Decellularized human pancreatic extracellular matrix-based physiomimetic microenvironment for human islet culture.

A strategy that seeks to combine the biophysical properties of inert encapsulation materials like alginate with the biochemical niche provided by pancreatic extracellular matrix (ECM)-derived biomaterials, could provide a physiomimetic pancreatic microenvironment for maintaining long-term islet viability and function in culture. Herein, we have demonstrated that incorporating human pancreatic decellularized ECM within alginate microcapsules results in a significant increase in Glucose Stimulation Index (GSI) and total insulin secreted by encapsulated human islets, compared to free islets and islets encapsulated in only alginate. ECM supplementation also resulted in long-term (58 days) maintenance of GSI levels, similar to that observed in free islets at the first time point (day 5). At early time points in culture, ECM promoted gene expression changes through ECM- and cell adhesion-mediated pathways, while it demonstrated a mitochondria-protective effect in the long-term. STATEMENT OF SIGNIFICANCE: The islet isolation process can damage the islet extracellular matrix, resulting in loss of viability and function. We have recently developed a detergent-free, DI-water based method for decellularization of human pancreas to produce a potent solubilized ECM. This ECM was added to alginate for microencapsulation of human islets, which resulted in significantly higher stimulation index and total insulin production, compared to only alginate capsules and free islets, over long-term culture. Using ECM to preserve islet health and function can improve transplantation outcomes, as well as provide novel materials and platforms for studying islet biology in microfluidic, organ-on-a-chip, bioreactor and 3D bioprinted systems.

Differential diagnosis in Rosai-Dorfman disease: A rare case of isolated hepatic presentation mimicking a metastatic tumor with positive 18-FDG uptake.

Rosai-Dorfman disease (RDD) is also called sinus histiocytosis with massive lymphadenopathy, and it is caused by a histiocytic disorder with unclear etiology. It usually involves cervical lymph nodes, but it may also present with extranodal involvement. We report a rare condition of isolated hepatic RDD without nodal involvement, clinically manifested with three-month abdominal pain and tenderness of the right hypochondrium. CT- and PET-CT scans were compatible with a secondary lesion from an unknown primary tumor. Therefore, the patient underwent an atypical liver resection. Immunohistochemistry and histological results were compatible with a diagnosis of RDD. RDD is characterized by phenomena of emperipolesis, histiocytic proliferation and positive immunostaining for CD14, CD68 and S-100 protein. Cases of isolated gastrointestinal localization of RDD are particularly rare, especially in the liver. Instrumental exams might confuse RDD with other malignancies. RDD is a rare entity, which might be misdiagnosed using PET-CT due to its similarities with malignant tumors. An accurate multidisciplinary approach may help to clear diagnostic clues of this uncommon disease.

Graft weight integration in the early allograft dysfunction formula improves the prediction of early graft loss after liver transplantation.

The role of the graft-to-recipient weight ratio (GRWR) in adult liver transplantation (LT) has been poorly investigated so far. The aim is to evaluate the contribution of the GRWR to the well-recognized early allograft dysfunction (EAD) model (i.e., Olthoff model) for the prediction of 90-day graft loss after LT in adults. Three hundred thirty-one consecutive adult patients undergoing LT between 2009 and 2018 at Tor Vergata and Sapienza University in Rome, Italy, served as the Training-Set. The Validation-Set included 123 LTs performed at the Erasmus Medical Center, Rotterdam, the Netherlands. The mEAD model for 90-day graft loss included the following variables: GRWR [Formula: see text] 1.57 = 2.5, GRWR [Formula: see text] 2.13 = 2.5, total bilirubin ≥ 10.0 mg/dL = 2.0, INR ≥ 1.60 = 2.3, and aminotransferase > 2000 IU/L = 2.2. The mEAD model showed an AUC = 0.74 (95%CI = 0.66-0.82; p < 0.001) and AUC = 0.68 (95%CI = 0.58-0.88; p = 0.01) in the Training-Set and Validation-Set, respectively, outperforming conventional EAD in both cohorts (Training-Set: AUC = 0.64, 95%CI = 0.57-0.72; p = 0.001; Validation-Set: AUC = 0.52, 95%CI = 0.35-0.69, p = 0.87). Incorporation of graft weight in a composite multivariate model allowed for better prediction of patients who presented an aminotransferase peak > 2000 IU/L after LT (OR = 2.39, 95%CI = 1.47-3.93, p = 0.0005). The GRWR is important in determining early graft loss after adult LT, and the mEAD model is a useful predictive tool in this perspective, which may assist in improving the graft allocation process.

