Application of cell growth analysis to the quality assessment of human cell-processed therapeutic products as a testing method for immortalized cellular impurities

A risk-based approach for cell line development, manufacturing and characterization of genetically engineered, induced pluripotent stem cell-derived allogeneic cell therapies

Advances in cellular reprogramming and gene-editing approaches have opened up the potential for a new class of ex vivo cell therapies based on genetically engineered, induced pluripotent stem cell (iPSC)-derived allogeneic cells. While these new therapies share some similarities with their primary cell-derived autologous and allogeneic cell therapy predecessors, key differences exist in the processes used for generating genetically engineered, iPSC-derived allogeneic therapies. Specifically, in iPSC-derived allogeneic therapies, donor selection and gene-editing are performed once over the lifetime of the product as opposed to as part of the manufacturing of each product batch. The introduction of a well-characterized, fully modified, clonally derived master cell bank reduces risks that have been inherent to primary-cell derived autologous and allogeneic therapies. Current regulatory guidance, which was largely developed based on the learnings gained from earlier generation therapies, leaves open questions around considerations for donor eligibility, starting materials and critical components, cell banking and genetic stability. Here, a risk-based approach is proposed to address these considerations, while regulatory guidance continues to evolve.

Current status and future directions of clinical applications using iPS cells-focus on Japan

Regenerative medicine using iPS cell technologies has progressed remarkably in recent years. In this review, we summarize these technologies and their clinical application. First, we discuss progress in the establishment of iPS cells, including the HLA-homo iPS cell stock project in Japan and the advancement of low antigenic iPS cells using genome-editing technology. Then, we describe iPS cell-based therapies in or approaching clinical application, including those for ophthalmological, neurological, cardiac, hematological, cartilage, and metabolic diseases. Next, we introduce disease models generated from patient iPS cells and successfully used to identify therapeutic agents for intractable diseases. Clinical medicine using iPS cells has advanced safely and effectively by making full use of current scientific standards, but tests on cell safety need to be further developed and validated. The next decades will see the further spread of iPS cell technology-based regenerative medicine.

Evaluation of the reproducibility and positive controls of cellular immortality test for the detection of immortalized cellular impurities in human cell-processed therapeutic products

INTRODUCTION

Contamination of human cell-processed therapeutic products (hCTPs) with tumorigenic/immortalized cellular impurities is a major concern in the manufacturing and quality control of hCTPs. The cellular immortality test based on cell growth analysis is a method for detecting tumorigenic/immortalized cellular impurities in hCTPs. However, the performance of the cellular immortality test has not yet been well characterized. In this study, we examined the reproducibility of the cellular immortality test in detecting HeLa cells as a model of tumorigenic cellular impurities, as well as the applicability of other models of cellular impurities with different tumorigenicity to the cellular immortality test.

METHODS

Using HeLa cells as a model for cellular impurities, we measured the growth rate of human mesenchymal stem cells (hMSCs) supplemented with HeLa cells at concentrations ranging from 0.01 to 0.0001% at each passage in three laboratories and evaluated the reproducibility of the detection of immortalized cellular impurities. In addition, HEK293 cells (another immortalized cell line) and MRC-5 cells (a non-immortalized cell line) were employed as cellular impurity models that exhibit different growth characteristics from HeLa cells, and the ability of the cellular immortality test to detect these different impurities when mixed with hMSCs was examined.

RESULTS

In the multisite study, the growth rate of hMSCs supplemented with 1 and 10 HeLa cells (0.0001% and 0.001%) significantly increased and reached a plateau in all three laboratories, whereas those of hMSCs alone eventually decreased. Moreover, when hMSCs were supplemented with 10 and 100 HEK293 and MRC-5 cells (0.001% and 0.01%), the growth rate significantly increased. The growth rate of hMSCs supplemented with HEK293 cells increased with passage and remained high, whereas that of hMSCs supplemented with MRC-5 cells eventually decreased, as in the case of hMSCs alone.

CONCLUSIONS

These results indicate that the cellular immortality test is reproducible and can detect immortalized (i.e., potentially tumorigenic) cells such as HEK293 cells with a lower growth rate than HeLa cells by discriminating against normal cells, which could contribute to ensuring the safety and quality of hCTPs.

Transplantation of iPSC-derived corneal endothelial substitutes in a monkey corneal edema model

OBJECTIVE

In order to provide regenerative therapy for millions of patients suffering from corneal blindness globally, we derived corneal endothelial cell substitute (CECSi) cells from induced pluripotent stem cells (iPSCs) to treat corneal edema due to endothelial dysfunction (bullous keratopathy).

