Using qPCR and ddPCR to study biodistribution of cell therapy products: a multi-site evaluation.

BACKGROUD AIMS: Regenerative therapies employing cell therapy products (CTPs) have attracted considerable attention. Biodistribution (BD) evaluation of CTPs is mainly performed to clarify the cell survival time, engraftment, and distribution site. This evaluation is crucial for predicting the efficacy and safety profiles of clinical studies based on non-clinical BD study outcomes. However, no internationally unified method has been established for assessing cell BD after administration. Here, we aimed to standardize the BD assay method used for CTPs, conducting the following evaluations using the same protocol across multiple study facilities: (1) in vitro validation of quantitative polymerase chain reaction (qPCR) and droplet digital PCR (ddPCR) analyses using the primate-specific Alu gene, and (2) in vivo BD studies after the intravenous administration of human mesenchymal stem cells (hMSCs) to immunodeficient mice, commonly used in non-clinical tumorigenicity studies. METHODS: Quality control samples were prepared and analyzed by adding a fixed number of human-derived cells to several mouse tissues. The respective quantitative performances of the qPCR and ddPCR methods were compared for accuracy and precision. hMSCs were intravenously administered to immunodeficient mice, and tissues were collected at 1, 4, and 24 h after administration. RESULTS: Both methods demonstrated an accuracy (relative error) generally within ±50% and a precision (coefficient of variation) generally less than 50%. While differences in calibration curve ranges were observed between qPCR and ddPCR, no significant differences in quantification were found among the assay facilities. The BD of hMSCs in mice was evaluated at seven facilities (qPCR at three facilities; ddPCR at four facilities), revealing similar tissue distribution profiles in all facilities, with the lungs showing the highest cell distribution among the tissues tested. CONCLUSIONS: Quantitative evaluation of qPCR and ddPCR using Alu sequences was conducted, demonstrating that the test method can be adapted for BD evaluation.

Application of the Thermal Analysis of Frozen Aqueous Solutions to Assess the Miscibility of Hyaluronic Acid and Polymers Used for Dissolving Microneedles.

Background: The combination of multiple polymers is anticipated to serve as a means to diversify the physical properties and functionalities of dissolving microneedles. The mixing state of components is considered as a crucial factor in determining their suitability. Objectives: The purpose of this study was to elucidate whether thermal analysis of frozen aqueous solutions can appropriately predict the miscibility of hyaluronic acid (HA) and other polymers used for dissolving microneedles prepared by a micromolding method. Methods: Aliquots of aqueous polymer solutions were applied for thermal analysis by heating the samples from -70 °C at 5 °C/min to obtain the transition temperature of amorphous polymers and/or the crystallization/melting peaks of polymers (e.g., polyethylene glycol (PEG)). Films and dissolving microneedles were prepared by air-drying of the aqueous polymer solutions to assess the polymer miscibility in the solids. Results: The frozen aqueous single-solute HA solutions exhibited a clear Tg' (the glass transition temperature of maximally freeze-concentrated solutes) at approximately -20 °C. The combination of HA with several polymers (e.g., dextran FP40, DEAE-dextran, dextran sulfate, and gelatin) showed a single Tg' transition at temperatures that shifted according to their mass ratio, which strongly suggested the mixing of the freeze-concentrated solutes. By contrast, the observation of two Tg' transitions in a scan strongly suggested the separation of HA and polyvinylpyrrolidone (PVP) or HA and polyacrylic acid (PAA) into different freeze-concentrated phases, each of which was rich in an amorphous polymer. The combination of HA and PEG exhibited the individual physical changes of the polymers. The polymer combinations that showed phase separation in the frozen solution formed opaque films and microneedles upon their preparation by air-drying. Coacervation occurring in certain polymer combinations was also suggested as a factor contributing to the formation of cloudy films. Conclusions: Freezing aqueous polymer solutions creates a highly concentrated polymer environment that mimics the matrix of dissolving microneedles prepared through air drying. This study demonstrated that thermal analysis of the frozen solution offers insights into the mixing state of condensed polymers, which can be useful for predicting the physical properties of microneedles.

