Standardization of Good Manufacturing Practice-compliant production of bone marrow-derived human mesenchymal stromal cells for immunotherapeutic applications

Allogenic bone marrow-derived mesenchymal stromal cell-based therapy for patients with chronic low back pain: a prospective, multicentre, randomised placebo controlled trial (RESPINE study)

OBJECTIVES

To assess the efficacy of a single intradiscal injection of allogeneic bone marrow mesenchymal stromal cells (BM-MSCs) versus a sham placebo in patients with chronic low back pain (LBP).

METHODS

Participants were randomised in a prospective, double-blind, controlled study to receive either sham injection or intradiscal injection of 20 million allogeneic BM-MSC, between April 2018 and December 2022. The first co-primary endpoint was the rate of responders defined by improvement of the Visual Analogue Scale (VAS) for pain of at least 20% and 20 mm, or improvement of the Oswestry Disability Index (ODI) of 20% between baseline and month 12. The secondary structural co-primary endpoint was assessed by the disc fluid content measured by quantitative MRI T2, between baseline and month 12. Secondary endpoints included pain VAS, ODI, the Short Form (SF)-36 and the minimal clinically important difference in all timepoints (1, 3, 6, 12 and 24 months). We determined the immune response associated with allogeneic cell injection between baseline and 6 months. Serious adverse events (SAEs) were recorded.

RESULTS

114 patients were randomised (n=58, BM-MSC group; n=56, sham placebo group). At 12 months, the primary outcome was not reached (74% in the BM-MSC group vs 69% in the placebo group; p=0.77). The groups did not differ in all secondary outcomes. No SAE related to the intervention occurred.

CONCLUSIONS

While our study did not conclusively demonstrate the efficacy of allogeneic BM-MSCs for LBP, the procedure was safe. Long-term outcomes of MSC therapy for LBP are still being studied.

TRIAL REGISTRATION NUMBER

EudraCT 2017-002092-25/ClinicalTrials.gov: NCT03737461.

Investigation of MSC potency metrics via integration of imaging modalities with lipidomic characterization

Mesenchymal stem/stromal cell (MSC) therapies have had limited success so far in clinical trials due in part to heterogeneity in immune-responsive phenotypes. Therefore, techniques to characterize these properties of MSCs are needed during biomanufacturing. Imaging cell shape, or morphology, has been found to be associated with MSC immune responsivity-but a direct relationship between single-cell morphology and function has not been established. We used label-free differential phase contrast imaging and matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) to evaluate single-cell morphology and explore relationships with lipid metabolic immune response. In interferon gamma (IFN-γ)-stimulated MSCs, we found higher lipid abundances from the ceramide-1-phosphate (C1P), phosphatidylcholine (PC), LysoPC, and triglyceride (TAG) families that are involved in cell immune function. Furthermore, we identified differences in lipid signatures in morphologically defined MSC subpopulations. The use of single-cell optical imaging coupled with single-cell spatial lipidomics could assist in optimizing the MSC production process and improve mechanistic understanding of manufacturing process effects on MSC immune activity and heterogeneity.

Fibronectin and vitronectin alleviate adipose-derived stem cells senescence during long-term culture through the AKT/MDM2/P53 pathway

Cellular senescence plays a role in the development of aging-associated degenerative diseases. Cell therapy is recognized as a candidate treatment for degenerative diseases. To achieve the goal of cell therapy, the quality and good characteristics of cells are concerned. Cell expansion relies on two-dimensional culture, which leads to replicative senescence of expanded cells. This study aimed to investigate the effect of cell culture surface modification using fibronectin (FN) and vitronectin (VN) in adipose-derived stem cells (ADSCs) during long-term expansion. Our results showed that ADSCs cultured in FN and VN coatings significantly enhanced adhesion, proliferation, and slow progression of cellular senescence as indicated by lower SA-β-gal activities and decreased expression levels of genes including p16, p21, and p53. The upregulation of integrin α5 and αv genes influences phosphatidylinositol 4,5-bisphosphate 3-kinase (PI3K), and AKT proteins. FN and VN coatings upregulated AKT and MDM2 leading to p53 degradation. Additionally, MDM2 inhibition by Nutlin-3a markedly elevated p53 and p21 expression, increased cellular senescence, and induced the expression of inflammatory molecules including HMGB1 and IL-6. The understanding of FN and VN coating surface influencing ADSCs, especially senescence characteristics, offers a promising and practical point for the cultivation of ADSCs for future use in cell-based therapies.

Local manufacturing processes contribute to variability in human mesenchymal stromal cell expansion while growth media supplements contribute to variability in gene expression and cell function: a Biomedical Excellence for Safer Transfusion (BEST) collaborative study

BACKGROUND AIMS

Culture-derived mesenchymal stromal cells (MSCs) exhibit variable characteristics when manufactured using different methods, source material and culture media. The purpose of this multicenter study was to assess the impact on MSC expansion, gene expression and other characteristics when different laboratories expanded MSCs from cultures initiated with bone marrow-MSC aliquots derived from the same donor source material yet with different growth media.

METHODS

Eight centers expanded MSCs using four human platelet lysate (HPL) and one fetal bovine serum (FBS) products as media supplements. The expanded cells were taken through two passages then assessed for cell count, viability, doubling time, immunophenotype, cell function, immunosuppression and gene expression. Results were analyzed by growth media and by center.

RESULTS

Center methodologies varied by their local seeding density, feeding regimen, inoculation density, base media and other growth media features (antibiotics, glutamine, serum). Doubling times were more dependent on center than on media supplements. Two centers had appropriate immunophenotyping showing all MSC cultures were positive for CD105, CD73, CD90 and negative for CD34, CD45, CD14, HLA-DR. MSCs cultured in media supplemented with FBS compared with HPL featured greater T-cell inhibition potential. Gene expression analysis showed greater impact of the type of media supplement (HPL versus FBS) than the manufacturing center. Specifically, nine genes were decreased in expression and six increased when combining the four HPL-grown MSCs versus FBS (false discovery rate [FDR] <0.01), however, without significant difference between different sources of HPL (FDR <0.01).

CONCLUSIONS

Local manufacturing process plays a critical role in MSC expansion while growth media may influence function and gene expression. All HPL and FBS products supported cell growth.

Translating mesenchymal stem cell and their exosome research into GMP compliant advanced therapy products: Promises, problems and prospects

Mesenchymal stem cells (MSCs) are one of the few stem cell types used in clinical practice as therapeutic agents for immunomodulation and ischemic tissue repair, due to their unique paracrine capacity, multiple differentiation potential, active components in exosomes, and effective mitochondria donation. At present, MSCs derived from tissues such as bone marrow and umbilical cord are widely applied in preclinical and clinical studies. Nevertheless, there remain challenges to the maintenance of consistently good quality MSCs derived from different donors or tissues, directly impacting their application as advanced therapy products. In this review, we discuss the promises, problems, and prospects associated with translation of MSC research into a pharmaceutical product. We review the hurdles encountered in translation of MSCs and MSC-exosomes from the research bench to an advanced therapy product compliant with good manufacturing practice (GMP). These difficulties include how to set up GMP-compliant protocols, what factors affect raw material selection, cell expansion to product formulation, establishment of quality control (QC) parameters, and quality assurance to comply with GMP standards. To avoid human error and reduce the risk of contamination, an automatic, closed system that allows real-time monitoring of QC should be considered. We also highlight potential advantages of pluripotent stem cells as an alternative source for MSC and exosomes generation and manufacture.

Morphology-based deep learning enables accurate detection of senescence in mesenchymal stem cell cultures

BACKGROUND

Cell senescence is a sign of aging and plays a significant role in the pathogenesis of age-related disorders. For cell therapy, senescence may compromise the quality and efficacy of cells, posing potential safety risks. Mesenchymal stem cells (MSCs) are currently undergoing extensive research for cell therapy, thus necessitating the development of effective methods to evaluate senescence. Senescent MSCs exhibit distinctive morphology that can be used for detection. However, morphological assessment during MSC production is often subjective and uncertain. New tools are required for the reliable evaluation of senescent single cells on a large scale in live imaging of MSCs.

RESULTS

We have developed a successful morphology-based Cascade region-based convolution neural network (Cascade R-CNN) system for detecting senescent MSCs, which can automatically locate single cells of different sizes and shapes in multicellular images and assess their senescence state. Additionally, we tested the applicability of the Cascade R-CNN system for MSC senescence and examined the correlation between morphological changes with other senescence indicators.

CONCLUSIONS

This deep learning has been applied for the first time to detect senescent MSCs, showing promising performance in both chronic and acute MSC senescence. The system can be a labor-saving and cost-effective option for screening MSC culture conditions and anti-aging drugs, as well as providing a powerful tool for non-invasive and real-time morphological image analysis integrated into cell production.