Vascular Involvements in Cholangiocarcinoma: Tips and Tricks.

Cholangiocarcinoma (CCA) is an aggressive malignancy of the biliary tract. To date, surgical treatment remains the only hope for definitive cure of CCA patients. Involvement of major vascular structures was traditionally considered a contraindication for resection. Nowadays, selected cases of CCA with vascular involvement can be successfully approached. Intrahepatic CCA often involves the major hepatic veins or the inferior vena cava and might necessitate complete vascular exclusion, in situ hypothermic perfusion, ex situ surgery and reconstruction with autologous, heterologous or synthetic grafts. Hilar CCA more frequently involves the portal vein and hepatic artery. Resection and reconstruction of the portal vein is now considered a relatively safe and beneficial technique, and it is accepted as a standard option either with direct anastomosis or jump grafts. However, hepatic artery resection remains controversial; despite accumulating positive reports, the procedure remains technically challenging with increased rates of morbidity. When arterial reconstruction is not possible, arterio-portal shunting may offer salvage, while sometimes an efficient collateral system could bypass the need for arterial reconstructions. Keys to achieve success are represented by accurate selection of patients in high-volume referral centres, adequate technical skills and eclectic knowledge of the various possibilities for vascular reconstruction.

Current Strategies to Minimize Ischemia-Reperfusion Injury in Liver Transplantation: A Systematic Review.

BACKGROUND: Hepatic Ischemia Reperfusion Injury (IRI) is a serious threat that characterizes the liver but also other transplantable organs. The worst effect of long-term IRI on an impaired graft could lead to irreversible damage and organ failure. Several events characterize the cascade that ultimately leads to organ failure. Among all, multiple strategies have been attempted to identify early phenomena of IRI with divergent results, and biomarkers might represent a novel approach to early detect ischemic damage. METHODS: A literature review of the current state-of-the-art on IRI was conducted in the present manuscript. Information was collected from worldwide clinical trials conducted in highly specialized institutions. Experiments conducted on IRI animal models and clinical studies were screened. The final outcomes were analyzed and reported in the present review. RESULTS: Matrix Metalloproteinases (MMPs) represent an interesting example of the early detector of neutrophil invasion after acute and chronic hepatic IRI. Neutrophil Gelatinase-associated Lipocalin (NGAL) is another biomarker which seems more predictable of the IRI gravity phase. Mitochondrial flavin mononucleotide (FMN) was recently discovered and might become a reliable biomarker of hepatic IRI during Hypothermic Oxygenation Machine Perfusion (HOPE). CONCLUSION: The available strategies to avoid IRI, despite constantly improving, are still lacking a gold standard method. Further studies are still needed to explore new options in the IRI diagnosis and treatment, and to this purpose, regenerative medicine and tissue engineering surely can play a pivotal role in the transplantation field.

Comprehensive characterization of the human pancreatic proteome for bioengineering applications.

Interactions between the pancreatic extracellular matrix (ECM) and islet cells are known to regulate multiple aspects of islet physiology, including survival, proliferation, and glucose-stimulated insulin secretion. Recognizing the essential role of ECM in islet survival and function, various engineering approaches have been developed that aim to utilize ECM-based materials to recreate a native-like microenvironment. However, a major impediment to the success of these approaches has been the lack of a robust and comprehensive characterization of the human pancreatic proteome. Herein, by combining mass spectrometry (MS) and multiplex ELISA, we have provided an improved workflow for the in-depth profiling of the proteome, including minor constituents that are generally underrepresented. Moreover, we have further validated the effectiveness of our detergent-free decellularization protocol in the removal of cellular proteins and retention of the matrisome. It has also been established that the decellularized ECM and its derivatives can provide more tissue-specific cues than traditionally used biological scaffolds and are therefore more physiologically relevant for the development of hydrogels, bioinks and medium additives, in order to create a pancreatic niche. The data generated in this study would contribute significantly to the efforts of comprehensively defining the ECM atlas and also serve as a standard for the human pancreatic proteome to provide further guidance for design and engineering strategies for improved tissue engineering scaffolds.

Liver transplantation performed in a SARS-CoV-2 positive hospitalized recipient using a SARS-CoV-2 infected donor.

