The translation of cell-based therapies: clinical landscape and manufacturing challenges

The Progression of Regenerative Medicine and its Impact on Therapy Translation

Despite regenerative medicine (RM) being one of the hottest topics in biotechnology for the past 3 decades, it is generally acknowledged that the field's performance at the bedside has been somewhat disappointing. This may be linked to the novelty of these technologies and their disruptive nature, which has brought an increasing level of complexity to translation. Therefore, we look at how the historical development of the RM field has changed the translational strategy. Specifically, we explore how the pursuit of such novel regenerative therapies has changed the way experts aim to translate their ideas into clinical applications, and then identify areas that need to be corrected or reinforced in order for these therapies to eventually be incorporated into the standard-of-care. This is then linked to a discussion of the preclinical and postclinical challenges remaining today, which offer insights that can contribute to the future progression of RM.

Automated Large-Scale Production of Paclitaxel Loaded Mesenchymal Stromal Cells for Cell Therapy Applications

Mesenchymal stromal cells (MSCs) prepared as advanced therapies medicinal products (ATMPs) have been widely used for the treatment of different diseases. The latest developments concern the possibility to use MSCs as carrier of molecules, including chemotherapeutic drugs. Taking advantage of their intrinsic homing feature, MSCs may improve drugs localization in the disease area. However, for cell therapy applications, a significant number of MSCs loaded with the drug is required. We here investigate the possibility to produce a large amount of Good Manufacturing Practice (GMP)-compliant MSCs loaded with the chemotherapeutic drug Paclitaxel (MSCs-PTX), using a closed bioreactor system. Cells were obtained starting from 13 adipose tissue lipoaspirates. All samples were characterized in terms of number/viability, morphology, growth kinetics, and immunophenotype. The ability of MSCs to internalize PTX as well as the antiproliferative activity of the MSCs-PTX in vitro was also assessed. The results demonstrate that our approach allows a large scale expansion of cells within a week; the MSCs-PTX, despite a different morphology from MSCs, displayed the typical features of MSCs in terms of viability, adhesion capacity, and phenotype. In addition, MSCs showed the ability to internalize PTX and finally to kill cancer cells, inhibiting the proliferation of tumor lines in vitro. In summary our results demonstrate for the first time that it is possible to obtain, in a short time, large amounts of MSCs loaded with PTX to be used in clinical trials for the treatment of patients with oncological diseases.

Bioprocess Technologies that Preserve the Quality of iPSCs

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

Biomaterials for Personalized Cell Therapy

Cell therapy has already had an important impact on healthcare and provided new treatments for previously intractable diseases. Notable examples include mesenchymal stem cells for tissue regeneration, islet transplantation for diabetes treatment, and T cell delivery for cancer immunotherapy. Biomaterials have the potential to extend the therapeutic impact of cell therapies by serving as carriers that provide 3D organization and support cell viability and function. With the growing emphasis on personalized medicine, cell therapies hold great potential for their ability to sense and respond to the biology of an individual patient. These therapies can be further personalized through the use of patient-specific cells or with precision biomaterials to guide cellular activity in response to the needs of each patient. Here, the role of biomaterials for applications in tissue regeneration, therapeutic protein delivery, and cancer immunotherapy is reviewed, with a focus on progress in engineering material properties and functionalities for personalized cell therapies.

Engineered iron oxide nanoparticles to improve regenerative effects of mesenchymal stem cells

Abstract

Mesenchymal stem cells (MSCs) based therapies are a major field of regenerative medicine. However, the success of MSC therapy relies on the efficiency of its delivery and retention, differentiation, and secreting paracrine factors at the target sites. Recent studies show that superparamagnetic iron oxide nanoparticles (SPIONs) modulate the regenerative effects of MSCs. After interacting with the cell membrane of MSCs, SPIONs can enter the cells via the endocytic pathway. The physicochemical properties of nanoparticles, including size, surface charge (zeta-potential), and surface ligand, influence their interactions with MSC, such as cellular uptake, cytotoxicity, homing factors, and regenerative related factors (VEGF, TGF-β1). Therefore, in-depth knowledge of the physicochemical properties of SPIONs might be a promising lead in regenerative and anti-inflammation research using SPIONs mediated MSCs. In this review, recent research on SPIONs with MSCs and the various designs of SPIONs are examined and summarized.

Graphic abstract

A graphical abstract describes important parameters in the design of superparamagnetic iron oxide nanoparticles, affecting mesenchymal stem cells. These physicochemical properties are closely related to the mesenchymal stem cells to achieve improved cellular responses such as homing factors and cell uptake.

The clinical potential of gene editing as a tool to engineer cell-based therapeutics

The clinical application of ex vivo gene edited cell therapies first began a decade ago with zinc finger nuclease editing of autologous CD4+ T-cells. Editing aimed to disrupt expression of the human immunodeficiency virus co-receptor gene CCR5, with the goal of yielding cells resistant to viral entry, prior to re-infusion into the patient. Since then the field has substantially evolved with the arrival of the new editing technologies transcription activator-like effector nucleases (TALENs) and clustered regularly interspaced short palindromic repeats (CRISPR), and the potential benefits of gene editing in the arenas of immuno-oncology and blood disorders were quickly recognised. As the breadth of cell therapies available clinically continues to rise there is growing interest in allogeneic and off-the-shelf approaches and multiplex editing strategies are increasingly employed. We review here the latest clinical trials utilising these editing technologies and consider the applications on the horizon.

Effects of Physical, Chemical, and Biological Stimulus on h-MSC Expansion and Their Functional Characteristics

Human adult mesenchymal stem or stromal cells (h-MSC) therapy has gained considerable attention due to the potential to treat or cure diseases given their immunosuppressive properties and tissue regeneration capabilities. Researchers have explored diverse strategies to promote high h-MSC production without losing functional characteristics or properties. Physical stimulus including stiffness, geometry, and topography, chemical stimulus, like varying the surface chemistry, and biochemical stimuli such as cytokines, hormones, small molecules, and herbal extracts have been studied but have yet to be translated to industrial manufacturing practice. In this review, we describe the role of those stimuli on h-MSC manufacturing, and how these stimuli positively promote h-MSC properties, impacting the cell manufacturing field for cell-based therapies. In addition, we discuss other process considerations such as bioreactor design, good manufacturing practice, and the importance of the cell donor and ethics factors for manufacturing potent h-MSC.