Comparison of in vitro screening methods for evaluating the effects of pharmaceutical excipients on membrane permeability.

The effects of pharmaceutical excipients on intestinal drug absorption have been highlighted and careful excipient selection is required to develop biologically equivalent formulations. This study aimed to evaluate the effects of excipients on drug permeability and compare the characteristics of in vitro screening methods. Three in vitro models, the commercial precoated parallel artificial membrane permeability assay (PAMPA), PermeaPadTM, and Caco-2 monolayer, were used to evaluate the effects of 14 excipients on the permeability of several drugs with different biopharmaceutical classification system classes. Concentration-dependent effects were analyzed to distinguish non-specific effects. The permeability of low-permeability drugs was increased by excipients such as hydroxypropyl cellulose and povidone K30 in the precoated PAMPA model, whereas PermeaPadTM maintained membrane integrity at higher concentrations. Conversely, croscarmellose sodium and sodium lauryl sulfate (SLS) decreased the permeability of highly permeable drugs in both precoated PAMPA and PermeaPadTM assays in a concentration-dependent manner. In Caco-2 monolayer assays, most excipients showed minimal effects on drug permeability. However, SLS significantly reduces the permeability of highly permeable drugs at concentrations above the critical micelle concentration, thereby compromising the integrity of the cell monolayer. Our results suggested that most of excipients, except SLS, did not affect the membrane permeation of drugs at clinically used concentrations. The pre-coated PAMPA model demonstrated high sensitivity to excipient effects, making it suitable for conservative evaluation. The PermeaPadTM and Caco-2 models allowed assessment at higher excipient concentrations, with PermeaPadTM being particularly useful for excipients that cause toxicity in Caco-2 cells.

Detection of residual pluripotent stem cells in cell therapy products utilizing droplet digital PCR: an international multisite evaluation study.

The presence of residual undifferentiated pluripotent stem cells (PSCs) in PSC-derived cell therapy products (CTPs) is a major safety issue for their clinical application, due to the potential risk of PSC-derived tumor formation. An international multidisciplinary multisite study to evaluate a droplet digital PCR (ddPCR) approach to detect residual undifferentiated PSCs in PSC-derived CTPs was conducted as part of the Health and Environmental Sciences Institute Cell Therapy-TRAcking, Circulation & Safety Technical Committee. To evaluate the use of ddPCR in quantifying residual iPSCs in a cell sample, different quantities of induced pluripotent stem cells (iPSCs) were spiked into a background of iPSC-derived cardiomyocytes (CMs) to mimic different concentrations of residual iPSCs. A one step reverse transcription ddPCR (RT-ddPCR) was performed to measure mRNA levels of several iPSC-specific markers and to evaluate the assay performance (precision, sensitivity, and specificity) between and within laboratories. The RT-ddPCR assay variability was initially assessed by measuring the same RNA samples across all participating facilities. Subsequently, each facility independently conducted the entire process, incorporating the spiking step, to discern the parameters influencing potential variability. Our results show that a RT-ddPCR assay targeting ESRG, LINC00678, and LIN28A genes offers a highly sensitive and robust detection of impurities of iPSC-derived CMs and that the main contribution to variability between laboratories is the iPSC-spiking procedure, and not the RT-ddPCR. The RT-ddPCR assay would be generally applicable for tumorigenicity evaluation of PSC-derived CTPs with appropriate marker genes suitable for each CTP.

Physicochemical profiling of nanomedicines using centrifugal field flow fractionation.

