Simultaneous Pancreas and Kidney Transplantation from Donors after Circulatory Death in Switzerland.

Background: Simultaneous pancreas and kidney transplantation (SPK) remains the only curative treatment for type I diabetics with end-stage kidney disease. SPK using donors after circulatory death (DCD) is one important measure to expand the organ pool for pancreas transplantation (PT). After initial doubts due to higher complications, DCD SPK is now considered safe and equivalent to donation after brain death in terms of survival and graft function. Materials and Methods: We assessed pancreas and kidney graft function, as well as complications of the first three patients who underwent a DCD SPK in Switzerland. Two transplantations were after rapid procurement, one following normothermic regional perfusion (NRP). Results: Intra- and postoperative courses were uneventful and without major complications in all patients. In the two SPK after rapid procurement, pancreas graft function was excellent, with 100% insulin-free survival, and hemoglobin A1C dropped from 7.9 and 7.5 before SPK and to 5.1 and 4.3 after three years, respectively. Kidney graft function was excellent in the first year, followed by a gradual decline due to recurrent infections. The patient, after NRP SPK, experienced short-term delayed pancreatic graft function requiring low-dose insulin treatment for 5 days post-transplant, most likely due to increased peripheral insulin resistance in obesity. During follow-up, there was persistent euglycemia and excellent kidney function. Conclusions: We report on the first series of DCD SPK ever performed in Switzerland. Results were promising, with low complication rates and sustained graft survival. With almost half of all donors in Switzerland currently being DCD, we see great potential for the expansion of DCD PT.

Postmodification with Polycations Enhances Key Properties of Alginate-Based Multicomponent Microcapsules.

Postmodification of alginate-based microspheres with polyelectrolytes (PEs) is commonly used in the cell encapsulation field to control microsphere stability and permeability. However, little is known about how different applied PEs shape the microsphere morphology and properties, particularly in vivo. Here, we addressed this question using model multicomponent alginate-based microcapsules postmodified with PEs of different charge and structure. We found that the postmodification can enhance or impair the mechanical resistance and biocompatibility of microcapsules implanted into a mouse model, with polycations surprisingly providing the best results. Confocal Raman microscopy and confocal laser scanning microscopy (CLSM) analyses revealed stable interpolyelectrolyte complex layers within the parent microcapsule, hindering the access of higher molar weight PEs into the microcapsule core. All microcapsules showed negative surface zeta potential, indicating that the postmodification PEs get hidden within the microcapsule membrane, which agrees with CLSM data. Human whole blood assay revealed complex behavior of microcapsules regarding their inflammatory and coagulation potential. Importantly, most of the postmodification PEs, including polycations, were found to be benign toward the encapsulated model cells.

Phase-changing citrate macromolecule combats oxidative pancreatic islet damage, enables islet engraftment and function in the omentum.

Clinical outcomes for total-pancreatectomy followed by intraportal islet autotransplantation (TP-IAT) to treat chronic pancreatitis (CP) are suboptimal due to pancreas inflammation, oxidative stress during islet isolation, and harsh engraftment conditions in the liver's vasculature. We describe a thermoresponsive, antioxidant macromolecule poly(polyethylene glycol citrate-co-N-isopropylacrylamide) (PPCN) to protect islet redox status and function and to enable extrahepatic omentum islet engraftment. PPCN solution transitions from a liquid to a hydrogel at body temperature. Islets entrapped in PPCN and exposed to oxidative stress remain functional and support long-term euglycemia, in contrast to islets entrapped in a plasma-thrombin biologic scaffold. In the nonhuman primate (NHP) omentum, PPCN is well-tolerated and mostly resorbed without fibrosis at 3 months after implantation. In NHPs, autologous omentum islet transplantation using PPCN restores normoglycemia with minimal exogenous insulin requirements for >100 days. This preclinical study supports TP-IAT with PPCN in patients with CP and highlights antioxidant properties as a mechanism for islet function preservation.

Simultaneous split liver/kidney transplantation: A national and single center experience report.

