Ravi Katari

The human pancreas as a source of protolerogenic extracellular matrix scaffold for a new-generation bioartificial endocrine pancreas

Objectives: Our study aims at producing acellular extracellular matrix scaffolds from the human pancreas (hpaECMs) as a first critical step toward the production of a new-generation, fully human-derived bioartificial endocrine pancreas. In this bioartificial endocrine pancreas, the hardware will be represented by hpaECMs, whereas the software will consist in the cellular compartment generated from patients own cells. Background: Extracellular matrix (ECM)-based scaffolds obtained through the decellularization of native organs have become the favored platform in the field of complex organ bioengineering. However, the paradigm is now switching from the porcine to the human model. Methods: To achieve our goal, human pancreata were decellularized with Triton-based solution and thoroughly characterized. Primary endpoints were complete cell and DNA clearance, preservation of ECM components, growth factors and stiffness, ability to induce angiogenesis, conservation of the framework of the innate vasculature, and immunogenicity. Secondary endpoint was hpaECMs’ ability to sustain growth and function of human islet and human primary pancreatic endothelial cells. Results: Results show that hpaECMs can be successfully and consistently produced from human pancreata and maintain their innate molecular and spatial framework and stiffness, and vital growth factors. Importantly, hpaECMs inhibit human naïve CD4+ T-cell expansion in response to polyclonal stimuli by inducing their apoptosis and promoting their conversion into regulatory T cells. hpaECMs are cytocompatible and supportive of representative pancreatic cell types. Discussion: We, therefore, conclude that hpaECMs has the potential to become an ideal platform for investigations aiming at the manufacturing of a regenerative medicine-inspired bioartificial endocrine pancreas.

Semi-xenotransplantation: the regenerative medicine-based approach to immunosuppression-free transplantation and to meet the organ demand.

Although xenografts have always held immeasurable potential as an inexhaustible source of donor organs, immunological barriers and physiological incompatibility have proved to be formidable obstacles to clinical utility. An exciting, new regenerative medicine‐based approach termed “semi‐xenotransplantation” (SX) seeks to overcome these obstacles by combining the availability and reproducibility of animal organs with the biocompatibility and functionality of human allografts. Compared to conventional xenotransplantation wherein the whole organ is animal‐derived, SX grafts are cleansed of their antigenic cellular compartment to produce whole‐organ extracellular matrix scaffolds that retain their innate structure and vascular channels. These scaffolds are then repopulated with recipient or donor human stem cells to generate biocompatible semi‐xenografts with the structure and function of native human organs. While numerous hurdles must be still overcome in order for SX to become a viable treatment option for end‐stage organ failure, the immense potential of SX for meeting the urgent needs for a new source of organs and immunosuppression‐free transplantation justifies the interest that the transplant community is committing to the field.

Prospect for kidney bioengineering: shortcomings of the status quo

Introduction: Dialysis and renal transplantation are the only two therapeutic options offered to patients affected by end-stage kidney disease; however, neither treatment can be considered definitive. In fact, dialysis is able to replace only the filtration function of the kidney without substituting its endocrine and metabolic roles, and dramatically impacts on patient’s quality of life. On the other hand, kidney transplantation is severely limited by the shortage of transplantable organs, the need for immunosuppressive therapies and a narrow half-life. Regenerative medicine approaches are promising tools aiming to improve this condition. Areas covered: Cell therapies, bioartificial kidney, organ bioengineering, 3D printer and kidney-on-chip represent the most appealing areas of research for the treatment of end-stage kidney failure. The scope of this review is to summarize the state of the art, limits and directions of each branch. Expert opinion: In the future, these emerging technologies could provide definitive, curative and theoretically infinite options for the treatment of end-stage kidney disease. Progress in stem cells-based therapies, decellularization techniques and the more recent scientific know-how for the use of the 3D printer and kidney-on-chip could lead to a perfect cellular-based therapy, the futuristic creation of a bioengineered kidney in the lab or to a valid bioartificial alternative.