Scaling up stem cell production: harnessing the potential of microfluidic devices

Stem cells are specialised cells characterised by their unique ability to both self-renew and transform into a wide array of specialised cell types. The widespread interest in stem cells for regenerative medicine and cultivated meat has led to a significant demand for these cells in both research and practical applications. Despite the growing need for stem cell manufacturing, the industry faces significant obstacles, including high costs for equipment and maintenance, complicated operation, and low product quality and yield. Microfluidic technology presents a promising solution to the abovementioned challenges. As an innovative approach for manipulating liquids and cells within microchannels, microfluidics offers a plethora of advantages at an industrial scale. These benefits encompass low setup costs, ease of operation and multiplexing, minimal energy consumption, and the added advantage of being labour-free. This review presents a thorough examination of the prominent microfluidic technologies employed in stem cell research and explores their promising applications in the burgeoning stem cell industry. It thoroughly examines how microfluidics can enhance cell harvesting from tissue samples, facilitate mixing and cryopreservation, streamline microcarrier production, and efficiently conduct cell separation, purification, washing, and final cell formulation post-culture.

Optimized reagents for immunopotency assays on mesenchymal stromal cells for clinical use

Multipotent mesenchymal stromal cells (MSC) offer new therapeutic opportunities based on their ability to modulate an imbalanced immune system. Immunomodulatory potency is typically demonstrated in vitro by measuring the presence of surrogate markers (i.e., indoleamine-2,3-dioxygenase, IDO; tumor necrosis factor receptor type 1, TNFR1) and/or functional assays in co-cultures (i.e., inhibition of lymphoproliferation, polarization of macrophages). However, the biological variability of reagents used in the latter type of assays leads to unreliable and difficult to reproduce data therefore making cross-comparison between batches difficult, both at the intra- and inter-laboratory levels. Herein, we describe a set of experiments aiming at the definition and validation of reliable biological reagents as a first step towards standardization of a potency assay. This approach is based on the co-culture of Wharton's jelly (WJ)-derived MSC and cryopreserved pooled peripheral blood mononuclear cells. Altogether, we successfully defined a robust and reproducible immunopotency assay based on previously described methods incorporating substantial improvements such as cryopreservation of multiple vials of pooled peripheral blood mononuclear cells (PBMC) from 5 individual donors that enable a number of tests with same reagents, also reducing waste of PBMC from individual donors and therefore contributing to a more efficient and ethical method to use substances of human origin (SoHO). The new methodology was successfully validated using 11 batches of clinical grade MSC,WJ. Methods described here contribute to minimize PBMC donor variability while reducing costs, streamlining assay setup and convenience and laying the foundations for harmonization of biological reagents usage in standardized immunopotency assays for MSC. HIGHLIGHTS: • The use of pools of peripheral blood mononuclear cells (PBMCs) in potency assays contributes to robust and reproducible results, which is key in the assessment of mesenchymal stroma cells (MSC) potency for batch release. • Cryopreservation of PBMCs does not impact negatively on their activation and proliferation abilities. • Cryopreserved pools of PBMC constitutes convenient off-the-shelf reagents for potency assays. • Cryopreservation of pooled PBMCs from multiple donors is a way to reduce waste of donated PBMC and its associated costs, as well as reducing the impact of individual donor variability of substances of human origin (SoHO).

Intravitreal allogeneic mesenchymal stem cells: a non-randomized phase II clinical trial for acute non-arteritic optic neuropathy

BACKGROUND

An effective treatment for acute non-arteritic ischemic optic neuropathy (NA-AION) has not been known or proven yet. Previous studies have suggested a neuroprotective effect of allogeneic bone marrow-derived mesenchymal stem cells. This study aims to report the results of a clinical trial on patients with acute non-arteritic optic neuropathy (NA-AION) treated with an intravitreal injection of allogeneic bone marrow-derived mesenchymal stem cells (BM-MSCs) (MSV®).

METHODS

We conducted a prospective, non-randomized, clinical phase-II study (Eudra CT number 2016-003029-40; ClinicalTrials.gov Registry NCT03173638) that included 5 patients with acute unilateral NA-AION diagnosed within 2 weeks after symptom onset and who received an intravitreal injection of allogeneic BM-MSCs (0.05 ml; cell concentration: 1.5 × 106cells/mL). The patients underwent regular ophthalmological examinations and were followed for one year.

RESULTS

In this trial, allogeneic BM-MSCs appeared to be safe as no patients developed signs of acute nor chronic intraocular inflammation or a significant change in intraocular pressure, although an epiretinal membrane was developed in one patient. A retrolental aggregate formed shortly after the injection spontaneously disappeared within a few weeks in another phakic patient, leaving a subcapsular cataract. Visual improvement was noted in 4 patients, and amplitudes of P100 on the visually evoked potentials recordings increased in three patients. The retinal nerve fiber layer and macular ganglion cell layer thicknesses significantly decreased during the follow-up.

CONCLUSIONS

Besides the development of an epiretinal membrane in one patient, the intravitreal application of allogeneic BM-MSCs appeared to be intraocularly well tolerated. Consequently, not only NA-AION but also BM-MSCs deserve more clinical investigational resources and a larger randomized multicenter trial that would provide stronger evidence both about safety and the potential therapeutic efficacy of intravitreally injected allogeneic BM-MSCs in acute NA-AION.

TRIAL REGISTRATION

Safety Assessment of Intravitreal Mesenchymal Stem Cells for Acute Non-Arteritic Anterior Ischemic Optic Neuropathy (NEUROSTEM). NCT03173638. Registered June 02, 2017 https://clinicaltrials.gov/ct2/show/NCT03173638 .

Development of a Robust Consensus Modeling Approach for Identifying Cellular and Media Metabolites Predictive of Mesenchymal Stromal Cell Potency

Mesenchymal stromal cells (MSCs) have shown promise in regenerative medicine applications due in part to their ability to modulate immune cells. However, MSCs demonstrate significant functional heterogeneity in terms of their immunomodulatory function because of differences in MSC donor/tissue source, as well as non-standardized manufacturing approaches. As MSC metabolism plays a critical role in their ability to expand to therapeutic numbers ex vivo, we comprehensively profiled intracellular and extracellular metabolites throughout the expansion process to identify predictors of immunomodulatory function (T-cell modulation and indoleamine-2,3-dehydrogenase (IDO) activity). Here, we profiled media metabolites in a non-destructive manner through daily sampling and nuclear magnetic resonance (NMR), as well as MSC intracellular metabolites at the end of expansion using mass spectrometry (MS). Using a robust consensus machine learning approach, we were able to identify panels of metabolites predictive of MSC immunomodulatory function for 10 independent MSC lines. This approach consisted of identifying metabolites in 2 or more machine learning models and then building consensus models based on these consensus metabolite panels. Consensus intracellular metabolites with high predictive value included multiple lipid classes (such as phosphatidylcholines, phosphatidylethanolamines, and sphingomyelins) while consensus media metabolites included proline, phenylalanine, and pyruvate. Pathway enrichment identified metabolic pathways significantly associated with MSC function such as sphingolipid signaling and metabolism, arginine and proline metabolism, and autophagy. Overall, this work establishes a generalizable framework for identifying consensus predictive metabolites that predict MSC function, as well as guiding future MSC manufacturing efforts through identification of high-potency MSC lines and metabolic engineering.

Novel Potency Assay for MSC Secretome-Based Treatment of Idiopathic Male Infertility Employed Leydig Cells and Revealed Vascular Endothelial Growth Factor as a Promising Potency Marker

Idiopathic male infertility is a highly prevalent diagnosis in developed countries with no specific treatment options. Although empirical medical treatment is widely used to restore male fertility, its efficacy remains limited and inconclusively proven. Therefore, the development of novel therapeutic approaches in this field is a high-priority task. Since the failure of testicular microenvironment components might be involved in the pathogenesis of idiopathic male infertility, application of mesenchymal stromal cells (MSCs) as well as the MSC secretome is worth considering. Previously, we showed that the intratesticular injection of MSCs or the MSC secretome led to the recovery of spermatogenesis at least through replenishing the testicular microenvironment and its maintenance by MSC-secreted paracrine factors. However, the clinical use of such products has been limited to single trials to date. This may be due to the lack of relevant potency tests reflecting mechanisms of action of the MSC secretome in male infertility models. Based on the presumptive MSC secretome mode of action on the testicular microenvironment, we suggest a novel approach to test the potential efficacy of the MSC secretome for idiopathic male infertility treatment. It represents a potency assay based on evaluation of testosterone production by isolated Leydig cells. We demonstrated that the MSC secretome stimulated testosterone secretion by Leydig cells in vitro. We then hypothesized that among the major factors of the MSC secretome, vascular endothelial growth factor (VEGF) could be responsible for the observed effects, which we confirmed by the revealed correlation between the extent of stimulated testosterone production and VEGF concentration in the MSC secretome. The pilot results obtained from the doxorubicin-induced male infertility murine model also indicate the important impact of VEGF in the MSC secretome’s regenerative effects. Utilizing VEGF as a surrogate factor, a novel approach to study the potency of MSC secretome-based products for idiopathic male infertility treatment is suggested. Further validation is required for its implementation into the biopharmaceutical manufacturing process.

