Thomas Resch

Endothelial progenitor cells: current issues on characterization and challenging clinical applications.

Since their discovery about a decade ago, endothelial precursor cells (EPC) have been subjected to intensive investigation. The vision to stimulate respectively suppress a key player of vasculogenesis opened a plethora of clinical applications. However, as research opened deeper insights into EPC biology, the enthusiasm of the pioneer era has been damped in favour of a more critical view. Recent research is focused on three major questions: The fact that the number of EPC in peripheral blood is exceedingly low has consistently raised suspicion whether these cells can plausibly have an impact on physiological or pathophysiological processes. Secondly, whereas the key role of EPC in tumourigenesis has been strongly emphasized by various groups in the past, recent publications are challenging this hypothesis. Thirdly, the lack of consensus on EPC-defining markers and standardized protocols for their detection have repeatedly led to difficulties concerning comparability between papers. In this current review, an overview on recent findings on EPC biology is given, their challenging clinical implications are discussed and the perplexity underlying the current controversial debate is illustrated.

Combined pancreas-kidney transplantation for patients with end-stage nephropathy caused by type-2 diabetes mellitus.

Background Simultaneous pancreas-kidney (SPK) transplantation is widely accepted as an optimal therapeutic option for patients with type 1 diabetes mellitus (T1DM) and end-stage renal disease, but the indication for patients with type 2 diabetes mellitus (T2DM) is still controversially discussed. Methods Twenty-one T2DM recipients of a first combined pancreas-kidney graft performed at our center during a 9-year period were retrospectively analyzed with regard to demographic characteristics; cardiovascular risk factors; surgical, immunological, and infectious complications; and patient and graft survivals and compared with T1DM recipients (n=195) and 32 T2DM patients who received a kidney transplant alone (KTA) during the same period. Results Patient survival at 1 and 5 years was 96.9% and 91.6% for the T1DM group, 90.5% and 80.1% for the T2DM group, and 87.1% and 54.2% for the T2DM KTA group, respectively (P<0.001). Actuarial pancreas graft survival for SPK recipients at 1 and 5 years was calculated to be 92.6% and 80.7% for the T1DM group and 81.0% and 75.9% for the T2DM group, respectively (P=0.19). Kidney allograft survival at 5 years was 83.6% for T1DM, 80.4% for T2DM, and 52.7% for T2DM KTA (P<0.0001). Multivariate analysis adjusting for donor and recipient age, secondary complications of diabetes, body mass index, waiting time, cold ischemic time, delayed graft function, and coronary risk factors showed that differences did not remain statistically significant. Conclusion Favorable results can be achieved with SPK transplantation in type 2 diabetics with a low coronary risk profile. A high cardiac death rate impacts results of KTA and calls for stringent selection.

Enteroscopic biopsies in the management of pancreas transplants: a proof of concept study for a novel monitoring tool.

Background. Although percutaneous biopsies are considered to be the gold standard in diagnosing pancreas graft rejection, they are not performed routinely because of their association with severe complications. On the other hand, correct diagnosis of rejection is essential but may be difficult in cases of enteric drainage, particularly in patients with a pancreas transplant alone or a pancreas after kidney transplant. Methods. Pancreas recipients who underwent enteroscopy between May 2005 and September 2009 were included in this retrospective analysis. Biopsies were graded 0 to 4 for interstitial and vascular changes. Results. During the study period a total of 65 simultaneous pancreas-kidney transplants, 13 pancreas after kidney transplants and 4 pancreas transplants alone were performed. Sixty-three patients underwent a single enteroscopy, 10 had two, and 6 had three or more. Indications were protocol graft monitoring (n=73), graft dysfunction (n=17), enteric hemorrhage (n=9), or other (n=3). The duodenal segment was accessed in 76 instances (75%) with abnormal findings in 23. A total of 69 biopsies were obtained and revealed normal mucosa in 49 cases (71%). Histology showed signs of acute rejection in 11 cases. The upper gastrointestinal tract was also assessed, and, in 13 cases, additional pathologies were identified including gastroduodenitis (n=10), gastric/duodenal ulcer (n=2), and hemorrhagic esophagitis (n=1). No procedure-related complication occurred. Conclusions. This series of enteroscopies demonstrates that the duodenal segment of a pancreatic graft is accessible using our implant technique, and thus permitting biopsies to be obtained and endoscopic interventions to be performed.

The Role of Natural Killer Cells in Humoral Rejection.