Predicting in vitro human mesenchymal stromal cell expansion based on individual donor characteristics using machine learning

BACKGROUND

Human mesenchymal stromal cells (hMSCs) have become attractive candidates for advanced medical cell-based therapies. An in vitro expansion step is routinely used to reach the required clinical quantities. However, this is influenced by many variables including donor characteristics, such as age and gender, and culture conditions, such as cell seeding density and available culture surface area. Computational modeling in general and machine learning in particular could play a significant role in deciphering the relationship between the individual donor characteristics and their growth dynamics.

METHODS

In this study, hMSCs obtained from 174 male and female donors, between 3 and 64 years of age with passage numbers ranging from 2 to 27, were studied. We applied a Random Forests (RF) technique to model the cell expansion procedure by predicting the population doubling time (PDT) for each passage, taking into account individual donor-related characteristics.

RESULTS

Using the RF model, the mean absolute error between model predictions and experimental results for the PDT in passage 1 to 4 is significantly lower compared with the errors obtained with theoretical estimates or historical data. Moreover, statistical analysis indicate that the PD and PDT in different age categories are significantly different, especially in the youngest group (younger than 10 years of age) compared with the other age groups.

DISCUSSION

In summary, we introduce a predictive computational model describing in vitro cell expansion dynamics based on individual donor characteristics, an approach that could greatly assist toward automation of a cell expansion culture process.

Extracellular blebs: Artificially-induced extracellular vesicles for facile production and clinical translation

Extracellular vesicles (EVs) have emerged as promising biologic and comprehensive therapies for precision medicine. Despite their potential demonstrated at the benchtop, few EV formulations have made it to the clinic due to challenges in regulatory compliant scalable production; including purity, homogeneity, and reproducibility. For translation of this technology, there is a strong need for novel production methods that can meet clinical production criteria. Initial research aimed to address these challenges by taking advantage of natural pathways to increase EV yields. Such "conventional" approaches moderately increased yields but produced inhomogeneous EVs. Additionally, as there are currently no standard methods for isolation, characterization, or quantification, isolated EVs were often impure, contaminated with proteins and other biomacromolecules, and highly diverse in function. The use of shear stress and extrusion methods for EV-like vesicle production has also been investigated. While these processes can produce large EV-like vesicle yields nearly immediately, the harsh processes still result in inhomogeneous loading, and still suffer from poor purity. Chemically-induced membrane blebbing is a promising alternative production method that has the potential to overcome the previously insurmountable barriers of these current methods. This technique produces pure, and well defined EV-like vesicles, termed extracellular blebs (EBs), in clinically relevant scales over the course of minutes to hours. Furthermore, blebbing agents act on the cell in a way which locks the current surface properties and contents, preventing change, allowing for homogeneous EB production, and further preventing post-production changes. EBs may provide a promising pathway for clinical translation of EV technology.

Magnetic Nanomaterials for Advanced Regenerative Medicine: The Promise and Challenges

The recent emergence of numerous nanotechnologies is expected to facilitate the development of regenerative medicine, which is a tissue regeneration technique based on the replacement/repair of diseased tissue or organs to restore the function of lost, damaged, and aging cells in the human body. In particular, the unique magnetic properties and specific dimensions of magnetic nanomaterials make them promising innovative components capable of significantly advancing the field of tissue regeneration. Their potential applications in tissue regeneration are the focus here, beginning with the fundamentals of magnetic nanomaterials. How nanomaterials-both those that are intrinsically magnetic and those that respond to an externally applied magnetic field-can enhance the efficiency of tissue regeneration is also described. Applications including magnetically controlled cargo delivery and release, real-time visualization and tracking of transplanted cells, magnetic regulation of cell proliferation/differentiation, and magnetic activation of targeted ion channels and signal pathways involved in regeneration are highlighted, and comments on the perspectives and challenges in magnetic nanomaterial-based tissue regeneration are given.

Expansion processes for cell-based therapies

Living cells are emerging as therapeutic entities for the treatment of patients affected with severe and chronic diseases where no conventional drug can provide a definitive cure. At the same time, the promise of cell-based therapies comes with several biological, regulatory, economic, logistical, safety and engineering challenges that need to be addressed before translating into clinical practice. Among the complex operations required for their manufacturing, cell expansion occupies a significant part of the entire process and largely determines the number, the phenotype and several other critical quality attributes of the final cell therapy products (CTPs). This review aims at characterizing the main culture systems and expansion processes used for CTP production, highlighting the need to implement scalable, cost-efficient technologies together with process optimization strategies to bridge the gap between basic scientific research and commercially available therapies.

Treatment With Tumor-infiltrating Lymphocytes in Advanced Melanoma: Evaluation of Early Clinical Implementation of an Advanced Therapy Medicinal Product

Tumor-infiltrating lymphocytes (TIL)-therapy in advanced melanoma is an advanced therapy medicinal product (ATMP) which, despite promising results, has not been implemented widely. In a European setting, TIL-therapy has been in use since 2011 and is currently being evaluated in a randomized controlled trial. As clinical implementation of ATMPs is challenging, this study aims to evaluate early application of TIL-therapy, through the application of a constructive technology assessment (CTA). First the literature on ATMP barriers and facilitators in clinical translation was summarized. Subsequently, application of TIL-therapy was evaluated through semistructured interviews with 26 stakeholders according to 6 CTA domains: clinical, economic, patient-related, organizational, technical, and future. In addition, treatment costs were estimated. A number of barriers to clinical translation were identified in the literature, including: inadequate financial support, lack of regulatory knowledge, risks in using live tissues, and the complex path to market approval. Innovative reimbursement procedures could particularly facilitate translation. The CTA survey of TIL-therapy acknowledged these barriers, and revealed the following facilitators: the expected effectiveness resulting in institutional support for an internal pilot, the results of which led to the inclusion of TIL-therapy in a national coverage with evidence development program, the availability of an in-house pharmacist, quality assurance expertise and a TIL-skilled technician. Institutional and national implementation of TIL-therapy remains complex. The promising clinical effectiveness is expected to facilitate the adoption of TIL-therapy, especially when validated through a randomized controlled trial. Innovative and conditional reimbursement procedures, together with the organization of knowledge transfer, could support and improve clinical translation of TIL and ATMPs.