Nanomedicines comprise multiple components, and particle density is considered an important property that regulates the biodistribution of administered nanomedicines. The density of nanoparticles is characterized by centrifugal methods, such as analytical ultracentrifugation. Particle size and distribution are key physicochemical and quality attributes of nanomedicines. In this study, we developed a novel profiling method applicable to liposomes and lipid nanoparticles (LNPs), based on particle size and density, using centrifugal field-flow fractionation (CF3). We evaluated the elution profiles of PEGylated liposomes of different sizes with various doxorubicin (DOX)-loading amounts using CF3. This method was applied to evaluate the drug release of DOX-loaded liposomes, intra- and inter-batch variability, reconstitution reproducibility of AmBisome®, and elution characteristics of LNPs in COVID-19 vaccines (Comirnaty® and SpikevaxTM). The data obtained in the present study underscore the significance of the proposed methodology and highlight the importance of profiling and characterizing liposomes and LNPs using CF3 fractograms and a multi-angle light-scattering detector.

Considerations for the development of iPSC-derived cell therapies: a review of key challenges by the JSRM-ISCT iPSC Committee.

Since their first production in 2007, human induced pluripotent stem cells (iPSCs) have provided a novel platform for the development of various cell therapies targeting a spectrum of diseases, ranging from rare genetic eye disorders to cancer treatment. However, several challenges must be tackled for iPSC-based cell therapy to enter the market and achieve broader global adoption. This white paper, authored by the Japanese Society for Regenerative Medicine (JSRM) - International Society for Cell Therapy (ISCT) iPSC Committee delves into the hurdles encountered in the pursuit of safe and economically viable iPSC-based therapies, particularly from the standpoint of the cell therapy industry. It discusses differences in global guidelines and regulatory frameworks, outlines a series of quality control tests required to ensure the safety of the cell therapy, and provides details and important considerations around cost of goods (COGs), including the impact of automated advanced manufacturing.

Multisite studies for optimization of a highly efficient culture assay used for in vitro detection of residual undifferentiated human pluripotent stem cells intermingled in cell therapy products.

Introduction: MEASURE2 (Multisite Evaluation Study on Analytical Methods for Non-clinical Safety Assessment of HUman-derived REgenerative Medical Products 2) is a Japanese experimental public-private partnership initiative that aims to standardize testing methods for tumorigenicity evaluation of human pluripotent stem cell (hPSC)-derived cell therapy products (CTPs). MEASURE2 organized multisite studies to optimize the methodology of the highly efficient culture (HEC) assay, a sensitive culture-based in vitro assay for detecting residual undifferentiated hPSCs in CTPs. Methods: In these multisite studies, 1) the efficiency of colony formation by human induced pluripotent stem cells (hiPSCs) under two different culture conditions and 2) the sorting efficiency of microbeads conjugated to various anti-hPSC markers during hiPSC enrichment were evaluated using samples in which hiPSCs were spiked into hiPSC-derived mesenchymal stem cells. Results: The efficiency of colony formation was significantly higher under culture conditions with the combination of Chroman 1, Emricasan, Polyamines, and Trans-ISRIB (CEPT) than with Y-27632, which is widely used for the survival of hPSCs. Between-laboratory variance was also smaller under the condition with CEPT than with Y-27632. The sorting efficiency of microbeads conjugated with the anti-Tra-1-60 antibody was sufficiently higher (>80%) than those of the other various microbeads investigated. Conclusions: Results of these multisite studies are expected to contribute to improvements in the sensitivity and robustness of the HEC assay, as well as to the future standardization of the tumorigenicity risk assessment of hPSC-derived CTPs.

Protocol improvement and multisite validation of a digital soft agar colony formation assay for tumorigenic transformed cells intermingled in cell therapy products.

