Types of cells

Human embryonic stem cellsedit

Research into human embryonic stem cells is controversial, and regulation varies from country to country, with some countries banning it outright. Nevertheless, these cells are being investigated as the basis for a number of therapeutic applications, including possible treatments for diabetes and Parkinson's disease.

Neural Stem Cell Therapyedit

Neural stem cells (NSCs) are the subject of ongoing research for possible therapeutic applications, for example for treating a number of neurological disorders such as Parkinson's disease and Huntington's disease.

Mesenchymal Stem Cell Therapyedit

MSCs are immunomodulatory, multipotent and fast proliferating and these unique capabilities mean they can be used for a wide range of treatments including immune-modulatory therapy, bone and cartilage regeneration, myocardium regeneration and the treatment of Hurler syndrome, a skeletal and neurological disorder.

Researchers have demonstrated the use of MSCs for the treatment of osteogenesis imperfecta (OI). Horwitz et al. transplanted bone marrow (BM) cells from human leukocyte antigen (HLA)-identical siblings to patients suffering from OI. Results show that MSCs can develop into normal osteoblasts, leading to fast bone development and reduced fracture frequencies. A more recent clinical trial showed that allogeneic fetal MSCs transplanted in utero in patients with severe OI can engraft and differentiate into bone in a human fetus.

Besides bone and cartilage regeneration, cardiomyocyte regeneration with autologous BM MSCs has also been reported recently. Introduction of BM MSCs following myocardial infarction (MI) resulted in significant reduction of damaged regions and improvement in heart function. Clinical trials for treatment of acute MI with Prochymal by Osiris Therapeutics are underway. Also, a clinical trial revealed huge improvements in nerve conduction velocities in Hurler's Syndrome patients infused with BM MSCs from HLA-identical siblings.

Hematopoietic stem cell transplantationedit

Hematopoietic stem cells (HSCs), derived from bone marrow or blood, are cells with the abilities to self-renew and to differentiate into all types of blood cells, especially those involved in the human immune system. Thus, they can be used to treat blood and immune disorders. Since human bone marrow grafting was first published in 1957, there have been significant advancements in HSCs therapy. Following that, syngeneic marrow infusion and allogeneic marrow grafting were performed successfully. HSCs therapy can also render its cure by reconstituting damaged blood-forming cells and restoring the immune system after high-dose chemotherapy to eliminate disease.

There are three types of HSC transplantation: syngeneic, autologous, and allogeneic transplants. Syngeneic transplantations occur between identical twins. Autologous transplantations use the HSCs obtained directly from the patient and hence avoid complications of tissue incompatibility; whereas allogeneic transplantations involve the use of donor HSCs, either genetically related or unrelated to the recipient. To lower the risks of transplant, which include graft rejection and Graft-Versus-Host Disease (GVHD), allogeneic HSCT must satisfy compatibility at the HLA loci (i.e. genetic matching to reduce the immunogenicity of the transplant).

In addition to bone marrow-derived HSCs, the use of alternative sources such as umbilical cord blood (UCB) and peripheral blood stem cells (PBSCs) has been increasing. In comparison with bone marrow-derived HSC recipients, PBSC recipients afflicted with myeloid malignancies reported a faster engraftment and better overall survival. The use of UCB requires less stringent HLA loci matching, although the time of engraftment is longer and graft failure rate is higher.

Differentiated or Mature cell transplantationedit

Alternative to stem- or progenitor cells, investigations are exploring the transplantation of differentiated cells that only possess low or no proliferation ability. This tends to involve specialized cells able to facilitate specific function in the patients body (for example, transplantation of cardiomyocytes to repair heart function or islet cell transplantation for establishing insulin homeostasis in diabetes patients) or support/regenerate the extracellular matrix production of specific tissues (for example intervertebral disc repair by transplanting chondrocytes).