Practical Considerations for Translating Mesenchymal Stromal Cell-Derived Extracellular Vesicles from Bench to Bed

Extracellular vesicles (EVs) derived from mesenchymal stromal cells (MSCs) have shown potential for the treatment of tendon and ligament injuries. This approach can eliminate the need to transplant live cells to the human body, thereby reducing issues related to the maintenance of cell viability and stability and potential erroneous differentiation of transplanted cells to bone or tumor. Despite these advantages, there are practical issues that need to be considered for successful clinical application of MSC-EV-based products in the treatment of tendon and ligament injuries. This review aims to discuss the general and tissue-specific considerations for manufacturing MSC-EVs for clinical translation. Specifically, we will discuss Good Manufacturing Practice (GMP)-compliant manufacturing and quality control (parent cell source, culture conditions, concentration method, quantity, identity, purity and impurities, sterility, potency, reproducibility, storage and formulation), as well as safety and efficacy issues. Special considerations for applying MSC-EVs, such as their compatibility with arthroscopy for the treatment of tendon and ligament injuries, are also highlighted.

Optimization of Mesenchymal Stromal Cell (MSC) Manufacturing Processes for a Better Therapeutic Outcome

MSCs products as well as their derived extracellular vesicles, are currently being explored as advanced biologics in cell-based therapies with high expectations for their clinical use in the next few years. In recent years, various strategies designed for improving the therapeutic potential of mesenchymal stromal cells (MSCs), including pre-conditioning for enhanced cytokine production, improved cell homing and strengthening of immunomodulatory properties, have been developed but the manufacture and handling of these cells for their use as advanced therapy medicinal products (ATMPs) remains insufficiently studied, and available data are mainly related to non-industrial processes. In the present article, we will review this topic, analyzing current information on the specific regulations, the selection of living donors as well as MSCs from different sources (bone marrow, adipose tissue, umbilical cord, etc.), in-process quality controls for ensuring cell efficiency and safety during all stages of the manual and automatic (bioreactors) manufacturing process, including cryopreservation, the use of cell banks, handling medicines, transport systems of ATMPs, among other related aspects, according to European and US legislation. Our aim is to provide a guide for a better, homogeneous manufacturing of therapeutic cellular products with special reference to MSCs.

Comparative analysis of mesenchymal stem cells cultivated in serum free media

Stem cells are attractive candidates for the regeneration of tissue and organ. Mesenchymal stem cells (MSCs) have been extensively investigated for their potential applications in regenerative medicine and cell therapy. For developing effective stem cell therapy, the mass production of consistent quality cells is required. The cell culture medium is the most critical aspect of the mass production of qualified stem cells. Classically, fetal bovine serum (FBS) has been used as a culture supplement for MSCs. Due to the undefined and heterologous composition of animal origin components in FBS, efforts to replace animal-derived components with non-animal-derived substances led to safe serum free media (SFM). Adipose derived mesenchymal stem cells (ADSCs) cultivated in SFM provided a more stable population doubling time (PDT) to later passage and more cells in a shorter time compared to FBS containing media. ADSCs cultivated in SFM had lower cellular senescence, lower immunogenicity, and higher genetic stability than ADSCs cultivated in FBS containing media. Differential expression analysis of mRNAs and proteins showed that the expression of genes related with apoptosis, immune response, and inflammatory response were significantly up-regulated in ADSCs cultivated in FBS containing media. ADSCs cultivated in SFM showed similar therapeutic efficacy in an acute pancreatitis mouse model to ADSCs cultivated in FBS containing media. Consideration of clinical trials, not only pre-clinical trial, suggests that cultivation of MSCs using SFM might offer more safe cell therapeutics as well as repeated administration due to low immunogenicity.

Hematopoietic stem cell transplantation with mesenchymal stromal cells in children with metachromatic leukodystrophy

Metachromatic leukodystrophy (MLD) is a lysosomal storage disorder primarily affecting the white matter of the nervous system that results from a deficiency of the arylsulfatase A (ARSA). Mesenchymal stem cells (MSCs) are able to secrete ARSA and have shown beneficial effects in MLD patients. In this retrospective analysis, 10 pediatric MLD patients (MSCG) underwent allogeneic hematopoietic stem cell transplantation (HSCT) and received two applications of 2 x 106 MSCs/kg bodyweight at day +30 and +60 after HSCT between 2007 and 2018. MSC safety, occurrence of graft-versus-host disease (GvHD), blood ARSA levels, chimerism, cell regeneration and engraftment, MRI changes, and the gross motor function were assessed within the first year of HSCT. The long-term data included clinical outcomes and safety aspects of MSCs. Data were compared to a control cohort of seven pediatric MLD patients (CG) who underwent HSCT only. The application of MSC in pediatric MLD patients after allogeneic HSCT was safe and well tolerated and long-term potentially MSC-related adverse effects up to 13.5 years after HSCT were not observed. Patients achieved significantly higher ARSA levels (CG: median 1.03 nmol∙10-6, range 0.41-1.73 | MSCG: median 1.58 nmol∙10-6, range 0.44-2.6; p<0.05), as well as significantly higher leukocyte (p<0.05) and thrombocyte (p<0.001) levels within 365 days of MSC application compared to CG patients. Statistically significant effects on acute GvHD, regeneration of immune cells, engraftment, MRI changes, gross motor function, and clinical outcomes were not detected. In conclusion, the application of MSCs in pediatric MLD patients after allogeneic HSCT was safe and well tolerated. The two applications of 2 x 106/kg allogeneic MSCs were followed by improved engraftment and hematopoiesis within the first year after HSCT. Larger, prospective trials are necessary to evaluate the impact of MSC application on engraftment and hematopoietic recovery.

Extracellular Vesicles of Mesenchymal Stromal Cells Can be Taken Up by Microglial Cells and Partially Prevent the Stimulation Induced by β-amyloid

Mesenchymal stromal/stem cells (MSCs) have great capacity for immune regulation. MSCs provide protective paracrine effects, which are partially exerted by extracellular vesicles (EVs). It has been reported that MSCs-derived EVs (MSC-EVs) contain soluble factors, such as cytokines, chemokines, growth factors and even microRNAs, which confer them similar anti-inflammatory and regenerative effects to MSCs. Moreover, MSCs modulate microglia activation through a dual mechanism of action that relies both on cell contact and secreted factors. Microglia cells are the central nervous system immune cells and the main mediators of the inflammation leading to neurodegenerative disorders. Here, we investigated whether MSC-EVs affect the activation of microglia cells by β-amyloid aggregates. We show that the presence of MSC-EVs can prevent the upregulation of pro-inflammatory mediators such as tumor necrosis factor (TNF)-α and nitric oxide (NO). Both are up-regulated in neurodegenerative diseases representing chronic inflammation, as in Alzheimer’s disease. We demonstrate that MSC-EVs are internalized by the microglia cells. Further, our study supports the use of MSC-EVs as a promising therapeutic tool to treat neuroinflammatory diseases.

Significance Statement

It has been reported that mesenchymal stromal/stem cells and MSC-derived small extracellular vesicles have therapeutic effects in the treatment of various degenerative and inflammatory diseases. Extracellular vesicles are loaded with proteins, lipids and RNA and act as intercellular communication mediators. Here we show that extracellular vesicles can be taken up by murine microglial cells. In addition, they partially reduce the activation of microglial cells against β-amyloid aggregates. This inhibition of microglia activation may present an effective strategy for the control/therapy of neurodegenerative diseases such as Alzheimer’s disease.