BACKGROUND AIMS: The administration of human cell-processed therapeutic products (hCTPs) is associated with a risk of tumorigenesis due to the transformed cellular contaminants. To mitigate this risk, these impurities should be detected using sensitive and validated assays. The digital soft agar colony formation (D-SAC) assay is an ultrasensitive in vitro test for detecting tumorigenic transformed cells in hCTPs. METHODS: In this study, we first evaluated the colony formation efficiency (CFE) precision of tumorigenic reference cells in positive control samples according to a previously reported D-SAC assay protocol (Protocol I) from multiple laboratories. However, the CFE varied widely among laboratories. Thus, we improved and optimized the test protocol as Protocol II to reduce variability in the CFE of tumorigenic reference cells. Subsequently, the improved protocol was validated at multiple sites. Human mesenchymal stromal cells (hMSCs) were used as model cells, and positive control samples were prepared by spiking them with HeLa cells. RESULTS: Based on the previously reported protocol, the CFE was estimated using an ultra-low concentration (0.0001%) of positive control samples in multiple plates. Next, we improved the protocol to reduce the CFE variability. Based on the CFE results, we estimated the sample size as the number of wells (Protocol II) and assessed the detectability of 0.0001% HeLa cells in hMSCs to validate the protocol at multiple sites. Using Protocol I yielded low CFEs (mean: 30%) and high variability between laboratories (reproducibility coefficient of variance [CV]: 72%). In contrast, Protocol II, which incorporated a relatively high concentration (0.002%) of HeLa cells in the positive control samples, resulted in higher CFE values (mean: 63%) and lower variability (reproducibility CV: 18%). Moreover, the sample sizes for testing were estimated as the number of wells per laboratory (314-570 wells) based on the laboratory-specific CFE (42-76%). Under these conditions, all laboratories achieved a detection limit of 0.0001% HeLa cells in hMSCs in a predetermined number of wells. Moreover, colony formation was not observed in the wells seeded with hMSCs alone. CONCLUSIONS: The D-SAC assay is a highly sensitive and robust test for detecting malignant cells as impurities in hCTPs. In addition, optimal assay conditions were established to test tumorigenic impurities in hCTPs with high sensitivity and an arbitrary false negative rate.

Mechanical Characterization of Dissolving Microneedles: Factors Affecting Physical Strength of Needles.

Dissolving microneedles (MNs) are novel transdermal drug delivery systems that can be painlessly self-administered. This study investigated the effects of experimental conditions on the mechanical characterization of dissolving MNs for quality evaluation. Micromolding was used to fabricate polyvinyl alcohol (PVA)-based dissolving MN patches with eight different cone-shaped geometries. Axial force mechanical characterization test conditions, in terms of compression speed and the number of compression needles per test, significantly affected the needle fracture force of dissolving MNs. Characterization using selected test conditions clearly showed differences in the needle fracture force of dissolving MNs prepared under various conditions. PVA-based MNs were divided into two groups that showed buckling and unbuckling deformation, which occurred at aspect ratios (needle height/base diameter) of 2.8 and 1.8, respectively. The needle fracture force of PVA-based MNs was negatively correlated with an increase in the needle's aspect ratio. Higher residual water or higher loading of lidocaine hydrochloride significantly decreased the needle fracture force. Therefore, setting appropriate methods and parameters for characterizing the mechanical properties of dissolving MNs should contribute to the development and supply of appropriate products.

ROR2 expression predicts human induced pluripotent stem cell differentiation into neural stem/progenitor cells and GABAergic neurons.

Despite the development of various in vitro differentiation protocols for the efficient derivation of specific cell types, human induced pluripotent stem cell (hiPSC) lines have varing ability to differentiate into specific lineages. Therefore, surrogate markers for accurately predicting the differentiation propensity of hiPSC lines may facilitate cell-based therapeutic product development and manufacture. We attempted to identify marker genes that could predict the differentiation propensity of hiPSCs into neural stem/progenitor cells (NS/PCs). Using Spearman's rank correlation coefficients, we investigated genes in the undifferentiated state, the expression levels of which were significantly correlated with the neuronal differentiation propensity of several hiPSC lines. Among genes significantly correlated with NS/PC differentiation (P < 0.01), we identified ROR2 as a novel predictive marker. ROR2 expression in hiPSCs was negatively correlated with NS/PC differentiation tendency, regardless of the differentiation method, whereas its knockdown enhanced differentiation. ROR2 regulates NS/PC differentiation, suggesting that ROR2 is functionally essential for NS/PC differentiation. Selecting cell lines with relatively low ROR2 expression facilitated identification of hiPSCs that can differentiate into NS/PCs. Cells with ROR2 knockdown showed increased efficiency of differentiation into forebrain GABAergic neurons compared to controls. These findings suggest that ROR2 is a surrogate marker for selecting hiPSC lines appropriate for NS/PC and GABAergic neuronal differentiations.

