Cryopreserved mesenchymal stromal cells display impaired immunosuppressive properties as a result of heat-shock response and impaired interferon-γ licensing

Adipose-derived mesenchymal stromal cells in clinical trials: Insights from single-cell studies

Mesenchymal Stromal Cells (MSCs) offer tremendous potential for the treatment of various diseases and their healing properties have been explored in hundreds of clinical trials. These trails primarily focus on immunological and neurological disorders, as well as regenerative medicine. Adipose tissue is a rich source of mesenchymal stromal cells and methods to obtain and culture adipose-derived MSCs (AD-MSCs) have been well established. Promising results from pre-clinical testing of AD-MSCs activity prompted clinical trials that further led to the approval of AD-MSCs for the treatment of complex perianal fistulas in Crohn's disease and subcutaneous tissue defects. However, AD-MSC heterogeneity along with various manufacturing protocols or different strategies to boost their activity create the need for standardized quality control procedures and safety assessment of the intended cell product. High-resolution transcriptomic methods have been recently gaining attention, as they deliver insight into gene expression profiles of individual cells, helping to deconstruct cellular hierarchy and differentiation trajectories, and to understand cell-cell interactions within tissues. This article presents a comprehensive overview of completed clinical trials evaluating the safety and efficacy of AD-MSC treatment, together with current single-cell studies of human AD-MSC. Furthermore, our work emphasizes the increasing significance of single-cell research in elucidating the mechanisms of cellular action and predicting their therapeutic effects.

Mesenchymal stem cells biological and biotechnological advances: Implications for clinical applications

BACKGROUND

Mesenchymal stem cells (MSCs) are multipotent stem cells that are able to differentiate into multiple lineages including bone, cartilage, muscle and fat. They hold immunomodulatory properties and therapeutic ability to treat multiple diseases, including autoimmune and chronic degenerative diseases. In this article, we reviewed the different biological properties, applications and clinical trials of MSCs. Also, we discussed the basics of manufacturing conditions, quality control, and challenges facing MSCs in the clinical setting.

METHODS

Extensive review of the literature was conducted through the databases PubMed, Google Scholar, and Cochrane. Papers published since 2015 and covering the clinical applications and research of MSC therapy were considered. Furthermore, older papers were considered when referring to pioneering studies in the field.

RESULTS

The most widely studied stem cells in cell therapy and tissue repair are bone marrow-derived mesenchymal stem cells. Adipose tissue-derived stem cells became more common and to a lesser extent other stem cell sources e.g., foreskin derived MSCs. MSCs therapy were also studied in the setting of COVID-19 infections, ischemic strokes, autoimmune diseases, tumor development and graft rejection. Multiple obstacles, still face the standardization and optimization of MSC therapy such as the survival and the immunophenotype and the efficiency of transplanted cells. MSCs used in clinical settings displayed heterogeneity in their function despite their extraction from healthy donors and expression of similar surface markers.

CONCLUSION

Mesenchymal stem cells offer a rising therapeutic promise in various diseases. However, their potential use in clinical applications requires further investigation.

Cryopreservation of mesenchymal stem/stromal cells using a DMSO-free solution is comparable to DMSO-containing cryoprotectants: results of an international multicenter PACT/BEST collaborative study

BACKGROUND AND AIM

An essential aspect of ensuring availability and stability of mesenchymal stem/stromal cells (MSCs) products for clinical use is that these cells are cryopreserved before individual infusion into patients. Currently, cryopreservation of MSCs involves use of a cryoprotectant solution containing dimethyl sulfoxide (DMSO). However, it is recognized that DMSO may be toxic for both the patient and the MSC product. In this Production Assistance for Cellular Therapies (PACT) and Biomedical Excellence for Safer Transfusion (BEST) Collaborative study, we compared a novel DMSO-free solution with DMSO containing cryoprotectant solutions for freezing MSCs.

METHODS

A DMSO-free cryoprotectant solution containing sucrose, glycerol, and isoleucine (SGI) in a base of Plasmalyte A was prepared at the University of Minnesota. Cryoprotectant solutions containing 5-10% DMSO (in-house) were prepared at seven participating centers (five from USA, one each from Australia and Germany). The MSCs were isolated from bone marrow or adipose tissue and cultured ex vivo per local protocols at each center. The cells in suspension were frozen by aliquoting into vials/bags. For six out of the seven centers, the vials/bags were placed in a controlled rate freezer (one center placed them at -80°C freezer overnight) before transferring to liquid nitrogen. The cells were kept frozen for at least one week before thawing and testing. Pre- and post-thaw assessment included cell viability and recovery, immunophenotype as well as transcriptional and gene expression profiles. Linear regression, mixed effects models and two-sided t-tests were applied for statistical analysis.

RESULTS

MSCs had an average viability of 94.3% (95% CI: 87.2-100%) before cryopreservation, decreasing by 4.5% (95% CI: 0.03-9.0%; P: 0.049) and 11.4% (95% CI: 6.9-15.8%; P< 0.001), for MSCs cryopreserved in the in-house and SGI solutions, respectively. The average recovery of viable MSCs cryopreserved in the SGI was 92.9% (95% CI: 85.7-100.0%), and it was lower by 5.6% (95% CI: 1.3-9.8%, P < 0.013) for the in-house solution. Additionally, MSCs cryopreserved in the two solutions had expected level of expressions for CD45, CD73, CD90, and CD105 with no significant difference in global gene expression profiles.

CONCLUSION

MSCs cryopreserved in a DMSO-free solution containing sucrose, glycerol, and isoleucine in a base of Plasmalyte A had slightly lower cell viability, better recovery, and comparable immunophenotype and global gene expression profiles compared to MSCs cryopreserved in DMSO containing solutions. The average viability of MSCs in the novel solution was above 80% and, thus, likely clinically acceptable. Future studies are suggested to test the post-thaw functions of MSCs cryopreserved in the novel DMSO-free solution.

Systematic review and meta-analysis of the effect of bone marrow-derived cell therapies on hind limb perfusion

Preclinical and clinical studies on the administration of bone marrow-derived cells to restore perfusion show conflicting results. We conducted a systematic review and meta-analysis on preclinical studies to assess the efficacy of bone marrow-derived cells in the hind limb ischemia model and identify possible determinants of therapeutic efficacy. In vivo animal studies were identified using a systematic search in PubMed and EMBASE on 10 January 2022. 85 studies were included for systematic review and meta-analysis. Study characteristics and outcome data on relative perfusion were extracted. The pooled mean difference was estimated using a random effects model. Risk of bias was assessed for all included studies. We found a significant increase in perfusion in the affected limb after administration of bone marrow-derived cells compared to that in the control groups. However, there was a high heterogeneity between studies, which could not be explained. There was a high degree of incomplete reporting across studies. We therefore conclude that the current quality of preclinical research is insufficient (low certainty level as per GRADE assessment) to identify specific factors that might improve human clinical trials.

Mesenchymal stromal cells for improvement of cardiac function following acute myocardial infarction: a matter of timing

Acute myocardial infarction (AMI) is the leading cause of cardiovascular death and remains the most common cause of heart failure. Reopening of the occluded artery, i.e., reperfusion, is the only way to save the myocardium. However, the expected benefits of reducing infarct size are disappointing due to the reperfusion paradox, which also induces specific cell death. These ischemia-reperfusion (I/R) lesions can account for up to 50% of final infarct size, a major determinant for both mortality and the risk of heart failure (morbidity). In this review, we provide a detailed description of the cell death and inflammation mechanisms as features of I/R injury and cardioprotective strategies such as ischemic postconditioning as well as their underlying mechanisms. Due to their biological properties, the use of mesenchymal stromal/stem cells (MSCs) has been considered a potential therapeutic approach in AMI. Despite promising results and evidence of safety in preclinical studies using MSCs, the effects reported in clinical trials are not conclusive and even inconsistent. These discrepancies were attributed to many parameters such as donor age, in vitro culture, and storage time as well as injection time window after AMI, which alter MSC therapeutic properties. In the context of AMI, future directions will be to generate MSCs with enhanced properties to limit cell death in myocardial tissue and thereby reduce infarct size and improve the healing phase to increase postinfarct myocardial performance.

Optimizing cryopreservation conditions for use of fucosylated human mesenchymal stromal cells in anti-inflammatory/immunomodulatory therapeutics

Mesenchymal stem/stromal cells (MSCs) are being increasingly used in cell-based therapies due to their broad anti-inflammatory and immunomodulatory properties. Intravascularly-administered MSCs do not efficiently migrate to sites of inflammation/immunopathology, but this shortfall has been overcome by cell surface enzymatic fucosylation to engender expression of the potent E-selectin ligand HCELL. In applications of cell-based therapies, cryopreservation enables stability in both storage and transport of the produced cells from the manufacturing facility to the point of care. However, it has been reported that cryopreservation and thawing dampens their immunomodulatory/anti-inflammatory activity even after a reactivation/reconditioning step. To address this issue, we employed a variety of methods to cryopreserve and thaw fucosylated human MSCs derived from either bone marrow or adipose tissue sources. We then evaluated their immunosuppressive properties, cell viability, morphology, proliferation kinetics, immunophenotype, senescence, and osteogenic and adipogenic differentiation. Our studies provide new insights into the immunobiology of cryopreserved and thawed MSCs and offer a readily applicable approach to optimize the use of fucosylated human allogeneic MSCs as immunomodulatory/anti-inflammatory therapeutics.

