Browsing by Author "Ekser, Burcin"
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Item A brief history of clinical xenotransplantation(Elsevier, 2015-11) Cooper, David K. C.; Ekser, Burcin; Tector, A. Joseph; Department of Surgery, IU School of MedicineBetween the 17th and 20th centuries, blood was transfused from various animal species into patients with a variety of pathological conditions. Skin grafts were carried out in the 19th century, with grafts from a variety of animals, with frogs being the most popular. In the 1920s, Voronoff advocated the transplantation of slices of chimpanzee testis into elderly men, believing that the hormones produced by the testis would rejuvenate his patients. In 1963-4, when human organs were not available and dialysis was not yet in use, Reemtsma transplanted chimpanzee kidneys into 13 patients, one of whom returned to work for almost 9 months before suddenly dying from what was believed to be an electrolyte disturbance. The first heart transplant in a human ever performed was by Hardy in 1964, using a chimpanzee heart, but the patient died within 2 h. Starzl carried out the first chimpanzee-to-human liver transplantation in 1966; in 1992 he obtained patient survival for 70 days following a baboon liver transplant. The first clinical pig islet transplant was carried out by Groth in 1993. Today, genetically-modified pigs offer hope of a limitless supply of organs and cells for those in need of a transplant.Item Challenges with Intestine and Multivisceral Re-Transplantation: Importance of Timing of Re-Transplantation and Optimal Immunosuppression(Springer, 2018-02-06) Kubal, Chandrashekhar A.; Pennington, Catherine; Fridell, Jonathan; Ekser, Burcin; Muhaylov, Plamen; Mangus, Richard; Surgery, School of MedicineBACKGROUND Patients undergoing re-transplantation often receive high doses of immunosuppression, which may lead to an immunocompromised status of the recipient. This study investigates the outcomes after intestine/multivisceral re-transplantation. MATERIAL AND METHODS Clinical outcomes of 23 patients undergoing 24 re-transplantations at a single intestine transplant center were reviewed. Bone marrow suppression was used as a surrogate marker of immunocompromised status, and was defined as platelet count <50 k/mm3 and absolute lymphocyte count <200/mm³. RESULTS All re-transplants except one were liver inclusive. Fifteen of 23 patients died at a median time of 12 months (range 0.2-75) after re-transplantation. Of the 15 deaths, nine (60%) resulted from complications associated with a compromised host immune status: graft versus host disease (GVHD) affecting bone marrow (three cases), persistent viral infection (three cases), post-transplant lymphoproliferative disorder (PTLD (one case), metastatic cancer (one case), multi-drug resistant polymicrobial sepsis (one case). Four deaths (27%) resulted from severe rejection. Non-survivors were more likely to have received alemtuzumab, and had higher incidence of bone marrow suppression. In addition to immunocompromised status and rejection, the use of alemtuzumab was associated with mortality after intestinal/multivisceral re-transplantation. CONCLUSIONS High mortality was associated with intestine/multivisceral re-transplantation. To improve clinical outcomes of intestine and multivisceral transplantation, it is important to allow reconstitution of host immunity. Longer interval between the two transplantations, and strategies such as allograft specific immunosuppression, may spare the host from the devastating effects of potent immunosuppression currently used.Item Clinical Islet Xenotransplantation: A Step Forward(Elsevier, 2016-10) Ekser, Burcin; Bottino, Rita; Cooper, David K. C.; Department of Surgery, IU School of MedicineItem Comparison of porcine corneal decellularization methods and importance of preserving corneal limbus through decellularization(PLOS, 2021-03-05) Isidan, Abdulkadir; Liu, Shaohui; Chen, Angela M.; Zhang, Wenjun; Li, Ping; Smith, Lester J.; Hara, Hidetaka; Cooper, David K. C.; Ekser, Burcin; Surgery, School of MedicineBackground: The aim of this study is to compare the three previously applied, conventional porcine corneal decellularization methods and to demonstrate the importance of preserving the corneal limbus through decellularization. Methods: Fresh, wild-type (with or without) limbus porcine corneas were decellularized using three different methods, including (i) sodium dodecyl sulfate (SDS), (ii) hypertonic saline (HS), and (iii) N2 gas (NG). Post-treatment evaluation was carried out