Analysis of Factors Related to Variation in Dissolution Profiles Estimated from Continuously Conducted Dissolution Tests of Generic Products.

The development of generic pharmaceuticals involves a bioequivalence study to ensure the therapeutic equivalence of the test formulation to the original innovative product. The formulation characteristics of generic products are expected to be maintained in the long term after approval. This study analyzed the factors contributing to the changes in the dissolution profiles of approved products during their life cycles. Cumulative data on the dissolution similarity of 1675 products of 127 ingredients tested by official laboratories in Japan were assessed according to Japanese bioequivalence guidelines with slight modifications. The products showing dissimilarities in dissolution profiles were analyzed for reporting year, therapeutic category, co-development, physical properties of the active pharmaceutical ingredient (API), and suspected reasons for dissolution change. The increase in the number of dissimilar products is related to the co-development of generic products. Although the solubility of the API was not associated with the dissolution change in the analysis of the total dissolution data, control of the API particle size is suggested to be important for drugs with poorly soluble APIs. Additionally, a risk factor for dissolution changes in the test solutions at a certain pH was the presence of acidic or basic residues. These results indicate the importance of proper development through a thorough evaluation of the formulation and process factors affecting the dissolution properties throughout the product lifecycle.

Fabrication and Characterization of Dissolving Microneedles for Transdermal Drug Delivery of Apomorphine Hydrochloride in Parkinson's Disease.

PURPOSE: We fabricated and characterized polyvinyl alcohol (PVA)-based dissolving microneedles (MNs) for transdermal drug delivery of apomorphine hydrochloride (APO), which is used in treating the wearing-off phenomenon observed in Parkinson's disease. METHODS: We fabricated MN arrays with 11 × 11 needles of four different lengths (300, 600, 900, and 1200 µm) by micromolding. The APO-loaded dissolving MNs were characterized in terms of their physicochemical and functional properties. We also compared the pharmacokinetic parameters after drug administration using MNs with those after subcutaneous injection by analyzing the blood concentration of APO in rats. RESULTS: PVA-based dissolving MNs longer than 600 µm could effectively puncture the stratum corneum of the rat skin with penetrability of approximately one-third of the needle length. Although APO is known to have chemical stability issues in aqueous solutions, the drug content in APO-loaded MNs was retained at 25°C for 12 weeks. The concentration of APO after the administration of APO-loaded 600-µm MNs that dissolved completely in skin within 60 min was 81%. The absorption of 200-µg APO delivered by MNs showed a Tmax of 20 min, Cmax of 76 ng/mL, and AUC0-120 min of 2,829 ng・min/mL, compared with a Tmax of 5 min, Cmax of 126 ng/mL, and AUC0-120 min of 3,224 ng・min/mL for subcutaneous injection. The bioavailability in terms of AUC0-120 min of APO delivered by MNs was 88%. CONCLUSION: APO-loaded dissolving MNs can deliver APO via skin into the systemic circulation with rapid absorption and high bioavailability.

Evaluation of next-generation sequencing performance for in vitro detection of viruses in biological products.

