Generation and manipulation of human iPSC-derived platelets

The future of blood services amid a tight balance between the supply and demand of blood products: Perspectives from the ISBT Young Professional Council

BACKGROUND AND OBJECTIVES

Blood services manage the increasingly tight balance between the supply and demand of blood products, and their role in health research is expanding. This review explores the themes that may define the future of blood banking.

MATERIALS AND METHODS

We reviewed the PubMed database for articles on emerging/new blood-derived products and the utilization of blood donors in health research.

RESULTS

In high-income countries (HICs), blood services may consider offering these products: whole blood, cold-stored platelets, synthetic blood components, convalescent plasma, lyophilized plasma and cryopreserved/lyophilized platelets. Many low- and middle-income countries (LMICs) aim to establish a pool of volunteer, non-remunerated blood donors and wean themselves off family replacement donors; and many HICs are relaxing the deferral criteria targeting racial and sexual minorities. Blood services in HICs could achieve plasma self-sufficiency by building plasma-dedicated centres, in collaboration with the private sector. Lastly, blood services should expand their involvement in health research by establishing donor cohorts, conducting serosurveys, studying non-infectious diseases and participating in clinical trials.

CONCLUSION

This article provides a vision of the future for blood services. The introduction of some of these changes will be slower in LMICs, where addressing key operational challenges will likely be prioritized.

Megakaryocyte-induced contraction of plasma clots: cellular mechanisms and structural mechanobiology

ABSTRACT

Nonmuscle cell contractility is an essential feature underlying diverse cellular processes such as motility, morphogenesis, division and genome replication, intracellular transport, and secretion. Blood clot contraction is a well-studied process driven by contracting platelets. Megakaryocytes (MKs), which are the precursors to platelets, can be found in bone marrow and lungs. Although they express many of the same proteins and structures found in platelets, little is known about their ability to engage with extracellular proteins such as fibrin and contract. Here, we have measured the ability of MKs to compress plasma clots. Megakaryocytes derived from human induced pluripotent stem cells (iPSCs) were suspended in human platelet-free blood plasma and stimulated with thrombin. Using real-time macroscale optical tracking, confocal microscopy, and biomechanical measurements, we found that activated iPSC-derived MKs (iMKs) caused macroscopic volumetric clot shrinkage, as well as densification and stiffening of the fibrin network via fibrin-attached plasma membrane protrusions undergoing extension-retraction cycles that cause shortening and bending of fibrin fibers. Contraction induced by iMKs involved 2 kinetic phases with distinct rates and durations. It was suppressed by inhibitors of nonmuscle myosin IIA, actin polymerization, and integrin αIIbβ3-fibrin interactions, indicating that the molecular mechanisms of iMK contractility were similar or identical to those in activated platelets. Our findings provide new insights into MK biomechanics and suggest that iMKs can be used as a model system to study platelet contractility. Physiologically, the ability of MKs to contract plasma clots may play a role in the mechanical remodeling of intravascular blood clots and thrombi.

Platelet-Rich Plasma in Dermatology: New Insights on the Cellular Mechanism of Skin Repair and Regeneration

The skin's recognised functions may undergo physiological alterations due to ageing, manifesting as varying degrees of facial wrinkles, diminished tautness, density, and volume. Additionally, these functions can be disrupted (patho)physiologically through various physical and chemical injuries, including surgical trauma, accidents, or chronic conditions like ulcers associated with diabetes mellitus, venous insufficiency, or obesity. Advancements in therapeutic interventions that boost the skin's innate regenerative abilities could significantly enhance patient care protocols. The application of Platelet-Rich Plasma (PRP) is widely recognized for its aesthetic and functional benefits to the skin. Yet, the endorsement of PRP's advantages often borders on the dogmatic, with its efficacy commonly ascribed solely to the activation of fibroblasts by the factors contained within platelet granules. PRP therapy is a cornerstone of regenerative medicine which involves the autologous delivery of conditioned plasma enriched by platelets. This is achieved by centrifugation, removing erythrocytes while retaining platelets and their granules. Despite its widespread use, the precise sequences of cellular activation, the specific cellular players, and the molecular machinery that drive PRP-facilitated healing are still enigmatic. There is still a paucity of definitive and robust studies elucidating these mechanisms. In recent years, telocytes (TCs)-a unique dermal cell population-have shown promising potential for tissue regeneration in various organs, including the dermis. TCs' participation in neo-angiogenesis, akin to that attributed to PRP, and their role in tissue remodelling and repair processes within the interstitia of several organs (including the dermis), offer intriguing insights. Their potential to contribute to, or possibly orchestrate, the skin regeneration process following PRP treatment has elicited considerable interest. Therefore, pursuing a comprehensive understanding of the cellular and molecular mechanisms at work, particularly those involving TCs, their temporal involvement in structural recovery following injury, and the interconnected biological events in skin wound healing and regeneration represents a compelling field of study.