Abstract Antibody-mediated rejection (AMR) has been identified among the most important factors limiting long-term outcome in cardiac and renal transplantation. Therapeutic management remains challenging and the development of effective treatment modalities is hampered by insufficient understanding of the underlying pathophysiology. However, recent findings indicate that in addition to AMR-triggered activation of the classical complement pathway, antibody-dependent cellular cytotoxicity by innate immune cell subsets also promotes vascular graft injury. This review summarizes the accumulating evidence for the contribution of natural killer cells, the key mediators of antibody-dependent cellular cytotoxicity, to human AMR in allotransplantation and xenotransplantation and illustrates the current mechanistic conceptions drawn from animal models.

Donor brain death leads to differential immune activation in solid organs but does not accelerate ischaemia-reperfusion injury.

A comparative analysis of inflammation between solid organs following donor brain death (BD) is still lacking and the detailed influence of BD accelerating ischaemia–reperfusion injury (IRI) post‐transplantation remains to be addressed. Applying a murine model of BD, we demonstrated that 4 h after BD organs were characterized by distinct inflammatory expression patterns. For instance, lipocalin 2 (LCN2), a marker of acute kidney injury, was selectively induced in BD livers but not in kidneys. BD further resulted in significantly reduced frequencies of CD3+CD4+, CD3+CD8+ T cells and NKp46+ NK cells in the liver, whereas BD kidneys and hearts were characterized by significantly lower frequencies of conventional dendritic cells (cDCs). Syngeneic models of kidney (KTx) and heart transplantation (HTx) illustrated stronger gene expression in engrafted BD hearts only, but 20 h post‐transplantation both organs displayed comparable intragraft lymphocyte frequencies, except for NK cells and graft function. Moreover, the complement factor C3d deposit detected in small vessels and capillaries in cardiac syngrafts did not significantly differ between BD and sham‐transplanted groups. Finally, no further influence of donor BD on graft survival was detected in an allogeneic heart transplantation setting (C57BL/6 grafts into BALB/c recipients). We show for the first time that BD organs are characterized by a varying inflammatory profile; however, BD does not accelerate IRI in syngeneic KTx and HTx. Copyright

Treatment With Tetrahydrobiopterin Overcomes Brain Death–Associated Injury in a Murine Model of Pancreas Transplantation

Brain death (BD) has been associated with an immunological priming of donor organs and is thought to exacerbate ischemia reperfusion injury (IRI). Recently, we showed that the essential nitric oxide synthase co‐factor tetrahydrobiopterin (BH4) abrogates IRI following experimental pancreas transplantation. We therefore studied the effects of BD in a murine model of syngeneic pancreas transplantation and tested the therapeutic potential of BH4 treatment. Compared with sham‐operated controls, donor BD resulted in intragraft inflammation reflected by induced IL‐1ß, IL‐6, VCAM‐1, and P‐selectin mRNA expression levels and impaired microcirculation after reperfusion (p < 0.05), whereas pretreatment of the BD donor with BH4 significantly improved microcirculation after reperfusion (p < 0.05). Moreover, BD had a devastating impact on cell viability, whereas BH4‐treated grafts showed a significantly higher percentage of viable cells (p < 0.001). Early parenchymal damage in pancreatic grafts was significantly more pronounced in organs from BD donors than from sham or non‐BD donors (p < 0.05), but BH4 pretreatment significantly ameliorated necrotic lesions in BD organs (p < 0.05). Pretreatment of the BD donor with BH4 resulted in significant recipient survival (p < 0.05). Our data provide novel insights into the impact of BD on pancreatic isografts, further demonstrating the potential of donor pretreatment strategies including BH4 for preventing BD‐associated injury after transplantation.

Disturbances in iron homeostasis result in accelerated rejection after experimental heart transplantation

BACKGROUND Clinical data suggest that iron disturbances deleteriously affect graft survival after heart transplantation (HTx), but immunological mechanisms underlying this phenomenon have not yet been elucidated. METHODS To identify the mechanistic influence of iron in a murine model of HTx, fully allogeneic BALB/c donor organs were transplanted into iron-overloaded or iron-deficient C57BL/6 mice, and recipients were analyzed for functional and immunological parameters. RESULTS After HTx, iron overload accelerated acute rejection as observed by shortened graft survival (HTx vs HTx + iron; p = 0.01), elevated rejection score (p < 0.01), and induction of troponin T (p < 0.01). Compared with controls, allografts and recipient spleens derived from iron-overloaded recipients were characterized by a pronounced graft infiltration of CD4+ T cells (p < 0.01), CD3-NKp46+ natural killer cells (p < 0.05), and reduced frequencies of regulatory T cells (p < 0.01). This was accompanied by lower mRNA expression levels of anti-inflammatory cytokines, including interleukin-10, transforming graft factor-β, and Foxp3. Cardiac allograft survival was further tested under co-stimulation blockade (CTLA4-Ig) showing that naïve grafts transplanted into iron-overloaded recipients illustrated restricted graft outcome compared with wild types (p = 0.0051), which was rescued after treatment with the iron chelator deferoxamine. Iron deficiency (ID) also resulted in enhanced intragraft infiltration of inflammatory cells and accelerated rejection in the acute setting (HTx vs HTx + ID; p = 0.02) and after co-stimulation blockade (p = 0.0059). CONCLUSIONS We provide novel insights into the understanding of disturbances in iron homeostasis and their consequences after HTX, allowing novel insights regarding improvements in personalized immunosuppression to prolong allograft survival.

