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11
September, 2013

16th Congress of The European Society for Organ Transplantation.

Overview

On 8-11 September in Vienna (Austria) the 16th Congress of the European Society for Organ Transplantation was held. For the first time stem cell transplantation results were presented in this Congress.
In particular results of experiments on T-regulatory lymphocytes production from embryonic stem cells were analyzed.

Guests

Professor Wim Fibbe from Leiden (Netherlands) reported on large scale clinical trials with T-regulatory cells using to induce tolerance to kidney transplant, which 10 countries attended.

Professor Benedict Cosimi from Boston (USA) presented the results of practical work on the induction of immunological tolerance to the transplanted kidney with simultaneous kidney and stem cells transplantation of the same donor. After such procedures 12 patients are living without receiving immunosuppressive drugs.
Mrs. Qizhi Tang from San Francisco (USA) announced the readiness of carrying out clinical trials on practical application of T-regulatory lymphocytes during kidney transplantation.

EmProCell Clinical Research Pvt. Ltd. also took part in the Congress. Abstracts of our report are presented below:

Background

The molecular origin of graft rejection is an interaction between T-lymphocytes receptors and molecules of MHC (HLA). In transplantation currently used such methods for prevention of transplant rejection: immune suppression, non-reactivity induction through a direct change of the cytokine regulation of immune response, modulation between type 1 and type 2 T-lymphocytes generation and antibodies against CD3+ cells, etc.

Prolonged chimerism of the donors and recipient blood cells after hemotransfusion, and likewise increase in therapeutic efficacy of stem cells by increasing their doses (Fandrrich et al., 2002; Down, White-Scharf, 2003) evidences about the active interaction of transplanted cells with recipient’s immune system. Result of the interaction is induction of central immune tolerance that makes through establishing in thymus the double standard molecule MHC (HLA), by means of which it further causes to occur the positive and negative selection of T-lymphocytes. In nature, such situation is observed in the true hermaphrodites who do not reject organs of both the parents.

We studied possibility of allogeneic tissue engraftment while simultaneous transplantation fetal stem/progenitor cells (FSP/Cs).

Material Methods

Rats of 550 in number were used. FSP/Cs isolated from rats' fetuses according to original method (Patent Ukraine Invention ¹ UA 72796). FSP/Cs (5-8 ×106/ml) introduced intravenously. Spleen transplantation was done in pairs: control (½ of allogeneic spleen + 0.9% sodium chloride) & experimental (½ of allogeneic spleen + FSP/Cs) animals. After the median laparotomy in both anaesthetized rats, were removed ½ of the spleen and then, they were decapsulated and stitched in created pouch of the recipient's omentum. Same design (pair's transplantation) was performed in skin flaps grafting. Caspase-3, -8 activity were identified in thymus, bone marrow, spleen and lymph nodes. To estimate FSP/Cs in immune system organs staining of FSP/Cs membranes was done by PKH 67 (Sigma). In half of the experimental animals after 3-6 months, pair transplantation were repeated: In the same pair of rats transplantation of the remaining half of the spleen was carried out, but FSP/Cs were not introduced repeatedly.

Results

Re-laparotomy was carried out after 1, 2, 6 and 12 months that revealed spleen engraftment only in those rats received FSP/Cs, and likewise in skin transplants (Fig. 1).
After tag-PKH-67-FSP/Cs introduction marked cells appear in thymus, lymph nodes, spleen and bone marrow. Analysis of an apoptotic cells showed that apoptosis intensity in thymus and bone marrow of animals those received FSP/Cs was much higher compared to the control data.
After 3-6 months in some animals repeated spleen transplantation was carried out by following scheme: In pair rats those earlier underwent spleen transplantation from each other, re-laprotomy were carried out and removed half of the spleen remaining after first operation and transplanted in the omentum from one rat to the other rat. Thus, both the rats became recipients of two parts of one and the same allogenic spleen. Significant that during this second operation animal were not introduced FSP/Cs. As the result one out of two rats received FSP/Cs only during first operation (3-6 months earlier), and second FSP/Cs were not introduced at all (control).
In re-laparotomy after 12 months from the starting of experiment (first operation) was observed that in control rats first transplanted part of spleen calcified, and second – necrotized. Where as in animals of those received FSP/Cs, both first and second part of transplanted spleen got engrafted in omentum and vacularized. (Fig. 2, 3).

Discussion

Based on the selection of thymocytes clones lies the capability of their membrane receptors to recognize ligands which is present on stromal cell surface of the thymus. T-cells with phenotype CD4+CD8+ receives protection signal (Вс1-2) from epithelial cells of the thymus only in the case if they are capable to recognize autologous molecule histocompatibility (positive selection). Further these same cells receive signals to apoptosis if they react to autologous peptide (negative selection). As the result from thymus comes out the mature T-cells capable to react on only with foreign peptides which presents with autologous molecule of histocompatibility. Shall be permitted that FSP/Cs integrates in the recipient’s thymus, where they differentiate into epithelial cell and expresses donor set of MHC molecule. In this case, restriction of CD4+CD8+-cells occurs by means of two standards (MHC donor and recipient), and emergence of alloantigens by the transplanted organs in de novo generated thymus cells can be related with the fusion of FSP/Cs and splenocytes that expands spectrum “own” antigens and provides specific unresponsiveness to spleen allograft. The results of our biological experiments evidences about the possibility of inducing tolerance to allogeneic tissues with the help of FSP/Cs (Patent Ukraine Invention ¹ UA 72310).

Thus, stem cells are progressing into transplantology through the induction of immunological tolerance. This is a testament to that the scientific world of Europe regards stem cells as transplant and not as a pharmacological drug.