Baffled-flow culture system enables the mass production of megakaryocytes from human embryonic stem cells by enhancing mitochondrial function

Human embryonic stem cells (hESCs) have become an ideal cell source for the ex vivo generation of megakaryocyte (MK) and platelet products for clinical applications. However, an ongoing challenge is to establish scalable culture systems to maximize the yield of stem cell-derived MKs that release platelets. We defined a specific dynamic 3D manufacturing system in a baffled-flow manner that could remarkably facilitate megakaryopoiesis and increase the yield of platelet-producing MKs from hESCs within a 12-day induction period. Additionally, an increased number of >16N ploidy MKs, proplatelets, and platelets were generated from induced cells harvested on Day 12 using the specific dynamic culture method. The specific dynamic culture method significantly enhanced endothelium-to-haematopoietic transition and early haematopoiesis. More importantly, MK fate was significantly facilitated in a specific dynamic manner during early haematopoiesis. Mechanistically, this dynamic culture significantly enhanced mitochondrial function via the oxidative phosphorylation pathway and caused differentiation skewing of hESCs toward megakaryopoiesis. This study can aid in the automatic and scalable production of MKs from stem cells using baffled-flow bioreactors and assist in the manufacturing of hESC-derived MK and platelet products.

Current status of platelet manufacturing in 3D or bioreactors

Blood shortages for transfusion are global issues of grave concern. As in vitro manufactured platelets are promising substitutes for blood donation, recent research has shown progresses including different cell sources, different bioreactors, and three-dimensional materials. The first-in-human clinical trial of cultured platelets using induced pluripotent stem cell-derived platelets began in Japan and demonstrated its quality, safety, and efficacy. A novel bioreactor with fluid motion for platelet production has been reported. Herein, we discuss various cell sources for blood cell production, recent advances in manufacturing processes, and clinical applications of cultured blood.

Ex vivo manufacturing of platelets: beyond the first-in-human clinical trial using autologous iPSC-platelets

Platelet transfusion is a common clinical approach to providing platelets to patients suffering from thrombocytopenia or other ailments that require an additional platelet source. However, a stable supply of platelet products is challenged by aging societies, pandemics, and other factors. Many groups have made extensive efforts toward the in vitro generation of platelets for clinical application. We established immortalized megakaryocyte progenitor cell lines (imMKCLs) from human induced pluripotent stem cells (iPSCs) and achieved clinical-scale manufacturing of iPSC-derived platelets (iPSC-PLTs) from them by identifying turbulent flow as a key physical condition. We later completed the iPLAT1 study, the first-in-human clinical trial using autologous iPSC-PLTs. This review summarizes current findings on the ex vivo generation of iPSC-PLTs that led to the iPLAT1 study and beyond. We also discuss new insights regarding the heterogeneity of megakaryocytes and the implications for the ex vivo generation of iPSC-PLTs.

Production and nonclinical evaluation of an autologous iPSC-derived platelet product for the iPLAT1 clinical trial

Donor-derived platelets are used to treat or prevent hemorrhage in patients with thrombocytopenia. However, ∼5% or more of these patients are complicated with alloimmune platelet transfusion refractoriness (allo-PTR) due to alloantibodies against HLA-I or human platelet antigens (HPA). In these cases, platelets from compatible donors are necessary, but it is difficult to find such donors for patients with rare HLA-I or HPA. To produce platelet products for patients with aplastic anemia with allo-PTR due to rare HPA-1 mismatch in Japan, we developed an ex vivo good manufacturing process (GMP)-based production system for an induced pluripotent stem cell-derived platelet product (iPSC-PLTs). Immortalized megakaryocyte progenitor cell lines (imMKCLs) were established from patient iPSCs, and a competent imMKCL clone was selected for the master cell bank (MCB) and confirmed for safety, including negativity of pathogens. From this MCB, iPSC-PLTs were produced using turbulent flow bioreactors and new drugs. In extensive nonclinical studies, iPSC-PLTs were confirmed for quality, safety, and efficacy, including hemostasis in a rabbit model. This report presents a complete system for the GMP-based production of iPSC-PLTs and the required nonclinical studies and thus supports the iPLAT1 study, the first-in-human clinical trial of iPSC-PLTs in a patient with allo-PTR and no compatible donor using the autologous product. It also serves as a comprehensive reference for the development of widely applicable allogeneic iPSC-PLTs and other cell products that use iPSC-derived progenitor cells as MCB.