Effects of hypoxia‑inducible factor‑1α on the proliferation and apoptosis of human synovial mesenchymal stem cells

Hypoxia is a constant feature of the synovial microenvironment. How synovial mesenchymal stem cells (SMSCs) proliferate and differentiate in a hypoxic environment over a long period of time has aroused the interest of researchers. The aim of the present study was to explore the effects of hypoxia‑inducible factor‑1α (HIF‑1α) on the proliferation and apoptosis of human SMSCs. SMSCs were harvested and cultured under different concentration of oxygen, normoxia (21% O2), hypoxia (5% O2) and severe hypoxia (0.5% O2) to determine its effect on the expression of HIF‑1α. Then, the cells were collected and cell proliferation and apoptosis were detected at severe hypoxia (0.5% O2) and hypoxia (5% O2) conditions following HIF‑1α siRNA transfection. There were no significant changes in cellular proliferation or apoptosis when cultured in normoxia (21% O2), hypoxia (5% O2) or severe hypoxia (0.5% O2). However, the mRNA and protein expression of HIF‑1α were markedly upregulated in the hypoxic conditions. Further experiments suggested that the proliferation of SMSCs was obviously suppressed and apoptosis was markedly increased under severe hypoxic (0.5%) and hypoxic (5% O2) conditions following HIF‑1α siRNA transfection. In conclusion, HIF‑1α effectively improved the tolerance of SMSCs to hypoxia, which may promote cellular proliferation and prevent the apoptosis of SMSCs under hypoxic conditions.

Current understanding of the therapeutic benefits of mesenchymal stem cells in acute respiratory distress syndrome

The acute respiratory distress syndrome (ARDS) is a multifaceted lung disorder in which no specific therapeutic intervention is able to effectively improve clinical outcomes. Despite an improved understanding of molecular mechanisms and advances in supportive care strategies, ARDS remains associated with high mortality, and survivors usually face long-term morbidity. In recent years, preclinical studies have provided mounting evidence of the potential of mesenchymal stem cell (MSC)-based therapies in lung diseases and critical illnesses. In several models of ARDS, MSCs have been demonstrated to induce anti-inflammatory and anti-apoptotic effects, improve epithelial and endothelial cell recovery, and enhance microbial and alveolar fluid clearance, thus resulting in improved lung and distal organ function and survival. Early-stage clinical trials have also demonstrated the safety of MSC administration in patients with ARDS, but further, large-scale investigations are required to assess the safety and efficacy profile of these therapies. In this review, we summarize the main mechanisms whereby MSCs have been shown to exert therapeutic effects in experimental ARDS. We also highlight questions that need to be further elucidated and barriers that must be overcome in order to efficiently translate MSC research into clinical practice.

The Effects of Different Dynamic Culture Systems on Cell Proliferation and Osteogenic Differentiation in Human Mesenchymal Stem Cells

The culture environment plays an important role for stem cells' cultivation. Static or dynamic culture preserve differential potentials to affect human mesenchymal stem cells' (hMSCs) proliferation and differentiation. In this study, hMSCs were seeded on fiber disks and cultured in a bidirectional-flow bioreactor or spinner-flask bioreactor with a supplement of osteogenic medium. The hMSCs' proliferation, osteogenic differentiation, and extracellular matrix deposition of mineralization were demonstrated. The results showed that the spinner flask improved cell viability at the first two weeks while the bidirectional-flow reactor increased the cell proliferation of hMSCs through the four-week culture period. Despite the flow reactor having a higher cell number, a lower lactose/glucose ratio was noted, revealing that the bidirectional-flow bioreactor provides better oxygen accessibility to the cultured cells/disk construct. The changes of calcium ions in the medium, the depositions of Ca²⁺ in the cells/disk constructs, and alkaline phosphate/osteocalcin activities showed the static culture of hMSCs caused cells to mineralize faster than the other two bioreactors but without cell proliferation. Otherwise, cells were distributed uniformly with abundant extracellular matrix productions using the flow reactor. This reveals that the static and dynamic cultivations regulated the osteogenic process differently in hMSCs. The bidirectional-flow bioreactor can be used in the mass production and cultivation of hMSCs for applications in bone regenerative medicine.

IFN-γ-tethered hydrogels enhance mesenchymal stem cell-based immunomodulation and promote tissue repair

Because of their immunomodulatory activities, human mesenchymal stem cells (hMSCs) are being explored to treat a variety of chronic conditions such as inflammatory bowel disorders and graft-vs-host disease. Treating hMSCs with IFN-γ prior to administration augments these immunomodulatory properties; however, this ex vivo treatment limits the broad applicability of this therapy due to technical and regulatory issues. In this study, we engineered an injectable synthetic hydrogel with tethered recombinant IFN-γ that activates encapsulated hMSCs to increase their immunomodulatory functions and avoids the need for ex vivo manipulation. Tethering IFN-γ to the hydrogel increases retention of IFN-γ within the biomaterial while preserving its biological activity. hMSCs encapsulated within hydrogels with tethered IFN-γ exhibited significant differences in cytokine secretion and showed a potent ability to halt activated T-cell proliferation and monocyte-derived dendritic cell differentiation compared to hMSCs that were pre-treated with IFN-γ and untreated hMSCs. Importantly, hMSCs encapsulated within hydrogels with tethered IFN-γ accelerated healing of colonic mucosal wounds in both immunocompromised and immunocompetent mice. This novel approach for licensing hMSCs with IFN-γ may enhance the clinical translation and efficacy of hMSC-based therapies.