Efficient In Vitro Generation of IL-22-Secreting ILC3 From CD34+ Hematopoietic Progenitors in a Human Mesenchymal Stem Cell Niche

Innate lymphoid cells (ILCs) and in particular ILC3s have been described to be vital for mucosal barrier functions and homeostasis within the gastrointestinal (GI) tract. Importantly, IL-22-secreting ILC3 have been implicated in the control of inflammatory bowel disease (IBD) and were shown to reduce the incidence of graft-versus-host disease (GvHD) as well as the risk of transplant rejection. Unfortunately, IL-22-secreting ILC3 are primarily located in mucosal tissues and are not found within the circulation, making access to them in humans challenging. On this account, there is a growing desire for clinically applicable protocols for in vitro generation of effector ILC3. Here, we present an approach for faithful generation of functionally competent human ILC3s from cord blood-derived CD34+ hematopoietic progenitors on layers of human mesenchymal stem cells (MSCs) generated in good manufacturing practice (GMP) quality. The in vitro-generated ILC3s phenotypically, functionally, and transcriptionally resemble bona fide tissue ILC3 with high expression of the transcription factors (TF) RorγT, AHR, and ID2, as well as the surface receptors CD117, CD56, and NKp44. Importantly, the majority of ILC3 belonged to the desired effector subtype with high IL-22 and low IL-17 production. The protocol thus combines the advantages of avoiding xenogeneic components, which were necessary in previous protocols, with a high propensity for generation of IL-22-producing ILC3. The present approach is suitable for the generation of large amounts of ILC3 in an all-human system, which could facilitate development of clinical strategies for ILC3-based therapy in inflammatory diseases and cancer.

Preclinical Assessment of Mesenchymal-Stem-Cell-Based Therapies in Spinocerebellar Ataxia Type 3

The low regeneration potential of the central nervous system (CNS) represents a challenge for the development of new therapeutic strategies for neurodegenerative diseases, including spinocerebellar ataxias. Spinocerebellar ataxia type 3 (SCA3)—or Machado–Joseph disease (MJD)—is the most common dominant ataxia, being mainly characterized by motor deficits; however, SCA3/MJD has a complex and heterogeneous pathophysiology, involving many CNS brain regions, contributing to the lack of effective therapies. Mesenchymal stem cells (MSCs) have been proposed as a potential therapeutic tool for CNS disorders. Beyond their differentiation potential, MSCs secrete a broad range of neuroregulatory factors that can promote relevant neuroprotective and immunomodulatory actions in different pathophysiological contexts. The objective of this work was to study the effects of (1) human MSC transplantation and (2) human MSC secretome (CM) administration on disease progression in vivo, using the CMVMJD135 mouse model of SCA3/MJD. Our results showed that a single CM administration was more beneficial than MSC transplantation—particularly in the cerebellum and basal ganglia—while no motor improvement was observed when these cell-based therapeutic approaches were applied in the spinal cord. However, the effects observed were mild and transient, suggesting that continuous or repeated administration would be needed, which should be further tested.

Quality control methods in musculoskeletal tissue engineering: from imaging to biosensors

Tissue engineering is rapidly progressing toward clinical application. In the musculoskeletal field, there has been an increasing necessity for bone and cartilage replacement. Despite the promising translational potential of tissue engineering approaches, careful attention should be given to the quality of developed constructs to increase the real applicability to patients. After a general introduction to musculoskeletal tissue engineering, this narrative review aims to offer an overview of methods, starting from classical techniques, such as gene expression analysis and histology, to less common methods, such as Raman spectroscopy, microcomputed tomography, and biosensors, that can be employed to assess the quality of constructs in terms of viability, morphology, or matrix deposition. A particular emphasis is given to standards and good practices (GXP), which can be applicable in different sectors. Moreover, a classification of the methods into destructive, noninvasive, or conservative based on the possible further development of a preimplant quality monitoring system is proposed. Biosensors in musculoskeletal tissue engineering have not yet been used but have been proposed as a novel technology that can be exploited with numerous advantages, including minimal invasiveness, making them suitable for the development of preimplant quality control systems.

Hematopoiesis during Ontogenesis, Adult Life, and Aging

In the bone marrow of vertebrates, two types of stem cells coexist-hematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs). Hematopoiesis only occurs when these two stem cell types and their descendants interact. The descendants of HSCs supply the body with all the mature blood cells, while MSCs give rise to stromal cells that form a niche for HSCs and regulate the process of hematopoiesis. The studies of hematopoiesis were initially based on morphological observations, later extended by the use of physiological methods, and were subsequently augmented by massive application of sophisticated molecular techniques. The combination of these methods produced a wealth of new data on the organization and functional features of hematopoiesis in the ontogenesis of mammals and humans. This review summarizes the current views on hematopoiesis in mice and humans, discusses the development of blood elements and hematopoiesis in the embryo, and describes how the hematopoietic system works in the adult organism and how it changes during aging.

Mesenchymal Stromal Cells Attenuate Infection-Induced Acute Respiratory Distress Syndrome in Animal Experiments: A Meta-Analysis

Mesenchymal stromal cell (MSC) therapy is a potential therapy for treating acute lung injury (ALI) or acute respiratory distress syndrome (ARDS), which was widely studied in the last decade. The purpose of our meta-analysis was to investigate the efficacy of MSCs for simulated infection-induced ALI/ARDS in animal trials. PubMed and EMBASE were searched to screen relevant preclinical trials with a prespecified search strategy. 57 studies met the inclusion criteria and were included in our study. Our meta-analysis showed that MSCs can reduce the lung injury score of ALI caused by lipopolysaccharide or bacteria (standardized mean difference (SMD) = −2.97, 95% CI [−3.64 to −2.30], P < 0.00001) and improve the animals’ survival (odds ratio = 3.64, 95% CI [2.55 to 5.19], P < 0.00001). Our study discovered that MSCs can reduce the wet weight to dry weight ratio of the lung (SMD = −2.58, 95% CI [−3.24 to −1.91], P < 0.00001). The proportion of the alveolar sac in the MSC group was higher than that in the control group (SMD = 1.68, 95% CI [1.22 to 2.13], P < 0.00001). Moreover, our study detected that MSCs can downregulate the levels of proinflammatory factors such as interleukin (IL)-1β, IL-6, and tumor necrosis factor-α in the lung and it can upregulate the level of anti-inflammatory factor IL-10. MSCs were also found to reduce the level of neutrophils and total protein in bronchoalveolar lavage fluid, decrease myeloperoxidase (MPO) activity in the lung, and improve lung compliance. MSC therapy may be a promising treatment for ALI/ARDS since it may mitigate the severity of lung injury, modulate the immune balance, and ameliorate the permeability of lung vessels in ALI/ARDS, thus facilitating lung regeneration and repair.

A Step Toward Optimizing Regenerative Medicine Principle to Combat COVID-19

Drugs are currently not licensed in specific to pulverize COVID-19. On an emergency basis, vaccines were approved to prevent the further spread of COVID-19. This serves as a potential background for considering the optimization of biologics. In this context, evidence on convalescent plasma and stem cells has shown a beneficial role. Here, we have considered this as plausible therapy, and further hypothesize that their cocktails will synergistically boost the immunogenicity to relegate COVID-19. This warrants a large volume clinical trial on an emergent basis, because the sooner we establish a safe and effective cure, the better.

MSC Manufacturing for Academic Clinical Trials: From a Clinical-Grade to a Full GMP-Compliant Process

Following European regulation 1394/2007, mesenchymal stromal cell (MSCs) have become an advanced therapy medicinal product (ATMP) that must be produced following the good manufacturing practice (GMP) standards. We describe the upgrade of our existing clinical-grade MSC manufacturing process to obtain GMP certification. Staff organization, premises/equipment qualification and monitoring, raw materials management, starting materials, technical manufacturing processes, quality controls, and the release, thawing and infusion were substantially reorganized. Numerous studies have been carried out to validate cultures and demonstrate the short-term stability of fresh or thawed products, as well their stability during long-term storage. Detailed results of media simulation tests, validation runs and early MSC batches are presented. We also report the validation of a new variant of the process aiming to prepare fresh MSCs for the treatment of specific lesions of Crohn's disease by local injection. In conclusion, we have successfully ensured the adaptation of our clinical-grade MSC production process to the GMP requirements. The GMP manufacturing of MSC products is feasible in the academic setting for a limited number of batches with a significant cost increase, but moving to large-scale production necessary for phase III trials would require the involvement of industrial partners.