Extracellular Matrix Scaffold Technology for Bioartificial Pancreas Engineering: State of the Art and Future Challenges

Emergent technologies in regenerative medicine may soon overcome the limitations of conventional diabetes therapies. Collaborative efforts across the subfields of stem cell technology, islet encapsulation, and biomaterial carriers seek to produce a bioengineered pancreas capable of restoring endocrine function in patients with insulin-dependent diabetes. These technologies rely on a robust understanding of the extracellular matrix (ECM), the supportive 3-dimensional network of proteins necessary for cellular attachment, proliferation, and differentiation. Although these functions can be partially approximated by biosynthetic carriers, novel decellularization protocols have allowed researchers to discover the advantages afforded by the native pancreatic ECM. The native ECM has proven to be an optimal platform for recellularization and whole-organ pancreas bioengineering, an exciting new field with the potential to resolve the dire shortage of transplantable organs. This review seeks to contextualize recent findings, discuss current research goals, and identify future challenges of regenerative medicine as it applies to diabetes management.

Tissue Engineering and Regenerative Medicine: Semantic Considerations for an Evolving Paradigm

Tissue engineering (TE) and regenerative medicine (RM) are rapidly evolving fields that are often obscured by a dense cloud of hype and commercialization potential. We find, in the literature and general commentary, that several of the associated terms are casually referenced in varying contexts that ultimately result in the blurring of the distinguishing boundaries which define them. “TE” and “RM” are often used interchangeably, though some experts vehemently argue that they, in fact, represent different conceptual entities. Nevertheless, contemporary scientists have a general idea of the experiments and milestones that can be classified within either or both categories. Given the groundbreaking achievements reported within the past decade and consequent watershed potential of this field, we feel that it would be useful to properly contextualize these terms semantically and historically. In this concept paper, we explore the various definitions proposed in the literature and emphasize that ambiguous terminology can lead to misplaced apprehension. We assert that the central motifs of both concepts have existed within the surgical sciences long before their appearance as terms in the scientific literature.

Heterogeneity of Scaffold Biomaterials in Tissue Engineering

Tissue engineering (TE) offers a potential solution for the shortage of transplantable organs and the need for novel methods of tissue repair. Methods of TE have advanced significantly in recent years, but there are challenges to using engineered tissues and organs including but not limited to: biocompatibility, immunogenicity, biodegradation, and toxicity. Analysis of biomaterials used as scaffolds may, however, elucidate how TE can be enhanced. Ideally, biomaterials should closely mimic the characteristics of desired organ, their function and their in vivo environments. A review of biomaterials used in TE highlighted natural polymers, synthetic polymers, and decellularized organs as sources of scaffolding. Studies of discarded organs supported that decellularization offers a remedy to reducing waste of donor organs, but does not yet provide an effective solution to organ demand because it has shown varied success in vivo depending on organ complexity and physiological requirements. Review of polymer-based scaffolds revealed that a composite scaffold formed by copolymerization is more effective than single polymer scaffolds because it allows copolymers to offset disadvantages a single polymer may possess. Selection of biomaterials for use in TE is essential for transplant success. There is not, however, a singular biomaterial that is universally optimal.

Regeneration and Bioengineering of the Kidney: Current Status and Future Challenges

The prevalence of chronic kidney disease continues to outpace the development of effective treatment strategies. For patients with advanced disease, renal replacement therapies approximate the filtration functions of the kidney at considerable cost and inconvenience, while failing to restore the resorptive and endocrine functions. Allogeneic transplantation remains the only restorative treatment, but donor shortage, surgical morbidity and the need for lifelong immunosuppression significantly limit clinical application. Emerging technologies in the fields of regenerative medicine and tissue engineering strive to address these limitations. We review recent advances in cell-based therapies, primordial allografts, bio-artificial organs and whole-organ bioengineering as they apply to renal regeneration. Collaborative efforts across these fields aim to produce a bioengineered kidney capable of restoring renal function in patients with end-stage disease.