Next-Generation Sequencing (NGS) can detect nucleic acid sequences in a massively parallel sequencing. This technology is expected to be widely applied for the detection of viral contamination in biologics. The recently published ICH-Q5A (R2) draft indicates that NGS could be an alternative or supplement to in vitro viral tests. To examine the performance of NGS for the in vitro detection of viruses, adenovirus type 5 (Ad5), a model virus, was inoculated into Vero cells, which are the most popular indicator cells for the detection of adventitious viruses in the in vitro test. Total RNA extracted from the Vero cells infected with Ad5 was serially diluted with that from non-infected Vero cells, and each sample was analyzed using short- or long-read NGSs. The limits of detection of both NGS methods were almost the same and both methods were sensitive enough to detect viral sequences as long as there was at least one copy in one assay. Although the multiplexing in NGS carries the risk of cross-contamination among the samples, which could lead to false positives, this technology has the potential to become a rapid and sensitive method for detecting adventitious agents in biologics.

Effects of Apex Size on Dissolution Profiles in the USP II Paddle Apparatus.

The use of apex vessels may solve coning problems associated with dissolution testing. However, excessive dissolution acceleration can reduce the discriminatory power. This study aimed to clarify how different apex vessel sizes affect the dissolution behavior of cone-forming formulations. Five apex vessels with different heights, centralities, and compendial vessels were used. The paddle rotation speed at which the coning phenomenon resolved was measured using standard particles of different densities. Three model formulations-USP prednisone tablets, atorvastatin calcium hydrate tablets, and levofloxacin fine granules-were selected, and dissolution tests were conducted at 30-100 revolutions per minute (rpm). Compared to the compendial vessels, the disappearance of standard particles at the apex base at lower paddle speeds in apex vessels was observed. Standard particles tended to remain in the center of the apex vessels and disappear at rotational speeds comparable to those of the compendial vessels. Dissolution increased in an apex height-dependent manner in the model formulations, except for the atorvastatin calcium hydrate tablets at 50 rpm. For levofloxacin fine granules, dissolution was also improved by reducing the paddle agitation speed to 30 rpm in the compendial vessels. Differences in apex centrality by 3 mm did not affect the dissolution rate. Our results indicate that apex vessels with low apex heights have a mount-resolving effect, but the degree of dissolution improvement by avoiding the coning phenomenon depends on the formulation characteristics used in the dissolution tests.

Structural flexibility of apolipoprotein E-derived arginine-rich peptides improves their cell penetration capability.

Amphipathic arginine-rich peptide, A2-17, exhibits moderate perturbation of lipid membranes and the highest cell penetration among its structural isomers. We investigated the direct cell-membrane penetration mechanism of the A2-17 peptide while focusing on structural flexibility. We designed conformationally constrained versions of A2-17, stapled (StpA2-17) and stitched (StchA2-17), whose α-helical conformations were stabilized by chemical crosslinking. Circular dichroism confirmed that StpA2-17 and StchA2-17 had higher α-helix content than A2-17 in aqueous solution. Upon liposome binding, only A2-17 exhibited a coil-to-helix transition. Confocal microscopy revealed that A2-17 had higher cell penetration efficiency than StpA2-17, whereas StchA2-17 remained on the cell membrane without cell penetration. Although the tryptophan fluorescence analysis suggested that A2-17 and its analogs had similar membrane-insertion positions between the interface and hydrophobic core, StchA2-17 exhibited a higher membrane affinity than A2-17 or StpA2-17. Atomic force microscopy demonstrated that A2-17 reduced the mechanical rigidity of liposomes to a greater extent than StpA2-17 and StchA2-17. Finally, electrophysiological analysis showed that A2-17 induced a higher charge influx through transient pores in a planer lipid bilayer than StpA2-17 and StchA2-17. These findings indicate that structural flexibility, which enables diverse conformations of A2-17, leads to a membrane perturbation mode that contributes to cell membrane penetration.

ISSCR standards for the use of human stem cells in basic research.

