Chimerism: a new look

Microchimerism has become a familiar term in the past few years. Many groups all over the globe, specializing in a diverse array of basic and medical sciences, have turned their attention to microchimerism, its possible role in disease or repair, and its mechanism of action in the host body. We reviewed the current knowledge about this novel term. We search the PubMed, using all the derivatives of chimera. All papers and their bibliographic information published by December 2005 were reviewed and 61 were selected. Microchimerism is the presence of foreign or nonhost cells in a body. These are cells that live, differentiate, and persist in the host body by definition. These cells can enter the host body in a variety of manners. The most familiar aspect is microchimerism resulting from organ transplant. For many years now scientists have been debating over the interpretation of this phenomenon. We know that donor cell engraftment in the recipient body is a sign of transplantation success. What this means is that the body has developed tolerance toward the foreign organ and created a chimer. How long this chimeric state will last, whether these cells will induce or be induced to create a chronic complication in the long run, or will these genetically distinct cell types live peacefully in one body to the end of the host's life are the essence of the ongoing discussion and what probes researchers to continue their search

Does mesenchymal stem cell therapy help multiple sclerosis patients? report of a pilot study

Mesenchymal stem cells [MSCs] with their potential to differentiate into mesodermal and non-mesodermal lineages have several immunomodulatory characteristics. These properties make them promising tools in cell and gene therapy. To evaluate the potential therapeutic applications of autologous MSC in improving clinical manifestations of MS patients. Ten patients were included in this pilot study. All had progressive disease that had not responded to disease modifying agents including Mitoxantrone. Their Expanded Disability Status Scale [EDSS] score ranged from 3.5 to 6. Patients were injected intrathecally with culture expanded MSCs. They were followed with monthly neurological assessment and a MRI scan at the end of the first year. During 13 to 26 months of follow up [mean: 19 months], the EDSS of one patient improved from 5 to 2.5 score. Four patients showed no change in EDSS. Five patients' EDSS increased from 0.5 to 2.5. In the functional system assessment, six patients showed some degree of improvement in their sensory, pyramidal, and cerebellar functions. One showed no difference in clinical assessment and three deteriorated. The result of MRI assessment after 12 months was as following: seven patients with no difference, two showed an extra plaque, and one patient showed decrease in the number of plaques. This preliminary report emphasizes on the feasibility of autologous MSC for treatment of MS patients. However, in order to draw a definitive conclusion a larger sample size is required

Ethics of tissue and stem cell trasplantation

Tissue and cell transplantation are regarded as a popular procedure in clinical sciences, prospecting a new horizon for several incurable diseases. Along with its usefulness, many ethical concerns accompany this development. The ethical issue of organ transplant is unique to the source used which includes: living related, living unrelated, cadaveric, and xenotransplant. Obtaining organs has a separate set of ethical concerns which are discussed under two headings, namely salvage and donation. Then there is the issue of organ marketing and the ethical, social, and economical issues it encompasses. All these are active areas of debate, and we have touched upon them by turn. This century has brought a new aspect of transplantation into the light, stem cell transplantation. Here we present some work done recently on mesenchymal stem cells and their outcome. These cells are now being employed in the therapy of some incurable ailments. It seems this kind of transplantation, although possessing its own range of issues, could prove to be the way of the future

Microchimerism and renal transplantation: doubt still persists

Background: The Presence of donor leukocytes in recipients of organ allograft has been shown even several years after transplantation. However, it remains unclear whether this donor cell microchimerism plays an effective role in allograft acceptance or is simply a consequence of immunosuppressive conditions in recipients

Objective: To study microchimerism in a group of kidney transplant recipients

Methods: In this study, the Peripheral Blood Microchimerism [PBM] after renal transplantation was retrospectively evaluated in 32 male-to-female recipients of living [unrelated] and cadaveric donor renal transplants. Using a Nested Polymerase Chain Reaction [Nested-PCR] amplification specific for SRY region of the Y chromosome, microchimerism was detected with a sensitivity of 1:1000000. Recipients were classified and compared according to the presence of PBM, acute and chronic rejection episodes, type of allotransplant, recipient and donor age at transplantation, previous male labor or blood transfusion, allograft function [serum creatinine level], and body mass index

Results: Among 32 recipients, 7 [21.9] were positive for PBM in multiple testing at different post-transplantation times. All microchimeric recipients had received kidney from living-unrelated donors. No significant difference was observed with regard to other parameters mentioned above. In addition, acute rejection rate in the microchimeric group was 3 [42%] versus 4 [16%] in the nonmicrochimeric recipients [not significant]

Conclssion: Our results demonstrate better establishment of microchimerism after living donor kidney transplantation. However, concerning the true effect of microchimerism after renal transplantation doubt still persists; and it seems that microchimerism alone has no major protective role in renal allograft survival