Regenerative Medicine: "Are We There Yet?"

Translation of regenerative therapies to the patient-bench-to-bedside-is one of the global multidisciplinary challenges of our time. New cell-based therapies are reaching the clinic through staged trials leading eventually to routine adoption. The roots of stem cell therapy lie in surgical practice and transplantation medicine with multiple multidisciplinary challenges emerging to support the new therapies. Control of stem cell behavior in line with regulatory confidence is an example of these challenges. One successful journey from bench-to-bedside is the generation of cartilage through autologous cell-based approaches for use in the repair of the knee joint. An analysis of this journey in Europe reveals success and failure; new initiatives include adopting more quantitative modelling and "organ on a chip" approaches to be used in clinical translation reducing experimental time and redressing the lack of preclinical models. The current state and challenges for the field are outlined with the question posed, "are we there yet?"

Preparing for cell culture scale-out: establishing parity of bioreactor- and flask-expanded mesenchymal stromal cell cultures

Background

Cell-based therapies have the potential to become treatment options for many diseases, but efficient scale-out of these therapies has proven to be a major hurdle. Bioreactors can be used to overcome this hurdle, but changing the culture method can introduce unwanted changes to the cell product. Therefore, it is important to establish parity between products generated using traditional methods versus those generated using a bioreactor.

Methods

Mesenchymal stromal cells (MSCs) are cultured in parallel using either traditional culture flasks, spinner vessels or a new bioreactor system. To investigate parity between the cells obtained from different methods, harvested cells are compared in terms of yield, phenotype and functionality.

Results

Bioreactor-based expansion yielded high cell numbers (222–510 million cells). Highest cell expansion was observed upon culture in flasks [average 5.0 population doublings (PDL)], followed by bioreactor (4.0 PDL) and spinner flasks (3.3 PDL). Flow cytometry confirmed MSC identity (CD73⁺, CD90⁺ and CD105⁺) and lack of contaminating hematopoietic cell populations. Cultured MSCs did not display genetic aberrations and no difference in differentiation and immunomodulatory capacity was observed between culture conditions. The response to IFNγ stimulation was similar for cells obtained from all culture conditions, as was the capacity to inhibit T cell proliferation.

Conclusions

The new bioreactor technology can be used to culture large amounts of cells with characteristics equivalent to those cultured using traditional, flask based, methods.

Electronic supplementary material

The online version of this article (10.1186/s12967-019-1989-x) contains supplementary material, which is available to authorized users.

Dissecting Allo-Sensitization After Local Administration of Human Allogeneic Adipose Mesenchymal Stem Cells in Perianal Fistulas of Crohn's Disease Patients

Adipose mesenchymal stem cells (ASC) are considered minimally immunogenic. This is due to the low expression of human leukocyte antigens I (HLA-I), lack of HLA-II expression and low expression of co-stimulatory molecules such as CD40 and CD80. The low rate of observed immunological rejection as well as the immunomodulatory qualities, position ASC as a promising cell-based therapy for the treatment of a variety of inflammatory indications. Yet, few studies have addressed relevant aspects of immunogenicity such as ASC donor-to-patient HLA histocompatibility or assessment of immune response triggered by ASC administration, particularly in the cases of presensitization. The present study aims to assess allo-immune responses in a cohort of Crohn's disease patients administered with allogeneic ASC (darvadstrocel formerly Cx601) for the treatment of complex perianal fistulas. We identified donor-specific antibodies (DSA) generation in a proportion of patients and observed that patients showing preexisting immunity were prone to generating DSA after allogeneic therapy. Noteworthy, naïve patients generating DSA at week 12 (W12) showed a significant reduction in DSA titer at week 52 (W52), whereas DSA titer was reduced in pre-sensitized patients only with no specificities against the donor administered. Remarkably, we did not observe any correlation of DSA generation with ASC therapeutic efficacy. In vitro complement-dependent cytotoxicity (CDC) studies have revealed limited cytotoxic levels based upon HLA-I expression and binding capacity even in pro-inflammatory conditions. We sought to identify CDC coping mechanisms contributing to the limited cytotoxic killing observed in ASC in vitro. We found that ASC express membrane-bound complement regulatory proteins (mCRPs) CD55, CD46, and CD59 at basal levels, with CD46 more actively expressed in pro-inflammatory conditions. We demonstrated that CD46 is a main driver of CDC signaling; its depletion significantly enhances sensitivity of ASC to CDC. In summary, despite relatively high clearance, DSA generation may represent a major challenge for allogeneic cell therapy management. Sensitization may be a significant concern when evaluating re-treatment or multi-donor trials. It is still unknown whether DSA generation could potentially be the consequence of donor-to-patient interaction and, therefore, subsequently link to efficacy or biological activity. Lastly, we propose that CDC modulators such as CD46 could be used to ultimately link CDC specificity with allogeneic cell therapy efficacy.

