's microenvironment, including cell-cell interactions, the extracellular matrix's composition, and the existence of local growth factors. Mesenchymal stem cells (MSCs), which possess the capacity to self-renew and specialize in many directions, respond to cues from the microenvironment, and aid in the regeneration of bone and cartilage, are crucial to this process. Changes in the microenvironment (such as an increase in inflammatory mediators or the breakdown of the extracellular matrix) in the pathological context of arthritis might interfere with stem cell activation and reduce their ability to regenerate. This paper investigates the potential role of joint microenvironmental variables in promoting or inhibiting the development of arthritis by influencing stem cells' ability to regenerate. The present status of research on stem cell activity in the joint microenvironment is also outlined, and potential directions for developing new treatments for arthritis that make use of these intervention techniques to boost stem cell regenerative potential through altering the intra-articular environment are also investigated. This review's objectives are to investigate these processes, offer fresh perspectives, and offer a solid scientific foundation for the creation of arthritic treatment plans in the future.

Extracellular Vesicles Generated by Mesenchymal Stem Cells in Stirred Suspension Bioreactors Promote Angiogenesis in Human-Brain-Derived Endothelial Cells

Interrupted blood flow in the brain due to ischemic injuries such as ischemic stroke or traumatic brain injury results in irreversible brain damage, leading to cognitive impairment associated with inflammation, disruption of the blood-brain barrier (BBB), and cell death. Since the BBB only allows entry to a small class of drugs, many drugs used to treat ischemia in other tissues have failed in brain-related disorders. The administration of mesenchymal stem cell (MSC)-derived extracellular vesicles (EVs) has shown promise in improving the functional recovery of the brain following cerebral ischemia by inducing blood vessel formation. To facilitate such a treatment approach, it is necessary to develop bioprocesses that can produce therapeutically relevant MSC-EVs in a reproducible and scalable manner. This study evaluated the feasibility of using stirred suspension bioreactors (SSBs) to scale-up the serum-free production of pro-angiogenic MSC-EVs under clinically relevant physioxic conditions. It was found that MSCs grown in SSBs generated EVs that stimulated angiogenesis in cerebral microvascular endothelial cells, supporting the use of SSBs to produce MSC-EVs for application in cerebral ischemia. These properties were impaired at higher cell confluency, outlining the importance of considering the time of harvest when developing bioprocesses to manufacture EV populations.

Probiotic cultivated meat: bacterial-based scaffolds and products to improve cultivated meat

Cultivated meat is emerging to replace traditional livestock industries, which have ecological costs, including land and water overuse and considerable carbon emissions. During cultivated meat production, mammalian cells can increase their numbers dramatically through self-renewal/proliferation and transform into mature cells, such as muscle or fat cells, through maturation/differentiation. Here, we address opportunities for introducing probiotic bacteria into the cultivated meat industry, including using them to produce renewable antimicrobials and scaffolding materials. We also offer solutions to challenges, including the growth of bacteria and mammalian cells, the effect of probiotic bacteria on production costs, and the effect of bacteria and their products on texture and taste. Our summary provides a promising framework for applying microbial composites in the cultivated meat industry.

Identification of critical process parameters for expansion of clinical grade human Wharton's jelly-derived mesenchymal stromal cells in stirred-tank bioreactors

Cell therapies based on multipotent mesenchymal stromal cells (MSCs) are traditionally produced using 2D culture systems and platelet lysate- or serum-containing media (SCM). Although cost-effective for single-dose autologous treatments, this approach is not suitable for larger scale manufacturing (e.g., multiple-dose autologous or allogeneic therapies with banked MSCs); automated, scalable and Good Manufacturing Practices (GMP)-compliant platforms are urgently needed. The feasibility of transitioning was evaluated from an established Wharton's jelly MSCs (WJ-MSCs) 2D production strategy to a new one with stirred-tank bioreactors (STRs). Experimental conditions included four GMP-compliant xeno- and serum-free media (XSFM) screened in 2D conditions and two GMP-grade microcarriers assessed in 0.25 L-STRs using SCM. From the screening, a XSFM was selected and compared against SCM using the best-performing microcarrier. It was observed that SCM outperformed the 2D-selected medium in STRs, reinforcing the importance of 2D-to-3D transition studies before translation into clinical production settings. It was also found that attachment efficiency and microcarrier colonization were essential to attain higher fold expansions, and were therefore defined as critical process parameters. Nevertheless, WJ-MSCs were readily expanded in STRs with both media, preserving critical quality attributes in terms of identity, viability and differentiation potency, and yielding up to 1.47 × 109 cells in a real-scale 2.4-L batch.

Cell culture design for homogeneous proliferation of cells in three-dimensional nonwoven polymer scaffolds

The objective of this study is to establish strategies to uniformly proliferate cells in a three-dimensional nonwoven polyethylene terephthalate (PET)/ethylene vinyl alcohol (EVOH) scaffold by simple adjustments in seeding and culture methods and the scaffold design. The combined dynamic and static seeding (intermittent agitations at 300 rpm with 1 h interval) resulted in the highest seeding efficiency (71%) comparing to the static and continuous agitating seeding methods. Cell-attached scaffolds were cultivated under different conditions. The stirring culture permitted cells to proliferate to a significantly greater extent than the static or agitating cultures, although faster cell proliferation in the outer region of the scaffold was observed. Next, based on this observation, scaffolds were opened with holes to alleviate the cell aggregation. The effect of hole size and number of scaffolds on the distribution of cells proliferated in the scaffold was evaluated. Two of 1-mm holes showed to be an optimal adjustment to allow cells to proliferate in a homogeneous manner. After 14 days culture, both of the holes were filled by cells proliferated with a fourfold increase in the cell number. The cell viability in the scaffolds was also high upon evaluating the live/dead and 3[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) staining examinations. Different cell types of 3T3-L1, C3H/10T1/2, and KUM6 cells showed similar behavior of cell proliferation and distribution in the scaffold, indicating the applicability of the established procedure. It is concluded that the nonwoven PET/EVOH scaffold serves as a potential cell culture substrate for an efficient cell proliferation.