BACKGROUND: End-stage liver disease (ESLD) and end-stage renal disease (ESRD) are prevalent diseases for which the definitive treatment is transplantation. With limited organ supply, strategies to maximize organ availability has led to increasing rates of split liver transplantations for ESLD patients. Therefore, simultaneous split liver and kidney transplantations (SSLK) for patients with ESLD and ESRD could represent a treatment option for comorbid patients. However, current practice and outcomes after SSLK are unknown. METHODS: We aim to report national trends and our experience with patients undergoing SSLK. We performed a retrospective review of the United Network for Organ Sharing (UNOS) Standard Transplant Analysis and Research file from January 2011-April 2022. Descriptive analysis of preoperative characteristics, postoperative outcomes and actuarial graft and patient survivals are reported. RESULTS: National review of the UNOS transplant registry from 2011-2021 of adult patients undergoing initial transplantation via SSLK demonstrates that this procedure remains uncommon, with only 76 such cases captured in that time. Nevertheless, survival rates at 1, 3, and 5 years remains robust, at 94%, 92%, and 90% for patients overall, 90%, 88%, 88%, for the liver graft, and 93%, 91%, 88% for the kidney graft, respectively. Review of a single center experience with three such patients from 2019-2021 has shown a safe, enduring transplant option with no graft complications seen. CONCLUSIONS: SSLK is both safe and a feasible option to optimize organ supply while allowing recipients to receive quality liver and kidney grafts and should be considered more often by transplant centers going forward.

Characterizing the risk of human leukocyte antigen-incompatible living donor kidney transplantation in older recipients.

Older compatible living donor kidney transplant (CLDKT) recipients have higher mortality and death-censored graft failure (DCGF) compared to younger recipients. These risks may be amplified in older incompatible living donor kidney transplant (ILDKT) recipients who undergo desensitization and intense immunosuppression. In a 25-center cohort of ILDKT recipients transplanted between September 24, 1997, and December 15, 2016, we compared mortality, DCGF, delayed graft function (DGF), acute rejection (AR), and length of stay (LOS) between 234 older (age ≥60 years) and 1172 younger (age 18-59 years) recipients. To investigate whether the impact of age was different for ILDKT recipients compared to 17 542 CLDKT recipients, we used an interaction term to determine whether the relationship between posttransplant outcomes and transplant type (ILDKT vs CLDKT) was modified by age. Overall, older recipients had higher mortality (hazard ratio: 1.632.072.65, P < .001), lower DCGF (hazard ratio: 0.360.530.77, P = .001), and AR (odds ratio: 0.390.540.74, P < .001), and similar DGF (odds ratio: 0.461.032.33, P = .9) and LOS (incidence rate ratio: 0.880.981.10, P = 0.8) compared to younger recipients. The impact of age on mortality (interaction P = .052), DCGF (interaction P = .7), AR interaction P = .2), DGF (interaction P = .9), and LOS (interaction P = .5) were similar in ILDKT and CLDKT recipients. Age alone should not preclude eligibility for ILDKT.

Survival after LDLT in recipients ≥70 years old in the United States. An OPTN/UNOS liver transplant registry analysis.

BACKGROUND: Living donor liver transplantation (LDLT) in the elderly population is currently not well studied. There are single-center studies indicating that patient age should not be a barrier to LDLT, with similar outcomes compared to younger recipients. METHODS: Using UNOS/STAR data from 2010 to 2022 we retrospectively analyzed patients ≥70 years old receiving a living donor graft (LDLT ≥70y group) versus a deceased donor graft (DDLT ≥70y group). In addition, we compared recipients ≥70 years old undergoing LDLT versus patients 18-69 years old also undergoing LDLT. Donor and recipient baseline characteristics, as well as postoperative outcomes including graft and patient survival were analyzed and compared between groups. RESULTS: Recipients in the LDLT ≥70y group showed less disease burden and spent significantly less time on the waitlist when compared to recipients in the DDLT ≥70y group (102 [49-201] days versus 170 [36-336] days) respectively; p = .004. With the exception of a longer length of stay (LOS) in the LDLT ≥70y group (p ≤ .001), postoperative outcomes were comparable with recipients in the DDLT ≥70y group, including similar graft and patient survival rates at 1-, 3-, and 5-years. When compared to younger recipients of a graft from a living donor, patients in the LDLT ≥70y group had similar post-transplant functional status, re-transplant rates and similar causes contributing to graft failure. However, significantly lower graft and patient survival rates were observed. CONCLUSION: LDLT for recipients aged 70 or greater represents a faster access to transplantation in a safe and feasible manner when compared to similar- aged recipients undergoing DDLT.

Application of robotics in abdominal organ transplantation: A bibliometric analysis.