Engineered cord blood megakaryocytes evade killing by allogeneic T-cells for refractory thrombocytopenia

The current global platelet supply is often insufficient to meet all the transfusion needs of patients, in particular for those with alloimmune thrombocytopenia. To address this issue, we have developed a strategy employing a combination of approaches to achieve more efficient production of functional megakaryocytes (MKs) and platelets collected from cord blood (CB)-derived CD34+ hematopoietic cells. This strategy is based on ex-vivo expansion and differentiation of MKs in the presence of bone marrow niche-mimicking mesenchymal stem cells (MSCs), together with two other key components: (1) To enhance MK polyploidization, we used the potent pharmacological Rho-associated coiled-coil kinase (ROCK) inhibitor, KD045, resulting in liberation of increased numbers of functional platelets both in-vitro and in-vivo; (2) To evade HLA class I T-cell-driven killing of these expanded MKs, we employed CRISPR-Cas9-mediated β-2 microglobulin (β2M) gene knockout (KO). We found that coculturing with MSCs and MK-lineage-specific cytokines significantly increased MK expansion. This was further increased by ROCK inhibition, which induced MK polyploidization and platelet production. Additionally, ex-vivo treatment of MKs with KD045 resulted in significantly higher levels of engraftment and donor chimerism in a mouse model of thrombocytopenia. Finally, β2M KO allowed MKs to evade killing by allogeneic T-cells. Overall, our approaches offer a novel, readily translatable roadmap for producing adult donor-independent platelet products for a variety of clinical indications.

Evaluation and management of platelet transfusion refractoriness

Platelet transfusion refractoriness (PTR), in which platelet counts do not increase after transfusion, occurs in many patients receiving platelet transfusions. PTR is a clinical condition that can harm patients. The causes of PTR can be divided into two types: immune and non-immune. Most cases of PTR are non-immune. Among immune causes, the most common is human leukocyte antigen (HLA) class I molecules. PTR caused by anti-HLA antibodies is usually managed by transfusing HLA-matched platelets. Therefore, it is important, especially for hemato-oncologists who frequently perform transfusion, to accurately diagnose whether the cause of platelet transfusion failure is alloimmune or non-immunological when determining the treatment direction for the patient. In this review, we discuss the definitions, causes, countermeasures, and prevention methods of PTR.

Genetic correction of concurrent α- and β-thalassemia patient-derived pluripotent stem cells by the CRISPR-Cas9 technology

BACKGROUND

Thalassemia is a genetic blood disorder characterized by decreased hemoglobin production. Severe anemia can damage organs and severe threat to life safety. Allogeneic transplantation of bone marrow-derived hematopoietic stem cell (HSCs) at present represents a promising therapeutic approach for thalassemia. However, immune rejection and lack of HLA-matched donors limited its clinical application. In recent years, human-induced pluripotent stem cells (hiPSCs) technology offers prospects for autologous cell-based therapy since it could avoid the immunological problems mentioned above.

METHODS

In the present study, we established a new hiPSCs line derived from amniotic cells of a fetus with a homozygous β41-42 (TCTT) deletion mutation in the HBB gene and a heterozygous Westmead mutation (C > G) in the HBA2 gene. We designed a CRISPR-Cas9 to target these casual mutations and corrected them. Gene-corrected off-target analysis was performed by whole-exome capture sequencing. The corrected hiPSCs were analyzed by teratoma formation and erythroblasts differentiation assays.

RESULTS

These mutations were corrected with linearized donor DNA through CRISPR/Cas9-mediated homology-directed repair. Corrections of hiPSCs were validated by sequences. The corrected hiPSCs retain normal pluripotency. Moreover, they could be differentiated into hematopoietic progenitors, which proves that they maintain the multilineage differentiation potential.