Factors Defining Human Adipose Stem/Stromal Cell Immunomodulation in Vitro

Human adipose tissue-derived stem/stromal cells (hASCs) are adult multipotent mesenchymal stem/stromal cells with immunomodulatory capacities. Here, we present up-to-date knowledge on the impact of different experimental and donor-related factors on hASC immunoregulatory functions in vitro. The experimental determinants include the immunological status of hASCs relative to target immune cells, contact vs. contactless interaction, and oxygen tension. Factors such as the ratio of hASCs to immune cells, the cellular context, the immune cell activation status, and coculture duration are also discussed. Conditioning of hASCs with different approaches before interaction with immune cells, hASC culture in xenogenic or xenofree culture medium, hASC culture in two-dimension vs. three-dimension with biomaterials, and the hASC passage number are among the experimental parameters that greatly may impact the hASC immunosuppressive potential in vitro, thus, they are also considered. Moreover, the influence of donor-related characteristics such as age, sex, and health status on hASC immunomodulation in vitro is reviewed. By analysis of the literature studies, most of the indicated determinants have been investigated in broad non-standardized ranges, so the results are not univocal. Clear conclusions cannot be drawn for the fine-tuned scenarios of many important factors to set a standard hASC immunopotency assay. Such variability needs to be carefully considered in further standardized research. Importantly, field experts' opinions may help to make it clearer.

Resveratrol promotes the differentiation of human umbilical cord mesenchymal stem cells into esophageal fibroblasts via AKT signaling pathway

Objectives: Resveratrol has been implicated in the differentiation and development of human umbilical cord mesenchymal stem cells. The differentiation of into esophageal fibroblasts is a promising strategy for esophageal tissue engineering. However, the pharmacological effect and underlying mechanism of resveratrol on human umbilical cord mesenchymal stem cells differentiation are unknown. Here, we investigated the effects and mechanism of resveratrol on the differentiation of human umbilical cord mesenchymal stem cells. Methods: Using a transwell-membrane coculture system to culture human umbilical cord mesenchymal stem cells and esophageal fibroblasts, we examined how resveratrol act on the differentiation of human umbilical cord mesenchymal stem cells. Immunocytochemistry, Sirius red staining, quantitative real-time PCR, and Western blotting were performed to examine collagen synthesis and possible signaling pathways in human umbilical cord mesenchymal stem cells. Results: We found that resveratrol promoted collagen synthesis and AKT phosphorylation. However, co-treatment of cells with resveratrol and the PI3K inhibitor LY294002 inhibited collagen synthesis and AKT phosphorylation. We demonstrated that resveratrol down-regulated the expression of IL-6, TGF-β, caspase-9, and Bax by activating the AKT pathway in human umbilical cord mesenchymal stem cell. Furthermore, resveratrol inhibited phosphorylated NF-ĸB in human umbilical cord mesenchymal stem cells. Conclusion: Our data suggest that resveratrol promotes the differentiation of human umbilical cord mesenchymal stem cells into fibroblasts. The underlying mechanism is associated with the downregulation of IL-6 and TGF-β via the AKT pathway and by inhibiting the NF-ĸB pathway. Resveratrol may be useful for esophageal tissue engineering.

Media matters: culture medium-dependent hypervariable phenotype of mesenchymal stromal cells

BACKGROUND

Despite a long history of investigation and sustained efforts in clinical testing, the number of market authorisations for mesenchymal stromal cell (MSC) therapies remains limited, with none approved by the United States Food and Drug Administration. Several barriers are impeding the clinical progression of MSC therapies, to the forefront of these is a lack of standardised manufacturing protocols which is further compounded by an absence of biologically meaningful characterisation and release assays. A look at clinical trial registries demonstrates the diversity of MSC expansion protocols with variabilities in cell source, isolation method and expansion medium, among other culture variables, making it extraordinarily difficult to compare study outcomes. Current identification and characterisation standards are insufficient; they are not specific to MSCs and do not indicate cell function or therapeutic action.

METHODS

This work analysed the influence of five widely used culture media formulations on the colony-forming potential, proliferation kinetics, trilineage differentiation potential and immunomodulatory potential of human bone marrow-derived MSCs (BM-MSCs). The surface marker expression profiles were also characterised using a high-content flow cytometry screening panel of 243 markers.

RESULTS

Significant differences in the biological attributes of BM-MSCs including clonogenicity, proliferation, differentiation propensity and immunomodulatory capacity were revealed in response to the composition of the culture medium. Despite their biological differences, all cell preparations uniformly and strongly expressed the standard positive markers proposed for BM-MSCs: CD73, CD90 and CD105. Immunophenotypic profiling revealed that the culture medium also had a significant influence on the surface proteome, with one-third of tested markers exhibiting variable expression profiles. Principal component analysis demonstrated that BM-MSCs isolated and expanded in a proprietary xeno- and serum-free medium displayed the most consistent cell phenotypes with little variability between donors compared to platelet lysate and foetal bovine serum-containing media.

CONCLUSIONS

These data suggest that media composition has a highly significant impact on the biological attributes of MSCs, but standard surface marker tests conceal these differences. The results indicate a need for (1) standardised approaches to manufacturing, with an essential focus on defined media and (2) new biologically relevant tests for MSC characterisation and product release.

Identification of a fundamental cryoinjury mechanism in MSCs and its mitigation through cell-cycle synchronization prior to freezing

Clinical development of cellular therapies, including mesenchymal stem/stromal cell (MSC) treatments, has been hindered by ineffective cryopreservation methods that result in substantial loss of post-thaw cell viability and function. Proposed solutions to generate high potency MSC for clinical testing include priming cells with potent cytokines such as interferon gamma (IFNγ) prior to cryopreservation, which has been shown to enhance post-thaw function, or briefly culturing to allow recovery from cryopreservation injury prior to administering to patients. However, both solutions have disadvantages: cryorecovery increases the complexity of manufacturing and distribution logistics, while the pleiotropic effects of IFNγ may have uncharacterized and unintended consequences on MSC function. To determine specific cellular functions impacted by cryoinjury, we first evaluated cell cycle status. It was discovered that S phase MSC are exquisitely sensitive to cryoinjury, demonstrating heightened levels of delayed apoptosis post-thaw and reduced immunomodulatory function. Blocking cell cycle progression at G0/G1 by growth factor deprivation (commonly known as serum starvation) greatly reduced post-thaw dysfunction of MSC by preventing apoptosis induced by double-stranded breaks in labile replicating DNA that form during the cryopreservation and thawing processes. Viability, clonal growth and T cell suppression function were preserved at pre-cryopreservation levels and were no different than cells prior to freezing or frozen after priming with IFNγ. Thus, we have developed a robust and effective strategy to enhance post-thaw recovery of therapeutic MSC.

Opportunities and challenges: mesenchymal stem cells in the treatment of multiple sclerosis

Multiple sclerosis (MS) was once considered an untreatable disease. Through years of research, many drugs have been discovered and are widely used for the treatment of MS. However, the current treatment can only alleviate the clinical symptoms of MS and has serious side effects. Mesenchymal stem cells (MSCs) provide neuroprotection by migrating to injured tissues, suppressing inflammation, and fostering neuronal repair. Therefore, MSCs therapy holds great promise for MS treatment. This review aimed to assess the feasibility and safety of use of MSCs in MS treatment as well as its development prospect in clinical treatment by analysing the existing clinical studies.

Comparative Analysis of Biological Signatures between Freshly Preserved and Cryo-Preserved Bone Marrow Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) can differentiate into multiple connective tissue lineages, including osteoblasts, chondrocytes, and adipocytes. MSCs secrete paracrine molecules that are associated with immunomodulation, anti-fibrotic effects, and angiogenesis. Due to their orchestrative potential, MSCs have been therapeutically applied for several diseases. An important aspect of this process is the delivery of high-quality MSCs to patients at the right time, and cryo-biology and cryo-preservation facilitate the advancement of the logistics thereof. This study aimed to compare the biological signatures between freshly preserved and cryo-preserved MSCs by using big data sourced from the Pharmicell database. From 2011 to 2022, data on approximately 2300 stem cell manufacturing cases were collected. The dataset included approximately 60 variables, including viability, population doubling time (PDT), immunophenotype, and soluble paracrine molecules. In the dataset, 671 cases with no missing data were able to receive approval from an Institutional Review Board and were analyzed. Among the 60 features included in the final dataset, 20 were selected by experts and abstracted into two features by using a principal component analysis. Circular clustering did not introduce any differences between the two MSC preservation methods. This pattern was also observed when using viability, cluster of differentiation (CD) markers, and paracrine molecular indices as inputs for unsupervised analysis. The individual average PDT and cell viability at most passages did not differ according to the preservation method. Most immunophenotypes (except for the CD14 marker) and paracrine molecules did not exhibit different mean levels or concentrations between the frozen and unfrozen MSC groups. Collectively, the biochemical signatures of the cryo-preserved and unfrozen bone marrow MSCs were comparable.

