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Updated: Jul 14, 2026
A Modified Heterotopic Swine Hind Limb Transplant Model for Translational Vascularized Composite Allotransplantation (VCA) Research
Published on: October 14, 2013
Enhanced cardiac allograft survival by Vav1-Rac signaling blockade in a mouse model
Shuang Wang1, Hong Diao, Qiunong Guan
1Department of Medicine, The University of Western Ontario, London, Ontario, Canada.
Background:
Vav1-Rac signaling plays a pivotal role in TCR/antigen and CD28 signals for T cell activation. However, pharmacological interference of this signaling has not been tested in the prevention of alloimmune-mediated allograft rejection. It has been demonstrated that 6-thio-GTP, a metabolite of azathioprine, specifically inhibits Vav1-Rac activity in T lymphocytes. Here we show the immunosuppressive efficacy of 6-thio-GTP in the prevention of cardiac allograft rejection.
Methods:
T cell proliferations were measured by (3)H-thymidine uptake. The immunosuppressive activities of 6-thio-GTP were tested in the cardiac allograft model of C57BL/6 (H-2(b)) to Balb/c (H-2(d)) mice.
Results:
6-Thio-GTP inhibited TCR/alloantigen stimulated T cell proliferation and CD28-dependent T cell survival. Administration of 6-thio-GTP (0.5 mg/kg) prolonged graft survival to 13.8+/-2.39 days compared to 8.3+/-0.48 days in PBS controls (p<0.0001). Combination of 6-thio-GTP (0.5 mg/kg) with CsA (15 mg/kg) enhanced graft survival from 15.0+/-1.61 days in CsA treated recipients to 36.8+/-2.17 days in those received 20 days of combination therapy of CsA and 6-thio-GTP (p<0.0001), or to 42.7+/-16.63 days in the group treated with 20 days of CsA and 60 days of 6-thio-GTP (p<0.0001). Lymphocytes from 6-thio-GTP treated recipients with long-term surviving grafts (>60 days) displayed reduced proliferative response to alloantigen and higher frequencies of regulatory T cells (Treg).
Conclusion:
Vav1-Rac inhibitor 6-thio-GTP prolongs allograft survival alone or in combination with CsA by suppression of alloreactive T cell activation. Our findings suggest the therapeutic potential of pharmacological interference of Vav1-Rac signaling for transplantation.
Insights
The T-cell signaling inhibitor 6-thio-GTP effectively prevents cardiac allograft rejection by suppressing T-cell activation. This compound, alone or with cyclosporine, shows significant potential for improving transplant outcomes.
Area of Science:
- Immunology
- Pharmacology
- Transplantation
Background:
- Vav1-Rac signaling is crucial for T cell activation via TCR/antigen and CD28 pathways.
- Pharmacological targeting of Vav1-Rac signaling has not been explored for preventing allograft rejection.
- 6-thio-GTP, an azathioprine metabolite, selectively inhibits Vav1-Rac activity in T lymphocytes.
Purpose of the Study:
- To investigate the immunosuppressive efficacy of 6-thio-GTP in preventing cardiac allograft rejection.
- To evaluate the therapeutic potential of targeting Vav1-Rac signaling in transplantation.
Main Methods:
- Assessed T cell proliferation using (3H)-thymidine uptake.
- Evaluated 6-thio-GTP's immunosuppressive activity in a mouse cardiac allograft model (C57BL/6 to Balb/c).
Main Results:
- 6-thio-GTP inhibited TCR/alloantigen-stimulated T cell proliferation and CD28-dependent T cell survival.
- Administration of 6-thio-GTP (0.5 mg/kg) significantly prolonged cardiac allograft survival (13.8 days vs. 8.3 days).
- Combination therapy with 6-thio-GTP and cyclosporine (CsA) further enhanced graft survival (up to 42.7 days).
- Long-term surviving grafts in 6-thio-GTP treated recipients showed reduced alloantigen response and increased regulatory T cells (Tregs).
Conclusions:
- 6-thio-GTP, a Vav1-Rac inhibitor, prolongs allograft survival as a monotherapy or in combination with CsA.
- The mechanism involves suppressing alloreactive T cell activation.
- Targeting Vav1-Rac signaling represents a promising therapeutic strategy for transplantation.
