Identification and Re-consent of Existing Cord Blood Donors for Creation of Induced Pluripotent Stem Cell Lines for Potential Clinical Applications

Harnessing global HLA data for enhanced patient matching in iPSC haplobanks

BACKGROUND

Several countries have either developed or are developing national induced pluripotent stem cell (iPSC) banks of cell lines derived from donors with HLA homozygous genotypes (two identical haplotypes) prevalent in their local populations to provide immune matched tissues and cells to support regenerative medicine therapies. This 'haplobank' approach relies on knowledge of the HLA genotypes of the population to identify the most beneficial haplotypes for patient coverage, and ultimately identify donors or cord blood units carrying two copies of the target haplotype.

AIMS

A potentially more efficient alternative to a national bank approach is to assess the haplotypes required to provide global patient coverage and to produce a single, global haplobank. Toward that end, we have developed an algorithm to prioritize HLA haplotypes that optimize coverage across the global population.

METHODS

We analyzed data from eighteen countries participating in the Global Alliance for iPS Therapy (GAiT). A representative pool of HLA genotypes, reflecting the HLA of patients, was derived by sampling from each country's WMDA hematopoietic stem cell donor registry, or surrogate population. An algorithm was created based on HLA-A, -B and -DRB1 haplotype homozygous types with population HLA matching coverage defined by the absence of Host versus Graft (HvG) mismatches at these loci. HLA matching coverage was determined by iteratively selecting HLA haplotypes that provide the largest coverage against patient HLA genotypes sampled from the same population, excluding genotypes compatible with previous iterations.

RESULTS

The top 10 haplotypes for each of the 18 countries were identified with patient coverage ranging from 19.5% in Brazil to 63.8% in Japan, with a mean coverage of 33.3%. In a 'global' model, utilizing the 180 most frequent haplotypes across all 18 populations (equivalent to 10 lines per country), the patient coverage ranged from 54.6% in India to 81.7% in Sweden, with a mean of 68.4%. Our findings demonstrate that global collaboration could more than double the potential for patient HLA matching coverage.

CONCLUSIONS

Interrogation of unrelated hematopoietic stem cell donor registry and cord blood bank HLA data demonstrated that HLA-A, -B, and -DRB1 homozygous donors for the top 180 global haplotypes are widely available. These results show that a globally coordinated strategy for haplobanking would reduce redundancy and allow more patients to be treated with the same investment.

Constructing a potential HLA haplo-homozygous induced pluripotent stem cell haplobank using data from an umbilical cord blood bank

BACKGROUND

Induced pluripotent stem cells (iPSCs) can differentiate into any type of cell and have potential uses in regenerative medicine for the treatment of many diseases. However, reducing immune rejection is a key problem in the application of iPSCs that can be solved by the development of haplobanks containing specially selected iPSC lines.

METHODS

To study the feasibility of constructing an HLA (human leukocyte antigen)-matched induced pluripotent stem cell haplobank in China, 5421 umbilical cord blood samples were randomly collected from the Umbilical Cord Blood Bank of Zhejiang Province, China. The HLA-A, HLA-B, HLA-C, HLA-DRB1, and HLA-DQB1 loci were genotyped using next-generation sequencing. Using HLA genotype data at the high-resolution level, the number of HLA homozygous donors needed to cover a certain percentage of the Chinese population and the feasibility of constructing a high-matching iPSC haplobank were estimated.

RESULTS

Thirteen HLA-A, -B, and -DRB1 and 11 HLA-A, -B, -C, -DRB1, and -DQB1 haplotype homozygotes were observed among the stored umbilical CB units which were as HLA zero-mismatched iPSC donors cumulatively matched 37.01% and 32.99% of 5421 potential patients respectively. The analysis showed that 100 distinct HLA-A, -B, and -DRB1 and HLA-A, -B, -C, -DRB1, and -DQB1 homozygous haplotypes would cover 72.74% and 67.87% of Chinese populations, respectively, and 600 HLA-A, -B, -C, -DRB1, and -DQB1 homozygous haplotypes would cover more than 90% of Chinese populations. PCA (principal component analysis) of published HLA data from different populations revealed that the frequency of these haplotypes in Asian populations is different from those in European populations.

