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Background: Platelets play a key role in the treatment of thrombocytopenia. Nowadays, platelets (PLTs) are only obtained through blood donation. However, due to the limitations in their preparation and storage, they are produced in laboratories, especially through bioreactors that convert megakaryocytes from stem cells into large-scale injectable PLTs. Materials and Methods: In this study, the CD34 cells isolated from cord blood were differentiated into megakaryocytes. A 6-chamber bioreactor with a two-layer collagen scaffold, several ECM factors, and human cryoprecipitate were used to simulate the structure of the bone marrow. After the addition of megakaryocytes to the scaffold, PLTs were produced due to the flow pressure and the interaction between the scaffold structure and the ECM factors. Results: CD41 + cells were expanded 100 times as much as CD34 + cord blood stem cells. The mean PLT release from one megakaryocyte in the pure collagen scaffold was 17.42 PLTs. Once fibrin, fibronectin, hyaluronic acid, and cryoprecipitates were added to collagen, the mean PLT release was 21.4, 22.4, 23.9, and 27.37, respectively. With the simultaneous addition of three factors to collagen (CFFH) and then four factors (CFFHC), the number of PLTs reached 30.52 and then 34. Conclusion: Functional PLTs can be produced on a large scale with a multi-chamber bioreactor using a combination of ECM and cryoprecipitate with collagen scaffolding. [ABSTRACT FROM AUTHOR]

Background: To date, platelet (PLT) transfusion is the main medical option for the treatment of thrombocytopenia. Nowadays, allogenic PLTs are commonly used for blood donation. Due to the limitations in the preparation and storage of PLTs, researchers try to develop alternative modalities such as bioreactors for the in-vitro expansion and production of PLTs for therapeutic purposes by promoting the differentiation of different types of stem cells into megakaryocytes (MK) and PLTs. Materials and Methods: In this experimental study, umbilical cord blood stem cells (UCB-SC) were differentiated into MK. To this end, a new bioreactor system consisting of six compartments and a two-layer scaffold made of collagen and natural tragacanth gum was developed to mimic a bone marrow-like structure. After MKs were loaded to the top layer of the scaffold, the production rate of PLTs was analyzed under shear stress. Results: Based on the estimation, each MK produced about 17.42 PLTs loaded into the scaffold collagen. This value emerged to be 23.46 and 9.44 PLTs in the collagen-tragacanth and the pure tragacanth scaffold groups, respectively, the increase of PLTs in the collagen-tragacanth scaffold was statistically significant (p < 0.001).The generated PLTs had a positive response in aggregometry as well as interaction with normal PLTs. Conclusion: Taken together, the designed bioreactor with a collagen-tragacanth substrate can be used for the production of a sufficient number of PLTs for clinical purposes. [ABSTRACT FROM AUTHOR]