Mesenchymal stromal cells in hepatic fibrosis/cirrhosis: from pathogenesis to treatment

Hepatic fibrosis/cirrhosis is a significant health burden worldwide, resulting in liver failure or hepatocellular carcinoma (HCC) and accounting for many deaths each year. The pathogenesis of hepatic fibrosis/cirrhosis is very complex, which makes treatment challenging. Endogenous mesenchymal stromal cells (MSCs) have been shown to play pivotal roles in the pathogenesis of hepatic fibrosis. Paradoxically, exogenous MSCs have also been used in clinical trials for liver cirrhosis, and their effectiveness has been observed in most completed clinical trials. There are still many issues to be resolved to promote the use of MSCs in the clinic in the future. In this review, we will examine the controversial role of MSCs in the pathogenesis and treatment of hepatic fibrosis/cirrhosis. We also investigated the clinical trials involving MSCs in liver cirrhosis, summarized the parameters that need to be standardized, and discussed how to promote the use of MSCs from a clinical perspective.

Culture-expanded mesenchymal stromal cell therapy: does it work in knee osteoarthritis? A pathway to clinical success

Osteoarthritis (OA) is a degenerative multifactorial disease with concomitant structural, inflammatory, and metabolic changes that fluctuate in a temporal and patient-specific manner. This complexity has contributed to refractory responses to various treatments. MSCs have shown promise as multimodal therapeutics in mitigating OA symptoms and disease progression. Here, we evaluated 15 randomized controlled clinical trials (RCTs) and 11 nonrandomized RCTs using culture-expanded MSCs in the treatment of knee OA, and we found net positive effects of MSCs on mitigating pain and symptoms (improving function in 12/15 RCTs relative to baseline and in 11/15 RCTs relative to control groups at study endpoints) and on cartilage protection and/or repair (18/21 clinical studies). We examined MSC dose, tissue of origin, and autologous vs. allogeneic origins as well as patient clinical phenotype, endotype, age, sex and level of OA severity as key parameters in parsing MSC clinical effectiveness. The relatively small sample size of 610 patients limited the drawing of definitive conclusions. Nonetheless, we noted trends toward moderate to higher doses of MSCs in select OA patient clinical phenotypes mitigating pain and leading to structural improvements or cartilage preservation. Evidence from preclinical studies is supportive of MSC anti-inflammatory and immunomodulatory effects, but additional investigations on immunomodulatory, chondroprotective and other clinical mechanisms of action are needed. We hypothesize that MSC basal immunomodulatory "fitness" correlates with OA treatment efficacy, but this hypothesis needs to be validated in future studies. We conclude with a roadmap articulating the need to match an OA patient subset defined by molecular endotype and clinical phenotype with basally immunomodulatory "fit" or engineered-to-be-fit-for-OA MSCs in well-designed, data-intensive clinical trials to advance the field.

Harmonised culture procedures minimise but do not eliminate mesenchymal stromal cell donor and tissue variability in a decentralised multicentre manufacturing approach

BACKGROUND

Mesenchymal stromal cells (MSCs), commonly sourced from adipose tissue, bone marrow and umbilical cord, have been widely used in many medical conditions due to their therapeutic potential. Yet, the still limited understanding of the underlying mechanisms of action hampers clinical translation. Clinical potency can vary considerably depending on tissue source, donor attributes, but importantly, also culture conditions. Lack of standard procedures hinders inter-study comparability and delays the progression of the field. The aim of this study was A- to assess the impact on MSC characteristics when different laboratories, performed analysis on the same MSC material using harmonised culture conditions and B- to understand source-specific differences.

METHODS

Three independent institutions performed a head-to-head comparison of human-derived adipose (A-), bone marrow (BM-), and umbilical cord (UC-) MSCs using harmonised culture conditions. In each centre, cells from one specific tissue source were isolated and later distributed across the network to assess their biological properties, including cell expansion, immune phenotype, and tri-lineage differentiation (part A). To assess tissue-specific function, angiogenic and immunomodulatory properties and the in vivo biodistribution were compared in one expert lab (part B).

RESULTS

By implementing a harmonised manufacturing workflow, we obtained largely reproducible results across three independent laboratories in part A of our study. Unique growth patterns and differentiation potential were observed for each tissue source, with similar trends observed between centres. Immune phenotyping verified expression of typical MSC surface markers and absence of contaminating surface markers. Depending on the established protocols in the different laboratories, quantitative data varied slightly. Functional experiments in part B concluded that conditioned media from BM-MSCs significantly enhanced tubulogenesis and endothelial migration in vitro. In contrast, immunomodulatory studies reported superior immunosuppressive abilities for A-MSCs. Biodistribution studies in healthy mice showed lung entrapment after administration of all three types of MSCs, with a significantly faster clearance of BM-MSCs.

CONCLUSION

These results show the heterogeneous behaviour and regenerative properties of MSCs as a reflection of intrinsic tissue-origin properties while providing evidence that the use of harmonised culture procedures can reduce but do not eliminate inter-lab and operator differences.

Bioengineered tissue and cell therapy products are efficiently cryopreserved with pathogen-inactivated human platelet lysate-based solutions

BACKGROUND

There remains much interest in improving cryopreservation techniques for advanced therapy medicinal products (ATMPs). Recently, human platelet lysate (hPL) has emerged as a promising candidate to replace fetal bovine serum (FBS) as a xeno-free culture supplement for the expansion of human cell therapy products. Whether hPL can also substitute for FBS in cryopreservation procedures remains poorly studied. Here, we evaluated several cryoprotective formulations based on a proprietary hPL for the cryopreservation of bioengineered tissues and cell therapy products.

METHODS

We tested different xenogeneic-free, pathogen-inactivated hPL (ihPL)- and non-inactivated-based formulations for cryopreserving bioengineered tissue (cellularized nanostructured fibrin agarose hydrogels (NFAHs)) and common cell therapy products including bone marrow-derived mesenchymal stromal cells (BM-MSCs), human dermal fibroblasts (FBs) and neural stem cells (NSCs). To assess the tissue and cellular properties post-thaw of NFAHs, we analyzed their cell viability, identity and structural and biomechanical properties. Also, we evaluated cell viability, recovery and identity post-thaw in cryopreserved cells. Further properties like immunomodulation, apoptosis and cell proliferation were assessed in certain cell types. Additionally, we examined the stability of the formulated solutions. The formulations are under a bidding process with MD Bioproducts (Zurich, Switzerland) and are proprietary.

RESULTS

Amongst the tissue-specific solutions, Ti5 (low-DMSO and ihPL-based) preserved the viability and the phenotype of embedded cells in NFAHs and preserved the matrix integrity and biomechanical properties similar to those of the standard cryopreservation solution (70% DMEM + 20% FBS + 10% DMSO). All solutions were stable at - 20 °C for at least 3 months. Regarding cell-specific solutions, CeA maintained the viability of all cell types > 80%, preserved the immunomodulatory properties of BM-MSCs and promoted good recovery post-thaw. Besides, both tested solutions were stable at - 20 °C for 18 months. Finally, we established that there is a 3-h window in which thawed NFAHs and FBs maintain optimum viability immersed in the formulated solutions and at least 2 h for BM-MSCs.

CONCLUSIONS

Our results show that pathogen-inactivated solutions Ti5 allocated for bioengineered tissues and CeA allocated for cells are efficient and safe candidates to cryopreserve ATMPs and offer a xenogeneic-free and low-DMSO alternative to commercially available cryoprotective solutions.

Stem cell therapies for neonatal lung diseases: Are we there yet?

Lung diseases are a main cause of mortality and morbidity in neonates. Despite major breakthroughs, therapies remain supportive and, in some instances, contribute to lung injury. Because the neonatal lung is still developing, the ideal therapy should be capable of preventing/repairing lung injury while at the same time, promoting lung growth. Cell-based therapies hold high hopes based on laboratory experiments in animal models of neonatal lung injury. Mesenchymal stromal cells and amnion epithelial cells are now in early phase clinical trials to test the feasibility, safety and early signs of efficacy in preterm infants at risk of developing bronchopulmonary dysplasia. Other cell-based therapies are being explored in experimental models of congenital diaphragmatic hernia and alveolar capillary dysplasia. This review will summarize current evidence that has lead to the clinical translation of cell-based therapies and highlights controversies and the numerous questions that remain to be addressed to harness the putative repair potential of cell-based therapies.