Nature vs. Nurture: Defining the Effects of Mesenchymal Stromal Cell Isolation and Culture Conditions on Resiliency to Palmitate Challenge

As MSC products move from early development to clinical translation, culture conditions shift from xeno- to xeno-free systems. However, the impact of isolation and culture-expansion methods on the long-term resiliency of MSCs within challenging transplant environments is not fully understood. Recent work in our lab has shown that palmitate, a saturated fatty acid elevated in the serum of patients with obesity, causes MSCs to convert from an immunosuppressive to an immunostimulatory state at moderate to high physiological levels. This demonstrated that metabolically-diseased environments, like obesity, alter the immunomodulatory efficacy of healthy donor MSCs. In addition, it highlighted the need to test MSC efficacy not only in ideal conditions, but within challenging metabolic environments. To determine how the choice of xeno- vs. xeno-free media during isolation and expansion would affect future immunosuppressive function, umbilical cord explants from seven donors were subdivided and cultured within xeno- (fetal bovine serum, FBS) or xeno-free (human platelet lysate, PLT) medias, creating 14 distinct MSC preparations. After isolation and primary expansion, umbilical cord MSCs (ucMSC) were evaluated according to the ISCT minimal criteria for MSCs. Following baseline characterization, ucMSC were exposed to physiological doses of palmitate and analyzed for metabolic health, apoptotic induction, and immunomodulatory potency in co-cultures with stimulated human peripheral blood mononuclear cells. The paired experimental design (each ucMSC donor grown in two distinct culture environments) allowed us to delineate the contribution of inherent (nature) vs. environmentally-driven (nurture) donor characteristics to the phenotypic response of ucMSC during palmitate exposure. Culturing MSCs in PLT-media led to more consistent growth characteristics during the isolation and expansion for all donors, resulting in faster doubling times and higher cell yields compared to FBS. Upon palmitate challenge, PLT-ucMSCs showed a higher susceptibility to palmitate-induced metabolic disturbance, but less susceptibility to palmitate-induced apoptosis. Most striking however, was that the PLT-ucMSCs resisted the conversion to an immunostimulatory phenotype better than their FBS counterparts. Interestingly, examining MSC suppression of PBMC proliferation at physiologic doses of palmitate magnified the differences between donors, highlighting the utility of evaluating MSC products in stress-based assays that reflect the challenges MSCs may encounter post-transplantation.

Insights into Inflammatory Priming of Adipose-Derived Mesenchymal Stem Cells: Validation of Extracellular Vesicles-Embedded miRNA Reference Genes as A Crucial Step for Donor Selection

Mesenchymal stem cells (MSCs) are promising tools for cell-based therapies due to their homing to injury sites, where they secrete bioactive factors such as cytokines, lipids, and nucleic acids, either free or conveyed within extracellular vesicles (EVs). Depending on the local environment, MSCs’ therapeutic value may be modulated, determining their fate and cell behavior. Inflammatory signals may induce critical changes on both the phenotype and secretory portfolio. Intriguingly, in animal models resembling joint diseases as osteoarthritis (OA), inflammatory priming enhanced the healing capacity of MSC-derived EVs. In this work, we selected miRNA reference genes (RGs) from the literature (let-7a-5p, miR-16-5p, miR-23a-3p, miR-26a-5p, miR-101-3p, miR-103a-3p, miR-221-3p, miR-423-5p, miR-425-5p, U6 snRNA), using EVs isolated from adipose-derived MSCs (ASCs) primed with IFNγ (iASCs). geNorm, NormFinder, BestKeeper, and ΔCt methods identified miR-26a-5p/16-5p as the most stable, while miR-103a-rp/425-5p performed poorly. Our results were validated on miRNAs involved in OA cartilage trophism. Only a proper normalization strategy reliably identified the differences between donors, a critical factor to empower the therapeutic value of future off-the-shelf MSC-EV isolates. In conclusion, the proposed pipeline increases the accuracy of MSC-EVs embedded miRNAs assessment, and help predicting donor variability for precision medicine approaches.

Chimeric antigen receptor-T cell therapy manufacturing: modelling the effect of offshore production on aggregate cost of goods

Cell and gene therapies have demonstrated excellent clinical results across a range of indications with chimeric antigen receptor (CAR)-T cell therapies among the first to reach market. Although these therapies are currently manufactured using patient-derived cells, therapies using healthy donor cells are in development, potentially offering avenues toward process improvement and patient access. An allogeneic model could significantly reduce aggregate cost of goods (COGs), potentially improving market penetration of these life-saving treatments. Furthermore, the shift toward offshore production may help reduce manufacturing costs. In this article, we examine production costs of an allogeneic CAR-T cell process and the potential differential manufacturing costs between regions. Two offshore locations are compared with regions within the United States. The critical findings of this article identify the COGs challenges facing manufacturing of allogeneic CAR-T immunotherapies, how these may evolve as production is sent offshore and the wider implication this trend could have.

GMP-compatible and xeno-free cultivation of mesenchymal progenitors derived from human-induced pluripotent stem cells

Background

Human mesenchymal stem cells are a strong candidate for cell therapies owing to their regenerative potential, paracrine regulatory effects, and immunomodulatory activity. Yet, their scarcity, limited expansion potential, and age-associated functional decline restrict the ability to consistently manufacture large numbers of safe and therapeutically effective mesenchymal stem cells for routine clinical applications. To overcome these limitations and advance stem cell treatments using mesenchymal stem cells, researchers have recently derived mesenchymal progenitors from human-induced pluripotent stem cells. Human-induced pluripotent stem cell-derived progenitors resemble adult mesenchymal stem cells in morphology, global gene expression, surface antigen profile, and multi-differentiation potential, but unlike adult mesenchymal stem cells, it can be produced in large numbers for every patient. For therapeutic applications, however, human-induced pluripotent stem cell-derived progenitors must be produced without animal-derived components (xeno-free) and in accordance with Good Manufacturing Practice guidelines.

Methods

In the present study we investigate the effects of expanding mesodermal progenitor cells derived from two human-induced pluripotent stem cell lines in xeno-free medium supplemented with human platelet lysates and in a commercial high-performance Good Manufacturing Practice-compatible medium (Unison Medium).

Results

The results show that long-term culture in xeno-free and Good Manufacturing Practice-compatible media somewhat affects the morphology, expansion potential, gene expression, and cytokine profile of human-induced pluripotent stem cell-derived progenitors but supports cell viability and maintenance of a mesenchymal phenotype equally well as medium supplemented with fetal bovine serum.

Conclusions

The findings support the potential to manufacture large numbers of clinical-grade human-induced pluripotent stem cell-derived mesenchymal progenitors for applications in personalized regenerative medicine.