CONCLUSIONS

We designed sgRNAs and demonstrated that these sgRNAs facilitating the CRISPR-Cas9 genomic editing system could be applied to correct concurrent α- and β-thalassemia in patient-derived hiPSCs. In the future, these corrected hiPSCs can be applied for autologous transplantation in patients with concurrent α- and β-thalassemia.

Relationship between Hepatitis B virus infection and platelet production and dysfunction

Hepatitis B virus (HBV) is a kind of hepatotropic DNA virus. The main target organ is liver, except for liver, HBV has been found in a variety of extrahepatic tissues, such as kidney, thyroid, pancreas, bone marrow, etc. HBV can cause severe complications by invading these tissues. Among them, pancytopenia is one of the common complications, especially thrombocytopenia that causes life-threatening bleeding. However, the mechanism of thrombocytopenia is unclear and the treatment is extremely difficult. It has been confirmed that HBV has a close relationship with platelets. HBV can directly infect bone marrow, inhibit platelet production, and accelerate platelet destruction by activating monocyte-macrophage system and immune system. While platelets act as a double-edged sword to HBV. On one hand, the activated platelets can degranulate and release inflammatory mediators to help clear the viruses. Furthermore, platelets can provide anti-fibrotic molecules to improve liver functions and reduce hepatic fibrosis. On the other hand, platelets can also cause negative effects. The infected platelets collect HBV-specific CD8⁺ T cells and nonspecific inflammatory cells into liver parenchyma, inducing chronic inflammation, liver fibrosis and hepatic carcinoma. This article explores the interaction between HBV infection and platelets, providing a theoretical basis for clinical treatment of thrombocytopenia and severe hemorrhage caused by HBV infection.

Modeling genetic platelet disorders with human pluripotent stem cells: mega-progress but wanting more on our plate(let)

PURPOSE OF REVIEW

Megakaryocytes are rare hematopoietic cells that play an instrumental role in hemostasis, and other important biological processes such as immunity and wound healing. With the advent of cell reprogramming technologies and advances in differentiation protocols, it is now possible to obtain megakaryocytes from any pluripotent stem cell (PSC) via hematopoietic induction. Here, we review recent advances in PSC-derived megakaryocyte (iMK) technology, focusing on platform validation, disease modeling and current limitations.

RECENT FINDINGS

A comprehensive study confirmed that iMK can recapitulate many transcriptional and functional aspects of megakaryocyte and platelet biology, including variables associated with complex genetic traits such as sex and race. These findings were corroborated by several pathological models in which iMKs revealed molecular mechanisms behind inherited platelet disorders and assessed the efficacy of novel pharmacological interventions. However, current differentiation protocols generate primarily embryonic iMK, limiting the clinical and translational potential of this system.

SUMMARY

iMK are strong candidates to model pathologic mutations involved in platelet defects and develop innovative therapeutic strategies. Future efforts on generating definitive hematopoietic progenitors would improve current platelet generation protocols and expand our capacity to model neonatal and adult megakaryocyte disorders.

Improving Human Induced Pluripotent Stem Cell-Derived Megakaryocyte Differentiation and Platelet Production

Several protocols exist for generating megakaryocytes (MKs) and platelets from human induced pluripotent stem cells (hiPSCs) with limited efficiency. We observed previously that mesoderm induction improved endothelial and stromal differentiation. We, therefore, hypothesized that a protocol modification prior to hemogenic endothelial cell (HEC) differentiation will improve MK progenitor (MKP) production and increase platelet output. We further asked if basic media composition affects MK maturation. In an iterative process, we first compared two HEC induction protocols. We found significantly more HECs using the modified protocol including activin A and CHIR99021, resulting in significantly increased MKs. MKs released comparable platelet amounts irrespective of media conditions. In a final validation phase, we obtained five-fold more platelets per hiPSC with the modified protocol (235 ± 84) compared to standard conditions (51 ± 15; p < 0.0001). The regenerative potency of hiPSC-derived platelets was compared to adult donor-derived platelets by profiling angiogenesis-related protein expression. Nineteen of 24 angiogenesis-related proteins were expressed equally, lower or higher in hiPSC-derived compared to adult platelets. The hiPSC-platelet's coagulation hyporeactivity compared to adult platelets was confirmed by thromboelastometry. Further stepwise improvement of hiPSC-platelet production will, thus, permit better identification of platelet-mediated regenerative mechanisms and facilitate manufacture of sufficient amounts of functional platelets for clinical application.