Amniotic membrane-mesenchymal stromal cells secreted factors and extracellular vesicle-miRNAs: Anti-inflammatory and regenerative features for musculoskeletal tissues

Human amniotic membrane‐derived mesenchymal stromal cells (hAMSCs) are easily obtained in large quantities and free from ethical concerns. Promising therapeutic results for both hAMSCs and their secreted factors (secretome) were described by several in vitro and preclinical studies, often for treatment of orthopedic disorders such as osteoarthritis (OA) and tendinopathy. For clinical translation of the hAMSC secretome as cell‐free therapy, a detailed characterization of hAMSC‐secreted factors is mandatory. Herein, we tested the presence of 200 secreted factors and 754 miRNAs in extracellular vesicles (EVs). Thirty‐seven cytokines/chemokines were identified at varying abundance, some of which involved in both chemotaxis and homeostasis of inflammatory cells and in positive remodeling of extracellular matrix, often damaged in tendinopathy and OA. We also found 336 EV‐miRNAs, 51 of which accounted for more than 95% of the genetic message. A focused analysis based on miRNAs related to OA and tendinopathy showed that most abundant EV‐miRNAs are teno‐ and chondro‐protective, able to induce M2 macrophage polarization, inhibit inflammatory T cells, and promote Treg. Functional analysis on IL‐1β treated tenocytes and chondrocytes resulted in downregulation of inflammation‐associated genes. Overall, presence of key regulatory molecules and miRNAs explain the promising therapeutic results of hAMSCs and their secretome for treatment of musculoskeletal conditions and are a groundwork for similar studies in other pathologies. Furthermore, identified molecules will pave the way for future studies aimed at more sharply predicting disease‐targeted clinical efficacy, as well as setting up potency and release assays to fingerprint clinical‐grade batches of whole secretome or purified components.

Long-Term Follow-Up After the Application of Mesenchymal Stromal Cells in Children and Adolescents with Steroid-Refractory Graft-Versus-Host Disease

Steroid-refractory graft-versus-host disease (GvHD) is a life-threatening complication after allogeneic hematopoietic stem cell transplantation (alloHSCT). Alternative treatment options are often insufficient. Several studies have proven the efficacy of mesenchymal stromal cells (MSCs) in the treatment of therapy-refractory acute GvHD in adult and pediatric patients. Long-term data in pediatric patients are scarce. In this retrospective analysis, a total of 25 patients with a median age of 10.6 years (range 0.6-22.1 years) who received bone marrow-derived MSCs after alloHSCT for the treatment of steroid-refractory III and IV GvHD were analyzed. The median observation period of the surviving patients was 9.3 years (1.3-12.7 years) after HSCT. Among the 25 patients, 10 (40.0%) died [relapse (n = 3), multiorgan failure (n = 6), cardiorespiratory failure (n = 1)] at median 0.5 years (0.2-2.3 years) after HSCT. Partial response and complete remission (PR, CR) of the GvHD were achieved in 76.0% and 24.0% of the patients, respectively. Transplant-related mortality was 0% in the patients who achieved CR after MSC treatment and 26.3% for those with PR. A median improvement by one intestinal or liver GvHD stage (range 1-4) could be achieved after MSC application. No potentially MSC-related long-term adverse effects, for example, secondary malignancy, were identified. In conclusion, the intravenous application of allogeneic MSCs was safe and proved effective for the treatment of steroid-refractory GvHD. However, larger, prospective, and randomized trials are needed to evaluate these findings.

Therapeutic Use of Mesenchymal Stromal Cells: The Need for Inclusive Characterization Guidelines to Accommodate All Tissue Sources and Species

Following their discovery over 50 years ago, mesenchymal stromal cells (MSCs) have become one of the most studied cellular therapeutic products by both academia and industry due to their regenerative potential and immunomodulatory properties. The promise of MSCs as a therapeutic modality has been demonstrated by preclinical data yet has not translated to consistent, successful clinical trial results in humans. Despite the disparities across the field, MSC shareholders are unified under one common goal-to use MSCs as a therapeutic modality to improve the quality of life for those suffering from a malady in which the standard of care is suboptimal or no longer effective. Currently, there is no Food and Drug Administration (FDA)-approved MSC therapy on the market in the United States although several MSC products have been granted regulatory approval in other countries. In this review, we intend to identify hurdles that are impeding therapeutic progress and discuss strategies that may aid in accomplishing this universal goal of widespread therapeutic use.

Cell-Based Therapy Manufacturing in Stirred Suspension Bioreactor: Thoughts for cGMP Compliance

Cell-based therapy (CBT) is attracting much attention to treat incurable diseases. In recent years, several clinical trials have been conducted using human pluripotent stem cells (hPSCs), and other potential therapeutic cells. Various private- and government-funded organizations are investing in finding permanent cures for diseases that are difficult or expensive to treat over a lifespan, such as age-related macular degeneration, Parkinson’s disease, or diabetes, etc. Clinical-grade cell manufacturing requiring current good manufacturing practices (cGMP) has therefore become an important issue to make safe and effective CBT products. Current cell production practices are adopted from conventional antibody or protein production in the pharmaceutical industry, wherein cells are used as a vector to produce the desired products. With CBT, however, the “cells are the final products” and sensitive to physico- chemical parameters and storage conditions anywhere between isolation and patient administration. In addition, the manufacturing of cellular products involves multi-stage processing, including cell isolation, genetic modification, PSC derivation, expansion, differentiation, purification, characterization, cryopreservation, etc. Posing a high risk of product contamination, these can be time- and cost- prohibitive due to maintenance of cGMP. The growing demand of CBT needs integrated manufacturing systems that can provide a more simple and cost-effective platform. Here, we discuss the current methods and limitations of CBT, based upon experience with biologics production. We review current cell manufacturing integration, automation and provide an overview of some important considerations and best cGMP practices. Finally, we propose how multi-stage cell processing can be integrated into a single bioreactor, in order to develop streamlined cGMP-compliant cell processing systems.

The efficacy of mesenchymal stromal cell-derived therapies for acute respiratory distress syndrome-a meta-analysis of preclinical trials

Background

The investigation of mesenchymal stromal cell (MSC)-conditioned medium or extracellular vesicles (exosomes or microvesicles) as a remedy for acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) has become a fast-growing field in recent years. Our purpose was to conduct a meta-analysis to investigate the efficacy of MSC-derived therapies (MDTs) for ALI/ARDS in animal models.

Methods

A meta-analysis of MDTs for ALI/ARDS in animal trials was performed. PubMed and EMBASE were searched to screen relevant preclinical trials with a predetermined search strategy.

Results

A total of 17 studies that compared MDT with the ALI control group were included in our study. The pooled result derived from the comparison of the two groups suggested that MDT could significantly reduce the lung injury score (standardized mean difference (SMD) = − 4.02, 95% CI [− 5.28, − 2.23], P < 0.0001) and improve animal survival (OR = − 6.45, 95% CI [2.78, 14.97], P < 0.0001). MDT mitigated the infiltration of neutrophils in alveoli (SMD = − 3.38, 95% CI [− 4.58, − 2.18], P < 0.00001). MDT also reduced the wet-dry weight ratio of the lung (SMD = − 2.34, 95% CI [− 3.42, − 1.26], P < 0.0001) and the total protein in BALF (SMD = − 2.23, 95% CI [− 3.07, − 1.40], P < 0.00001). Furthermore, MDT was found to downregulate proinflammatory mediators such as IL-1, IL-6 and TNF-a and to upregulate anti-inflammatory mediators such as IL-10.

Conclusion

MDT reduces lung injury and improves survival in animal ARDS models since it can ameliorate lung permeability, decrease inflammatory cell infiltration, downregulate proinflammatory mediators, and upregulate anti-inflammatory mediators. However, more animal studies and human trials are needed for further investigation.

Considerations on chemistry, manufacturing, and control of stem cell products for Investigational New Drug application in China

Tremendous progress has been made in recent years to produce functional cells for cell therapy products. Hundreds of clinical trials of stem cell products (SCPs) have shown promising therapeutic potential worldwide, including the products derived from human pluripotent stem cells (hPSCs), adult stem cells and mesenchymal stem cells (MSC). Before starting a clinical trial, comprehensive chemistry, manufacturing and control (CMC) study is required to assure the safety and quality consistency of SCPs. The heterogeneity of stem cell products arises from the variability in the donor tissues, isolation of cells and differentiation processes, and appropriate testing approaches are needed to characterize and release SCPs. Here we summarize the regulatory considerations of CMC study in Investigational New Drug (IND) application of SCPs in China based on the current knowledge, and they will be updated in the future with the advance of stem cell biology and regulatory science.

Identification and characterization of a large source of primary mesenchymal stem cells tightly adhered to bone surfaces of human vertebral body marrow cavities

Background:

Therapeutic allogeneic mesenchymal stromal cells (MSCs) are currently in clinical trials to evaluate their effectiveness in treating many different disease indications. Eventual commercialization for broad distribution will require further improvements in manufacturing processes to economically manufacture MSCs at scales sufficient to satisfy projected demands. A key contributor to the present high cost of goods sold for MSC manufacturing is the need to create master cell banks from multiple donors, which leads to variability in large-scale manufacturing runs. Therefore, the availability of large single donor depots of primary MSCs would greatly benefit the cell therapy market by reducing costs associated with manufacturing.