Rapid and effective preparation of clonal bone marrow-derived mesenchymal stem/stromal cell sheets to reduce renal fibrosis

Allogeneic "off-the-shelf" mesenchymal stem/stromal cell (MSC) therapy requires scalable, quality-controlled cell manufacturing and distribution systems to provide clinical-grade products using cryogenic cell banking. However, previous studies report impaired cell function associated with administering freeze-thawed MSCs as single cell suspensions, potentially compromising reliable therapeutic efficacy. Using long-term culture-adapted clinical-grade clonal human bone marrow MSCs (cBMSCs) in this study, we engineered cBMSC sheets in 24 h to provide rapid preparation. We then sought to determine the influence of cBMSC freeze-thawing on both in vitro production of pro-regenerative factors and in vivo ability to reduce renal fibrosis in a rat model compared to freshly harvested cBMSCs. Sheets from freeze-thawed cBMSCs sheets exhibited comparable in vitro protein production and gene expression of pro-regenerative factors [e.g., hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), and interleukin 10 (IL-10)] to freshly harvested cBMSC sheets. Additionally, freeze-thawed cBMSC sheets successfully suppressed renal fibrosis in vivo in an established rat ischemia-reperfusion injury model. Despite previous studies reporting that freeze-thawed MSCs exhibit impaired cell functions compared to fresh MSC single cell suspensions, cell sheets engineered from freeze-thawed cBMSCs do not exhibit impaired cell functions, supporting critical steps toward future clinical translation of cBMSC-based kidney disease treatment.

Functional enhancement strategies to potentiate the therapeutic properties of mesenchymal stromal cells for respiratory diseases

Respiratory diseases remain a major health concern worldwide because they subject patients to considerable financial and psychosocial burdens and result in a high rate of morbidity and mortality. Although significant progress has been made in understanding the underlying pathologic mechanisms of severe respiratory diseases, most therapies are supportive, aiming to mitigate symptoms and slow down their progressive course but cannot improve lung function or reverse tissue remodeling. Mesenchymal stromal cells (MSCs) are at the forefront of the regenerative medicine field due to their unique biomedical potential in promoting immunomodulation, anti-inflammatory, anti-apoptotic and antimicrobial activities, and tissue repair in various experimental models. However, despite several years of preclinical research on MSCs, therapeutic outcomes have fallen far short in early-stage clinical trials for respiratory diseases. This limited efficacy has been associated with several factors, such as reduced MSC homing, survival, and infusion in the late course of lung disease. Accordingly, genetic engineering and preconditioning methods have emerged as functional enhancement strategies to potentiate the therapeutic actions of MSCs and thus achieve better clinical outcomes. This narrative review describes various strategies that have been investigated in the experimental setting to functionally potentiate the therapeutic properties of MSCs for respiratory diseases. These include changes in culture conditions, exposure of MSCs to inflammatory environments, pharmacological agents or other substances, and genetic manipulation for enhanced and sustained expression of genes of interest. Future directions and challenges in efficiently translating MSC research into clinical practice are discussed.

What is the need and why is it time for innovative models for understanding lung repair and regeneration?

Advances in tissue engineering continue at a rapid pace and have provided novel methodologies and insights into normal cell and tissue homeostasis, disease pathogenesis, and new potential therapeutic strategies. The evolution of new techniques has particularly invigorated the field and span a range from novel organ and organoid technologies to increasingly sophisticated imaging modalities. This is particularly relevant for the field of lung biology and diseases as many lung diseases, including chronic obstructive pulmonary disease (COPD) and idiopathic fibrosis (IPF), among others, remain incurable with significant morbidity and mortality. Advances in lung regenerative medicine and engineering also offer new potential avenues for critical illnesses such as the acute respiratory distress syndrome (ARDS) which also continue to have significant morbidity and mortality. In this review, an overview of lung regenerative medicine with focus on current status of both structural and functional repair will be presented. This will serve as a platform for surveying innovative models and techniques for study, highlighting the need and timeliness for these approaches.

Mesenchymal stem cells in the treatment of osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a disease caused by mutations in different genes resulting in mild, severe, or lethal forms. With no cure, researchers have investigated the use of cell therapy to correct the underlying molecular defects of OI. Mesenchymal stem cells (MSCs) are of particular interest because of their differentiation capacity, immunomodulatory effects, and their ability to migrate to sites of damage. MSCs can be isolated from different sources, expanded in culture, and have been shown to be safe in numerous clinical applications. This review summarizes the preclinical and clinical studies of MSCs in the treatment of OI. Altogether, the culmination of these studies show that MSCs from different sources: 1) are safe to use in the clinic, 2) migrate to fracture sites and growth sites in bone, 3) engraft in low levels, 4) improve clinical outcome but have a transient effect, 5) have a therapeutic effect most likely due to paracrine mechanisms, and 6) have a reduced therapeutic potential when isolated from patients with OI.

Industrial Biotechnology Conservation Processes: Similarities with Natural Long-Term Preservation of Biological Organisms

Cryopreservation and lyophilization processes are widely used for conservation purposes in the pharmaceutical, biotechnological, and food industries or in medical transplantation. Such processes deal with extremely low temperatures (e.g., -196 °C) and multiple physical states of water, a universal and essential molecule for many biological lifeforms. This study firstly considers the controlled laboratory/industrial artificial conditions used to favor specific water phase transitions during cellular material cryopreservation and lyophilization under the Swiss progenitor cell transplantation program. Both biotechnological tools are successfully used for the long-term storage of biological samples and products, with reversible quasi-arrest of metabolic activities (e.g., cryogenic storage in liquid nitrogen). Secondly, similarities are outlined between such artificial localized environment modifications and some natural ecological niches known to favor metabolic rate modifications (e.g., cryptobiosis) in biological organisms. Specifically, examples of survival to extreme physical parameters by small multi-cellular animals (e.g., tardigrades) are discussed, opening further considerations about the possibility to reversibly slow or temporarily arrest the metabolic activity rates of defined complex organisms in controlled conditions. Key examples of biological organism adaptation capabilities to extreme environmental parameters finally enabled a discussion about the emergence of early primordial biological lifeforms, from natural biotechnology and evolutionary points of view. Overall, the provided examples/similarities confirm the interest in further transposing natural processes and phenomena to controlled laboratory settings with the ultimate goal of gaining better control and modulation capacities over the metabolic activities of complex biological organisms.

M. Rocco P, Cuenca J. Safety and efficacy of clinical-grade, cryopreserved menstrual blood mesenchymal stromal cells in experimental acute respiratory distress syndrome

Background: Treatment for critical care conditions, such as acute respiratory distress syndrome (ARDS), requires ready-to-administer injectable mesenchymal stromal cells (MSCs). A validated cryopreserved therapy based on MSCs derived from menstrual blood (MenSCs) is an attractive option that offers advantages over freshly cultured cells and allows its use as an off-the-shelf therapy in acute clinical conditions. The main goal of this study is to provide evidence on the impact of cryopreservation on different biological functions of MenSCs and to determine the optimal therapeutic dose, safety, and efficacy profile of clinical-grade, cryopreserved (cryo)-MenSCs in experimental ARDS. Methods: Biological functions of fresh versus cryo-MenSCs were compared in vitro. The effects of cryo-MenSCs therapy were evaluated in vivo in ARDS-induced (Escherichia coli lipopolysaccharide) C57BL/6 mice. After 24 h, the animals were treated with five doses ranging from 0.25×10⁵ to 1.25×10⁶ cells/animal. At 2 and 7 days after induction of ARDS, safety and efficacy were evaluated. Results: Clinical-grade cryo-MenSCs injections improved lung mechanics and reduced alveolar collapse, tissue cellularity, and remodelling, decreasing elastic and collagen fiber content in alveolar septa. In addition, administration of these cells modulated inflammatory mediators and promoted pro-angiogenic and anti-apoptotic effects in lung-injured animals. More beneficial effects were observed with an optimal dose of 4×10⁶ cells/Kg than with higher or lower doses. Conclusion: From a translational perspective, the results showed that clinical-grade cryopreserved MenSCs retain their biological properties and exert a therapeutic effect in mild to moderate experimental ARDS. The optimal therapeutic dose was well-tolerated, safe, and effective, favouring improved lung function. These findings support the potential value of an off-the-shelf MenSCs-based product as a promising therapeutic strategy for treating ARDS.

Immunomodulation by placenta-derived decidua stromal cells. Role of histocompatibility, accessory cells and freeze-thawing

BACKGROUND AIMS

Human placenta-derived decidua stromal cells (DSCs) are newly introduced stromal cells that have successfully been used in several clinical trials for the treatment of acute inflammatory diseases. Despite published data about DSCs, deeper exploration of mechanisms of action and crosstalk with other immune cells need to be explored.

