Encapsulation of human hematopoietic stem cells with a biocompatible polymer

Hematopoietic stem cells (HSCs) are the progenitor for all blood types including leukocytes, erythrocytes and platelets. Normally, the human body is programmed to maintain sufficient level of hematopoietic stem cells or derivatives. However, in certain conditions, including repeated chemotherapy, leukemic cancer, or genetic mutation, bone marrow disorders; the HSC transplantation becomes necessary. HSC transplantation deals with two major obstacles: human leukocyte antigen (HLA) matching and high cell dose. Non-match HSC transplantation activates immune reaction and induces graft versus host diseases, which can be fatal to the recipient. Hydrogel encapsulation technology offers a promising method to solve these problems. In this study, we introduced a feasible HSC encapsulation technique with a biocompatible polymer. The cells were isolated from umbilical cord blood with a density gradient method and continued by a magnetic bead separation based on CD34 expression. HSCs, identified as CD34⁺ cells, were encapsulated with collagen type 1 by a hanging drop method. The encapsulated cells were cultured at 37°C with 5% CO₂ in a fully humidified incubator. On day three, the capsule was degraded with collagenase treatment and the cells were analyzed to evaluate the effect of encapsulation on cell viability and stemness. It was found that the cell viability remained high on encapsulated cells. However, the ratio of CD34⁺ cells was slightly decreased on encapsulated cells than non-encapsulated cells. As a conclusion, the employed method is suitable to encapsulate HSCs without compromising its viability and the modification of coating material is needed to maintain the stemness of HSCs.