High throughput screening of mesenchymal stromal cell morphological response to inflammatory signals for bioreactor-based manufacturing of extracellular vesicles that modulate microglia

Due to their immunomodulatory function, mesenchymal stromal cells (MSCs) are a promising therapeutic with the potential to treat neuroinflammation associated with neurodegenerative diseases. This function can be mediated by secreted extracellular vesicles (MSC-EVs). Despite established safety, MSC clinical translation has been unsuccessful due to inconsistent clinical outcomes resulting from functional heterogeneity. Current approaches to mitigate functional heterogeneity include 'priming' MSCs with inflammatory signals to enhance function. However, comprehensive evaluation of priming and its effects on MSC-EV function has not been performed. Clinical translation of MSC-EV therapies requires significant manufacturing scale-up, yet few studies have investigated the effects of priming in bioreactors. As MSC morphology has been shown to predict their immunomodulatory function, we screened MSC morphological response to an array of priming signals and evaluated MSC-EV identity and potency in response to priming in flasks and bioreactors. We identified unique priming conditions corresponding to distinct morphologies. These conditions demonstrated a range of MSC-EV preparation quality and lipidome, allowing us to discover a novel MSC-EV manufacturing condition, as well as gain insight into potential mechanisms of MSC-EV microglia modulation. Our novel screening approach and application of priming to MSC-EV bioreactor manufacturing informs refinement of larger-scale manufacturing and enhancement of MSC-EV function.

Poly(ethylene glycol)-Based Hydrogel Microcarriers Alter Secretory Activity of Genetically Modified Mesenchymal Stromal Cells

In order to scale up culture therapeutic cells, such as mesenchymal stromal cells (MSCs), culture in suspension bioreactors using microcarriers (μCs) is preferred. However, the impact of microcarrier type on the resulting MSC secretory activity has not been investigated. In this study, two poly(ethylene glycol) hydrogel formulations with different swelling ratios (named "stiffer" and "softer") were fabricated as μC substrates to culture MSCs and MSCs genetically modified to express the interleukin-1 receptor antagonist (IL-1Ra-MSCs). Changes in cell number, secretory and angiogenic activity, and changes in MAPK signaling were evaluated when cultured on hydrogel μCs, as well as on tissue culture plastic-based Synthemax μCs. We demonstrated that culture on stiffer μCs increased secretion of IL-1Ra compared to culture on Synthemax μCs by IL-1Ra-MSCs by 1.2- to 1.6-fold, as well as their in vitro angiogenic activity, compared to culture on Synthemax μCs, while culture on both stiffer and softer μCs altered the secretion of several other factors compared to culture on Synthemax μCs. Changes in angiogenic activity corresponded with increased gene expression and secretion of hepatocyte growth factor by MSCs cultured on softer μCs by 2.5- to 6-fold compared to MSCs cultured on Synthemax μCs. Quantification of phosphoprotein signaling with the MAPK pathway revealed broad reduction of pathway activation by IL-1Ra-MSCs cultured on both stiffer and softer μCs compared to Synthemax, where phosphorylated c-Jun, ATF2, and MEK1 were reduced specifically on softer μCs. Overall, this study showed that μC surfaces can influence the secretory activity of genetically modified MSCs and identified associated changes in MAPK pathway signaling, which is a known central regulator of cytokine secretion.

Efficient expansion and delayed senescence of hUC-MSCs by microcarrier-bioreactor system

BACKGROUND

Human umbilical cord mesenchymal stem cells (hUC-MSCs) are widely used in cell therapy due to their robust immunomodulatory and tissue regenerative capabilities. Currently, the predominant method for obtaining hUC-MSCs for clinical use is through planar culture expansion, which presents several limitations. Specifically, continuous cell passaging can lead to cellular aging, susceptibility to contamination, and an absence of process monitoring and control, among other limitations. To overcome these challenges, the technology of microcarrier-bioreactor culture was developed with the aim of ensuring the therapeutic efficacy of cells while enabling large-scale expansion to meet clinical requirements. However, there is still a knowledge gap regarding the comparison of biological differences in cells obtained through different culture methods.

METHODS

We developed a culture process for hUC-MSCs using self-made microcarrier and stirred bioreactor. This study systematically compares the biological properties of hUC-MSCs amplified through planar culture and microcarrier-bioreactor systems. Additionally, RNA-seq was employed to compare the differences in gene expression profiles between the two cultures, facilitating the identification of pathways and genes associated with cell aging.

RESULTS

The findings revealed that hUC-MSCs expanded on microcarriers exhibited a lower degree of cellular aging compared to those expanded through planar culture. Additionally, these microcarrier-expanded hUC-MSCs showed an enhanced proliferation capacity and a reduced number of cells in the cell cycle retardation period. Moreover, bioreactor-cultured cells differ significantly from planar cultures in the expression of genes associated with the cytoskeleton and extracellular matrix.

CONCLUSIONS

The results of this study demonstrate that our microcarrier-bioreactor culture method enhances the proliferation efficiency of hUC-MSCs. Moreover, this culture method exhibits the potential to delay the process of cell aging while preserving the essential stem cell properties of hUC-MSCs.

Osteogenic microenvironment affects palatal development through glycolysis

Palate development involves various events, including proliferation, osteogenic differentiation, and epithelial-mesenchymal transition. Disruption of these processes can result in the cleft palate (CP). Mouse embryonic palatal mesenchyme (MEPM) cells are commonly used to explore the mechanism of palatal development and CP. However, the role of the microenvironment in the biological properties of MEPM cells, which undergoes dynamic changes during palate development, is rarely reported. In this study, we investigated whether there were differences between the palatal shelf mesenchyme at different developmental stages. Our results found that the palatal shelves facilitate proliferation at the early palate stage at mouse embryonic day (E) 13.5 and the tendency towards osteogenesis at E15.5, the late palate development stage. And the osteogenic microenvironment, which was mimicked by osteogenic differentiation medium (OIM), affected the biological properties of MEPM cells when compared to the routine medium. Specifically, MEPM cells showed slower proliferation, shorter S phase, increased apoptosis, and less migration distance after osteogenesis. E15.5 MEPM cells were more sensitive than E13.5, showing an earlier change. Moreover, E13.5 MEPM cells had weaker osteogenic ability than E15.5, and both MEPM cells exhibited different Lactate dehydrogenase A (LDHA) and Cytochrome c (CytC) expressions in OIM compared to routine medium, suggesting that glycolysis might be associated with the influence of the osteogenic microenvironment on MEPM cells. By comparing the stemness of the two cells, we investigated that the stemness of E13.5 MEPM cells was stronger than that of E15.5 MEPM cells, and E15.5 MEPM cells were more like differentiated cells than stem cells, as their capacity to differentiate into multiple cell fates was reduced. E13.5 MEPM cells might be the precursor cells of E15.5 MEPM cells. Our results enriched the understanding of the effect of the microenvironment on the biological properties of E13.5 and E15.5 MEPM cells, which should be considered when using MEPM cells as a model for palatal studies in the future.