Methods:

We have discovered that an abundant population of cells possessing all the hallmarks of MSCs is tightly associated with the vertebral body (VB) bone matrix and only liberated by proteolytic digestion. Here we demonstrate that these vertebral bone-adherent (vBA) MSCs possess all the International Society of Cell and Gene Therapy-defined characteristics (e.g., plastic adherence, surface marker expression and trilineage differentiation) of MSCs, and we have therefore termed them vBA-MSCs to distinguish this population from loosely associated MSCs recovered through aspiration or rinsing of the bone marrow compartment.

Results:

Pilot banking and expansion were performed with vBA-MSCs obtained from 3 deceased donors, and it was demonstrated that bank sizes averaging 2.9 × 10⁸ ± 1.35 × 10⁸ vBA-MSCs at passage 1 were obtainable from only 5 g of digested VB bone fragments. Each bank of cells demonstrated robust proliferation through a total of 9 passages, without significant reduction in population doubling times. The theoretical total cell yield from the entire amount of bone fragments (approximately 300 g) from each donor with limited expansion through 4 passages is 100 trillion (1 × 10¹⁴) vBA-MSCs, equating to over 10⁵ doses at 10 × 10⁶ cells/kg for an average 70-kg recipient.

Discussion:

Thus, we have established a novel and plentiful source of MSCs that will benefit the cell therapy market by overcoming manufacturing and regulatory inefficiencies due to donor-to-donor variability.

The Therapeutic Potential of Mesenchymal Stromal Cells in the Treatment of Chemotherapy-Induced Tissue Damage

Chemotherapy constitutes one of the key treatment modalities for solid and hematological malignancies. Albeit being an effective treatment, chemotherapy application is often limited by its damage to healthy tissues, and curative treatment options for chemotherapy-related side effects are largely missing. As mesenchymal stromal cells (MSCs) are known to exhibit regenerative capacity mainly by supporting a beneficial microenvironment for tissue repair, MSC-based therapies may attenuate chemotherapy-induced tissue injuries. An increasing number of animal studies shows favorable effects of MSC-based treatments; however, clinical trials for MSC therapies in the context of chemotherapy-related side effects are rare. In this concise review, we summarize the current knowledge of the effects of MSCs on chemotherapy-induced tissue toxicities. Both preclinical and early clinical trials investigating MSC-based treatments for chemotherapy-related side reactions are presented, and mechanistic explanations about the regenerative effects of MSCs in the context of chemotherapy-induced tissue damage are discussed. Furthermore, challenges of MSC-based treatments are outlined that need closer investigations before these multipotent cells can be safely applied to cancer patients. As any pro-tumorigenicity of MSCs needs to be ruled out prior to clinical utilization of these cells for cancer patients, the pro- and anti-tumorigenic activities of MSCs are discussed in detail.

Longtime Outcome After Intraosseous Application of Autologous Mesenchymal Stromal Cells in Pediatric Patients and Young Adults with Avascular Necrosis After Steroid or Chemotherapy

Avascular necrosis (AVN) is a severe complication of immunosuppressant therapy or chemotherapy. A beneficial AVN therapy with core decompression (CD) and intraosseous infusion of mesenchymal stromal cells (MSCs) has been described in adult patients, but there are only few data on MSC applications in pediatric and young adult patients (PYAP). Between 2006 and 2015, 14 AVN lesions of 10 PYAP (6 females) with a median age of 16.9 years (range 8.5-25.8 years) received CD and intraosseous application of autologous MSCs. Data of these patients were analyzed regarding efficacy, safety, and feasibility of this procedure as AVN therapy and compared with a control group of 13 AVN lesions of 11 PYAP (5 females) with a median age of 17.9 years (range 13.5-27.5 years) who received CD only. During the follow-up analysis [MSC group: median 3.1 (1.6-5.8) years after CD; CD group: median 2.0 (1.5-8.5) years after CD], relative lesion sizes (as assessed by magnetic resonance imaging) compared with the initial lesion volume, were significantly lower (P < 0.05) in the MSC group (volume reduction to a median of 18.5%) when compared with the CD group (58.0%). One lesion in the MSC group comprised a complete remission. Size progression was not observed in either group. Clinical improvement (pain, mobility) was not significantly different between the two groups. None of the patients experienced treatment-related adverse effects. CD and additional MSC application was regarded safe, effective, feasible, and superior in reducing the lesion size when compared with CD only. Prospective, randomized clinical trials are needed to further evaluate these findings.

Chemical-defined medium supporting the expansion of human mesenchymal stem cells

Objectives

Mesenchymal stem cells (MSCs) have been intensively investigated as to their therapeutic potentials. However, the full chemical-defined medium supporting the isolation and expansion of human MSCs has not been developed yet.

Materials and methods

Here, we developed the full chemical-defined medium, NBVbe medium, via RNA sequencing, bioinformatic analysis, and growth factor screening.

Results

The NBVbe medium contains N2B27 medium with the BSA (bovine serum albumin) replaced by the recombinant human albumin, bFGF (basic fibroblast growth factor), vitamin C, and EGF (epidermal growth factor). The NBVbe medium could support the isolation and expansion of human MSCs from the umbilical cords.

Conclusions

The full chemical-defined medium supporting the isolation and expansion of human MSCs has been developed. This would be helpful for further optimization of the MSC medium, their clinical applications, and molecular characterization.

Clinical Translation of Mesenchymal Stromal Cell Therapy for Graft Versus Host Disease

Graft versus host disease (GVHD) is a common condition in patients subjected to allogeneic hematopoietic stem cell transplantation (HSCT). The immune cells derived from the grafted stem cells attack recipient's tissues, including those from the skin, liver, eyes, mouth, lungs, gastrointestinal tract, neuromuscular system, and genitourinary tract, may lead to severe morbidity and mortality. Acute GVHD can occur within few weeks after the allogeneic cells have engrafted in the recipient while chronic GVHD may occur any time after transplant, typically within months. Although treatable by systemic corticosteroid administration, effective responses are not achieved for a significant proportion of patients, a condition associated with poor prognosis. The use of multipotent mesenchymal stromal cells (MSCs) as an alternative to treat steroid-refractory GVHD had improved last decade, but the results are still controversial. Some studies have shown improvement in the life quality of patients after MSCs treatment, while others have found no significant benefits. In addition to variations in trial design, discrepancies in protocols for MSCs isolation, characterization, and ex vivo manipulation, account for inconsistent clinical results. In this review, we discuss the immunomodulatory properties supporting the therapeutic use of MSCs in GVHD and contextualize the main clinical findings of recent trials using these cells. Critical parameters for the clinical translation of MSCs, including consistent production of MSCs according to Good Manufacturing Practices (GMPs) and informative potency assays for product quality control (QC), are addressed.

Principal Criteria for Evaluating the Quality, Safety and Efficacy of hMSC-Based Products in Clinical Practice: Current Approaches and Challenges

Human Mesenchymal Stem Cells (hMSCs) play an important role as new therapeutic alternatives in advanced therapies and regenerative medicine thanks to their regenerative and immunomodulatory properties, and ability to migrate to the exact area of injury. These properties have made hMSCs one of the more promising cellular active substances at present, particularly in terms of the development of new and innovative hMSC-based products. Currently, numerous clinical trials are being conducted to evaluate the therapeutic activity of hMSC-based products on specific targets. Given the rapidly growing number of hMSC clinical trials in recent years and the complexity of these products due to their cellular component characteristics and medicinal product status, there is a greater need to define more stringent, specific, and harmonized requirements to characterize the quality of the hMSCs and enhance the analysis of their safety and efficacy in final products to be administered to patients. These requirements should be implemented throughout the manufacturing process to guarantee the function and integrity of hMSCs and to ensure that the hMSC-based final product consistently meets its specifications across batches. This paper describes the principal phases involved in the design of the manufacturing process and updates the specific technical requirements needed to address the appropriate clinical use of hMSC-based products. The challenges and limitations to evaluating the safety, efficacy, and quality of hMSCs have been also reviewed and discussed.

Mesenchymal Stromal Cell Therapeutic Delivery: Translational Challenges to Clinical Application

For several decades, multipotent mesenchymal stromal cells (MSCs) have been extensively studied for their therapeutic potential across a wide range of diseases. In the preclinical setting, MSCs demonstrate consistent ability to promote tissue healing, down-regulate excessive inflammation and improve outcomes in animal models. Several proposed mechanisms of action have been posited and demonstrated across an array of in vitro models. However, translation into clinical practice has proven considerably more difficult. A number of prominent well-funded late-phase clinical trials have failed, thus calling out for new efforts to optimize product delivery in the clinical setting. In this review, we discuss novel topics critical to the successful translation of MSCs from pre-clinical to clinical applications. In particular, we focus on the major routes of cell delivery, aspects related to hemocompatibility, and potential safety concerns associated with MSC therapy in the different settings.