using histological, residual nuclear material, and ultrastructural analyses. Glycerol was used to help reduce the adverse effects of decellularization. The corneas were preserved for two weeks in cornea storage medium. Results: All three decellularization methods reduced the number of keratocytes at different rates in the stromal tissue. However, all methods, except SDS, resulted in the retention of large numbers of cells and cell fragments. The SDS method (0.1% SDS, 48h) resulted in almost 100% decellularization in corneas without limbus. Low decellularization capacity of the NG method (<50%) could make it unfavorable. Although HS method had a more balanced damage-decellularization ratio, its decellularization capacity was lower than SDS method. Preservation of the corneoscleral limbus could partially prevent structural damage and edema, but it would reduce the decellularization capacity. Conclusion: Our results suggest that SDS is a very powerful decellularization method, but it damages the cornea irreversibly. Preserving the corneoscleral limbus reduces the efficiency of decellularization, but also reduces the damage.Item Computational fluid dynamic analysis of bioprinted self-supporting perfused tissue models(Wiley, 2020-03) Sego, T. J.; Prideaux, Matthew; Sterner, Jane; McCarthy, Brian Paul; Li, Ping; Bonewald, Lynda F.; Ekser, Burcin; Tovar, Andres; Smith, Lester Jeshua; Anatomy and Cell Biology, School of MedicineNatural tissues are incorporated with vasculature, which is further integrated with a cardiovascular system responsible for driving perfusion of nutrient‐rich oxygenated blood through the vasculature to support cell metabolism within most cell‐dense tissues. Since scaffold‐free biofabricated tissues being developed into clinical implants, research models, and pharmaceutical testing platforms should similarly exhibit perfused tissue‐like structures, we generated a generalizable biofabrication method resulting in self‐supporting perfused (SSuPer) tissue constructs incorporated with perfusible microchannels and integrated with the modular FABRICA perfusion bioreactor. As proof of concept, we perfused an MLO‐A5 osteoblast‐based SSuPer tissue in the FABRICA. Although our resulting SSuPer tissue replicated vascularization and perfusion observed in situ, supported its own weight, and stained positively for mineral using Von Kossa staining, our in vitro results indicated that computational fluid dynamics (CFD) should be used to drive future construct design and flow application before further tissue biofabrication and perfusion. We built a CFD model of the SSuPer tissue integrated in the FABRICA and analyzed flow characteristics (net force, pressure distribution, shear stress, and oxygen distribution) through five SSuPer tissue microchannel patterns in two flow directions and at increasing flow rates. Important flow parameters include flow direction, fully developed flow, and tissue microchannel diameters matched and aligned with bioreactor flow channels. We observed that the SSuPer tissue platform is capable of providing direct perfusion to tissue constructs and proper culture conditions (oxygenation, with controllable shear and flow rates), indicating that our approach can be used to biofabricate tissue representing primary tissues and that we can model the system in silico.Item Corrigendum to "The Role of Costimulation Blockade in Solid Organ and Islet Xenotransplantation"(Hindawi, 2018-03-22) Samy, Kannan P.; Butler, James R.; Li, Ping; Cooper, David K. C.; Ekser, Burcin; Surgery, School of MedicineItem Decellularization methods for developing porcine corneal xenografts and future perspectives(Wiley, 2019-11) Isidan, Abdulkadir; Liu, Shaohui; Li, Ping; Lashmet, Matthew; Smith, Lester J.; Hara, Hidetaka; Cooper, David K. C.; Ekser, Burcin; Ophthalmology, School of MedicineCorneal transplantation is the only option to cure corneal opacities. However, there is an imbalance between supply and demand of corneal tissues in the world. To solve the problem of corneal shortage, corneal xenotransplantation studies have been implemented in the past years using porcine corneas. The corneal xenografts could come from (a) wild-type pigs, (b) genetically engineered pigs, (c) decellularized porcine corneas, and (d) decellularized porcine corneas that are recellularized with human corneal cells, eventually with patients' own cells, as in all type of xenografts. All approaches except, the former would reduce or mitigate recipient immune responses. Although several techniques in decellularization have been