The coronavirus disease 2019 (COVID-19) is a novel infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). COVID-19 currently affected more than 108 million people worldwide with a fatality rate of 2.2%. Herein, we report the first case of liver transplantation (LT) performed with a liver procured from a SARS-CoV-2 positive donor. The recipient was a 35-year-old SARS-CoV-2 positive female patient affected by severe end-stage HBV-HDV-related liver disease (model of end-stage liver disease = 32) who had neutralizing SARS-CoV-2 antibodies (titers 1:320) at time of LT. The LT was successful, and the graft is functioning two months after surgery. The recipient cleared the SARS-CoV-2 infection 1 month after LT. The current case shows that the prompt use of SARS-CoV-2 infected liver donors offers an invaluable life-saving opportunity for SARS-CoV-2 positive wait-listed patients who developed neutralizing SARS-CoV-2 antibodies.

Moving forward in the treatment of cholangiocarcinoma.

Despite being the second most frequent primary liver tumor in humans, early diagnosis and treatment of cholangiocarcinoma (CCA) are still unsatisfactory. In fact, survival after 5 years is expected in less than one fourth of patients diagnosed with this disease. Rare incidence, late appearance of symptoms and heterogeneous biology are all factors contributing to our limited knowledge of this cancer and determining its poor prognosis in the clinical setting. Several efforts have been made in the last decades in order to achieve an improved classification/understanding with regard to the diverse CCA forms. Location within the biliary tree has helped to distinguish between intrahepatic, perihilar and distal CCA types. Sequence analysis contributed to identifying several characteristic genetic aberrations in CCA that may also serve as possible targets for therapy. Novel findings are expected to significantly improve the management of this malignancy in the near future. In this changing scenario our review focuses on the current and future strategies for CCA treatment. Both systemic and surgical treatments are discussed in detail. The results of the main studies in this field are reported, together with the ongoing trials. The current findings suggest that an integrated multidisciplinary approach to this malignancy would be helpful to improve its outcome.

Effect of alginate matrix engineered to mimic the pancreatic microenvironment on encapsulated islet function.

Islet transplantation is emerging as a therapeutic option for type 1 diabetes, albeit, only a small number of patients meeting very stringent criteria are eligible for the treatment because of the side effects of the necessary immunosuppressive therapy and the relatively short time frame of normoglycemia that most patients achieve. The challenge of the immune-suppressive regimen can be overcome through microencapsulation of the islets in a perm-selective coating of alginate microbeads with poly-l-lysine or poly- l-ornithine. In addition to other issues including the nutrient supply challenge of encapsulated islets a critical requirement for these cells has emerged as the need to engineer the microenvironment of the encapsulation matrix to mimic that of the native pancreatic scaffold that houses islet cells. That microenvironment includes biological and mechanical cues that support the viability and function of the cells. In this study, the alginate hydrogel was modified to mimic the pancreatic microenvironment by incorporation of extracellular matrix (ECM). Mechanical and biological changes in the encapsulating alginate matrix were made through stiffness modulation and incorporation of decellularized ECM, respectively. Islets were then encapsulated in this new biomimetic hydrogel and their insulin production was measured after 7 days in vitro. We found that manipulation of the alginate hydrogel matrix to simulate both physical and biological cues for the encapsulated islets enhances the mechanical strength of the encapsulated islet constructs as well as their function. Our data suggest that these modifications have the potential to improve the success rate of encapsulated islet transplantation.

Ligasure Hemorrhoidectomy: Updates on Complications After an 18-Year Experience.

BACKGROUND: Hemorrhoidal disease represents one of the most common anorectal disorders in the general population. Energy devices, such as LigaSureTM scalpel, have reshaped the concept of hemorrhoid surgery and in turn, have improved patient outcomes and simplified the work of surgeon. OBJECTIVE: The study aims to evaluate the outcomes of LigaSureTM hemorrhoidectomy (LH) analyzing main post-operative complications rate, length of stay, operating time, and time to return to work. METHODS: In this monocentric descriptive study, from June 2001 to February 2019, 1454 consecutive patients, treated with LH for grade III and IV hemorrhoids, were analyzed. Complications were classified in early, late, and long-term if they occurred within 1 month, between 1 and 2 months or after 2 months, respectively. RESULTS: 90.2% of patients were treated in day surgery regimen and the mean operating time was 14.3 minutes. The post-operative pain decreased from 3.7 mean VAS on the 1st postoperative day to 0.1 mean VAS on 30th post-operative day. Early complications rate was 2.1%: urinary retention accounted for 1.8% of patients. 0.3%-of patients experienced postoperative bleeding and only one required reoperation. Late complications rate was 5.8%: anal stenosis, incomplete healing, and anal fissure were detected in 3.6%, 1.2%, and 1% of patients, respectively. The long term complications rate was 5.3%: anal fistula, soiling, perianal abscess, and recurrence were identified in 0.2%, 0.1%, 0.3%, and 4.8% of patients, respectively. CONCLUSION: LH is a safe and fast procedure with a proven minimal complication rate.