METHODS AND RESULTS

We developed an efficient xeno-free protocol to produce CECSi cells from both research grade (Ff-MH09s01 and Ff-I01s04) and clinical grade (QHJI01s04) iPSCs. CECSi cells formed a hexagonal confluent monolayer with Na, K-ATPase alpha 1 subunit expression (ATP1A1), tight junctions, N-cadherin adherence junction formation, and nuclear PITX2 expression, which are all characteristics of corneal endothelial cells. CECSi cells can be cryopreserved, and thawed CECSi cell suspensions also expressed N-cadherin and ATP1A1. Residual undifferentiated iPSCs in QHJI01s04-derived CECSi cells was below 0.01%. Frozen stocks of Ff-I01s04- and QHJI01s04-derived CECSi cells were transported, thawed and transplanted into a monkey corneal edema model. CECSi-transplanted eyes significantly reduced corneal edema compared to control group.

CONCLUSION

Our results show a promising approach to provide bullous keratopathy patients with an iPS-cell-based cell therapy to recover useful vision.

Principles for establishment of the stem cell bank and its applications on management of sports injuries

BACKGROUND

The stem cells of the stem cell banks have prominent problems for insufficient sources, easy contamination, unstable biological characteristics after serial subcultivations, and high cost.

METHODS

After collecting the construction processes of the existing stem cell banks and suggestions from authoritative experts in the past 10 years, 230 reference principles were obtained, and finally, the principles of "5C" for the establishment of modern standardized stem cell banks were summarized, and their related applications on the management of sports injuries were reviewed as well.

RESULTS

The basic principles of "5C" for the establishment of modern standardized stem cell banks include (1) principle of informed consent, (2) confidentiality principle, (3) conformity principle, (4) contamination-free principle, and (5) commonweal principle. The applications of stem cells on repairs, reconstructions, and regenerations of sports injuries were also reviewed, especially in tissue-engineered cartilage, tissue-engineered meniscus, and tissue-engineered ligament.

CONCLUSIONS

The proposal of the basic principles of "5C" is conducive to relevant stem cell researchers and clinical medical experts to build modern stem cell banks in a more standardized and efficient manner while avoiding some major mistakes or problems that may occur in the future. On this basis, stem cells from stem cell banks would be increasingly used in the management of sports injuries. More importantly, these days, getting stem cell samples are difficult in a short time, and such banks with proper legal consent may help the scientific community.

Ultrasensitive Detection and Depletion of Rare Leukemic B Cells in T Cell Populations via Immunomagnetic Cell Ranking

Rare CD19⁺ leukemic B cells present in purified T cell populations can cause disease relapse and even the failure of CD19-targeting CAR-T therapy as these rare cells have the ability to self-mask their surface CD19 and escape from the recognition of T cells. It is therefore critical to efficiently detect and robustly deplete rare leukemic B cells in samples of therapeutic T cells. Here, we present a novel microfluidic approach to address the challenges specific to quality control of therapeutic T cells - CAR-QC. CAR-QC utilizes immunomagnetic labeling with a highly selective microfluidic device to rank and isolate rare leukemic B cells in T cell populations. CAR-QC offers ultrasensitive detection of leukemic B cells at single-cell resolution and robust depletion efficiency up to 99.985%. We demonstrate that CAR-QC outperforms flow cytometry and magnetic-activated cell sorting for detecting or purifying spiked samples. In addition, we prove that the improved performance of CAR-QC helps to avoid the occurrence and possibly relapse of rare leukemic B cells in vitro.

Quality assessment tests for tumorigenicity of human iPS cell-derived cartilage

Articular cartilage damage does not heal spontaneously and causes joint dysfunction. The implantation of induced pluripotent stem cell (iPSC)-derived cartilage (iPS-Cart) is one candidate treatment to regenerate the damaged cartilage. However, concerns of tumorigenicity are associated with iPS-Cart, because the iPSC reprogramming process and long culture time for cartilage induction could increase the chance of malignancy. We evaluated the tumorigenic risks of iPS-Cart using HeLa cells as the reference. Spike tests revealed that contamination with 100 HeLa cells in 150 mg of iPS-Cart accelerated the cell growth rate. On the other hand, 150 mg of iPS-Cart without HeLa cells reached growth arrest and senescence after culture, suggesting less than 100 tumorigenic cells, assuming they behave like HeLa cells, contaminated iPS-Cart. The implantation of 10,000 or fewer HeLa cells into joint surface defects in the knee joint of nude rat did not cause tumor formation. These in vitro and in vivo studies collectively suggest that the implantation of 15 g or less iPS-Cart in the knee joint does not risk tumor formation if assuming that the tumorigenic cells in iPS-Cart are equivalent to HeLa cells and that nude rat knee joints are comparable to human knee joints in terms of tumorigenicity. However, considering the limited immunodeficiency of nude rats, the clinical amount of iPS-Cart for implantation needs to be determined cautiously.