Graphical abstract

Electronic supplementary material

The online version of this article (10.1186/s13287-018-1119-3) contains supplementary material, which is available to authorized users.

Toward the development of true "off-the-shelf" synthetic T-cell immunotherapy

Recent outstanding clinical results produced by engineered T cells, including chimeric antigen receptors, have already facilitated further research that broadens their applicability. One such direction is to explore new T cell sources for allogeneic “off‐the‐shelf” adoptive immunotherapy. Human pluripotent stem cells could serve as an alternative cell source for this purpose due to their unique features of infinite propagation ability and pluripotency. Here, we describe the current state of engineered T cell transfer with the focus on cell manufacturing processes and the potentials and challenges of induced pluripotent stem cell‐derived T cells as a starting material to construct off‐the‐shelf T‐cell banks.

Addressing the Manufacturing Challenges of Cell-Based Therapies

Exciting developments in the cell therapy field over the last decades have led to an increasing number of clinical trials and the first cell products receiving marketing authorization. In spite of substantial progress in the field, manufacturing of cell-based therapies presents multiple challenges that need to be addressed in order to assure the development of safe, efficacious, and cost-effective cell therapies.The manufacturing process of cell-based therapies generally requires tissue collection, cell isolation, culture and expansion (upstream processing), cell harvest, separation and purification (downstream processing), and, finally, product formulation and storage. Each one of these stages presents significant challenges that have been the focus of study over the years, leading to innovative and groundbreaking technological advances, as discussed throughout this chapter.Delivery of cell-based therapies relies on defining product targets while controlling process variable impact on cellular features. Moreover, commercial viability is a critical issue that has had damaging consequences for some therapies. Implementation of cost-effectiveness measures facilitates healthy process development, potentially being able to influence end product pricing.Although cell-based therapies represent a new level in bioprocessing complexity in every manufacturing stage, they also show unprecedented levels of therapeutic potential, already radically changing the landscape of medical care.

Pluripotent Stem Cells for Retinal Tissue Engineering: Current Status and Future Prospects

The retina is a very fine and layered neural tissue, which vitally depends on the preservation of cells, structure, connectivity and vasculature to maintain vision. There is an urgent need to find technical and biological solutions to major challenges associated with functional replacement of retinal cells. The major unmet challenges include generating sufficient numbers of specific cell types, achieving functional integration of transplanted cells, especially photoreceptors, and surgical delivery of retinal cells or tissue without triggering immune responses, inflammation and/or remodeling. The advances of regenerative medicine enabled generation of three-dimensional tissues (organoids), partially recreating the anatomical structure, biological complexity and physiology of several tissues, which are important targets for stem cell replacement therapies. Derivation of retinal tissue in a dish creates new opportunities for cell replacement therapies of blindness and addresses the need to preserve retinal architecture to restore vision. Retinal cell therapies aimed at preserving and improving vision have achieved many improvements in the past ten years. Retinal organoid technologies provide a number of solutions to technical and biological challenges associated with functional replacement of retinal cells to achieve long-term vision restoration. Our review summarizes the progress in cell therapies of retina, with focus on human pluripotent stem cell-derived retinal tissue, and critically evaluates the potential of retinal organoid approaches to solve a major unmet clinical need—retinal repair and vision restoration in conditions caused by retinal degeneration and traumatic ocular injuries. We also analyze obstacles in commercialization of retinal organoid technology for clinical application.

Growth Behavior of Human Adipose Tissue-Derived Stromal/Stem Cells at Small Scale: Numerical and Experimental Investigations

Human adipose tissue-derived stromal/stem cells (hASCs) are a valuable source of cells for clinical applications, especially in the field of regenerative medicine. Therefore, it comes as no surprise that the interest in hASCs has greatly increased over the last decade. However, in order to use hASCs in clinically relevant numbers, in vitro expansion is required. Single-use stirred bioreactors in combination with microcarriers (MCs) have shown themselves to be suitable systems for this task. However, hASCs tend to be less robust, and thus, more shear sensitive than conventional production cell lines for therapeutic antibodies and vaccines (e.g., Chinese Hamster Ovary cells CHO, Baby Hamster Kidney cells BHK), for which these bioreactors were originally designed. Hence, the goal of this study was to investigate the influence of different shear stress levels on the growth of humane telomerase reversed transcriptase immortalized hASCs (hTERT-ASC) and aggregate formation in stirred single-use systems at the mL scale: the 125 mL (= SP100) and the 500 mL (= SP300) disposable Corning^® spinner flask. Computational fluid dynamics (CFD) simulations based on an Euler⁻Euler and Euler⁻Lagrange approach were performed to predict the hydrodynamic stresses (0.06⁻0.87 Pa), the residence times (0.4⁻7.3 s), and the circulation times (1.6⁻16.6 s) of the MCs in different shear zones for different impeller speeds and the suspension criteria (Ns1u, Ns1). The numerical findings were linked to experimental data from cultivations studies to develop, for the first time, an unstructured, segregated mathematical growth model for hTERT-ASCs. While the 125 mL spinner flask with 100 mL working volume (SP100) provided up to 1.68^.10⁵ hTERT-ASC/cm² (= 0.63 × 10⁶ living hTERT-ASCs/mL, EF 56) within eight days, the peak living cell density of the 500 mL spinner flask with 300 mL working volume (SP300) was 2.46 × 10⁵ hTERT-ASC/cm² (= 0.88 × 10⁶ hTERT-ASCs/mL, EF 81) and was achieved on day eight. Optimal cultivation conditions were found for Ns1u < N < Ns1, which corresponded to specific power inputs of 0.3⁻1.1 W/m³. The established growth model delivered reliable predictions for cell growth on the MCs with an accuracy of 76⁻96% for both investigated spinner flask types.

Modeling biological and economic uncertainty on cell therapy manufacturing: the choice of culture media supplementation

AIM

To evaluate the cost-effectiveness of autologous cell therapy manufacturing in xeno-free conditions.