Detergent-Free Decellularization of the Human Pancreas for Soluble Extracellular Matrix (ECM) Production.

Islet transplantation (ITx) has the potential to become the standard of care in beta cell replacement medicine but its results remain inferior to those obtained with whole pancreas transplantation. The protocols currently used for human islet isolation are under scrutiny because they are based on the enzymatic digestion of the organ, whereby the pancreas is demolished, its connections to the body are lost and islets are irreversibly damaged. Islet damage is characterized by critical factors such as the destruction of the extracellular matrix (ECM), which represents the 3D framework of the islet niche and whose loss is incompatible with islet euphysiology. Researchers are proposing the use of ECM-based scaffolds derived from the mammalian pancreas to address this problem and ultimately improve islet viability, function, and lifespan. Currently available methods to obtain such scaffolds are harsh because they are largely detergent based. Thus, we propose a new, detergent-free method that creates less ECM damage and can preserve critical components of pancreatic ECM. The results show that the newly developed decellularization protocol allowed the achievement of complete DNA clearance while the ECM components were retained. The ECM obtained was tested for cytotoxicity and encapsulated with human pancreatic islets which showed a positive cellular behavior with insulin secretion when stimulated with glucose challenge. Collectively, we propose a new method for the decellularization of the human pancreas without the use of conventional ionic and non-ionic chemical detergents. This protocol and the ECM obtained with it could be of use for both in vitro and in vivo applications.

Awareness and Impact of Non-pharmaceutical Interventions During Coronavirus Disease 2019 Pandemic in Renal Transplant Recipients.

The concerns generated by coronavirus disease 2019 (COVID-19) pandemic are having profound impact on solid organ transplantation (SOT). Non-pharmaceutical interventions (NPI) are currently the only measures available to contain COVID-19 in the general population and in more vulnerable recipients of any organ transplant. In this cross-sectional case control study from a patient survey undertaken in 2 transplant centers (TxC) in the Kingdom of Saudi Arabia and Italy, we aimed to appraise awareness of the NPI implemented by respective these governments. We have also evaluated the impact of COVID-19 on our kidney transplant (KT) recipients and a control group of kidney living donors (KLD). In our series, there were zero cases of COVID-19 among 111 KT recipients and 70 KLD of the control group. Demography, transplant type, immunosuppression regimes, and, importantly, the different COVID-19 prevalence in the 2 regions of the TxC did not appear to influence incidence of COVID-19 in our KT recipients. The absence of COVID-19 cases in our series was unexpected. Our findings suggest that awareness of NPI is associated with a successful containment of COVID-19 in vulnerable, immunosuppressed KT recipients.

Hepatitis B virus recurrence after liver transplantation: An old tale or a clear and present danger?

Hepatitis B virus (HBV) recurrence after liver transplantation (LT) has been described more than 50 years ago. Similarly, to other clinical conditions, in which impairment of host immune defense favors viral replication, early reports described in details recurrence and reactivation of HBV in liver transplant recipients. The evidence of a possible, severe, clinical evolution of HBV reappearance in a significant percentage of these patients, allowed to consider, for some years, HBV positivity a contraindication for LT. Moving from the old to the new millennium this picture has changed dramatically. Several studies contributed to establish efficient prophylactic protocols for HBV recurrence and with the advent of more potent anti-viral drugs an increased control of infection was achieved in transplanted patients as well as in the general immune-competent HBV population. Success obtained in the last decade led some authors to the conclusion that HBV is now to consider just as a "mere nuisance". However, with regard to HBV and LT, outstanding issues are still on the table: (1) A standard HBV prophylaxis protocol after transplant has not yet been clearly defined; (2) The evidence of HBV resistant strains to the most potent antiviral agents is claiming for a new generation of drugs; and (3) The possibility of prophylaxis withdrawal in some patients has been demonstrated, but reliable methods for their selection are still lacking. The evolution of LT for HBV is examined in detail in this review together with the description of the strategies adopted to prevent HBV recurrence and their pros and cons.

