Disrupted regulation of serpinB9 in circulating T cells is associated with an increased risk for post-transplant skin cancer.

Cutaneous squamous cell carcinoma (cSCC) is a serious complication after organ transplantation and patients benefit from an early risk assessment. We hypothesized that functional differences in circulating T cells may represent risk factors for post-transplant cSCC development. Here, we analysed genome-wide DNA methylation of circulating T cells of kidney transplant recipients before the clinical onset of cSCC, to identify differences associated with post-transplant cSCC development. This analysis identified higher DNA methylation of SERPINB9, which is an intracellular inhibitor of granzyme B, a protein that induces apoptosis in target cells. High DNA methylation of SERPINB9 in circulating T cells was confirmed in a second patient cohort during recurrent cSCC, indicating that high SERPINB9 methylation represents a persistent risk factor for cSCC development. At the functional level, the inverse correlation between DNA methylation and messenger RNA expression present in non-cSCC patients was absent in the cSCC patients. Also, a significant difference in serpinB9 protein expression between cSCC patients and non-cSCC patients was observed. It was concluded that disturbed regulation of serpinB9 in circulating T cells represents a novel risk factor for post-transplant cSCC in kidney transplant recipients.

Discarded Human Thymus Is a Novel Source of Stable and Long-Lived Therapeutic Regulatory T Cells.

Regulatory T cell (Treg)-based therapy is a promising approach to treat many immune-mediated disorders such as autoimmune diseases, organ transplant rejection, and graft-versus-host disease (GVHD). Challenges to successful clinical implementation of adoptive Treg therapy include difficulties isolating homogeneous cell populations and developing expansion protocols that result in adequate numbers of cells that remain stable, even under inflammatory conditions. We investigated the potential of discarded human thymuses, routinely removed during pediatric cardiac surgery, to be used as a novel source of therapeutic Tregs. Here, we show that large numbers of FOXP3(+) Tregs can be isolated and expanded from a single thymus. Expanded thymic Tregs had stable FOXP3 expression and long telomeres, and suppressed proliferation and cytokine production of activated allogeneic T cells in vitro. Moreover, expanded thymic Tregs delayed development of xenogeneic GVHD in vivo more effectively than expanded Tregs isolated based on CD25 expression from peripheral blood. Importantly, in contrast to expanded blood Tregs, expanded thymic Tregs remained stable under inflammatory conditions. Our results demonstrate that discarded pediatric thymuses are an excellent source of therapeutic Tregs, having the potential to overcome limitations currently hindering the use of Tregs derived from peripheral or cord blood.

Donor-derived mesenchymal stem cells remain present and functional in the transplanted human heart.

Mesenchymal stem cells (MSC) are characterized by their multilineage differentiation capacity and immunosuppressive properties. They are resident in virtually all tissues and we have recently characterized MSC from the human heart. Clinical heart transplantation offers a model to study the fate of transplanted human MSC. In this study, we isolated and expanded MSC from heart tissue taken before, and 1 week up to 6 years after heart transplantation. MSC from posttransplantation tissue were all of donor origin, demonstrating the longevity of endogenous MSC and suggesting an absence of immigration of recipient MSC into the heart. MSC isolated from transplanted tissue showed an immunophenotype that was characteristic for MSC and maintained cardiomyogenic and osteogenic differentiation capacity. They furthermore preserved their ability to inhibit the proliferative response of donor-stimulated recipient peripheral blood mononuclear cells. In conclusion, functional MSC of donor origin remain present in the heart for several years after transplantation.

Human heart, spleen, and perirenal fat-derived mesenchymal stem cells have immunomodulatory capacities.

Mesenchymal stem cells (MSCs) have important tissue repair functions and show potent immunosuppressive capacities in vitro. Although usually isolated from the bone marrow, MSCs have been identified in other tissues, including the skin and liver. In the present study, we isolated and characterized MSCs from human heart, spleen, and perirenal adipose tissue. MSCs from these different tissue sites were similar to those derived from bone marrow in that they expressed comparable levels of the cell-surface markers CD90, CD105, CD166, and HLA class I, were negative for CD34, CD45, HLA class II, CD80, and CD86 expression, and were capable of osteogenic and adipogenic differentiation. Like bone marrow-derived MSCs, MSCs from these different tissue sources inhibited the proliferation of alloactivated peripheral blood mononuclear cells (PBMCs), giving 85%, 79%, 79%, and 81% inhibition, respectively. Also in line with bone marrow-derived MSCs they inhibited proliferative responses of PBMCs to phytohemagglutinin, a nonspecific stimulator of lymphocyte proliferation, and reduced-memory T lymphocyte responses to tetanus toxoid. The results of this study demonstrate that MSCs from various tissues have similar immunophenotypes, in vitro immunosuppressive properties, and differentiation potential.

Recipient gene polymorphisms in the Th-1 cytokines IL-2 and IFN-gamma in relation to acute rejection and graft vascular disease after clinical heart transplantation.

IL-2 and IFN-gamma are associated with acute rejection (AR) and graft vascular disease (GVD) after clinical heart transplantation. Polymorphisms in the genes of IL-2 (T-330G in the promoter) and IFN-gamma (CA repeat in the first intron) influence the production levels of these cytokines. Therefore, these polymorphisms might have an effect on the outcome after transplantation. To investigate possible effects of genetic variations in IL-2 and IFN-gamma genes on AR and GVD, we analyzed the IL-2 T-330G and the IFN-gamma CA repeat polymorphism in DNA of 301 heart transplant recipients. No associations were found for allele or genotype distributions between patients with or without AR (IL-2 allele frequency: P=0.44, genotype distribution: P=0.46; IFN-gamma allele frequency P=0.10, genotype distribution 12 repeats allele: P=0.21). Also, no associations were found analyzing the number (0 vs. 1 vs. >or=1) of AR (IL-2 allele frequency: P=0.59; genotype distribution: P=0.37; IFN-gamma allele frequency: P=0.27, genotype distribution 12 repeats allele: P=0.41) or analyzing the polymorphisms in patients with AR within the first month or thereafter (IL-2 allele frequency: P=0.45, genotype distribution: P=0.38; IFN-gamma allele frequency: P=0.21, genotype distribution 12 repeats allele: P=0.41). Analyzing both polymorphisms in relation to GVD, resulted in comparable allele and genotype distributions (IL-2 allele frequency: P=0.75; genotype distribution: P=0.77; IFN-gamma allele frequency: P=0.70, genotype distribution 12 repeats allele: P=0.63). In conclusion, we did not detect an association between the IL-2 T-330G promoter polymorphism and CA repeat polymorphism in the first intron of the IFN-gamma gene and AR or GVD after heart transplantation.