Advances in treating bronchopulmonary dysplasia

Introduction: Bronchopulmonary dysplasia (BPD) is a common long-term adverse complication of very premature delivery. Affected infants can suffer chronic respiratory morbidities including lung function abnormalities and reduced exercise capacity even as young adults. Many studies have investigated possible preventative strategies; however, it is equally important to identify optimum management strategies for infants with evolving or established BPD. Areas covered: Respiratory support modalities and established and novel pharmacological treatments. Expert opinion: Respiratory support modalities including proportional assist ventilation and neurally adjusted ventilatory assist are associated with short term improvements in oxygenation indices. Such modalities need to be investigated in appropriate RCTs. Many pharmacological treatments are routinely used with a limited evidence base, for example diuretics. Stem cell therapies in small case series are associated with promising results. More research is required before it is possible to determine if such therapies should be investigated in large RCTs with long-term outcomes.

Mass Spectrometry-based Absolute Quantification of 20S Proteasome Status for Controlled Ex-vivo Expansion of Human Adipose-derived Mesenchymal Stromal/Stem Cells

The proteasome controls a multitude of cellular processes through protein degradation and has been identified as a therapeutic target in oncology. However, our understanding of its function and the development of specific modulators are hampered by the lack of a straightforward method to determine the overall proteasome status in biological samples. Here, we present a method to determine the absolute quantity and stoichiometry of ubiquitous and tissue-specific human 20S proteasome subtypes based on a robust, absolute SILAC-based multiplexed LC-Selected Reaction Monitoring (SRM) quantitative mass spectrometry assay with high precision, accuracy, and sensitivity. The method was initially optimized and validated by comparison with a reference ELISA assay and by analyzing the dynamics of catalytic subunits in HeLa cells following IFNγ-treatment and in range of human tissues. It was then successfully applied to reveal IFNγ- and O2-dependent variations of proteasome status during primary culture of Adipose-derived-mesenchymal Stromal/Stem Cells (ADSCs). The results show the critical importance of controlling the culture conditions during cell expansion for future therapeutic use in humans. We hypothesize that a shift from the standard proteasome to the immunoproteasome could serve as a predictor of immunosuppressive and differentiation capacities of ADSCs and, consequently, that quality control should include proteasomal quantification in addition to examining other essential cell parameters. The method presented also provides a new powerful tool to conduct more individualized protocols in cancer or inflammatory diseases where selective inhibition of the immunoproteasome has been shown to reduce side effects.

Translation of a standardized manufacturing protocol for mesenchymal stromal cells: A systematic comparison of validation and manufacturing data

BACKGROUND

Many data are available on expansion protocols for mesenchymal stromal cells (MSCs) for both experimental settings and manufacturing for clinical trials. However, there is a lack of information on translation of established protocols for Good Manufacturing Practice (GMP) from validation to manufacturing for clinical application. We present the validation and translation of a standardized pre-clinical protocol for isolation and expansion of MSCs for a clinical trial for reconstitution of alveolar bone.

METHODS

Key parameters of 22 large-scale expansions of MSCs from bone marrow (BM) for validation were compared with 11 expansions manufactured for the clinical trial "Jaw bone reconstruction using a combination of autologous mesenchymal stromal cells and biomaterial prior to dental implant placement (MAXILLO1)" aimed at reconstruction of alveolar bone.

RESULTS

Despite variations of the starting material, the robust protocol led to stable performance characteristics of expanded MSCs. Manufacturing of the autologous advanced therapy medicinal product MAXILLO-1-MSC was possible, requiring 21 days for each product. Transport of BM aspirates and MSCs within 24 h was guaranteed. MSCs fulfilled quality criteria requested by the national competent authority. In one case, the delivered MSCs developed a mosaic in chromosomal finding, showing no abnormality in differentiation capacity, growth behavior or surface marker expression during long-term culture. The proportion of cells with the mosaic decreased in long-term culture and cells stopped growth after 38.4 population doublings.

CONCLUSIONS

Clinical use of freshly prepared MSCs, manufactured according to a standardized and validated protocol, is feasible for bone regeneration, even if there was a long local distance between manufacturing center and clinical site. Several parameters, such as colony forming units fibroblasts (CFU-F), percentage of CD34+ cells, cell count of mononuclear cells (MNCs) and white blood cells (WBCs), of the BM may serve as a predictive tool for the yield of MSCs and may help to avoid unnecessary costs for MSC manufacturing due to insufficient cell expansion rates.

A short-term plastic adherence incubation of the stromal vascular fraction leads to a predictable GMP-compliant cell-product

Introduction:Mesenchymal stromal/stem cells (MSCs) derived from fat tissue are an encouraging tool for regenerative medicine. They share properties similar to the bone marrow-derived MSCs, but the amount of MSCs per gram of fat tissue is 500x higher. The fat tissue can easily be digested by collagenase, releasing a heterogeneous cell fraction called stromal vascular fraction (SVF) which contains a variable amount of stromal/stem cells. In Europe, cell products like the SVF derived from fat tissue are considered advanced therapy medicinal product (ATMPs). As a consequence, the manufacturing process has to be approved via GMP-compliant process validation. The problem of the process validation for SVF is the heterogeneity of this fraction.

Methods: Here, we modified existing purification strategies by adding an additional plastic adherence incubation of maximal 20 hours after SVF isolation. The resulting cell fraction was characterized and compared to SVF as well as cultivated adipose-derived stromal/stem cells (ASCs) with respect to viability and cell yield, the expression of surface markers, differentiation potential and cytokine expression.

Results: Short-term incubation significantly reduced the heterogeneity of the resulting cell fraction compared to SVF. The cells were able to differentiate into adipocytes, chondrocytes, and osteoblasts. More importantly, they expressed trophic proteins which have been previously associated with the beneficial effects of MSCs. Furthermore, GMP compliance of the production process described herein was acknowledged by the national regulatory agencies (DE_BB_01_GMP_2017_1018).

Conclusion: Addition of a short purification-step after the SVF isolation is a cheap and fast strategy to isolate a homogeneous uncultivated GMP-compliant cell fraction of ASCs.

Analysis of the therapeutic potential of different administration routes and frequencies of human mesenchymal stromal cells in the SOD1G93A mouse model of amyotrophic lateral sclerosis

Cellular therapy represents a novel option for the treatment of neurodegenerative disorders such as amyotrophic lateral sclerosis (ALS). Its major aim is the generation of a protective environment for degenerating motor neurons. Mesenchymal stromal cells secrete different growth factors and have antiapoptotic and immunomodulatory properties. They can easily and safely be isolated from human bone marrow and are therefore considered promising therapeutic candidates. In the present study, we compared intraventricular application of human mesenchymal stromal cells (hMSCs) versus single and repeated intraspinal injections in the mutant SOD1^G93A transgenic ALS mouse model. We observed significant reduction of lifespan of animals treated by intraventricular hMSC injection compared with the vehicle treated control group, accompanied by changes in weight, general condition, and behavioural assessments. A potential explanation for these rather surprising deleterious effects lies in increased microgliosis detected in the hMSC treated animals. Repeated intraspinal injection at two time points resulted in a slight but not significant increase in survival and significant improvement of motor performance although no hMSC-induced changes of motor neuron numbers, astrogliosis, and microgliosis were detected. Quantitative real time polymerase chain reaction showed reduced expression of endothelial growth factor in animals having received hMSCs twice compared with the vehicle treated control group. hMSCs were detectable at the injection site at Day 20 after injection into the spinal cord but no longer at Day 70. Intraspinal injection of hMSCs may therefore be a more promising option for the treatment of ALS than intraventricular injection and repeated injections might be necessary to obtain substantial therapeutic benefit.

