Epitope-engineered human hematopoietic stem cells are shielded from CD123-targeted immunotherapy

Targeted eradication of transformed or otherwise dysregulated cells using monoclonal antibodies (mAb), antibody-drug conjugates (ADC), T cell engagers (TCE), or chimeric antigen receptor (CAR) cells is very effective for hematologic diseases. Unlike the breakthrough progress achieved for B cell malignancies, there is a pressing need to find suitable antigens for myeloid malignancies. CD123, the interleukin-3 (IL-3) receptor alpha-chain, is highly expressed in various hematological malignancies, including acute myeloid leukemia (AML). However, shared CD123 expression on healthy hematopoietic stem and progenitor cells (HSPCs) bears the risk for myelotoxicity. We demonstrate that epitope-engineered HSPCs were shielded from CD123-targeted immunotherapy but remained functional, while CD123-deficient HSPCs displayed a competitive disadvantage. Transplantation of genome-edited HSPCs could enable tumor-selective targeted immunotherapy while rebuilding a fully functional hematopoietic system. We envision that this approach is broadly applicable to other targets and cells, could render hitherto undruggable targets accessible to immunotherapy, and will allow continued posttransplant therapy, for instance, to treat minimal residual disease (MRD)

L’Aryl hydrocarbone récepteur, un acteur important de la biogenèse des plaquettes permettant la production de plaquettes de culture à visée transfusionnelle

Blood platelets play a key role in ensuring normal hemostasis. Abnormalities in the quantity or quality of platelets are responsible for serious bleeding events. In order to prevent these complications in patients with severely decreased platelet counts, transfusion is necessary. The increasing demand for controlled blood products, free of infectious, immune and inflammatory risks, coupled with the limited storage time of platelets (5 days) leads frequently to a "just-in-time" situation. In this context, an alternative to donation would be the availability of blood platelets produced under in vitro conditions. It is now possible to produce cultured platelets, which are similar in size and functionality to native platelets. The use of an AHR ligand, StemRegenin1 (SR1), promotes this production but the signalling pathways involved are not defined. Yields are still low and there are many scientific locks. It is therefore necessary to better understand the cellular and molecular mechanisms governing platelet biogenesis in order to improve in vitro platelet production for transfusion.Les plaquettes sanguines jouent un rôle vital en assurant l’hémostase normale. Les anomalies quantitatives ou qualitatives des plaquettes sont responsables d’accidents hémorragiques graves. Afin de prévenir ces complications chez des patients présentant des numérations plaquettaires fortement diminuées, il est nécessaire de les transfuser. La demande croissante en produits sanguins contrôlés, indemnes de risques infectieux, immunitaires et inflammatoires, couplée à la durée de stockage limitée des plaquettes (5 jours) conduisent fréquemment à des situations à flux tendus. Dans ce contexte, une alternative au don serait de disposer de plaquettes sanguines produites en conditions in vitro. Il est possible aujourd’hui de produire des plaquettes de culture, dont la taille et la fonctionnalité sont similaires aux plaquettes natives. L’utilisation d’un ligand de l’AHR le StemRegenin1 (SR1), favorise cette production, mais les voies de signalisation impliquées ne sont pas définies. Les rendements sont encore faibles et les verrous scientifiques nombreux. Il est donc nécessaire de mieux comprendre les mécanismes cellulaires et moléculaires qui gouvernent la biogenèse des plaquettes, afin d’améliorer la production de plaquettes in vitro à visée transfusionnelle

The aryl hydrocarbon receptor, important actor in platelets biogenesis allowing the cultured platelets production for transfusion purposes

Les plaquettes sanguines jouent un rôle vital en assurant l’hémostase normale. Les anomalies quantitatives ou qualitatives des plaquettes sont responsables d’accidents hémorragiques graves. Afin de prévenir ces complications chez des patients présentant des numérations plaquettaires fortement diminuées, il est nécessaire de les transfuser. La demande croissante en produits sanguins contrôlés, indemnes de risques infectieux, immunitaires et inflammatoires, couplée à la durée de stockage limitée des plaquettes (5 jours) conduisent fréquemment à des situations à flux tendus. Dans ce contexte, une alternative au don serait de disposer de plaquettes sanguines produites en conditions in vitro. Il est possible aujourd’hui de produire des plaquettes de culture, dont la taille et la fonctionnalité sont similaires aux plaquettes natives. L’utilisation d’un ligand de l’AHR le StemRegenin1 (SR1), favorise cette production, mais les voies de signalisation impliquées ne sont pas définies. Les rendements sont encore faibles et les verrous scientifiques nombreux. Il est donc nécessaire de mieux comprendre les mécanismes cellulaires et moléculaires qui gouvernent la biogenèse des plaquettes, afin d’améliorer la production de plaquettes in vitro à visée transfusionnelle.Blood platelets play a key role in ensuring normal hemostasis. Abnormalities in the quantity or quality of platelets are responsible for serious bleeding events. In order to prevent these complications in patients with severely decreased platelet counts, transfusion is necessary. The increasing demand for controlled blood products, free of infectious, immune and inflammatory risks, coupled with the limited storage time of platelets (5 days) leads frequently to a "just-in-time" situation. In this context, an alternative to donation would be the availability of blood platelets produced under in vitro conditions. It is now possible to produce cultured platelets, which are similar in size and functionality to native platelets. The use of an AHR ligand, StemRegenin1 (SR1), promotes this production but the signalling pathways involved are not defined. Yields are still low and there are many scientific locks. It is therefore necessary to better understand the cellular and molecular mechanisms governing platelet biogenesis in order to improve in vitro platelet production for transfusion