Scalable manufacturing of gene-modified human mesenchymal stromal cells with microcarriers in spinner flasks

Due to their immunomodulatory properties and in vitro differentiation ability, human mesenchymal stromal cells (hMSCs) have been investigated in more than 1000 clinical trials over the last decade. Multiple studies that have explored the development of gene-modified hMSC-based products are now reaching early stages of clinical trial programmes. From an engineering perspective, the challenge lies in developing manufacturing methods capable of producing sufficient doses of ex vivo gene-modified hMSCs for clinical applications. This work demonstrates, for the first time, a scalable manufacturing process using a microcarrier-bioreactor system for the expansion of gene-modified hMSCs. Upon isolation, umbilical cord tissue mesenchymal stromal cells (UCT-hMSCs) were transduced using a lentiviral vector (LV) with green fluorescent protein (GFP) or vascular endothelial growth factor (VEGF) transgenes. The cells were then seeded in 100 mL spinner flasks using Spherecol microcarriers and expanded for seven days. After six days in culture, both non-transduced and transduced cell populations attained comparable maximum cell concentrations (≈1.8 × 105 cell/mL). Analysis of the culture supernatant identified that glucose was fully depleted after day five across the cell populations. Lactate concentrations observed throughout the culture reached a maximum of 7.5 mM on day seven. Immunophenotype analysis revealed that the transduction followed by an expansion step was not responsible for the downregulation of the cell surface receptors used to identify hMSCs. The levels of CD73, CD90, and CD105 expressing cells were above 90% for the non-transduced and transduced cells. In addition, the expression of negative markers (CD11b, CD19, CD34, CD45, and HLA-DR) was also shown to be below 5%, which is aligned with the criteria established for hMSCs by the International Society for Cell and Gene Therapy (ISCT). This work provides a foundation for the scalable manufacturing of gene-modified hMSCs which will overcome a significant translational and commercial bottleneck. KEY POINTS: • hMSCs were successfully transduced by lentiviral vectors carrying two different transgenes: GFP and VEGF • Transduced hMSCs were successfully expanded on microcarriers using spinner flasks during a period of 7 days • The genetic modification step did not cause any detrimental impact on the hMSC immunophenotype characteristics.

Are genetic drift and stem cell adherence in laboratory culture issues for cultivated meat production?

Mesenchymal stem cell-based cultivated meat is a promising solution to the ecological and ethical problems posed by traditional meat production, since it exhibits a protein content and composition that is more comparable to original meat proteins than any other source of cultivated meat products, including plants, bacteria, and fungi. Nonetheless, the nature and laboratory behavior of mesenchymal stem cells pose two significant challenges for large-scale production: genetic drift and adherent growth in culture. Culture conditions used in the laboratory expose the cells to a selective pressure that causes genetic drift, which may give rise to oncogene activation and the loss of "stemness." This is why genetic and functional analysis of the cells during culture is required to determine the maximum number of passages within the laboratory where no significant mutations or loss of function are detected. Moreover, the adherent growth of mesenchymal stem cells can be an obstacle for their large-scale production since volume to surface ratio is limited for high volume containers. Multi-tray systems, roller bottles, and microcarriers have been proposed as potential solutions to scale-up the production of adherent cells required for cultivated meat. The most promising solutions for the safety problems and large-scale obstacles for cultivated meat production are the determination of a limit number of passages based on a genetic analysis and the use of microcarriers from edible materials to maximize the volume to surface proportion and decrease the downstream operations needed for cultivated meat production.

Comparison of Cost and Potency of Human Mesenchymal Stromal Cell Conditioned Medium Derived from 2- and 3-Dimensional Cultures

Mesenchymal stromal cell (MSC)-derived products, such as trophic factors (MTFs), have anti-inflammatory properties that make them attractive for cell-free treatment. Three-dimensional (3D) culture can enhance these properties, and large-scale expansion using a bioreactor can reduce manufacturing costs. Three lots of MTFs were obtained from umbilical cord MSCs produced by either monolayer culture (Monol MTF) or using a 3D microcarrier in a spinner flask dynamic system (Bioreactor MTF). The resulting MTFs were tested and compared using anti-inflammatory potency assays in two different systems: (1) a phytohemagglutinin-activated peripheral blood mononuclear cell (PBMNC) system and (2) a lipopolysaccharide (LPS)-activated macrophage system. Cytokine expression by macrophages was measured via RT-PCR. The production costs of hypothetical units of anti-inflammatory effects were calculated using the percentage of TNF-α inhibition by MTF exposure. Bioreactor MTFs had a higher inhibitory effect on TNF (p < 0.01) than monolayer MTFs (p < 0.05). The anti-inflammatory effect of Bioreactor MTFs on IL-1β, TNF-α, IL-8, IL-6, and MIP-1 was significantly higher than that of monolayer MTFs. The production cost of 1% inhibition of TNF-α was 11-40% higher using monolayer culture compared to bioreactor-derived MTFs. A 3D dynamic culture was, therefore, able to produce high-quality MTFs, with robust anti-inflammatory properties, more efficiently than monolayer static systems.

Cultured meat platform developed through the structuring of edible microcarrier-derived microtissues with oleogel-based fat substitute

With the increasing global demand for meat, cultured meat technologies are emerging, offering more sustainable solutions that aim to evade a future shortage of meat. Here, we demonstrate a cultured meat platform composed of edible microcarriers and an oleogel-based fat substitute. Scalable expansion of bovine mesenchymal stem cells on edible chitosan-collagen microcarriers is optimized to generate cellularized microtissues. In parallel, an oleogel system incorporated with plant protein is developed as a fat substitute, which is comparable to beef fat in appearance and texture. Combining the cellularized microtissues with the developed fat substitute, two types of cultured meat prototypes are introduced: layered cultured meat and burger-like cultured meat. While the layered prototype benefits enhanced stiffness, the burger-like prototype has a marbling meat-like appearance and a softer texture. Overall, this platform and the established technological basis may contribute to the development of different cultured meat products and promote their commercial production.