Clinically Relevant Solution for the Hypothermic Storage and Transportation of Human Multipotent Mesenchymal Stromal Cells

The wide use of human multipotent mesenchymal stromal cells (MSCs) in clinical trials requires a full-scale safety and identity evaluation of the cellular product and subsequent transportation between research/medical centres. This necessitates the prolonged hypothermic storage of cells prior to application. The development of new, nontoxic, and efficient media, providing high viability and well-preserved therapeutic properties of MSCs during hypothermic storage, is highly relevant for a successful clinical outcome. In this study, a simple and effective trehalose-based solution was developed for the hypothermic storage of human bone marrow MSC suspensions for further clinical applications. Human bone marrow MSCs were stored at 4°C for 24, 48, and 72 hrs in the developed buffered trehalose solution and compared to several research and clinical grade media: Plasma-Lyte® 148, HypoThermosol® FRS, and Ringer's solution. After the storage, the preservation of viability, identity, and therapeutically associated properties of MSCs were assessed. The hypothermic storage of MSCs in the new buffered trehalose solution provided significantly higher MSC recovery rates and ability of cells for attachment and further proliferation, compared to Plasma-Lyte® 148 and Ringer's solution, and was comparable to research-grade HypoThermosol® FRS. There were no differences in the immunophenotype, osteogenic, and adipogenic differentiation and the immunomodulatory properties of MSCs after 72 hrs of cold storage in these solutions. The obtained results together with the confirmed therapeutic properties of trehalose previously described provide sufficient evidence that the developed trehalose medium can be applied as a low-cost and efficient solution for the hypothermic storage of MSC suspensions, with a high potential for translation into clinical practice.

Nucleic acid delivery to mesenchymal stem cells: a review of nonviral methods and applications

Background

Mesenchymal stem cells (MSCs) are multipotent stem cells that can be isolated and expanded from many tissues, and are being investigated for use in cell therapies. Though MSC therapies have demonstrated some success, none have been FDA approved for clinical use. MSCs lose stemness ex vivo, decreasing therapeutic potential, and face additional barriers in vivo, decreasing therapeutic efficacy. Culture optimization and genetic modification of MSCs can overcome these barriers. Viral transduction is efficient, but limited by safety concerns related to mutagenicity of integrating viral vectors and potential immunogenicity of viral antigens. Nonviral delivery methods are safer, though limited by inefficiency and toxicity, and are flexible and scalable, making them attractive for engineering MSC therapies.

Main text

Transfection method and nucleic acid determine efficiency and expression profile in transfection of MSCs. Transfection methods include microinjection, electroporation, and nanocarrier delivery. Microinjection and electroporation are efficient, but are limited by throughput and toxicity. In contrast, a variety of nanocarriers have been demonstrated to transfer nucleic acids into cells, however nanocarrier delivery to MSCs has traditionally been inefficient. To improve efficiency, plasmid sequences can be optimized by choice of promoter, inclusion of DNA targeting sequences, and removal of bacterial elements. Instead of DNA, RNA can be delivered for rapid protein expression or regulation of endogenous gene expression. Beyond choice of nanocarrier and nucleic acid, transfection can be optimized by priming cells with media additives and cell culture surface modifications to modulate barriers of transfection. Media additives known to enhance MSC transfection include glucocorticoids and histone deacetylase inhibitors. Culture surface properties known to modulate MSC transfection include substrate stiffness and specific protein coating. If nonviral gene delivery to MSCs can be sufficiently improved, MSC therapies could be enhanced by transfection for guided differentiation and reprogramming, transplantation survival and directed homing, and secretion of therapeutics. We discuss utilized delivery methods and nucleic acids, and resulting efficiency and outcomes, in transfection of MSCs reported for such applications.

Conclusion

Recent developments in transfection methods, including nanocarrier and nucleic acid technologies, combined with chemical and physical priming of MSCs, may sufficiently improve transfection efficiency, enabling scalable genetic engineering of MSCs, potentially bringing effective MSC therapies to patients.

Proteomic Profiling of Native Unpassaged and Culture-Expanded Mesenchymal Stromal Cells (MSC)

Human culture-expanded mesenchymal stromal cells (MSC) are being considered for multiple therapeutic applications because of their regenerative and anti-inflammatory properties. Although a large number of MSC can be propagated from a small initial sample, several lines of evidence indicate that MSC lose their immunosuppressive and regenerative potency aftaer multiple passages. In this report, we use the FACSCAP Lyoplate proteomic analysis system to detect changes in cell surface protein expression of CD45^- /CD31^- /CD34^- /CD73⁺ /CD105⁺ stromal cells in unpassaged bone marrow (BM) and through 10 serial culture passages. We provide for the first time a detailed characterization of native unpassaged BM MSC (0.08% of BM mononuclear cells) as well as the changes that occur during the initial expansion. Adipogenic and osteogenic differentiative potential was determined though the serial passages and correlated with immunophenotypic changes and senescence. Among the most prominent were striking decreases in Fas ligand, CD98, CD205, and CD106, accompanied by a gain in the expression of CD49c, CD63, CD98, and class 1 and class 2 major histocompatibility complex (MHC) molecules. Other molecules that are down-modulated with later passage include CD24, CD54, CD59, CD243/P-glycoprotein, and CD273/PD-L2. Early senescence, as defined by the loss of replicative capacity occurring with the loss of differentiative capacity, increase in CDKN2A p16, and increased time to confluence, was accompanied by loss of the motility-associated metalloproteinase CD10 and the proliferation-associated transferrin receptor CD71. Among the strongest statistical associations were loss of MAC-inhibitory protein/CD59, loss of ICAM-1/CD54, and increase in CDKN2A as a function of increasing passage, as well as increased CD10 expression with adipogenic and osteogenic capacities. The data provide a clear set of markers that can be used to assess MSC quality. We suggest that clinically relevant numbers of highly functional low passage MSC can be manufactured starting with large quantities of BM, which are readily available from cadaveric organ donors.

Autologous Mesenchymal Stromal Cells Prevent Transfusion-elicited Sensitization and Upregulate Transitional and Regulatory B Cells

BACKGROUND

We hypothesized that immunomodulatory properties of mesenchymal stromal cells (MSC) may be considered for desensitization.

METHODS

Autologous or allogeneic bone marrow derived MSC were infused via tail vein at 0.5 M (0.5 × 106), 1 M, or 2 M cells/dose on days -2, 3, 6, 9, 12 (prevention) or 14, 17, 20, 23, 26 (treatment) relative to transfusion in a Brown Norway to Lewis rat model (10 groups total, n = 6 per group).

RESULTS

At 4 weeks, pooled analyses demonstrated that autologous and allogeneic MSC were equally effective in reducing IgG1 and IgG2a de novo donor-specific antibody (dnDSA, P < 0.001). Dose-response studies indicated that moderate-dose MSC (5 M total) was most effective in reducing IgG1, IgG2a, and IgG2c dnDSA (P ≤ 0.01). Time course studies determined that preventive and treatment strategies were equally effective in reducing IgG1 and IgG2a dnDSA (P ≤ 0.01). However, individual group analyses determined that moderate-dose (5 M) treatment with autologous MSC was most effective in reducing IgG1, IgG2a, and IgG2c dnDSA (P ≤ 0.01). In this group, dnDSA decreased after 1 week of treatment; regulatory B cells increased in the spleen and peripheral blood mononuclear cells; and transitional B cells increased in the spleen, peripheral blood mononuclear cells, and bone marrow (P < 0.05 for all).

CONCLUSIONS

Our findings indicate that autologous MSC prevent transfusion-elicited sensitization and upregulate transitional, and regulatory B cells. Additional studies are needed to determine the biological relevance of these changes after kidney transplantation.

Adipose tissue-derived mesenchymal stromal cells for clinical application: An efficient isolation approach

PURPOSE OF THE STUDY

Mesenchymal stromal cells (MSCs) are considered a promising tool for cell therapy approaches. The translation of research-based cell culture protocols into procedures that comply with Good Manufacturing Practice (GMP) is critical. The aim of this study was to design a new method for the expansion of MSCs from Adipose Tissue (AT-MSCs) in compliance with GMP, without enzymatic tissue digestion and without the use of animal proteins as source of growth factors.

PATIENTS AND METHODS

MSCs were expanded from 10 periumbilical biopsies. Our new isolation approach is based on: (1) disruption of AT with an automated, closed system; (2) use of GMP-grade medium without the addition of fetal bovine serum or platelet lysate; (3) use of human recombinant Trypsin. AT-MSCs cultured in α-MEM and minced by scalpel were used as control.

RESULTS

It was possible to expand MSCs from all the AT-samples for at least eight passages. MSCs displayed the typical spindle-shape morphology, a high viability, multilineage differentiation potential and high expression levels of the typical MSC-specific surface antigens and genes. Compared to standard method, MSCs obtained with the new method showed higher yield, up to passage 6, and higher purity in terms of percentage of CD34 and CD45 markers. All AT-MSCs exhibit in vitro immunosuppressive capacity and possess a normal karyotype.

CONCLUSIONS

Our data clearly demonstrate that our new approach permits to generate AT-MSCs fully compliant for therapeutic use and better at least in terms of quantity and purity than those obtained with the standard method.