The effect of thymus transplantation on donor‐specific chimerism in the rat model of composite osseomusculocutaneous sternum, ribs, thymus, pectoralis muscles, and skin allotransplantation

Abstract

IntroductionResearch on tolerance has proven that development of donor‐specific chimerism (DSC) may accompany tolerance induction in vascularized composite allotransplantation (VCA). In this study, we aimed to determine the effect of thymus transplantation on the induction of DSC in rat VCA model of osseomusculocutaneous sternum (OMCS) and osseomusculocutaneous sternum and thymus (OMCST) allotransplantation.Materials and MethodsA total of 20 Lewis‐Brown Norway and Lewis rats, 5–6 weeks old, weighting between 120 and 150 g, were used in the study. OMCS (n = 5) and OMCST (n = 5) allografts were harvested from Lewis‐Brown Norway donors (RT1l + n) based on the common carotid artery and external jugular vein, and a heterotopic transplantation was performed to the inguinal region of the Lewis (RT1l) recipients under cyclosporine A monotherapy (16 mg/kg) protocol tapered to 2 mg/kg and maintained for the duration of the study. The peripheral blood chimerism levels (T‐cell, B‐cell, and monocyte/granulocyte/dendritic cell–MGDC populations) were evaluated at days 7, 14, 35, 63, 100, and 150 posttransplant by flow cytometry. At Day 150, thymus, spleen, and liver samples were assessed by polymerase chain reaction (PCR) in the presence of DSC.ResultsTotal chimerism level increased in both OMCST and OMCS groups at all time points. At 150 days posttransplant, chimerism in OMCST group was significantly higher (12.91 ± 0.16%) than that in OMCS group (8.89 ± 0.53%%, p < .01), and PCR confirmed the presence of donor‐derived cells in the liver and spleen of all OMCST recipients and in one liver sample and two spleen samples in OMCS recipients without thymus transplant.ConclusionsThis study confirmed the direct effects of thymus transplantation on the induction and maintenance of DSC in T‐cell, B‐cell, and MGDC populations. These results confirm correlation between thymus transplantation and DSC induction.

Donor Recipient Chimeric Cells Induce Chimerism and Extend Survival of Vascularized Composite Allografts

“…These findings may provide foundation for the possible mechanism of action of DRCC in vivo, showing immunomodulatory effects, thus altering the T cell repertoire by presenting mixed antigens on DRCC surface and/or acting as cells stimulating the regulatory cells via cytokine signaling. Studies in solid organs, VCA and BMT reported migration of donor-derived cells to the recipient’s lymphoid tissues and organs as well as lungs, skin and liver and confirmed their role in tolerance induction process (Khan et al 1996 ; Ozmen et al 2006b ; Siemionow et al 2006 ; Zor et al 2020 ). Both thymus and spleen are considered as immune cell rich organs participating in innate and adaptive immune response (Dor et al 2003 ; Gagliani et al 2013 ).…”

Creation of human hematopoietic chimeric cell (HHCC) line as a novel strategy for tolerance induction in transplantation

“…Thus, there is an urgent need to develop new, cell-based therapies, which will extend allograft survival without the need for harmful conditioning protocols or life-long immunosuppression. New stem cell strategies are based on the tailored, customized approaches to address the individual patient needs and to change the current paradigm To address these limitations, for the past 20 years, our Laboratory has developed novel protocols for induction of tolerance via establishment of donor specific chimerism tested in different experimental models of VCA, including limb allograft transplant carrying vascularized BM component (8)(9)(10)(11)(12)(13)(14)(15). Based on this experience confirming a crucial role of the vascularized BM component of donor origin in induction of donor specific chimerism, we have created DRCC via PEG-mediated fusion of BM cells derived from two unrelated donors (13).…”

“…Our laboratory has over 20 years of research experience in chimerism induction and application of BM-based cell therapies in different VCA models (8)(9)(10)(11)(12)(13)(14)(15). These pioneering studies on tolerance induction in VCA encouraged us to create the donor-recipient chimeric cells (DRCC) via ex vivo, polyethylene glycol (PEG)-mediated fusion.…”

The intragraft vascularized bone marrow induces secondary donor-specific mystacial pad allograft tolerance

“…More specifically, our previous study proved that less donor-reactive Vβ5-expressing CD4 + T cells were detected in tolerant recipients, hence suggesting the role of thymus in central tolerance ( 38 ). Moreover, donor-specific chimerism was diminished in VCA recipients with thymectomy ( 43 – 45 ). The pilot data regarding engineered donor–recipient hybrid thymus were reported have potential to promote a dominant regulation of alloreactivity to achieve allograft tolerance ( 46 ).…”