Synergetic effect of 3D porous microsphere structure and activation of adenosine A2B receptor signal on promoting osteogenic differentiation of BMSCs

Biodegradable microspheres offer great potential as functional building blocks for bottom-up bone tissue engineering. However, it remains challenging to understand and regulate cell behaviors in fabrication of injectable bone microtissues using microspheres. The study aims to develop an adenosine functionalized poly (lactide-co-glycolide) (PLGA) microsphere to enhance cell loading efficiency and inductive osteogenesis potential, and subsequently to investigate adenosine signaling-mediated osteogenic differentiation in cells grown on three-dimensional (3D) microspheres and flat control. Adenosine was loaded on PLGA porous microspheres via polydopamine coating, and the cell adhesion and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) were improved on these microspheres. It was found that adenosine A2B receptor (A2BR) was further activated by adenosine treatment, which consequently enhanced osteogenic differentiation of BMSCs. This effect was more obvious on 3D microspheres compared to 2D flats. However, the promotion of osteogenesis on the 3D microspheres was not eliminated by blocking the A2BR with antagonist. Finally, adenosine functionalized microspheres could fabricate injectable microtissues in vitro, and improve cell delivery and osteogenic differentiation after injection in vivo. Therefore, it is considered that adenosine loaded PLGA porous microspheres will be of good value in minimally invasive injection surgery and bone tissue repair.

The role of biomechanical stress in extracellular vesicle formation, composition and activity

Extracellular vesicles (EVs) are cornerstones of intercellular communication with exciting fundamental, clinical, and more broadly biotechnological applications. However, variability in EV composition, which results from the culture conditions used to generate the EVs, poses significant fundamental and applied challenges and a hurdle for scalable bioprocessing. Thus, an understanding of the relationship between EV production (and for clinical applications, manufacturing) and EV composition is increasingly recognized as important and necessary. While chemical stimulation and culture conditions such as cell density are known to influence EV biology, the impact of biomechanical forces on the generation, properties, and biological activity of EVs remains poorly understood. Given the omnipresence of these forces in EV preparation and in biomanufacturing, expanding the understanding of their impact on EV composition-and thus, activity-is vital. Although several publications have examined EV preparation and bioprocessing and briefly discussed biomechanical stresses as variables of interest, this review represents the first comprehensive evaluation of the impact of such stresses on EV production, composition and biological activity. We review how EV biogenesis, cargo, efficacy, and uptake are uniquely affected by various types, magnitudes, and durations of biomechanical forces, identifying trends that emerge both generically and for individual cell types. We also describe implications for scalable bioprocessing, evaluating processes inherent in common EV production and isolation methods, and propose a path forward for rigorous EV quality control.

Biomanufacturing Recombinantly Expressed Cripto-1 Protein in Anchorage-Dependent Mammalian Cells Growing in Suspension Bioreactors within a Three-Dimensional Hydrogel Microcarrier

Biotherapeutic soluble proteins that are recombinantly expressed in mammalian cells can pose a challenge when biomanufacturing in three-dimensional (3D) suspension culture systems. Herein, we tested a 3D hydrogel microcarrier for a suspension culture of HEK293 cells overexpressing recombinant Cripto-1 protein. Cripto-1 is an extracellular protein that is involved in developmental processes and has recently been reported to have therapeutic effects in alleviating muscle injury and diseases by regulating muscle regeneration through satellite cell progression toward the myogenic lineage. Cripto-overexpressing HEK293 cell lines were cultured in microcarriers made from poly (ethylene glycol)-fibrinogen (PF) hydrogels, which provided the 3D substrate for cell growth and protein production in stirred bioreactors. The PF microcarriers were designed with sufficient strength to resist hydrodynamic deterioration and biodegradation associated with suspension culture in stirred bioreactors for up to 21 days. The yield of purified Cripto-1 obtained using the 3D PF microcarriers was significantly higher than that obtained with a two-dimensional (2D) culture system. The bioactivity of the 3D-produced Cripto-1 was equivalent to commercially available Cripto-1 in terms of an ELISA binding assay, a muscle cell proliferation assay, and a myogenic differentiation assay. Taken together, these data indicate that 3D microcarriers made from PF can be combined with mammalian cell expression systems to improve the biomanufacturing of protein-based therapeutics for muscle injuries.

The Evolving Landscape of Potency Assays

There is a "goldilocks" aspect to potency assays. On the one hand, a comprehensive evaluation of the cell product with detailed quantitative measurement of the critical quality attribute/s of the desired biological activity is required. On the other hand, the potency assay benefits from simplification and lean approaches that avoid unnecessary complication and enhance robustness, to provide a reproducible and scalable product. There is a need to balance insightful knowledge of complex biological healing processes with straightforward manufacture of an advanced therapeutic medicinal product (ATMP) that can be administered in a trustworthy cost-effective manner. While earlier chapters within this book have highlighted numerous challenges facing the potency assay conundrum, this chapter offers a forward-looking perspective regarding the many recent advances concerning acellular products, cryopreservation, induced MSC, cell priming, nanotechnology, 3D culture, regulatory guidelines and evolving institutional roles, that are likely to facilitate potency assay development in the future.

Defect-adaptive Stem-cell-microcarrier Construct Promotes Tissue Repair in Rabbits with Knee Cartilage Defects

Although various reconstruction techniques are available for cartilage defects, the repair effects and conveniences remain to be further improved due to the limited regenerative capacity of cartilaginous tissues and difficulties in seamlessly fulfilling irregularly shaped defects. In the current study, we explored the repair efficacy of stem cell microcarrier construct (microcarriers loaded with human chondrogenic progenitor cells or bone marrow mesenchymal stem cells) in cartilage defect models. A total of 39 healthy New Zealand white rabbits were included, and femoral trochlear cartilage defect models were established (n = 33). Stem cell microcarrier constructs were implanted into cartilage defects (n = 6), the maintenance conditions of the implanted constructs were observed on days 4, 8, and 30 post implantation (n = 3). Gross observation and pathological analysis were performed to assay the reconstitution of cartilage defects at 12 weeks post-cartilage defect repair(n = 6). The microcarriers could fill the defect model with good plasticity to integrate well with the boundary native normal cartilage. At 3 months after implantation, the defects were filled with fibrous cartilage tissues in the microcarrier without stem cells group. In the microcarrier loaded with BMSCs group, newly formed tissue with a similar appearance of boundary cartilage fulfilled the defects, but the surface was not completely smooth. Promisingly, the defects were almost completely filled with newly regenerated cartilaginous tissues, which had a smooth appearance similar to that of normal cartilage in the microcarrier loaded with CPCs group. These results suggest the feasibility of stem cell microcarrier construct in repairing cartilage defects, indicating promising clinical application prospects.

