Fetal cell/tissue therapy in adult disease: a new horizon in regenerative medicine.

Fetal tissue is the richest source of primordial stem cells and has several properties that make it particularly useful for transplantation. It is superior to adult (mature) tissue in certain respects. First, fetal cells are capable of proliferating faster and more often than mature, fully differentiated cells. This means that these donor cells are able to quickly reverse the lost function of the host. In addition, these fetal cells can often differentiate in response to the environmental cues around them. This is because of their location--they can grow, elongate, migrate, and establish functional connections with other cells around them in the host. It has been found that fetal tissue is not easily rejected by the recipient due to the low levels of histocompatibility antigens in the fetal tissue. At the same time, angiogenic and trophic factors are at high levels, enhancing their ability to grow once they are transplanted. Since early fetal hematopoietic tissue lacks lymphocytes, graft vs host reactions are minimized. Fetal cells tend to survive excision, dissection, and grafting better because they generally do not have long extensions or strong intercellular connections. Finally, fetal tissue can survive at lower oxygen levels than mature cells. This would make them more resistant to the ischemic conditions found during transplantation or in vitro situations. Studies on fetal cell/tissue transplant have been encouraging. Fetal tissue can be used in different indications, for instance, fetal liver transplants may be used in combating aplastic anemia, placental umbilical cord whole blood transfusion can serve as an emergency alternative to adult whole blood transfusion, fetal adrenal transplant has been tried in combating intractable pain in arthritis, and fetal thymic transplant in combating leucopenia in non-Hodgkin's lymhoma and other immunodeficiency conditions like DiGeorge Syndrome, only to name a few. Fetal brain tissue transplant has also been done in a heterotopic site and the proliferation of the tissue has been observed. Neurotransplantation with fetal tissue in Parkinsonism shows positive results in some globally accepted studies. There are futuristic potential uses of fetal tissue in bioengineering through coating/seedling of fetal tissue on implants, stents and other artificial surgical life-saving devices to improve their functioning, and it may also extend the life of these costly gadgets. By properly using pre-HLA fetal tissue seedling in orthopedic, thoracic and also neurosurgical appliances, there could be a reduction of long-term irritation sequelae of the implant and the host interphase, and thus, a better device, i.e., a more biofriendly interphase could be developed. This may help in the reduction of pseudomembrane formation, loss of patency and other resultant TH2 reactions of the host system.