The laboratory culture of human stem cells seeks to capture a cellular state as an in vitro surrogate of a biological system. For the results and outputs from this research to be accurate, meaningful, and durable, standards that ensure reproducibility and reliability of the data should be applied. Although such standards have been previously proposed for repositories and distribution centers, no widely accepted best practices exist for laboratory research with human pluripotent and tissue stem cells. To fill that void, the International Society for Stem Cell Research has developed a set of recommendations, including reporting criteria, for scientists in basic research laboratories. These criteria are designed to be technically and financially feasible and, when implemented, enhance the reproducibility and rigor of stem cell research.

Country-specific regulation and international standardization of cell-based therapeutic products derived from pluripotent stem cells.

Currently, many types of cell-based therapeutic products (CTPs) derived from pluripotent stem cells (PSCs) are being developed in a lot of countries, some of which are in clinical trial stages. CTPs are classified differently in different countries and regions. The evaluation of their efficacy, safety, and quality also differs from that for conventional small-molecule drugs and biopharmaceuticals, which reflects the complex properties of living cells and unmet medical needs. Since there are no international guidelines to evaluate CTPs, including PSC-derived products, it is necessary to be aware of differences in relevant laws and regulations in different countries and regions. International consortia are organized and actively working to standardize/harmonize the evaluation methods and regulations to facilitate the development and global distribution of PSC-derived CTPs. In this paper, we outline the regulations related to PSC-derived CTPs in the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use founding regions (US, EU/UK, Japan) and introduce representative consortia working on their standardization.

Single-Cell RNA-Seq Reveals LRRC75A-Expressing Cell Population Involved in VEGF Secretion of Multipotent Mesenchymal Stromal/Stem Cells Under Ischemia.

Human multipotent mesenchymal stromal/stem cells (MSCs) have been utilized in cell therapy for various diseases and their clinical applications are expected to increase in the future. However, the variation in MSC-based product quality due to the MSC heterogeneity has resulted in significant constraints in the clinical utility of MSCs. Therefore, we hypothesized that it might be important to identify and ensure/enrich suitable cell subpopulations for therapies using MSC-based products. In this study, we aimed to identify functional cell subpopulations to predict the efficacy of angiogenic therapy using bone marrow-derived MSCs (BM-MSCs). To assess its angiogenic potency, we observed various levels of vascular endothelial growth factor (VEGF) secretion among 11 donor-derived BM-MSC lines under in vitro ischemic culture conditions. Next, by clarifying the heterogeneity of BM-MSCs using single-cell RNA-sequencing analysis, we identified a functional cell subpopulation that contributed to the overall VEGF production in BM-MSC lines under ischemic conditions. We also found that leucine-rich repeat-containing 75A (LRRC75A) was more highly expressed in this cell subpopulation than in the others. Importantly, knockdown of LRRC75A using small interfering RNA resulted in significant inhibition of VEGF secretion in ischemic BM-MSCs, indicating that LRRC75A regulates VEGF secretion under ischemic conditions. Therefore, LRRC75A may be a useful biomarker to identify cell subpopulations that contribute to the angiogenic effects of BM-MSCs. Our work provides evidence that a strategy based on single-cell transcriptome profiles is effective for identifying functional cell subpopulations in heterogeneous MSC-based products.

International evaluation study of a highly efficient culture assay for detection of residual human pluripotent stem cells in cell therapies.

Aim & methods: The Health and Environmental Sciences Institute Cell Therapy-TRAcking, Circulation & Safety Technical Committee launched an international, multisite study to evaluate the sensitivity and reproducibility of the highly efficient culture (HEC) assay, an in vitro assay to detect residual undifferentiated human pluripotent stem cells (hPSCs) in cell therapy products. Results: All facilities detected colonies of human induced pluripotent stem cells (hiPSCs) when five hiPSCs were spiked into 1 million hiPSC-derived cardiomyocytes. Spiking with a trace amount of hiPSCs revealed that repeatability accounts for the majority of reproducibility while the true positive rate was high. Conclusion: The results indicate that the HEC assay is highly sensitive and robust and can be generally applicable for tumorigenicity evaluation of hPSC-derived cell therapy products.