Crosslinker structure modulates bulk mechanical properties and dictates hMSC behavior on hyaluronic acid hydrogels

Synthetic hydrogels are attractive platforms due in part to their highly tunable mechanics, which impact cell behavior and secretory profile. These mechanics are often controlled by altering the number of crosslinks or the total polymer concentration in the gel, leading to structure-property relationships that inherently couple network connectivity to the overall modulus. In contrast, the native extracellular matrix (ECM) contains structured biopolymers that enable stiff gels even at low polymer content, facilitating 3D cell culture and permeability of soluble factors. To mimic the hierarchical order of natural ECM, this work describes a synthetic hydrogel system in which mechanics are tuned using the structure of sequence-defined peptoid crosslinkers, while fixing network connectivity. Peptoid crosslinkers with different secondary structures are investigated: 1) a helical, molecularly stiff peptoid, 2) a non-helical, less stiff peptoid, and 3) an unstructured, relatively flexible peptoid. Bulk hydrogel storage modulus increases when crosslinkers of higher chain stiffness are used. In-vitro studies assess the viability, proliferation, cell morphology, and immunomodulatory activity of human mesenchymal stem cells (hMSCs) on each hydrogel substrate. Matrix mechanics regulate the morphology of hMSCs on the developed substrates, and all of the hydrogels studied upregulate IDO production over culture on TCP. Softer substrates further this upregulation to a plateau. Overall, this system offers a biomimetic strategy for decoupling hydrogel storage modulus from network connectivity, enabling systematic study of biomaterial properties on hMSC behavior and enhancement of cellular functionality for therapeutic applications. STATEMENT OF SIGNIFICANCE: Various strategies to tune hydrogel mechanics have been developed to control human mesenchymal stem cell (hMSC) behavior and regulate their immunomodulatory potential. However, these strategies typically couple mechanics to network connectivity, which in turn changes other hydrogel properties such as permeability that may have unintended effects on hMSC behavior. This work presents a strategy to tune hydrogel mechanics using crosslinkers with different secondary structure and molecular rigidity. This strategy successfully decouples hydrogel moduli from crosslinker stoichiometry and mimics the hierarchical nature of the native extracellular matrix. The moduli of the developed hydrogels led to significant impacts on hMSC morphology and proliferation, and increased immunomodulatory potential, indicating that molecular rigidity is a promising avenue to control engineered ECM mechanics for therapeutic applications.

Bioreactor Expansion Reconfigures Metabolism and Extracellular Vesicle Biogenesis of Human Adipose-derived Stem Cells In Vitro

Human mesenchymal stem cells (hMSCs), including human adipose tissue-derived stem cells (hASCs), as well as the secreted extracellular vesicles (EVs), are promising therapeutics in treating inflammatory and neural degenerative diseases. However, prolonged expansion can lead to cellular senescence characterized by a gradual loss of self-renewal ability while altering secretome composition and EV generation. Additionally, hMSCs are highly sensitive to biophysical microenvironment in bioreactor systems utilized in scaling production. In this study, hASCs grown on Plastic Plus or Synthemax II microcarriers in a spinner flask bioreactor (SFB) system were compared to traditional 2D culture. The SFB microenvironment was found to increase the expression of genes associated with hASC stemness, nicotinamide adenine dinucleotide (NAD+) metabolism, glycolysis, and the pentose phosphate pathway as well as alter cytokine secretion (e.g., PGE2 and CXCL10). Elevated reactive oxidative species levels in hASCs of SFB culture were observed without increasing rates of cellular senescence. Expression levels of Sirtuins responsible for preventing cellular senescence through anti-oxidant and DNA repair mechanisms were also elevated in SFB cultures. In particular, the EV biogenesis genes were significantly upregulated (3-10 fold) and the EV production increased 40% per cell in SFB cultures of hASCs. This study provides advanced understanding of hASC sensitivity to the bioreactor microenvironment for EV production and bio-manufacturing towards the applications in treating inflammatory and neural degenerative diseases.

Upscaling human mesenchymal stromal cell production in a novel vertical-wheel bioreactor enhances extracellular vesicle secretion and cargo profile

Human mesenchymal stromal cells (hMSCs) are mechanically sensitive undergoing phenotypic alterations when subjected to shear stress, cell aggregation, and substrate changes encountered in 3D dynamic bioreactor cultures. However, little is known about how bioreactor microenvironment affects the secretion and cargo profiles of hMSC-derived extracellular vesicles (EVs) including the subset, "exosomes", which contain therapeutic proteins, nucleic acids, and lipids from the parent cells. In this study, bone marrow-derived hMSCs were expanded on 3D Synthemax II microcarriers in the PBS mini 0.1L Vertical-Wheel bioreactor system under variable shear stress levels at 25, 40, and 64 RPM (0.1-0.3 dyn/cm²). The bioreactor system promotes EV secretion from hMSCs by 2.5-fold and upregulates the expression of EV biogenesis markers and glycolysis genes compared to the static 2D culture. The microRNA cargo was also altered in the EVs from bioreactor culture including the upregulation of miR-10, 19a, 19b, 21, 132, and 377. EV protein cargo was characterized by proteomics analysis, showing upregulation of metabolic, autophagy and ROS-related proteins comparing with 2D cultured EVs. In addition, the scalability of the Vertical-Wheel bioreactor system was demonstrated in a 0.5L bioreactor, showing similar or better hMSC-EV secretion and cargo content compared to the 0.1L bioreactor. This study advances our understanding of bio-manufacturing of stem cell-derived EVs for applications in cell-free therapy towards treating neurological disorders such as ischemic stroke, Alzheimer's disease, and multiple sclerosis.