The aryl hydrocarbon receptor, important actor in platelets biogenesis allowing the cultured platelets production for transfusion purposes

Les plaquettes sanguines jouent un rôle vital en assurant l’hémostase normale. Les anomalies quantitatives ou qualitatives des plaquettes sont responsables d’accidents hémorragiques graves. Afin de prévenir ces complications chez des patients présentant des numérations plaquettaires fortement diminuées, il est nécessaire de les transfuser. La demande croissante en produits sanguins contrôlés, indemnes de risques infectieux, immunitaires et inflammatoires, couplée à la durée de stockage limitée des plaquettes (5 jours) conduisent fréquemment à des situations à flux tendus. Dans ce contexte, une alternative au don serait de disposer de plaquettes sanguines produites en conditions in vitro. Il est possible aujourd’hui de produire des plaquettes de culture, dont la taille et la fonctionnalité sont similaires aux plaquettes natives. L’utilisation d’un ligand de l’AHR le StemRegenin1 (SR1), favorise cette production, mais les voies de signalisation impliquées ne sont pas définies. Les rendements sont encore faibles et les verrous scientifiques nombreux. Il est donc nécessaire de mieux comprendre les mécanismes cellulaires et moléculaires qui gouvernent la biogenèse des plaquettes, afin d’améliorer la production de plaquettes in vitro à visée transfusionnelle.Blood platelets play a key role in ensuring normal hemostasis. Abnormalities in the quantity or quality of platelets are responsible for serious bleeding events. In order to prevent these complications in patients with severely decreased platelet counts, transfusion is necessary. The increasing demand for controlled blood products, free of infectious, immune and inflammatory risks, coupled with the limited storage time of platelets (5 days) leads frequently to a "just-in-time" situation. In this context, an alternative to donation would be the availability of blood platelets produced under in vitro conditions. It is now possible to produce cultured platelets, which are similar in size and functionality to native platelets. The use of an AHR ligand, StemRegenin1 (SR1), promotes this production but the signalling pathways involved are not defined. Yields are still low and there are many scientific locks. It is therefore necessary to better understand the cellular and molecular mechanisms governing platelet biogenesis in order to improve in vitro platelet production for transfusion

Development of an efficient, ready to use, blood platelet-release device based on two new flow regime parameters: The periodic hydrodynamic loading and the shear stress accumulation.

International audienceIn vitro production of blood platelets for transfusion purposes is gaining interest. While platelet production is now possible on a laboratory scale, the challenge is to move towards industrial production. Attaining this goal calls for the development of platelet release devices capable of producing large quantities of platelets. To this end, we have developed a continuous-flow platelet release device composed of five spherical chambers each containing two calibrated cones placed in a staggered configuration. Following perfusion of proplatelet-bearing cultured megakaryocytes, the device achieves a high yield of about 100 bona-fide platelets/megakaryocyte, at a flow rate of ∼80 mL/min. Performances and operating conditions comply with the requirements of large-scale platelet production. Moreover, this device enabled an in-depth analysis of the flow regimes through Computational Fluid Dynamics (CFD). This revealed two new universal parameters to be taken into account for an optimal platelet release: i.e. a periodic hydrodynamic load and a sufficient accumulation of shear stress. An efficient 16 Pa.s shear stress accumulation is obtained in our system at a flow rate of 80 mL/min

Functional properties of human platelets derived in vitro from CD34+ cells

International audienceThe in vitro production of blood platelets for transfusion purposes is an important goal in the context of a sustained demand for controlled products free of infectious, immune and inflammatory risks. The aim of this study was to characterize human platelets derived from CD34+ progenitors and to evaluate their hemostatic properties. These cultured platelets exhibited a typical discoid morphology despite an enlarged size and expressed normal levels of the major surface glycoproteins. They aggregated in response to ADP and a thrombin receptor agonist peptide (TRAP). After infusion into NSG mice, cultured and native platelets circulated with a similar 24 h half-life. Notably, the level of circulating cultured platelets remained constant during the first two hours following infusion. During this period of time their size decreased to reach normal values, probably due to their remodeling in the pulmonary circulation, as evidenced by the presence of numerous twisted platelet elements in the lungs. Finally, cultured platelets were capable of limiting blood loss in a bleeding assay performed in thrombocytopenic mice. In conclusion, we show here that cultured platelets derived from human CD34+ cells display the properties required for use in transfusion, opening the way to clinical trials

AHR:IKAROS Interaction Promotes Platelet Biogenesis in Response to SR1

In vitro, the differentiation of megakaryocytes (MKs) is improved by aryl-hydrocarbon receptor (AHR) antagonists such as StemRegenin 1 (SR1), an effect physiologically recapitulated by the presence of stromal mesenchymal cells (MSC). This inhibition promotes the amplification of a CD34+CD41low population able to mature as MKs with a high capacity for platelet production. In this short report, we showed that the emergence of the thrombocytogenic precursors and the enhancement of platelet production triggered by SR1 involved IKAROS. The downregulation/inhibition of IKAROS (shRNA or lenalidomide) significantly reduced the emergence of SR1-induced thrombocytogenic population, suggesting a crosstalk between AHR and IKAROS. Interestingly, using a proximity ligation assay, we could demonstrate a physical interaction between AHR and IKAROS. This interaction was also observed in the megakaryocytic cells differentiated in the presence of MSCs. In conclusion, our study revealed a previously unknown AHR/ IKAROS -dependent pathway which prompted the expansion of the thrombocytogenic precursors. This AHR- IKAROS dependent checkpoint controlling MK maturation opens new perspectives to platelet production engineering