METHODS

In mixed lymphocyte culture (MLC), the splenocytes from Balb/c or B6 mice were stimulated using mitogen (concanavalin A), allogeneic (B6 or Balb/c splenocytes) or xenogeneic activation with human peripheral blood mononuclear cells.

RESULTS

When 10% of the mouse bone marrow-derived-MSC, being autologous, allogeneic or haploidentical (from F1), was added, >95% inhibition was seen. Using human (h)-DSCs, the inhibitory capacity was a median 68% as a xenogeneic immunomodulatory cell when used in mitogen and allogeneic setting in mice MLC. However, when human peripheral blood mononuclear cells were used as stimulator for mouse splenocyte (xenogeneic MLC), hDSC showed a median inhibition of 88%. We explored the presence and function of monocytes in the immunomodulatory function of stromal cells. CD14+ monocyte cells reduced the immunosuppressive effect by hDSC. hDSCs did not show any inhibitory effect on natural killer cell activation and proliferation by interleukin-2. In contrast DSCs increased natural killer proliferation by a median of 58%. Fresh or frozen-thawed hDSCs had similar inhibitory effects on human T-cell proliferation (both allo-stimulation and mitogen stimulation) in vitro. Cell viability at room temperature during 24 h was similar using fresh or freeze-thawed DSCs.

CONCLUSIONS

To conclude, histocompatibility and CD14+ monocyte cells had an impact on hDSC immunomodulation but frozen-thawed or freshly prepared cells did not.

Extracellular vesicles rejuvenate the microenvironmental modulating function of recipient tissue-specific mesenchymal stem cells in osteopenia treatment

Systemic transplantation of mesenchymal stem cells (MSCs), such as bone marrow MSCs (BMMSCs) and stem cells from human exfoliated deciduous teeth (SHED), is considered a prominent treatment for osteopenia. However, the mechanism of action of the transplanted MSCs has been poorly elucidated. In the recipient target tissue, including bone and bone marrow, only a few donor MSCs can be detected, suggesting that the direct contribution of donor MSCs may not be expected for osteopenia treatment. Meanwhile, secretomes, especially contents within extracellular vesicles (EVs) released from donor MSCs (MSC-EVs), play key roles in the treatment of several diseases. In this context, administrated donor MSC-EVs may affect bone-forming function of recipient cells. In this review, we discuss how MSC-EVs contribute to bone recovery recipient tissue in osteopenia. We also summarize a novel mechanism of action of systemic administration of SHED-derived EVs (SHED-EVs) in osteopenia. We found that reduced telomerase activity in recipient BMMSCs caused the deficiency of microenvironmental modulating function, including bone and bone marrow-like niche formation and immunomodulation in estrogen-deficient osteopenia model mice. Systemic administration of SHED-EVs could exert therapeutic effects on bone reduction via recovering the telomerase activity, leading to the rejuvenation of the microenvironmental modulating function in recipient BMMSCs, as seen in systemic transplantation of SHED. RNase-preconditioned donor SHED-EVs diminished the therapeutic benefits of administrated SHED-EVs in the recipient osteopenia model mice. These facts suggest that MSC-EV therapy targets the recipient BMMSCs to rejuvenate the microenvironmental modulating function via telomerase activity, recovering bone density. We then introduce future challenges to develop the reproducible MSC-EV therapy in osteopenia.

Placenta‐derived mesenchymal stromal cells as a treatment for refractory chronic gingivostomatitis in cats: eight cases (2018)

OBJECTIVES

The aim of this case series was to collect preliminary data on safety and efficacy of treating cats suffering from refractory feline chronic gingivostomatitis with a single intravenous therapy of cryopreserved placenta-derived mesenchymal stromal cells.

MATERIALS AND METHODS

We planned the prospective inclusion of cats suffering from refractory chronic gingivostomatitis in three veterinary clinics. All cats received a single infusion of 10×10⁶ cryopreserved cells. Follow-up evaluations were done at day 15 and at 2-, 3- and 6-months following infusion. Clinical disease severity was evaluated by dental specialists using a published stomatitis disease activity index scoring system coupled with an owners' assessment questionnaire.

RESULTS

All eight cats attended all follow up visits. Cryopreserved ready-to-use placenta-derived cells administered systemically were safe and resulted in notable clinical improvement in all cats as reported by stomatitis disease activity index scoring and owner's survey.

CLINICAL SIGNIFICANCE

Infusion of cryopreserved freshly thawed placenta-derived mesenchymal stromal cells appears to promote clinical and consequently behavioural benefits in cats with refractory chronic gingivostomatitis after having undergone full-mouth or premolar-molar tooth extraction. Future randomised studies are required to confirm safety and efficacy of this treatment.

Cryopreservation does not change the performance and characteristics of allogenic mesenchymal stem cells highly over-expressing a cytoplasmic therapeutic transgene for cancer treatment

Background

Mesenchymal stem cells (MSCs) driven gene directed enzyme prodrug therapy is a promising approach to deliver therapeutic agents to target heterogenous solid tumours. To democratize such a therapy, cryopreservation along with cold chain transportation is an essential part of the logistical process and supply chain. Previously, we have successfully engineered MSCs by a non-viral DNA transfection approach for prolonged and exceptionally high expression of the fused transgene cytosine deaminase, uracil phosphoribosyl transferase and green fluorescent protein (CD::UPRT::GFP). The aim of this study was to determine the effects of cryopreservation of MSCs engineered to highly overexpress this cytoplasmic therapeutic transgene.

Methods

Modified MSCs were preserved in a commercially available, GMP-grade cryopreservative—CryoStor10 (CS10) for up to 11 months. Performance of frozen-modified MSCs was compared to freshly modified equivalents in vitro. Cancer killing potency was evaluated using four different cancer cell lines. Migratory potential was assessed using matrigel invasion assay and flow cytometric analysis for CXCR4 expression. Frozen-modified MSC was used to treat canine patients via intra-tumoral injections, or by intravenous infusion followed by a daily dose of 5-flucytosine (5FC).

Results

We found that cryopreservation did not affect the transgene expression, cell viability, adhesion, phenotypic profile, and migration of gene modified canine adipose tissue derived MSCs. In the presence of 5FC, the thawed and freshly modified MSCs showed comparable cytotoxicity towards one canine and three human cancer cell lines in vitro. These cryopreserved cells were stored for about a year and then used to treat no-option-left canine patients with two different types of cancers and notably, the patients showed progression-free interval of more than 20 months, evidence of the effectiveness in treating spontaneously occurring cancers.

Conclusion

This study supports the use of cryopreserved, off-the-shelf transiently transfected MSCs for cancer treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03198-z.

Impact of cryopreservation on CAR T production and clinical response

Adoptive cell therapy with chimeric antigen receptor (CAR) T cells has become an efficient treatment option for patients with hematological malignancies. FDA approved CAR T products are manufactured in centralized facilities from fresh or frozen leukapheresis and the cryopreserved CAR T infusion product is shipped back to the patient. An increasing number of clinical centers produce CAR T cells on-site, which enables the use of fresh and cryopreserved PBMCs and CAR T cells. Here we determined the effect of cryopreservation on PBMCs and CD19 CAR T cells in a cohort of 118 patients treated with fresh CAR T cells and in several patients head-to-head. Cryopreserved PBMCs, obtained from leukapheresis products, contained less erythrocytes and T cells, but were sufficient to produce CAR T cells for therapy. There was no correlation between the recovery of PBMCs and the transduction efficacy, the number of CAR T cells obtained by the end of the manufacturing process, the in vitro reactivity, or the response rate to CAR T therapy. We could show that CAR T cells cryopreserved during the manufacturing process, stored and resumed expansion at a later time point, yielded sufficient cell numbers for treatment and led to complete remissions. Phenotype analysis including T cell subtypes, chemokine receptor and co-inhibitory/stimulatory molecules, revealed that fresh CAR T cells expressed significantly more TIM-3 and contained less effector T cells in comparison to their frozen counterparts. In addition, fresh CAR T infusion products demonstrated increased in vitro anti-tumor reactivity, however cryopreserved CAR T cells still showed high anti-tumor potency and specificity. The recovery of cryopreserved CAR T cells was similar in responding and non-responding patients. Although fresh CAR T infusion products exhibit higher anti-tumor reactivity, the use of frozen PBMCs as staring material and frozen CAR T infusion products seems a viable option, as frozen products still exhibit high in vitro potency and cryopreservation did not seem to affect the clinical outcome.

