CD34+ cells are used in a range of in vitro and in vivo experiments. Their most common use is to generate humanized mice that allow scientists to study the human immune system in a non-human model organism. Humanized mice are generated by taking certain strains of highly immunodeficient mice, ablating their bone marrow, and injecting them with human CD34+ cells. The cells then hone to the bone marrow and produce human immune cells.
HSC transplants, also known as bone marrow transplants, are used to treat a range of hematologic conditions. These treatments work by ablating the patient’s native bone marrow and then infusing HSCs (or a tissue containing HSCs) from an HLA-matched donor to reconstitute the patient’s blood and immune system. Companies are also investigating whether organ donor HSCs can enable immune tolerance in solid organ transplantation. The ability to engineer HSCs is also an intense area of research that may one day help to cure previously untreatable diseases.
MSCs are used in laboratories for the study of cellular differentiation, immune cell modulation, as well as to generate new tissues. There is still debate on how to biologically define MSCs. As a result, the behavior of MSCs over repeated passaging and how MSCs vary between donors are all active areas of investigation.
MSCs are being investigated for their potential to modulate the immune system and regenerate tissue. While there are currently no MSC products approved for use in the US, there are many clinical trials studying their use for a range of diseases. Companies and academic institutions are investigating the use of MSCs for treatment of GVHD by tamping down hyperactive immune systems, repair of knees by generating cartilage and connective tissue, and healing of ischemic heart tissue by promoting re-vascularization.