What are the similarities and differences between embryonic and adult stem cells?
Human embryonic and adult stem cells each have advantages and disadvantages regarding potential use for cell-based regenerative therapies. One major difference between adult and embryonic stem cells is their different abilities in the number and type of differentiated cell types they can become. Embryonic stem cells can become all cell types of the body because they are pluripotent. Adult stem cells are thought to be limited to differentiating into different cell types of their tissue of origin.
Embryonic stem cells can be grown relatively easily in culture. Adult stem cells are rare in mature tissues, so isolating these cells from an adult tissue is challenging, and methods to expand their numbers in cell culture have not yet been worked out. This is an important distinction, as large numbers of cells are needed for stem cell replacement therapies.
Scientists believe that tissues derived from embryonic and adult stem cells may differ in the likelihood of being rejected after transplantation. We don't yet know whether tissues derived from embryonic stem cells would cause transplant rejection, since the first phase 1 clinical trial testing the safety of cells derived from hESCS has only recently been approved by the United States Food and Drug Administration (FDA).
Adult stem cells, and tissues derived from them, are currently believed less likely to initiate rejection after transplantation. This is because a patient's own cells could be expanded in culture, coaxed into assuming a specific cell type (differentiation), and then reintroduced into the patient. The use of adult stem cells and tissues derived from the patient's own adult stem cells would mean that the cells are less likely to be rejected by the immune system. This represents a significant advantage, as immune rejection can be circumvented only by continuous administration of immunosuppressive drugs, and the drugs themselves may cause deleterious side effects.
Methods of use - adult stem cells
The use of endogenous adult stem cells is ethical and legally straightforward. Under German law, the extracted stem cells are categorized as drugs. Because they are exclusively for personal use, they are individual drugs, and under German law do not require the same governmental approval as other drugs. Despite this, the clinic still has to obtain a manufacturing license from the surveillance authority. In tx-bridge, it is guaranteed that the processes of extraction, cleaning and transplantation are all carried out in compliance with Good Manufacturing Practice (GMP) standards, thus guaranteeing maximum quality and safety for the patient.
For the last few years, attempts at therapy with adult stem cells from bone marrow have been carried out at university hospitals. This means that unlike animal testing with embryonic stem cells, adult stem cells are in-part, already being clinically tested. The well-documented success of the cardiologist Prof. Dr. Bodo Strauer from Düsseldorf can be seen as an example. He treated a patient suffering from a series of heart attacks for whom common therapies could not assure any chance of survival with the patient's own bone marrow stem cells. Nine days after the stem cells had been injected into the diseased area, the patient was able to leave the intensive care unit. Up to now, more than 300 patients have been treated in Düsseldorf using this procedure – most of them successfully.
Tx-bridge's treatment is based on the therapy experiences of more than 400 patients, treated both in tx-bridge directly and in cooperation with other universities and research institutes (standing: October 2007). At present, the results of treating diabetes mellitus and stroke with stem cell therapy are looking particularly auspicious. Initial results have also been obtained from the treatment of patients with Parkinson's, Alzheimer's or Multiple Sclerosis.