Safety of autologous freshly expanded mesenchymal stromal cells for the treatment of graft-versus-host disease

Despite the curative potential of hematopoietic cell transplantation (HCT) for hematologic malignancies, graft-versus-host disease (GVHD) remains a substantial cause of morbidity and mortality, particularly if treatment is refractory. Treatment with additional immunosuppression including steroids often leads to opportunistic infections and organ dysfunction. Novel therapies are greatly needed, specifically ones that lead to responses in treatment-refractory patients and are better tolerated. Mesenchymal stromal cells (MSCs) are non-hematopoietic tolerogenic cells present in normal bone marrow (BM), which can be expanded ex vivo to therapeutic doses. Their safety and efficacy have been assessed in inflammatory disorders including GVHD, but heterogeneity in clinical responses has led some to examine MSC manufacturing and administration procedures, which may impact in vivo efficacy. We hypothesized that autologous, early-passage, and culture-recovered (after freeze and thaw) MSCs would be safe and may have superior efficacy. In this phase I single-center trial, we assessed MSC safety and early efficacy of an escalating number of doses (2 × 10⁶/kg doses; dose level 1, single dose; dose level 2, two weekly doses; dose level 3, four weekly doses) in patients aged ≥12 years with treatment-refractory acute or chronic GVHD. Eleven enrolled patients received some or all planned MSC infusions, with a median age at enrollment of 37 years. The most common primary HCT indication was leukemia, and the median time from HCT to first MSC infusion was 2.6 years. MSC infusion was well tolerated, with all severe adverse events expected and determined to be unlikely or definitely not related to the study. Thus, no dose-limiting toxicities occurred in the three dose levels. Three of four patients with acute GVHD (or overlap with acute features) had responses seen at any timepoint, ranging from partial to complete. In those with a chronic GVHD indication (n = 7), an overall response at 3 months was partial in five, stable in one, and progressive in one. No appreciable differences were seen between dose levels in peripheral blood lymphocyte subsets. In conclusion, autologous and culture-recovered MSCs were safe in the setting of refractory GVHD following HCT for hematologic malignancy, and clinical responses were most notable in patients with acute GVHD.

Msx1+ stem cells recruited by bioactive tissue engineering graft for bone regeneration

Critical-sized bone defects often lead to non-union and full-thickness defects of the calvarium specifically still present reconstructive challenges. In this study, we show that neurotrophic supplements induce robust in vitro expansion of mesenchymal stromal cells, and in situ transplantation of neurotrophic supplements-incorporated 3D-printed hydrogel grafts promote full-thickness regeneration of critical-sized bone defects. Single-cell RNA sequencing analysis reveals that a unique atlas of in situ stem/progenitor cells is generated during the calvarial bone healing in vivo. Notably, we find a local expansion of resident Msx1+ skeletal stem cells after transplantation of the in situ cell culture system. Moreover, the enhanced calvarial bone regeneration is accompanied by an increased endochondral ossification that closely correlates to the Msx1+ skeletal stem cells. Our findings illustrate the time-saving and regenerative efficacy of in situ cell culture systems targeting major cell subpopulations in vivo for rapid bone tissue regeneration.

Critical-sized bone defects still present clinical challenges. Here the authors show that transplantation of neurotrophic supplement-incorporated hydrogel grafts promote full-thickness regeneration of the calvarium and perform scRNA-seq to reveal contributing stem/progenitor cells, notably a resident Msx1+ skeletal stem cell population.

Cryostorage of Mesenchymal Stem Cells and Biomedical Cell-Based Products

Mesenchymal stem cells (MSCs) manifest vast opportunities for clinical use due both to their ability for self-renewal and for effecting paracrine therapeutic benefits. At the same time, difficulties with non-recurrent generation of large numbers of cells due to the necessity for long-term MSC expansion ex vivo, or the requirement for repeated sampling of biological material from a patient significantly limits the current use of MSCs in clinical practice. One solution to these problems entails the creation of a biobank using cell cryopreservation technology. This review is aimed at analyzing and classifying literature data related to the development of protocols for the cryopreservation of various types of MSCs and tissue-engineered structures. The materials in the review show that the existing techniques and protocols for MSC cryopreservation are very diverse, which significantly complicates standardization of the entire process. Here, the selection of cryoprotectors and of cryoprotective media shows the greatest variability. Currently, it is the cryopreservation of cell suspensions that has been studied most extensively, whereas there are very few studies in the literature on the freezing of intact tissues or of tissue-engineered structures. However, even now it is possible to develop general recommendations to optimize the cryopreservation process, making it less traumatic for cells.

Pooled human bone marrow-derived mesenchymal stromal cells with defined trophic factors cargo promote dermal wound healing in diabetic rats by improved vascularization and dynamic recruitment of M2-like macrophages

Human Mesenchymal Stromal Cells (hMSCs) are a promising source for cell-based therapies. Yet, transition to phase III and IV clinical trials is remarkably slow. To mitigate donor variabilities and to obtain robust and valid clinical data, we aimed first to develop a manufacturing concept balancing large-scale production of pooled hMSCs in a minimal expansion period, and second to test them for key manufacture and efficacy indicators in the clinically highly relevant indication wound healing. Our novel clinical-scale manufacturing concept is comprised of six single donor hMSCs master cell banks that are pooled to a working cell bank from which an extrapolated number of 70,000 clinical doses of 1x10⁶ hMSCs/cm² wound size can be manufactured within only three passages. The pooled hMSC batches showed high stability of key manufacture indicators such as morphology, immune phenotype, proliferation, scratch wound healing, chemotactic migration and angiogenic support. Repeated topical hMSCs administration significantly accelerated the wound healing in a diabetic rat model by delivering a defined growth factor cargo (specifically BDNF, EGF, G-CSF, HGF, IL-1α, IL-6, LIF, osteopontin, VEGF-A, FGF-2, TGF-β, PGE-2 and IDO after priming) at the specific stages of wound repair, namely inflammation, proliferation and remodeling. Specifically, the hMSCs mediated epidermal and dermal maturation and collagen formation, improved vascularization, and promoted cell infiltration. Kinetic analyses revealed transient presence of hMSCs until day (d)4, and the dynamic recruitment of macrophages infiltrating from the wound edges (d3) and basis (d9), eventually progressing to the apical wound on d11. In the wounds, the hMSCs mediated M2-like macrophage polarization starting at d4, peaking at d9 and then decreasing to d11. Our study establishes a standardized, scalable and pooled hMSC therapeutic, delivering a defined cargo of trophic factors, which is efficacious in diabetic wound healing by improving vascularization and dynamic recruitment of M2-like macrophages. This decision-making study now enables the validation of pooled hMSCs as treatment for impaired wound healing in large randomized clinical trials.

Comparison of freshly cultured versus cryopreserved mesenchymal stem cells in animal models of inflammation: A pre-clinical systematic review

Background:

Mesenchymal stem cells (MSCs) are multipotent cells that demonstrate therapeutic potential for the treatment of acute and chronic inflammatory-mediated conditions. Although controversial, some studies suggest that MSCs may lose their functionality with cryopreservation which could render them non-efficacious. Hence, we conducted a systematic review of comparative pre-clinical models of inflammation to determine if there are differences in in vivo measures of pre-clinical efficacy (primary outcomes) and in vitro potency (secondary outcomes) between freshly cultured and cryopreserved MSCs.

Methods:

A systematic search on OvidMEDLINE, EMBASE, BIOSIS, and Web of Science (until January 13, 2022) was conducted. The primary outcome included measures of in vivo pre-clinical efficacy; secondary outcomes included measures of in vitro MSC potency. Risk of bias was assessed by the SYRCLE ‘Risk of Bias’ assessment tool for pre-clinical studies.

Results:

Eighteen studies were included. A total of 257 in vivo pre-clinical efficacy experiments represented 101 distinct outcome measures. Of these outcomes, 2.3% (6/257) were significantly different at the 0.05 level or less; 2 favoured freshly cultured and 4 favoured cryopreserved MSCs. A total of 68 in vitro experiments represented 32 different potency measures; 13% (9/68) of the experiments were significantly different at the 0.05 level or less, with seven experiments favouring freshly cultured MSC and two favouring cryopreserved MSCs.

Conclusions:

The majority of preclinical primary in vivo efficacy and secondary in vitro potency outcomes were not significantly different (p<0.05) between freshly cultured and cryopreserved MSCs. Our systematic summary of the current evidence base may provide MSC basic and clinical research scientists additional rationale for considering a cryopreserved MSC product in their pre-clinical studies and clinical trials as well as help identify research gaps and guide future related research.