High-Throughput Production of Microsponges from Platelet Lysate for Tissue Engineering Applications

Cell-based therapies require a large number of cells, as well as appropriate methods to deliver the cells to damaged tissue. Microcarriers provide an optimal platform for large-scale cell culture while also improving cell retention during cell delivery. However, this technology still presents significant challenges due to low-throughput fabrication methods and an inability of the microcarriers to recreate the properties of human tissue. This work proposes, for the first time, the use of methacryloyl platelet lysates (PLMA), a photocrosslinkable material derived from human platelet lysates, to produce porous microcarriers. Initially, high quantities of PLMA/alginate core-shell microcapsules are produced using coaxial electrospray. Subsequently, the microcapsules are collected, irradiated with ultraviolet light, washed, and freeze dried yielding PLMA microsponges. These microsponges are able to support the adhesion and proliferation of human adipose-derived stem cells, while also displaying potential in the assembly of autologous microtissues. Cell-laden microsponges were shown to self-organize into aggregates, suggesting possible applications in bottom-up tissue engineering applications. Impact Statement Microcarriers have increasingly been used as delivery platforms in cell therapy. Herein, the encapsulation of human-derived proteins in alginate microcapsules is proposed as a method to produce microcarriers from photopolymerizable materials. The capsules function as a template structure, which is then processed into spherical microparticles, which can be used in cell culture, cell delivery, and bottom-up assembly. As a proof of concept, this method was combined with lyophilization to process methacryloyl platelet lysates into injectable microsponges for cell delivery.

Physiologic isolation and expansion of human mesenchymal stem/stromal cells for manufacturing of cell-based therapy products

The utilization of mesenchymal stem/stromal cells raises new hopes in treatment of diseases and pathological conditions, while at the same time bringing immense challenges for researchers, manufacturers and physicians. It is essential to consider all steps along the in vitro fabrication of cell-based products in order to reach efficient and reproducible treatment outcomes. Here, the optimal protocols for isolation, cultivation and differentiation of mesenchymal stem cells are required. In this review we discuss these aspects and their influence on the final cell-based product quality. We demonstrate that physiological in vitro cell cultivation conditions play a crucial role in therapeutic functionalities of cultivated cells. We show that three-dimensional cell culture, dynamic culture conditions and physiologically relevant in vitro oxygen concentrations during isolation and expansion make a decisive contribution towards the improvement of cell-based products in regenerative medicine.

Rescuing emergency cases of COVID-19 patients: An intelligent real-time MSC transfusion framework based on multicriteria decision-making methods

Mesenchymal stem cells (MSCs) have shown promising ability to treat critical cases of coronavirus disease 2019 (COVID-19) by regenerating lung cells and reducing immune system overreaction. However, two main challenges need to be addressed first before MSCs can be efficiently transfused to the most critical cases of COVID-19. First is the selection of suitable MSC sources that can meet the standards of stem cell criteria. Second is differentiating COVID-19 patients into different emergency levels automatically and prioritising them in each emergency level. This study presents an efficient real-time MSC transfusion framework based on multicriteria decision-making(MCDM) methods. In the methodology, the testing phase represents the ability to adhere to plastic surfaces, the upregulation and downregulation of specific surface protein markers and finally the ability to differentiate into different kinds of cells. In the development phase, firstly, two scenarios of an augmented dataset based on the medical perspective are generated to produce 80 patients with different emergency levels. Secondly, an automated triage algorithm based on a formal medical guideline is proposed for real-time monitoring of COVID-19 patients with different emergency levels (i.e. mild, moderate, severe and critical) considering the improvement and deterioration procedures from one level to another. Thirdly, a unique decision matrix for each triage level (except mild) is constructed on the basis of the intersection between the evaluation criteria of each emergency level and list of COVID-19 patients. Thereafter, MCDM methods (i.e. analytic hierarchy process [AHP] and vlsekriterijumska optimizcija i kaompromisno resenje [VIKOR]) are integrated to assign subjective weights for the evaluation criteria within each triage level and then prioritise the COVID-19 patients on the basis of individual and group decision-making(GDM) contexts. Results show that: (1) in both scenarios, the proposed algorithm effectively classified the patients into four emergency levels, including mild, moderate, severe and critical, taking into consideration the improvement and deterioration cases. (2) On the basis of experts' perspectives, clear differences in most individual prioritisations for patients with different emergency levels in both scenarios were found. (3) In both scenarios, COVID-19 patients were prioritised identically between the internal and external group VIKOR. During the evaluation, the statistical objective method indicated that the patient prioritisations underwent systematic ranking. Moreover, comparison analysis with previous work proved the efficiency of the proposed framework. Thus, the real-time MSC transfusion for COVID-19 patients can follow the order achieved in the group VIKOR results.

Cell secretomes for wound healing and tissue regeneration: Next generation acellular based tissue engineered products

Wound represents a significant socioeconomic burden for both affected individuals and as a whole healthcare system. Accordingly, stem cells have garnered attention due to their differentiation capacity and ability to aid tissue regeneration by releasing biologically active molecules, found in the cells' cultivated medium which known as conditioned medium (CM) or secretomes. This acellular approach provides a huge advantage over conventional treatment options, which are mainly used cellular treatment at wound closure. Interestingly, the secretomes contained the cell-secreted proteins such as growth factors, cytokines, chemokines, extracellular matrix (ECM), and small molecules including metabolites, microvesicles, and exosomes. This review aims to provide a general view on secretomes and how it is proven to have great potential in accelerating wound healing. Utilizing the use of secretomes with its secreted proteins and suitable biomaterials for fabrications of acellular skin substitutes can be promising in treating skin loss and accelerate the healing process.