Idiopathic gastric fundus necrosis: Case report about a rare and fatal clinical condition.

INTRODUCTION: Gastric fundus ischemia is a rare event, which does not account for many significant clinical studies. This disorder could have different etiologies, but authors agree that a prompt diagnosis and a proper treatment could avoid dangerous complications and ultimately the death of the patient. PRESENTATION OF CASE: We herein report an interesting idiopathic case of acute gastric dilatation and fundus ischemia of an 83-year-old Caucasic woman who was admitted to the Emergency Department complaining of abdominal discomfort, vomiting and constipation. DISCUSSION: In literature, only a few case reports about this condition are reported. Possible risk factors, etiologies, and the different therapeutic options available for this condition are examined, in order to try to favor clinicians to formulate a timely diagnosis and provide patients with rapid healthcare services. CONCLUSION: Further investigations are still needed to analyze the pathophysiological pathways responsible of gastric fundus ischemia and to provide a definitive treatment to this dangerous disorder.

Molecular Pathways Underlying Adaptive Repair of the Injured Kidney: Novel Donation After Cardiac Death and Acute Kidney Injury Platforms.

OBJECTIVE: To test the hypothesis that gene expression profiling in peripheral blood from patients who have undergone kidney transplantation (KT) will provide mechanistic insights regarding graft repair and regeneration. BACKGROUND: Renal grafts obtained from living donors (LD) typically function immediately, whereas organs from donation after cardiac death (DCD) or acute kidney injury (AKI) donors may experience delayed function with eventual recovery. Thus, recipients of LD, DCD, and AKI kidneys were studied to provide a more complete understanding of the molecular basis for renal recovery. METHODS: Peripheral blood was collected from LD and DCD/AKI recipients before transplant and throughout the first 30 days thereafter. Total RNA was isolated and assayed on whole genome microarrays. RESULTS: Comparison of longitudinal gene expression between LD and AKI/DCD revealed 2 clusters, representing 141 differentially expressed transcripts. A subset of 11 transcripts was found to be differentially expressed in AKI/DCD versus LD. In all recipients, the most robust gene expression changes were observed in the first day after transplantation. After day 1, gene expression profiles differed depending upon the source of the graft. In patients receiving LD grafts, the expression of most genes did not remain markedly elevated beyond the first day post-KT. In the AKI/DCD groups, elevations in gene expression were maintained for at least 5 days post-KT. In all recipients, the pattern of coordinate gene overexpression subsided by 28 to 30 days. CONCLUSIONS: Gene expression in peripheral blood of AKI/DCD recipients offers a novel platform to understand the potential mechanisms and timing of kidney repair and regeneration after transplantation.

How Do Synchronous Lung Metastases Influence the Surgical Management of Children with Hepatoblastoma? An Update and Systematic Review of the Literature.

Approximately 20% of children with hepatoblastoma (HB) have metastatic disease at diagnosis, most frequently in the lungs. In children with HB, lung metastatic disease is associated with poorer prognosis. Its treatment has been approached with a variety of methods that integrate chemotherapy and surgical resection. The timing and feasibility of complete extirpation of lung metastases, by chemotherapy and/or metastasectomy, is crucial for the surgical treatment of the primary liver tumor, which can vary from major hepatic resections to liver transplantation (LT). In children with unresectable HB, which can be surgically treated only by LT, the persistence of unresectable metastases after neoadjuvant chemotherapy excludes the possibility of recurring to LT with consequent negative impact on patients' outcomes. Due to limited evidence and experience, there is no consensus amongst oncologists and surgeons across institutions regarding the surgical treatment for HB with synchronous metastatic lung disease. This narrative review aimed to update the current management of pulmonary metastasis in children with HB and to define its role in the decision-making strategy for the surgical approach to primary liver tumours.

De novo malignancies after liver transplantation: The effect of immunosuppression-personal data and review of literature.