Funding:

Ontario Institute for Regenerative Medicine

Possible Effect of the use of Mesenchymal Stromal Cells in the Treatment of Autism Spectrum Disorders: A Review

Autism spectrum disorder (ASD) represents a set of heterogeneous neurodevelopmental conditions defined by impaired social interactions and repetitive behaviors. The number of reported cases has increased over the past decades, and ASD is now a major public health burden. So far, only treatments to alleviate symptoms are available, with still unmet need for an effective disease treatment to reduce ASD core symptoms. Genetic predisposition alone can only explain a small fraction of the ASD cases. It has been reported that environmental factors interacting with specific inter-individual genetic background may induce immune dysfunctions and contribute to the incidence of ASD. Such dysfunctions can be observed at the central level, with increased microglial cells and activation in ASD brains or in the peripheral blood, as reflected by high circulating levels of pro-inflammatory cytokines, abnormal activation of T-cell subsets, presence of auto-antibodies and of dysregulated microbiota profiles. Altogether, the dysfunction of immune processes may result from immunogenetically-determined inefficient immune responses against a given challenge followed by chronic inflammation and autoimmunity. In this context, immunomodulatory therapies might offer a valid therapeutic option. Mesenchymal stromal cells (MSC) immunoregulatory and immunosuppressive properties constitute a strong rationale for their use to improve ASD clinical symptoms. In vitro studies and pre-clinical models have shown that MSC can induce synapse formation and enhance synaptic function with consequent improvement of ASD-like symptoms in mice. In addition, two preliminary human trials based on the infusion of cord blood-derived MSC showed the safety and tolerability of the procedure in children with ASD and reported promising clinical improvement of core symptoms. We review herein the immune dysfunctions associated with ASD provided, the rationale for using MSC to treat patients with ASD and summarize the current available studies addressing this subject.

Heterogeneity of In Vitro Expanded Mesenchymal Stromal Cells and Strategies to Improve Their Therapeutic Actions

Beneficial properties of mesenchymal stromal cells (MSCs) have prompted their use in preclinical and clinical research. Accumulating evidence has been provided for the therapeutic effects of MSCs in several pathologies, including neurodegenerative diseases, myocardial infarction, skin problems, liver disorders and cancer, among others. Although MSCs are found in multiple tissues, the number of MSCs is low, making in vitro expansion a required step before MSC application. However, culture-expanded MSCs exhibit notable differences in terms of cell morphology, physiology and function, which decisively contribute to MSC heterogeneity. The changes induced in MSCs during in vitro expansion may account for the variability in the results obtained in different MSC-based therapy studies, including those using MSCs as living drug delivery systems. This review dissects the different changes that occur in culture-expanded MSCs and how these modifications alter their therapeutic properties after transplantation. Furthermore, we discuss the current strategies developed to improve the beneficial effects of MSCs for successful clinical implementation, as well as potential therapeutic alternatives.

Impact of Cryopreservation and Freeze-Thawing on Therapeutic Properties of Mesenchymal Stromal/Stem Cells and Other Common Cellular Therapeutics

Purpose of Review

Cryopreservation and its associated freezing and thawing procedures–short “freeze-thawing”–are among the final steps in economically viable manufacturing and clinical application of diverse cellular therapeutics. Translation from preclinical proof-of-concept studies to larger clinical trials has indicated that these processes may potentially present an Achilles heel to optimal cell product safety and particularly efficacy in clinical trials and routine use.

Recent Findings

We review the current state of the literature on how cryopreservation of cellular therapies has evolved and how the application of this technique to different cell types is interlinked with their ability to engraft and function upon transfer in vivo, in particular for hematopoietic stem and progenitor cells (HSPCs), their progeny, and therapeutic cell products derived thereof. We also discuss pros and cons how this may differ for non-hematopoietic mesenchymal stromal/stem cell (MSC) therapeutics. We present different avenues that may be crucial for cell therapy optimization, both, for hematopoietic (e.g., effector, regulatory, and chimeric antigen receptor (CAR)-modified T and NK cell based products) and for non-hematopoietic products, such as MSCs and induced pluripotent stem cells (iPSCs), to achieve optimal viability, recovery, effective cell dose, and functionality of the cryorecovered cells.

Summary

Targeted research into optimizing the cryopreservation and freeze-thawing routines and the adjunct manufacturing process design may provide crucial advantages to increase both the safety and efficacy of cellular therapeutics in clinical use and to enable effective market deployment strategies to become economically viable and sustainable medicines.

The Role of Mesenchymal Stem Cells in the Induction of Cancer-Stem Cell Phenotype

Cancer stem cells (CSCs) modify and form their microenvironment by recruiting and activating specific cell types such as mesenchymal stem cells (MSCs). Tumor-infiltrating MSCs help to establish a suitable tumor microenvironment for the restoration of CSCs and tumor progression. In addition, crosstalk between cancer cells and MSCs in the microenvironment induces a CSC phenotype in cancer cells. Many mechanisms are involved in crosstalk between CSCs/cancer cells and MSCs including cell-cell interaction, secretion of exosomes, and paracrine secretion of several molecules including inflammatory mediators, cytokines, and growth factors. Since this crosstalk may contribute to drug resistance, metastasis, and tumor growth, it is suggested that blockade of the crosstalk between MSCs and CSCs/cancer cells can provide a new avenue to improving the cancer therapeutic tools. In this review, we will discuss the role of MSCs in the induction of cancer stem cell phenotype and the restoration of CSCs. We also discuss targeting the crosstalk between MSCs and CSCs/cancer cells as a therapeutic strategy.

Wharton's jelly-derived stromal cells and their cell therapy applications in allogeneic haematopoietic stem cell transplantation

For decades, mesenchymal stromal cells (MSCs) have been of great interest in the fields of regenerative medicine, tissue engineering and immunomodulation. Their tremendous potential makes it desirable to cryopreserve and bank MSCs to increase their accessibility and availability. Postnatally derived MSCs seem to be of particular interest because they are harvested after delivery without ethical controversy, they have the capacity to expand at a higher rate than adult‐derived MSCs, in which expansion decreases with ageing, and they have demonstrated immunological and haematological supportive properties similar to those of adult‐derived MSCs. In this review, we focus on MSCs obtained from Wharton's jelly (the mucous connective tissue of the umbilical cord between the amniotic epithelium and the umbilical vessels). Wharton's jelly MSCs (WJ‐MSCs) are a good candidate for cellular therapy in haematology, with accumulating data supporting their potential to sustain haematopoietic stem cell engraftment and to modulate alloreactivity such as Graft Versus Host Disease (GVHD). We first present an overview of their in‐vitro properties and the results of preclinical murine models confirming the suitability of WJ‐MSCs for cellular therapy in haematology. Next, we focus on clinical trials and discuss tolerance, efficacy and infusion protocols reported in haematology for GVHD and engraftment.

MSCs in Space: Mesenchymal Stromal Cell Therapeutics as Enabling Technology for Long-Distance Manned Space Travel

Purpose of Review

Advancements in space travel, such as space tourism into Earth’s orbit, but also the prospect of long-distance manned space travel to other celestial bodies such as Mars, has generated a clinical need for new enabling technologies to support the long-term well-being of humans during their passage. Here, we will give an outline on the clinical need and practical considerations to MSC therapy as enabling technology for long-distance manned space travel.

Recent Findings

Long-distance space travel entails a threat to the health of astronaut crews due to the low gravity environment and exposure to toxic radiation in space. Multi-organ-system degenerative changes, such as decline in musculoskeletal, hematopoietic, immune system function, and in particular risk of genetic mutations and cancer, are major health concerns. Physical training, pharmacological agents, and protective shielding are among the currently available methods to counteract harmful effects. However, a potential lack of adequate shielding, side effects of pharmacological compounds, and limitations to physical training suggest a need for new countermeasures, to protect space travellers to the best extent. Here, the prospect of cell-based therapy, e.g. mesenchymal stromal/stem cells (MSCs), has been subject to intense research, due to their potent regenerative and immunomodulatory properties. Off-the-shelf MSC therapeutics can be easily maintained in space due to the ambient extremely low-temperature environment, and cryorecovery and even culturing of MSCs under microgravity were shown to be feasible.

Summary

Designing new therapy against harmful radiation is urgent need in space travel. Here we will discuss aspects related to clinical MSC administration to optimize their therapeutic benefit. MSC-based therapy may aid in evolving protective countermeasures for space travellers.

Culture Condition of Bone Marrow Stromal Cells Affects Quantity and Quality of the Extracellular Vesicles

Extracellular vesicles (EVs) released by bone marrow stromal cells (BMSCs) have been shown to act as a transporter of bioactive molecules such as RNAs and proteins in the therapeutic actions of BMSCs in various diseases. Although EV therapy holds great promise to be a safer cell-free therapy overcoming issues related to cell therapy, manufacturing processes that offer scalable and reproducible EV production have not been established. Robust and scalable BMSC manufacturing methods have been shown to enhance EV production; however, the effects on EV quality remain less studied. Here, using human BMSCs isolated from nine healthy donors, we examined the effects of high-performance culture media that can rapidly expand BMSCs on EV production and quality in comparison with the conventional culture medium. We found significantly increased EV production from BMSCs cultured in the high-performance media without altering their multipotency and immunophenotypes. RNA sequencing revealed that RNA contents in EVs from high-performance media were significantly reduced with altered profiles of microRNA enriched in those related to cellular growth and proliferation in the pathway analysis. Given that pre-clinical studies at the laboratory scale often use the conventional medium, these findings could account for the discrepancy in outcomes between pre-clinical and clinical studies. Therefore, this study highlights the importance of selecting proper culture conditions for scalable and reproducible EV manufacturing.