Polysaccharide-Based Hydrogels for Microencapsulation of Stem Cells in Regenerative Medicine

Stem cell-based therapy appears as a promising strategy to induce regeneration of damaged and diseased tissues. However, low survival, poor engraftment and a lack of site-specificity are major drawbacks. Polysaccharide hydrogels can address these issues and offer several advantages as cell delivery vehicles. They have become very popular due to their unique properties such as high-water content, biocompatibility, biodegradability and flexibility. Polysaccharide polymers can be physically or chemically crosslinked to construct biomimetic hydrogels. Their resemblance to living tissues mimics the native three-dimensional extracellular matrix and supports stem cell survival, proliferation and differentiation. Given the intricate nature of communication between hydrogels and stem cells, understanding their interaction is crucial. Cells are incorporated with polysaccharide hydrogels using various microencapsulation techniques, allowing generation of more relevant models and further enhancement of stem cell therapies. This paper provides a comprehensive review of human stem cells and polysaccharide hydrogels most used in regenerative medicine. The recent and advanced stem cell microencapsulation techniques, which include extrusion, emulsion, lithography, microfluidics, superhydrophobic surfaces and bioprinting, are described. This review also discusses current progress in clinical translation of stem-cell encapsulated polysaccharide hydrogels for cell delivery and disease modeling (drug testing and discovery) with focuses on musculoskeletal, nervous, cardiac and cancerous tissues.

Cannabidiol loaded extracellular vesicles sensitize triple-negative breast cancer to doxorubicin in both in-vitro and in vivo models

Extracellular Vesicles (EVs) were isolated from human umbilical cord mesenchymal stem cells (hUCMSCs) and were further encapsulated with cannabidiol (CBD) through sonication method (CBD EVs). CBD EVs displayed an average particle size of 114.1 ± 1.02 nm, zeta potential of -30.26 ± 0.12 mV, entrapment efficiency of 92.3 ± 2.21% and stability for several months at 4 °C. CBD release from the EVs was observed as 50.74 ± 2.44% and 53.99 ± 1.4% at pH 6.8 and pH 7.4, respectively after 48 h. Our in-vitro studies demonstrated that CBD either alone or in EVs form significantly sensitized MDA-MB-231 cells to doxorubicin (DOX) (*P < 0.05). Flow cytometry and migration studies revealed that CBD EVs either alone or in combination with DOX induced G1 phase cell cycle arrest and decreased migration of MDA-MB-231 cells, respectively. CBD EVs and DOX combination significantly reduced tumor burden (***P < 0.001) in MDA-MB-231 xenograft tumor model. Western blotting and immunocytochemical analysis demonstrated that CBD EVs and DOX combination decreased the expression of proteins involved in inflammation, metastasis and increased the expression of proteins involved in apoptosis. CBD EVs and DOX combination will have profound clinical significance in not only decreasing the side effects but also increasing the therapeutic efficacy of DOX in TNBC.

A scalable system for generation of mesenchymal stem cells derived from induced pluripotent cells employing bioreactors and degradable microcarriers

Human mesenchymal stem cells (hMSCs) are effective in treating disorders resulting from an inflammatory or heightened immune response. The hMSCs derived from induced pluripotent stem cells (ihMSCs) share the characteristics of tissue derived hMSCs but lack challenges associated with limited tissue sources and donor variation. To meet the expected future demand for ihMSCs, there is a need to develop scalable methods for their production at clinical yields while retaining immunomodulatory efficacy. Herein, we describe a platform for the scalable expansion and rapid harvest of ihMSCs with robust immunomodulatory activity using degradable gelatin methacryloyl (GelMA) microcarriers. GelMA microcarriers were rapidly and reproducibly fabricated using a custom microfluidic step emulsification device at relatively low cost. Using vertical wheel bioreactors, 8.8 to 16.3‐fold expansion of ihMSCs was achieved over 8 days. Complete recovery by 5‐minute digestion of the microcarriers with standard cell dissociation reagents resulted in >95% viability. The ihMSCs matched or exceeded immunomodulatory potential in vitro when compared with ihMSCs expanded on monolayers. This is the first description of a robust, scalable, and cost‐effective method for generation of immunomodulatory ihMSCs, representing a significant contribution to their translational potential.

Culture Substrates for Improved Manufacture of Mesenchymal Stromal Cell Therapies

Recent developments in mesenchymal stromal cell (MSC) therapies have increased the demand for tools to improve their manufacture, including the selection of optimal culture substrate materials. While many clinical manufacturers use planar tissue culture plastic (TCP) surfaces for MSC production, others have begun exploring the use of alternative culture substrates that present a variety of spatial, mechanical, and biochemical cues that influence cell expansion and resulting cell quality. In this review, the effects of culture and material properties distinct from traditional planar TCP surfaces on MSC proliferation, surface marker expression, and commonly used indications for therapeutic potency are examined. The different properties summarized include the use of alternative culture formats such as cellular aggregates or 3D scaffolds, as well as the effects of culture substrate stiffness and presentation of specific adhesive ligands and topographical cues. Specific substrate properties can be related to greater cell expansion and improvement in specific therapeutic functionalities, demonstrating the utility of culture materials in further improving the clinical-scale manufacture of highly secretory MSC products.

Mesenchymal Stem Cell-Based Therapy as an Alternative to the Treatment of Acute Respiratory Distress Syndrome: Current Evidence and Future Perspectives

Acute respiratory distress syndrome (ARDS) represents a current challenge for medicine due to its incidence, morbidity and mortality and, also, the absence of an optimal treatment. The COVID-19 outbreak only increased the urgent demand for an affordable, safe and effective treatment for this process. Early clinical trials suggest the therapeutic usefulness of mesenchymal stem cells (MSCs) in acute lung injury (ALI) and ARDS. MSC-based therapies show antimicrobial, anti-inflammatory, regenerative, angiogenic, antifibrotic, anti-oxidative stress and anti-apoptotic actions, which can thwart the physiopathological mechanisms engaged in ARDS. In addition, MSC secretome and their derived products, especially exosomes, may reproduce the therapeutic effects of MSC in lung injury. This last strategy of treatment could avoid several safety issues potentially associated with the transplantation of living and proliferative cell populations and may be formulated in different forms. However, the following diverse limitations must be addressed: (i) selection of the optimal MSC, bearing in mind both the heterogeneity among donors and across different histological origins, (ii) massive obtention of these biological products through genetic manipulations of the most appropriate MSC, (iii) bioreactors that allow their growth in 3D, (iv) ideal culture conditions and (v) adequate functional testing of these obtaining biological products before their clinical application.