MATERIALS & METHODS

Published data on the isolation and expansion of mesenchymal stem/stromal cells introduced donor, multipassage and culture media variability on cell yields and process times on adherent culture flasks to drive cost simulation of a scale-out campaign of 1000 doses of 75 million cells each in a 400 square meter Good Manufacturing Practices facility.

RESULTS & CONCLUSION

Passage numbers in the expansion step are strongly associated with isolation cell yield and drive cost increases per donor of $1970 and 2802 for fetal bovine serum and human platelet lysate. Human platelet lysate decreases passage numbers and process costs in 94.5 and 97% of donors through lower facility and labor costs. Cost savings are maintained with full equipment depreciation and higher numbers of cells per dose, highlighting the number of cells per passage step as the key cost driver.

Overcoming barriers to facilitate the regulation of multi-centre regenerative medicine clinical trials

In the context of regenerative medicine and cellular therapies, the treatment under study often targets a less common disease or condition for which recruitment of a large number of research participants at any given site is challenging, if not impossible. One way to overcome this challenge is with a multi-centre clinical trial. This manuscript first aims to briefly outline the existing ethical, legal and social implications as well as the regulatory frameworks associated with multi-centre regenerative medicine clinical trials. Second, it considers the regulatory limitations and barriers surrounding the initiation of such trials in Canada, the USA and Europe. Third, it concludes with a set of recommendations for facilitating multi-centre clinical trials, at both national and international levels.

Bone regeneration strategies: Engineered scaffolds, bioactive molecules and stem cells current stage and future perspectives

Bone fractures are the most common traumatic injuries in humans. The repair of bone fractures is a regenerative process that recapitulates many of the biological events of embryonic skeletal development. Most of the time it leads to successful healing and the recovery of the damaged bone. Unfortunately, about 5-10% of fractures will lead to delayed healing or non-union, more so in the case of co-morbidities such as diabetes. In this article, we review the different strategies to heal bone defects using synthetic bone graft substitutes, biologically active substances and stem cells. The majority of currently available reviews focus on strategies that are still at the early stages of development and use mostly in vitro experiments with cell lines or stem cells. Here, we focus on what is already implemented in the clinics, what is currently in clinical trials, and what has been tested in animal models. Treatment approaches can be classified in three major categories: i) synthetic bone graft substitutes (BGS) whose architecture and surface can be optimized; ii) BGS combined with bioactive molecules such as growth factors, peptides or small molecules targeting bone precursor cells, bone formation and metabolism; iii) cell-based strategies with progenitor cells combined or not with active molecules that can be injected or seeded on BGS for improved delivery. We review the major types of adult stromal cells (bone marrow, adipose and periosteum derived) that have been used and compare their properties. Finally, we discuss the remaining challenges that need to be addressed to significantly improve the healing of bone defects.

Development and validation of broad-spectrum magnetic particle labelling processes for cell therapy manufacturing

Background

Stem cells are increasingly seen as a solution for many health challenges for an ageing population. However, their potential benefits in the clinic are currently curtailed by technical challenges such as high cell dose requirements and point of care delivery, which pose sourcing and logistics challenges. Cell manufacturing solutions are currently in development to address the supply issue, and ancillary technologies such as nanoparticle-based labelling are being developed to improve stem cell delivery and enable post-treatment follow-up.

Methods

The application of magnetic particle (MP) labelling to potentially scalable cell manufacturing processes was investigated in a range of therapeutically relevant cells, including mesenchymal stromal cells (MSC), cardiomyocytes (CMC) and neural progenitor cells (ReN). The efficiency and the biological effect of particle labelling were analysed using fluorescent imaging and cellular assays.

Results

Flow cytometry and fluorescent microscopy confirmed efficient labelling of monolayer cultures. Viability was shown to be retained post labelling for all three cell types. MSC and CMC demonstrated higher tolerance to MP doses up to 100× the standard concentration. This approach was also successful for MP labelling of suspension cultures, demonstrating efficient MP uptake within 3 h, while cell viability was unaffected by this suspension labelling process. Furthermore, a procedure to enable the storing of MP-labelled cell populations to facilitate cold chain transport to the site of clinical use was investigated. When MP-labelled cells were stored in hypothermic conditions using HypoThermosol solution for 24 h, cell viability and differentiation potential were retained post storage for ReN, MSC and beating CMC.

Conclusions

Our results show that a generic MP labelling strategy was successfully developed for a range of clinically relevant cell populations, in both monolayer and suspension cultures. MP-labelled cell populations were able to undergo transient low-temperature storage whilst maintaining functional capacity in vitro. These results suggest that this MP labelling approach can be integrated into cell manufacturing and cold chain transport processes required for future cell therapy approaches.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0968-0) contains supplementary material, which is available to authorized users.

Cell therapy in acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is driven by a severe pro-inflammatory response resulting in lung damage, impaired gas exchange and severe respiratory failure. There is no specific treatment that effectively improves outcome in ARDS. However, in recent years, cell therapy has shown great promise in preclinical ARDS studies. A wide range of cells have been identified as potential candidates for use, among these are mesenchymal stromal cells (MSCs), which are adult multi-lineage cells that can modulate the immune response and enhance repair of damaged tissue. The therapeutic potential of MSC therapy for sepsis and ARDS has been demonstrated in multiple in vivo models. The therapeutic effect of these cells seems to be due to two different mechanisms; direct cellular interaction, and paracrine release of different soluble products such as extracellular vesicles (EVs)/exosomes. Different approaches have also been studied to enhance the therapeutic effect of these cells, such as the over-expression of anti-inflammatory or pro-reparative molecules. Several clinical trials (phase I and II) have already shown safety of MSCs in ARDS and other diseases. However, several translational issues still need to be addressed, such as the large-scale production of cells, and their potentiality and variability, before the therapeutic potential of stem cells therapies can be realized.