Deletion of the Activating NK Cell Receptor NKG2D Accelerates Rejection of Cardiac Allografts

It has already been shown that neutralization of the activating NK cell receptor NKG2D in combination with co‐stimulation blockade prolongs graft survival of vascularized transplants. In order to clarify the underlying cellular mechanisms, we transplanted complete MHC‐disparate BALB/c‐derived cardiac grafts into C57BL/6 wildtypes or mice deficient for NKG2D (Klrk1−/−). Although median survival was 8 days for both recipient groups, we detected already at day 5 posttransplantation significantly greater intragraft frequencies of NKp46+ NK cells in Klrk1−/− recipients than in wildtypes. This was followed by a significantly greater infiltration of CD4+, but a lesser infiltration of CD8+ T cell frequencies. Contrary to published observations, co‐stimulation blockade with CTLA4‐Ig resulted in a significant acceleration of cardiac rejection by Klrk1−/− recipients, and this result was confirmed by applying a neutralizing antibody against NKG2D to wildtypes. In both experimental setups, grafts derived from Klrk1−/− recipients were characterized by significantly higher levels of interferon‐γ mRNA, and both CD4+ and CD8+ T cells displayed a greater capacity for degranulation and interferon‐γ production. In summary, our results clearly illustrate that NKG2D expression in the recipient is important for cardiac allograft survival, thus supporting the hypothesis that impairment of NK cells prevents the establishment of graft acceptance.

Liver transplantation for hilar cholangiocarcinoma (h-CCA): is it the right time?

Liver transplantation (LT) is the therapy of choice in selected patients with hepatocellular carcinoma (HCC). In light of the overall excellent results achieved for HCC, LT has been successfully adapted as a therapeutic option for several non-hepatocellular malignancies (1) including unresectable hepatic epithelioid hemangioendothelioma (HEHE) (2), neuroendocrine tumors (NET) (3) or even colorectal metastases in case of liver-only disease (4).

Graft Pre-conditioning by Peri-Operative Perfusion of Kidney Allografts With Rabbit Anti-human T-lymphocyte Globulin Results in Improved Kidney Graft Function in the Early Post-transplantation Period—a Prospective, Randomized Placebo-Controlled Trial

Introduction: Although prone to a higher degree of ischemia reperfusion injury (IRI), the use of extended criteria donor (ECD) organs has become reality in transplantation. We therefore postulated that peri-operative perfusion of renal transplants with anti-human T-lymphocyte globulin (ATLG) ameliorates IRI and results in improved graft function. Methods: We performed a randomized, single-blinded, placebo-controlled trial involving 50 kidneys (KTx). Prior to implantation organs were perfused and incubated with ATLG (AP) (n = 24 kidney). Control organs (CP) were perfused with saline only (n = 26 kidney). Primary endpoint was defined as graft function reflected by serum creatinine at day 7 post transplantation (post-tx). Results: AP-KTx recipients illustrated significantly better graft function at day 7 post-tx as reflected by lower creatinine levels, whereas no treatment effect was observed after 12 months surveillance. During the early hospitalization phase, 16 of the 26 CP-KTx patients required dialysis during the first 7 days post-tx, whereas only 10 of the 24 AP-KTx patients underwent dialysis. No treatment-specific differences were detected for various lymphocytes subsets in the peripheral blood of patients. Additionally, mRNA analysis of 0-h biopsies post incubation with ATLG revealed no changes of intragraft inflammatory expression patterns between AP and CP organs. Conclusion: We here present the first clinical study on peri-operative organ perfusion with ATLG illustrating improved graft function in the early period post kidney transplantation. Clinical Trial Registration: www.ClinicalTrials.gov, NCT03377283