Rational Biological Interface Engineering: Amyloidal Supramolecular Microstructure-Inspired Hydrogel

Amyloidal proteins, which are prone to form fibrillar and ordered aggregates in vivo and in vitro, underlie the mechanism for neurodegenerative disorders and also play essential functions in the process of life. Amyloid fibrils typically adopt a distinctive β-sheet structure, which renders them with inherent extracellular matrix (ECM)-mimicking properties, such as powerful mechanical strength, promising adhesion, and antibacterial activity. Additionally, amyloidal proteins are a category of programmable self-assembled macromolecules, and their assembly and consequent nanostructure can be manipulated rationally. The above advantages motivate researchers to investigate the potential of amyloidal proteins as a novel type of hydrogel material. Currently, the amyloid-inspired hydrogel has become an emerging area and has been widely applied in a variety of biomedical fields, such as tissue repair, cell scaffolds, and drug delivery. In this review, we focus on the discussion of molecular mechanisms underlying the hydrogenation of amyloidal proteins, and introduce the advances achieved in biomedical applications of amyloid-inspired hydrogels.

Preparation of thermosensitive PNIPAm-based copolymer coated cytodex 3 microcarriers for efficient nonenzymatic cell harvesting during 3D culturing

Enzymatic detachment of cells might damage important features and functions of cells and could affect subsequent cell-based applications. Therefore, nonenzymatic cell detachment using thermosensitive polymer matrix is necessary for maintaining cell quality after harvesting. In this study, we prepared thermosensitive PNIPAm-co-AAc-b-PS and PNIPAm-co-AAm-b-PS copolymers and low critical solution temperature (LCST) was tuned near to body temperature. Then, spin coated polymer films were prepared for cell adhesion and thermal-induced cell detachment. The alpha-step analysis and scanning electron microscope image of the films suggested that the thickness of the films depends on the molecular weight and concentration which ranged from 206 to 1330 nm for PNIPAm-co-AAc-b-PS and 97.5-497 nm for PNIPAm-co-AAm-b-PS. The contact angles of the films verified that the polymer surface was moderately hydrophilic at 37°C. Importantly, RAW264.7 cells were convincingly proliferated on the films to a confluent of >80% within 48 h and abled to detach by reducing the temperature. However, relatively more cells were grown on PNIPAm-co-AAm-b-PS (5%w/v) films and thermal-induced cell detachment was more abundant in this formulation. As a result, PNIPAm-co-AAm-b-PS (5%w/v) was further used to coat commercial cytodex 3 microcarriers for 3D cell culturing and interestingly enhanced cell detachment with preserved potential of recovery was observed at a temperature of below LCST. Thus, surface modification of microcarriers with thermosensitive PNIPAm-co-AAm-b-PS could be vital strategy for nonenzymatic cell detachment and to achieve adequate number of cells with maximum cell viability and functionality.

Bioprocessing of Human Mesenchymal Stem Cells: From Planar Culture to Microcarrier-Based Bioreactors

Human mesenchymal stem cells (hMSCs) have demonstrated great potential to be used as therapies for many types of diseases. Due to their immunoprivileged status, allogeneic hMSCs therapies are particularly attractive options and methodologies to improve their scaling and manufacturing are needed. Microcarrier-based bioreactor systems provide higher volumetric hMSC production in automated closed systems than conventional planar cultures. However, more sophisticated bioprocesses are necessary to successfully convert from planar culture to microcarriers. This article summarizes key steps involved in the planar culture to microcarrier hMSC manufacturing scheme, from seed train, inoculation, expansion and harvest. Important bioreactor parameters, such as temperature, pH, dissolved oxygen (DO), mixing, feeding strategies and cell counting techniques, are also discussed.

Human Adipose Stem Cells (hASCs) Grown on Biodegradable Microcarriers in Serum- and Xeno-Free Medium Preserve Their Undifferentiated Status

Human adipose stem cells (hASCs) are promising candidates for cell-based therapies, but they need to be efficiently expanded in vitro as they cannot be harvested in sufficient quantities. Recently, dynamic bioreactor systems operated with microcarriers achieved considerable high cell densities. Thus, they are a viable alternative to static planar cultivation systems to obtain high numbers of clinical-grade hASCs. Nevertheless, the production of considerable biomass in a short time must not be achieved to the detriment of the cells' quality. To facilitate the scalable expansion of hASC, we have developed a new serum- and xeno-free medium (UrSuppe) and a biodegradable microcarrier (BR44). In this study, we investigated whether the culture of hASCs in defined serum-free conditions on microcarriers (3D) or on planar (2D) cell culture vessels may influence the expression of some marker genes linked with the immature degree or the differentiated status of the cells. Furthermore, we investigated whether the biomaterials, which form our biodegradable MCs, may affect cell behavior and differentiation. The results confirmed that the quality and the undifferentiated status of the hASCs are very well preserved when they grow on BR44 MCs in defined serum-free conditions. Indeed, the ASCs showed a gene expression profile more compatible with an undifferentiated status than the same cells grown under standard planar conditions.

Mesenchymal Stem Cells as a Cornerstone in a Galaxy of Intercellular Signals: Basis for a New Era of Medicine

Around 40% of the population will suffer at some point in their life a disease involving tissue loss or an inflammatory or autoimmune process that cannot be satisfactorily controlled with current therapies. An alternative for these processes is represented by stem cells and, especially, mesenchymal stem cells (MSC). Numerous preclinical studies have shown MSC to have therapeutic effects in different clinical conditions, probably due to their mesodermal origin. Thereby, MSC appear to play a central role in the control of a galaxy of intercellular signals of anti-inflammatory, regenerative, angiogenic, anti-fibrotic, anti-oxidative stress effects of anti-apoptotic, anti-tumor, or anti-microbial type. This concept forces us to return to the origin of natural physiological processes as a starting point to understand the evolution of MSC therapy in the field of regenerative medicine. These biological effects, demonstrated in countless preclinical studies, justify their first clinical applications, and draw a horizon of new therapeutic strategies. However, several limitations of MSC as cell therapy are recognized, such as safety issues, handling difficulties for therapeutic purposes, and high economic cost. For these reasons, there is an ongoing tendency to consider the use of MSC-derived secretome products as a therapeutic tool, since they reproduce the effects of their parent cells. However, it will be necessary to resolve key aspects, such as the choice of the ideal type of MSC according to their origin for each therapeutic indication and the implementation of new standardized production strategies. Therefore, stem cell science based on an intelligently designed production of MSC and or their derivative products will be able to advance towards an innovative and more personalized medical biotechnology.