Banking of AT-MSC and its Influence on Their Application to Clinical Procedures

Processing of MSCs to obtain a therapeutic product consists of two main steps: 1) the in vitro expansion of the cells until an appropriate number of them is obtained, and 2) freezing and storage of the expanded cells. The last step is critical and must be optimized so that after thawing the cells retain all their physiological properties including the secretory function. In this paper, we evaluated physiological parameters of AT-MSC's after a full cycle of their processing, particularly freezing and storing at the liquid nitrogen vapor temperature. Based on the recovered proliferative and secretory capacities of the thawed cells, we have designed the optimal technique for processing of MSCs for clinical applications. In our work, we tried to select the best DMSO-based cryoprotectant mixture on the base of post thawing fully retain their properties. We have demonstrated the effectiveness of the use of DMSO in various configurations of the constituent cryoprotective fluids. We have also shown that AT-MSCs that show control levels in most standard tests (viability, shape, culture behaviour, and proliferative properties) after thawing, may show transient variations in some important physiological properties, such as the level of secreted growth factors. Obtained results let us to indicate how to optimize the AT-MSC preparation process for clinical applications. We suggest that before their clinical application the cells should be cultured for at least one passage to recover their physiological stability and thus assure their optimal therapeutic potential.

Steps Toward Standardized In Vitro Assessment of Immunomodulatory Equine Mesenchymal Stromal Cells Before Clinical Application

Inflammation-associated disorders are significant causes of morbidity in horses. Equine single-donor mesenchymal stromal cells (sdMSCs) hold promise as cell-therapy candidates due to their secretory nonprogenitor functions. This has been demonstrated by mononuclear cell suppression assays (MSAs) showing that sdMSCs are blood mononuclear cell (BMC) suppressive in vitro. sdMSCs derived from umbilical cord blood are of clinical interest due to their ease of procurement, multipotency, and immunomodulatory ability. Due to the inherent donor-to-donor heterogeneity of MSCs, the development of robust and easily deployable methods of potency assessment is critical for improving MSCs' predictability in treating inflammatory diseases. This study focuses on the development of robust in vitro potency assays and the assessment of potential sdMSC therapeutic end products generated from pooled sdMSCs (pMSCs). We hypothesized that, compared to MSA using only one donor, MSA using pooled BMCs (pBMCs) is a more robust sdMSC potency assay due to reduced donor BMC heterogeneity. pBMCs were generated by pooling equine BMCs isolated from peripheral blood of five donors in equal ratios. pBMCs were labeled with carboxyfluorescein succinimidyl ester (CFSE) and stored in liquid nitrogen until use. Similarly, pooling sdMSCs from multiple equine donors in equal ratios generated pMSCs. sdMSC cultures were assessed with pBMCs in MSA using Bromodeoxyuridine ELISA and CFSE. Proliferation assessment of BMCs from individual donors revealed varied responses to concanavalin A (ConA) stimulation. MSA using BMCs from single donors further demonstrated BMC donor variability. Utilizing this assay, we have also found that the immunosuppressive potencies of pMSCs are at least equal, if not more, than the calculated mean of individual cultures. MSA based on pBMCs provides a consistent and reproducible equine sdMSC potency assay. This knowledge could be used in production monitoring of cellular potency and as release criteria before clinical use.

Fresh and Cryopreserved Human Umbilical-Cord-Derived Mesenchymal Stromal Cells Attenuate Injury and Enhance Resolution and Repair following Ventilation-Induced Lung Injury

Background: Ventilator-induced lung injury (VILI) frequently worsens acute respiratory distress syndrome (ARDS) severity. Human mesenchymal stem/stromal cells (MSCs) offer considerable therapeutic promise, but the key impediments of clinical translation stem from limitations due to cell source and availability, and concerns regarding the loss of efficacy following cryopreservation. These experiments compared the efficacy of umbilical-cord-derived MSCs (UC-MSCs), a readily available and homogenous tissue source, to the previously more widely utilised bone-marrow-derived MSCs (BM-MSCs). We assessed their capacity to limit inflammation, resolve injury and enhance repair in relevant lung mechanical stretch models, and the impact of cryopreservation on therapeutic efficacy. Methods: In series 1, confluent alveolar epithelial layers were subjected to cyclic mechanical stretch (22% equibiaxial strain) and wound injury, and the potential of the secretome from BM- and UC-derived MSCs to attenuate epithelial inflammation and cell death, and enhance wound repair was determined. In series 2, anesthetized rats underwent VILI, and later received, in a randomised manner, 1 × 10⁷ MSCs/kg intravenously, that were: (i) fresh BM-MSCs, (ii) fresh UC-MSCs or (iii) cryopreserved UC-MSCs. Control animals received a vehicle (PBS). The extent of the resolution of inflammation and injury, and repair was measured at 24 h. Results: Conditioned medium from BM-MSCs and UC-MSCs comparably decreased stretch-induced pulmonary epithelial inflammation and cell death. BM-MSCs and UC-MSCs comparably enhanced wound resolution. In animals subjected to VILI, both fresh BM-MSCs and UC-MSCs enhanced injury resolution and repair, while cryopreserved UC-MSCs comparably retained their efficacy. Conclusions: Cryopreserved UC-MSCs can reduce stretch-induced inflammation and cell death, enhance wound resolution, and enhance injury resolution and repair following VILI. Cryopreserved UC-MSCs represent a more abundant, cost-efficient, less variable and equally efficacious source of therapeutic MSC product.

Single-cell RNA-seq of out-of-thaw mesenchymal stromal cells shows tissue-of-origin differences and inter-donor cell-cycle variations

Background

Human Mesenchymal stromal cells (hMSCs) from various tissue sources are widely investigated in clinical trials. These MSCs are often administered to patients immediately after thawing the cryopreserved product (out-of-thaw), yet little is known about the single-cell transcriptomic landscape and tissue-specific differences of out-of-thaw human MSCs.

Methods

13 hMSC samples derived from 10 “healthy” donors were used to assess donor variability and tissue-of-origin differences in single-cell gene expression profiles. hMSCs derived and expanded from the bone marrow (BM) or cord tissue (CT) underwent controlled-rate freezing for 24 h. Cells were then transferred to the vapor phase of liquid nitrogen for cryopreservation. hMSCs cryopreserved for at least one week, were characterized immediately after thawing using a droplet-based single-cell RNA sequencing method. Data analysis was performed with SC3 and SEURAT pipelines followed by gene ontology analysis.

Results

scRNA-seq analysis of the hMSCs revealed two major clusters of donor profiles, which differ in immune-signaling, cell surface properties, abundance of cell-cycle related transcripts, and metabolic pathways of interest. Within-sample transcriptomic heterogeneity is low. We identified numerous differentially expressed genes (DEGs) that are associated with various cellular functions, such as cytokine signaling, cell proliferation, cell adhesion, cholesterol/steroid biosynthesis, and regulation of apoptosis. Gene-set enrichment analyses indicated different functional pathways in BM vs. CT hMSCs. In addition, MSC-batches showed significant variations in cell cycle status, suggesting different proliferative vs. immunomodulatory potential. Several potential transcript-markers for tissue source differences were identified for further investigation in future studies. In functional assays, both BM and CT MSCs suppressed macrophage TNFα secretion upon interferon stimulation. However, differences between donors, tissue-of-origin, and cell cycle are evident in both TNF suppression and cytokine secretion.

Conclusions

This study shows that donor differences in hMSC transcriptome are minor relative to the intrinsic differences in tissue-of-origin. hMSCs with different transcriptomic profiles showed potential differences in functional characteristics. These findings contribute to our understanding of tissue origin-based differences in out-of-thaw therapeutic hMSC products and assist in the identification of cells with immune-regulatory or survival potential from a heterogeneous MSC population. Our results form the basis of future studies in correlating single-cell transcriptomic markers with immunomodulatory functions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02627-9.

Stem cell-based therapy for ameliorating intrauterine adhesion and endometrium injury

Intrauterine adhesion refers to endometrial repair disorders which are usually caused by uterine injury and may lead to a series of complications such as abnormal menstrual bleeding, recurrent abortion and secondary infertility. At present, therapeutic approaches to intrauterine adhesion are limited due to the lack of effective methods to promote regeneration following severe endometrial injury. Therefore, to develop new methods to prevent endometrial injury and intrauterine adhesion has become an urgent need. For severely damaged endometrium, the loss of stem cells in the endometrium may affect its regeneration. This article aimed to discuss the characteristics of various stem cells and their applications for uterine tissue regeneration.