CONCLUSION

The results suggested that at least some HLA-homozygous iPSC lines developed from Chinese individuals will not only be useful for covering the Chinese population but will also cover other Asian populations. A high-matching iPSC haplobank generated from umbilical CB units may be an economical and effective option in an allogeneic model of iPSC therapy.

Reprogramming of Expanded Cord Blood-Derived CD34+ Cells from Umbilical Cord-Mesenchymal Stromal Cell Co-Culture to Generate Human-Induced Pluripotent Stem Cells

Cord blood (CB) is widely stored as a source of hematopoietic stem cells for potential future use, though its application for autologous purposes remains limited. Repurposing CB into human-induced pluripotent stem cells (hiPSCs) can broaden its utility beyond hematological conditions. This study investigated the effects of umbilical cord-mesenchymal stromal cell (UC-MSC) co-culture on CB CD34+ cells and the characteristics of the resulting hiPSCs. CD34+ cells were isolated, expanded in UC-MSC co-culture for 3 days, and reprogrammed into hiPSCs using episomal vectors. Results showed that UC-MSC co-culture significantly increased CD34+ cell numbers (p < 0.0001, n = 6), with a reduced population doubling time of 25.1 ± 2.1 hours compared with the control (p < 0.0004, n = 6). The yield of CD34+ cells was substantially higher in the UC-MSC co-culture group. The hiPSCs exhibited comparable reprogramming efficiency, pluripotency marker expression, trilineage differentiation potential, and genomic stability to CD34+ cells expanded under standard culture conditions. These findings suggest that CD34+ cells from CB, expanded in UC-MSC co-culture, can be reprogrammed into functional hiPSCs without compromising cell quality or genetic stability.

Current Landscape of iPSC Haplobanks

The use of allogeneic induced pluripotent stem cell (iPSC)-derived cell therapies for regenerative medicine offers an affordable and realistic alternative to producing individual iPSC lines for each patient in need. Human Leukocyte Antigens (HLA)-homozygous iPSCs matched in hemi-similarity could provide cell therapies with reduced immune rejection covering a wide range of the population with a few iPSC lines. Several banks of HLA-homozygous iPSCs (haplobanks) have been established worldwide or are underway, to provide clinical grade starting material for cell therapies covering the most frequent HLA haplotypes for certain populations. Harmonizing quality standards among haplobanks and creating a global registry could minimize the collective effort and provide a much wider access to HLA-compatible cell therapies for patients with less frequent haplotypes. In this review we present all the current haplobank initiatives and their potential benefits for the global population.

Innovations in bio-engineering and cell-based approaches to address immunological challenges in islet transplantation