Integrated phosphorescence-based photonic biosensor (iPOB) for monitoring oxygen levels in 3D cell culture systems

Physiological processes, such as respiration, circulation, digestion, and many pathologies alter oxygen concentration in the blood and tissue. When designing culture systems to recapitulate the in vivo oxygen environment, it is important to integrate systems for monitoring and controlling oxygen concentration. Herein, we report the design and engineering of a system to remotely monitor and control oxygen concentration inside a device for 3D cell culture. We integrate a photonic oxygen biosensor into the 3D tissue scaffold and regulate oxygen concentration via the control of purging gas flow. The integrated phosphorescence-based oxygen biosensor employs the quenching of palladium-benzoporphyrin by molecular oxygen to transduce the local oxygen concentration in the 3D tissue scaffold. The system is validated by testing the effects of normoxic and hypoxic culture conditions on healthy and tumorigenic breast epithelial cells, MCF-10A cells and BT474 cells, respectively. Under hypoxic conditions, both cell types exhibited upregulation of downstream target genes for the hypoxia marker gene, hypoxia-inducible factor 1α (HIF1A). Lastly, by monitoring the real-time fluctuation of oxygen concentration, we illustrated the formation of hypoxic culture conditions due to limited diffusion of oxygen through 3D tissue scaffolds.

Impact of poloxamer 188 (Pluronic F-68) additive on cell mechanical properties, quantification by real-time deformability cytometry

Advances in cellular therapies have led to the development of new approaches for cell product purification and formulation, e.g., utilizing cell endogenous properties such as size and deformability as a basis for separation from potentially harmful undesirable by-products. However, commonly used additives such as Pluronic F-68 and other poloxamer macromolecules can change the mechanical properties of cells and consequently alter their processing. In this paper, we quantified the short-term effect of Pluronic F-68 on the mechanotype of three different cell types (Jurkat cells, red blood cells, and human embryonic kidney cells) using real-time deformability cytometry. The impact of the additive concentration was assessed in terms of cell size and deformability. We observed that cells respond progressively to the presence of Pluronic F-68 within first 3 h of incubation and become significantly stiffer (p-value < 0.001) in comparison to a serum-free control and a control containing serum. We also observed that the short-term response manifested as cell stiffening is true (p-value < 0.001) for the concentration reaching 1% (w/v) of the poloxamer additive in tested buffers. Additionally, using flow cytometry, we assessed that changes in cell deformability triggered by addition of Pluronic F-68 are not accompanied by size or viability alterations.

Dental Mesenchymal Stem Cell-Based Translational Regenerative Dentistry: From Artificial to Biological Replacement

Dentistry is a continuously changing field that has witnessed much advancement in the past century. Prosthodontics is that branch of dentistry that deals with replacing missing teeth using either fixed or removable appliances in an attempt to simulate natural tooth function. Although such "replacement therapies" appear to be easy and economic they fall short of ever coming close to their natural counterparts. Complications that arise often lead to failures and frequent repairs of such devices which seldom allow true physiological function of dental and oral-maxillofacial tissues. Such factors can critically affect the quality of life of an individual. The market for dental implants is continuously growing with huge economic revenues. Unfortunately, such treatments are again associated with frequent problems such as peri-implantitis resulting in an eventual loss or replacement of implants. This is particularly influential for patients having co-morbid diseases such as diabetes or osteoporosis and in association with smoking and other conditions that undoubtedly affect the final treatment outcome. The advent of tissue engineering and regenerative medicine therapies along with the enormous strides taken in their associated interdisciplinary fields such as stem cell therapy, biomaterial development, and others may open arenas to enhancing tissue regeneration via designing and construction of patient-specific biological and/or biomimetic substitutes. This review will overview current strategies in regenerative dentistry while overviewing key roles of dental mesenchymal stem cells particularly those of the dental pulp, until paving the way to precision/translational regenerative medicine therapies for future clinical use.

In situ formation of interpenetrating polymer network using sequential thermal and click crosslinking for enhanced retention of transplanted cells

Injectable hydrogels, which are used as scaffolds in cell therapy, provide a minimally invasive strategy to enhance cell retention and survival at injection site. However, till now, slow in situ gelation, undesired mechanical properties, and weak cell adhesion characteristics of reported hydrogels, have led to improper results. Here, we developed an injectable fully-interpenetrated polymer network (f-IPN) by integration of Diels-Alder (DA) crosslinked network and thermosensitive injectable hydrogel. The proposed DA hydrogels were formed in a slow manner showing robust mechanical properties. Interpenetration of thermosensitive network into DA hydrogel accelerated in situ gel-formation and masked the slow reaction rate of DA crosslinking while keeping its unique features. Two networks were formed by simple syringe injection without the need of any initiator, catalyst, or double barrel syringe. The DA and f-IPN hydrogels showed comparable viscoelastic properties along with outstanding load-bearing and shape-recovery even under high levels of compression. The subcutaneous administration of cardiomyocytes-laden f-IPN hydrogel into nude mice revealed high cell retention and survival after two weeks. Additionally, the cardiomyocyte's identity of retained cells was confirmed by detection of human and cardiac-related markers. Our results indicate that the thermosensitive-covalent networks can open a new horizon within the injection-based cell therapy applications.

Manufacturing human mesenchymal stem cells at clinical scale: process and regulatory challenges

Human mesenchymal stem cell (hMSC)-based therapies are of increasing interest in the field of regenerative medicine. As economic considerations have shown, allogeneic therapy seems to be the most cost-effective method. Standardized procedures based on instrumented single-use bioreactors have been shown to provide billion of cells with consistent product quality and to be superior to traditional expansions in planar cultivation systems. Furthermore, under consideration of the complex nature and requirements of allogeneic hMSC-therapeutics, a new equipment for downstream processing (DSP) was successfully evaluated. This mini-review summarizes both the current state of the hMSC production process and the challenges which have to be taken into account when efficiently producing hMSCs for the clinical scale. Special emphasis is placed on the upstream processing (USP) and DSP operations which cover expansion, harvesting, detachment, separation, washing and concentration steps, and the regulatory demands.