reported, there is still no standardized protocol for the complete decellularization of corneal tissue. Herein, we reviewed different decellularization methods for porcine corneas based on the mechanism of action, decellularization efficacy, biocompatibility, and the undesirable effects on corneal ultrastructure. We compared 9 decellularization methods including: (a) sodium dodecyl sulfate, (b) triton x-100, (c) hypertonic saline, (d) human serum with electrophoresis, (e) high hydrostatic pressure, (f) freeze-thaw, (h) nitrogen gas, (h) phospholipase A2 , and (i) glycerol with chemical crosslinking methods. It appears that combined methods could be more useful to perform efficient corneal decellularization.Item DELAYED KIDNEY TRANSPLANTATION AFTER 83 HOURS OF COLD ISCHEMIA TIME IN COMBINED LIVER-KIDNEY TRANSPLANT(Wolters Kluwer, 2019-02) Ekser, Burcin; Chen, Angela M.; Kubal, Chandrashekhar A.; Fridell, Jonathan A.; Mihaylov, Plamen; Goggins, William C.; Powelson, John A.; Surgery, School of MedicineItem Excellent outcomes in combined liver-kidney transplantation: Impact of KDPI and delayed kidney transplantation(Wiley, 2017) Ekser, Burcin; Mangus, Richard S.; Kubal, Chandrashekhar A.; Powelson, John A.; Fridell, Jonathan A.; Goggins, William C.; Surgery, School of MedicineThe positive impact of delayed kidney transplantation (KT) on patient survival for combined liver-KT (CLKT) has already been demonstrated by our group. The purpose of this study is to identify whether the quality of the kidneys (based on KDPI) or the delayed approach KT contributes to improved patient survival. 130 CLKT were performed between 2002-2015; 69 with simultaneous KT (Group S) and 61 with delayed KT (Group D) (performed as a second operation with a mean cold ischemia time [CIT] of 50±15h). All patients were categorized according to the KDPI score; 1-33%, 34-66%, and 67-99%. Recipient and donor characteristics were comparable within Groups S and D. Transplant outcomes were comparable within Groups S and D, including liver and kidney CIT, warm ischemia time, and delayed graft function. Lower KDPI kidneys (<34%) were associated with increased patient survival in both groups. Combination of delayed KT and KDPI 1-33% resulted in 100% patient survival at 3-years. These results support that delayed KT in CLKT improves patient survival. The combination of delayed KT and low KDPI offers excellent patient survival up to 3-years. Improved outcomes in the delayed KT group including high KDPI kidneys supports expansion of the donor pool with the use of more ECD and DCD kidneys.Item Expanding the Donor Pool with Utilization of Extended Criteria DCD Livers(AASLD, 2019) Mihaylov, Plamen; Mangus, Richard; Ekser, Burcin; Cabrales, Arianna; Timsina, Lava; Fridell, Jonathan; Lacerda, Marco; Ghabril, Marwan; Nephew, Lauren; Chalasani, Naga; Kubal, Chandrashekhar A.; Pediatrics, School of MedicineUtilization of donation after circulatory death donor (DCD) livers for transplantation has remained cautious in the U.S. The aim of this study was to demonstrate the expansion of DCD liver transplant (LT) program with the use of extended criteria DCD livers. After institutional review board approval, 135 consecutive DCD LTs were retrospectively studied. ECD DCD livers were defined as those with one of the followings: 1) donor age >50 years, 2) donor BMI >35 kg/m2, 3) donor functional warm ischemia time (fWIT) >30 minutes, and 4) donor liver macrosteatosis >30%. An optimization protocol was introduced in July 2011 to improve outcomes of DCD LT, which included thrombolytic donor flush, and efforts to minimize ischemic times. The impact of this protocol on outcomes was evaluated in terms of graft loss, ischemic cholangiopathy (IC) and change in DCD LT volume. Of 135 consecutive DCD LT, 62 were ECD DCDs. 24 ECD DCD LT were performed before (Era I) and 38 after the institution of optimization protocol (Era II), accounting for an increase in the use of ECD DCD livers from 39% to 52%. Overall outcomes of ECD DCD LT improved in Era II, with a significantly lower incidence of IC (5% vs. 17% in Era I; P = 0.03) and better 1‐year graft survival (93% vs. 75% in Era I, P = 0.07). Survival outcomes for ECD DCD LT in Era II were comparable to matched deceased donor (DBD) LT. With the expansion of the DCD donor pool, the number of DCD LT performed at our center gradually increased in Era II to account for > 20% of the center's LT volume. In conclusion, with the optimization of perioperative conditions, ECD DCD livers can be successfully transplanted to expand the donor pool for LT.