The efficacy and safety of mammalian target of rapamycin inhibitors ab initio after liver transplantation without corticosteroids or induction therapy

BACKGROUND Mammalian target of rapamycin inhibitors have been used along with corticosteroids and/or induction therapy immediately after liver transplantation. Our aim was to assess the safety and tolerability of everolimus ab initio after liver transplantation without corticosteroids or induction, as well as efficacy in terms of liver function, rejection and graft loss. METHODS A retrospective observational study of 50 adult patients (86% males, median age 54 years, range 25-68) who were liver transplanted between 2009 and 2013 and followed for 12 months. All recipients received everolimus plus low doses of calcineurin inhibitors (n=38) or mycophenolate (n=12) without corticosteroids and/or induction from the day of transplant. RESULTS The overall patient and graft survival was 80%. Liver function was stable during one year follow-up. No rejections or graft loss were observed. Only five patients (10%) required therapy for onset dyslipidemia. CONCLUSION Everolimus-based immunosuppression regimen without corticosteroids and/or induction immediately after liver transplantation seems to be safe and effective when administered with low doses of calcineurin-inhibitor or mycophenolate; although these findings require further investigation, these regimens could avoid adverse effects of standard immunosuppression regimens with higher doses.

One-shot versus multidose perioperative antibiotic prophylaxis after kidney transplantation: A randomized, controlled clinical trial

BACKGROUND There is no consensus on the optimal perioperative antibiotic prophylaxis regimen for renal transplant recipients. Some studies have reported that irrigation of the wound at the time of closure without systemic antibiotics may suffice to minimize the risk for surgical site infection (SSI), but many centers still use long-term, multidose regimens in which antibiotics are administered until removal of foreign bodies occur, such as the urethral catheter, drain and central line. METHODS We designed a prospective, randomized, multicenter, controlled trial to compare a single dose versus a multidose regimen of systemic antibiotic prophylaxis in adult, nondiabetic, non-morbidly obese patients undergoing renal transplantation. The primary endpoint was the incidence of SSI; the assessment of other infection in the first postoperative month was the secondary endpoint. RESULTS Two hundred five patients were enrolled and randomized to receive either a single (n = 103) or multidose antibiotic regimen (n = 102) for prophylaxis. The incidences of SSI and urinary tract infection were similar in both groups. CONCLUSION As the dramatic increase in antibiotic resistance has mandated the implementation of global programs to optimize the use of antibiotic agents in humans, we believe that the single dose regimen is preferred, at least in nondiabetic, non-morbidly obese, adult renal transplant recipients.

Sisyphus, the Giffen's paradox and the Holy Grail: time for organ transplantation to transition toward a regenerative medicine-focused type of research.

In the past 20 years, over 160 patients have received organs manufactured from autologous cells, which – in most cases – were seeded and expanded on a supportive scaffold and eventually transplanted into a patient, without any need for immunosuppression (IS) at any time after the implantation [2–7]. With these significant achievements, organ bioengineering and regeneration (OBR), a field of health sciences falling under the umbrella of regenerative medicine (RM), has shown the potential to revolutionize organ transplantation by addressing the two most urgent concerns: the need for an inexhaustible source of organs and the accomplishment of an IS-free state (IFS; more commonly referred to as tolerance). Accordingly, we recently authored a concept paper in Annals of Surgery which makes the argument that OBR has all the credentials to be correctly referred to as the new Holy Grail for organ transplantation [2]. As a corollary, transplantation research should transition towards a regenerative-medicine focus because the clinical trajectory of transplantation as a health sciences field is more suited to foster OBR than any other field. We use the metaphor of the Holy Grail in its capacity to describe an exceptionally rare object or a near-unattainable ideal. In the transplant jargon, the establishment of IFS has long been the primary ambition of transplant researchers and the main objective of several investigations that required massive investments. To date, however, IFS remains an elusive goal [8–10]. When considering the history of the quest of tolerance, it is incontrovertible that it is, indeed, a history of fiascos rather than successes. Nonetheless, investigations aimed at tolerance have certainly produced significant knowledge of the mechanisms underlying the immune system, yet the achievement of immediate, stable and durable IFS remains far from our grasp with current knowledge and technology. Ideally, patients would receive an organ with no need of IS at any time after the transplant. IFS would be immediate (i.e., established soon after reperfusion), stable (i.e., without fluctuation) and durable (i.e., lasting as long as the new organ) [11]. Unfortunately, that has never been the case. The few anecdotal, inconsistent reports describe patients