Human allogeneic pancreatic islet transplantation is a life-changing treatment for patients with severe Type 1 Diabetes (T1D) who suffer from hypoglycemia unawareness and high risk of severe hypoglycemia. However, intensive immunosuppression is required to prevent immune rejection of the graft, that may in turn lead to undesirable side effects such as toxicity to the islet cells, kidney toxicity, occurrence of opportunistic infections, and malignancies. The shortage of cadaveric human islet donors further limits islet transplantation as a treatment option for widespread adoption. Alternatively, porcine islets have been considered as another source of insulin-secreting cells for transplantation in T1D patients, though xeno-transplants raise concerns over the risk of endogenous retrovirus transmission and immunological incompatibility. As a result, technological advancements have been made to protect transplanted islets from immune rejection and inflammation, ideally in the absence of chronic immunosuppression, to improve the outcomes and accessibility of allogeneic islet cell replacement therapies. These include the use of microencapsulation or macroencapsulation devices designed to provide an immunoprotective environment using a cell-impermeable layer, preventing immune cell attack of the transplanted cells. Other up and coming advancements are based on the use of stem cells as the starting source material for generating islet cells 'on-demand'. These starting stem cell sources include human induced pluripotent stem cells (hiPSCs) that have been genetically engineered to avoid the host immune response, curated HLA-selected donor hiPSCs that can be matched with recipients within a given population, and multipotent stem cells with natural immune privilege properties. These strategies are developed to provide an immune-evasive cell resource for allogeneic cell therapy. This review will summarize the immunological challenges facing islet transplantation and highlight recent bio-engineering and cell-based approaches aimed at avoiding immune rejection, to improve the accessibility of islet cell therapy and enhance treatment outcomes. Better understanding of the different approaches and their limitations can guide future research endeavors towards developing more comprehensive and targeted strategies for creating a more tolerogenic microenvironment, and improve the effectiveness and sustainability of islet transplantation to benefit more patients.

Generation of a bank of clinical-grade, HLA-homozygous iPSC lines with high coverage of the Spanish population

BACKGROUND

Induced pluripotent stem cell (iPSC)-derived cell therapies are an interesting new area in the field of regenerative medicine. One of the approaches to decrease the costs of iPSC-derived therapies is the use of allogenic homozygous human leukocyte antigen (HLA)-matched donors to generate iPSC lines and to build a clinical-grade iPSC bank covering a high percentage of the Spanish population.

METHODS

The Spanish Stem Cell Transplantation Registry was screened for cord blood units (CBUs) homozygous for the most common HLA-A, HLA-B and HLA-DRB1 haplotypes. Seven donors were selected with haplotypes covering 21.37% of the haplotypes of the Spanish population. CD34-positive hematopoietic progenitors were isolated from the mononuclear cell fraction of frozen cord blood units from each donor by density gradient centrifugation and further by immune magnetic labeling and separation using purification columns. Purified CD34 + cells were reprogrammed to iPSCs by transduction with the CTS CytoTune-iPS 2.1 Sendai Reprogramming Kit.

RESULTS

The iPSCs generated from the 7 donors were expanded, characterized, banked and registered. Master cell banks (MCBs) and working cell banks (WCBs) from the iPSCs of each donor were produced under GMP conditions in qualified clean rooms.

CONCLUSIONS

Here, we present the first clinical-grade, iPSC haplobank in Spain made from CD34 + cells from seven cord blood units homozygous for the most common HLA-A, HLA-B and HLA-DRB1 haplotypes within the Spanish population. We describe their generation by transduction with Sendai viral vectors and their GMP-compliant expansion and banking. These haplolines will constitute starting materials for advanced therapy medicinal product development (ATMP).

Challenges of CRISPR/Cas-Based Cell Therapy for Type 1 Diabetes: How Not to Engineer a "Trojan Horse"

Type 1 diabetes mellitus (T1D) is an autoimmune disease caused by the destruction of insulin-producing β-cells in the pancreas by cytotoxic T-cells. To date, there are no drugs that can prevent the development of T1D. Insulin replacement therapy is the standard care for patients with T1D. This treatment is life-saving, but is expensive, can lead to acute and long-term complications, and results in reduced overall life expectancy. This has stimulated the research and development of alternative treatments for T1D. In this review, we consider potential therapies for T1D using cellular regenerative medicine approaches with a focus on CRISPR/Cas-engineered cellular products. However, CRISPR/Cas as a genome editing tool has several drawbacks that should be considered for safe and efficient cell engineering. In addition, cellular engineering approaches themselves pose a hidden threat. The purpose of this review is to critically discuss novel strategies for the treatment of T1D using genome editing technology. A well-designed approach to β-cell derivation using CRISPR/Cas-based genome editing technology will significantly reduce the risk of incorrectly engineered cell products that could behave as a "Trojan horse".