BACKGROUND: Immunosuppression has undoubtedly raised the overall positive outcomes in the post-operative management of solid organ transplantation. However, long-term exposure to immunosuppression is associated with critical systemic morbidities. De novo malignancies following orthotopic liver transplants (OLTs) are a serious threat in pediatric and adult transplant individuals. Data from different experiences were reported and compared to assess the connection between immunosuppression and de novo malignancies in liver transplant patients. AIM: To study the role of immunosuppression on the incidence of de novo malignancies in liver transplant recipients. METHODS: A systematic literature examination about de novo malignancies and immunosuppression weaning in adult and pediatric OLT recipients was described in the present review. Worldwide data were collected from highly qualified institutions performing OLTs. Patient follow-up, immunosuppression discontinuation and incidence of de novo malignancies were reported. Likewise, the review assesses the differences in adult and pediatric recipients by describing the adopted immunosuppression regimens and the different type of diagnosed solid and blood malignancy. RESULTS: Emerging evidence suggests that the liver is an immunologically privileged organ able to support immunosuppression discontinuation in carefully selected recipients. Malignancies are often detected in liver transplant patients undergoing daily immunosuppression regimens. Post-transplant lymphoproliferative diseases and skin tumors are the most detected de novo malignancies in the pediatric and adult OLT population, respectively. To date, immunosuppression withdrawal has been achieved in up to 40% and 60% of well-selected adult and pediatric recipients, respectively. In both populations, a clear benefit of immunosuppression weaning protocols on de novo malignancies is difficult to ascertain because data have not been specified in most of the clinical experiences. CONCLUSION: The selected populations of tolerant pediatric and adult liver transplant recipients greatly benefit from immunosuppression weaning. There is still no strong clinical evidence on the usefulness of immunosuppression withdrawal in OLT recipients on malignancies. An interesting focus is represented by the complete reconstitution of the immunological pathways that could help in decreasing the incidence of de novo malignancies and may also help in treating liver transplant patients suffering from cancer.

Extracellular matrix-based hydrogels obtained from human tissues: a work still in progress.

PURPOSE OF REVIEW: The current review summarizes contemporary decellularization and hydrogel manufacturing strategies in the field of tissue engineering and regenerative medicine. RECENT FINDINGS: Decellularized extracellular matrix (ECM) bioscaffolds are a valuable biomaterial that can be purposed into various forms of synthetic tissues such as hydrogels. ECM-based hydrogels can be of animal or human origin. The use of human tissues as a source for ECM hydrogels in the clinical setting is still in its infancy and current literature is scant and anecdotal, resulting in inconclusive results. SUMMARY: Thus far the methods used to obtain hydrogels from human tissues remains a work in progress. Gelation, the most complex technique in obtaining hydrogels, is challenging due to remarkable heterogeneity of the tissues secondary to interindividual variability. Age, sex, ethnicity, and preexisting conditions are factors that dramatically undermine the technical feasibility of the gelation process. This is contrasted with animals whose well defined anatomical and histological characteristics have been selectively bred for the goal of manufacturing hydrogels.

Clinical Operational Tolerance and Immunosuppression Minimization in Kidney Transplantation: Where Do We Stand?

BACKGROUND: The 20th century represents a breakthrough in the transplantation era, since the first kidney transplantation between identical twins was performed. This was the first case of tolerance, since the recipient did not need immunosuppression. However, as transplantation became possible, an immunosuppression-free status became the ultimate goal, since the first tolerance case was a clear exception from the hard reality nowadays represented by rejection. METHODS: A plethora of studies was described over the past decades to understand the molecular mechanisms responsible for rejection. This review focuses on the most relevant studies found in the literature where renal tolerance cases are claimed. Contrasting, and at the same time, encouraging outcomes are herein discussed and a glimpse on the main renal biomarkers analyzed in this field is provided. RESULTS: The activation of the immune system has been shown to play a central role in organ failure, but also it seems to induce a tolerance status when an allograft is performed, despite tolerance is still rare to register. Although there are still overwhelming challenges to overcome and various immune pathways remain arcane; the immunosuppression minimization might be more attainable than previously believed. CONCLUSION: . Multiple biomarkers and tolerance mechanisms suspected to be involved in renal transplantation have been investigated to understand their real role, with still no clear answers on the topic. Thus, the actual knowledge provided necessarily leads to more in-depth investigations, although many questions in the past have been answered, there are still many issues on renal tolerance that need to be addressed.