BACKGROUND: Robotic transplant surgery has garnered worldwide attention since 2002. Discussions on this issue have led to more publications over the past decade. This study assessed global robotic organ transplantation studies using bibliometric analysis. METHOD: The study sample was robotic technique use in organ transplantation publications from 2002 to 2021 in the Web of Science database. We analysed top-cited authors, countries, institutions, journals, and keywords. Citations were used to visualise and analyse target literature in VOSviewer. RESULTS: 160 articles were included in the bibliometric study. Among the nations that are presently involved in the use of robotics in organ transplantation research, the United States of America leads robotic organ transplantation studies. The American Journal of Transplantation published the most articles overall. CONCLUSION: Based on publication and citation numbers, robotic organ transplantation techniques are becoming more global attention. This robotic abdominal organ transplant surgery bibliometric analysis review covers research output and hotspots.

Screening hydrogels for antifibrotic properties by implanting cellularly barcoded alginates in mice and a non-human primate.

Screening implantable biomaterials for antifibrotic properties is constrained by the need for in vivo testing. Here we show that the throughput of in vivo screening can be increased by cellularly barcoding a chemically modified combinatorial library of hydrogel formulations. The method involves the implantation of a mixture of alginate formulations, each barcoded with human umbilical vein endothelial cells from different donors, and the association of the identity and performance of each formulation by genotyping single nucleotide polymorphisms of the cells via next-generation sequencing. We used the method to screen 20 alginate formulations in a single mouse and 100 alginate formulations in a single non-human primate, and identified three lead hydrogel formulations with antifibrotic properties. Encapsulating human islets with one of the formulations led to long-term glycaemic control in a mouse model of diabetes, and coating medical-grade catheters with the other two formulations prevented fibrotic overgrowth. High-throughput screening of barcoded biomaterials in vivo may help identify formulations that enhance the long-term performance of medical devices and of biomaterial-encapsulated therapeutic cells.

Correction: Angiopoetin-2 Signals Do Not Mediate the Hypervascularization of Islets in Type 2 Diabetes.

[This corrects the article DOI: 10.1371/journal.pone.0161834.].

Visualizing hypoxic modulation of beta cell secretions via a sensor augmented oxygen gradient.

One distinct advantage of microfluidic-based cell assays is their scalability for multiple concentrations or gradients. Microfluidic scaling can be extremely powerful when combining multiple parameters and modalities. Moreover, in situ stimulation and detection eliminates variability between individual bioassays. However, conventional microfluidics must combat diffusion, which limits the spatial distance and time for molecules traveling through microchannels. Here, we leveraged a multilayered microfluidic approach to integrate a novel oxygen gradient (0-20%) with an enhanced hydrogel sensor to study pancreatic beta cells. This enabled our microfluidics to achieve spatiotemporal detection that is difficult to achieve with traditional microfluidics. Using this device, we demonstrated the in situ detection of calcium, insulin, and ATP (adenosine triphosphate) in response to glucose and oxygen stimulation. Specifically, insulin was quantified at levels as low as 25 pg/mL using our imaging technique. Furthermore, by analyzing the spatial detection data dynamically over time, we uncovered a new relationship between oxygen and beta cell oscillations. We observed an optimum oxygen level between 10 and 12%, which is neither hypoxic nor normoxic in the conventional cell culture sense. These results provide evidence to support the current islet oscillator model. In future applications, this spatial microfluidic technique can be adapted for discrete protein detection in a robust platform to study numerous oxygen-dependent tissue dysfunctions.

Treatment of De Novo Renal Transplant Recipients With Calcineurin Inhibitor-free, Belatacept Plus Everolimus-based Immunosuppression.

Compared with calcineurin inhibitor-based immunosuppression, belatacept (BELA)-based treatment has been associated with better renal function but higher acute rejection rates. This phase 2 study (NCT02137239) compared the antirejection efficacy of BELA plus everolimus (EVL) with tacrolimus (TAC) plus mycophenolate mofetil (MMF), each following lymphocyte-depleting induction and rapid corticosteroid withdrawal. Methods: Patients who were de novo renal transplant recipients seropositive for Epstein-Barr virus were randomized to receive BELA+EVL or TAC+MMF maintenance therapy after rabbit antithymocyte globulin induction and up to 7 d of corticosteroids. The primary endpoint was the rate of biopsy-proven acute rejection at month 6. Results: Because of an unanticipated BELA supply constraint, enrollment was prematurely terminated at 68 patients, of whom 58 were randomized and transplanted (intention-to-treat [ITT] population: n = 26, BELA+EVL; n = 32, TAC+MMF). However, 25 patients received BELA+EVL' and 33 received TAC+MMF (modified ITT population). In the ITT population, the 6-mo biopsy-proven acute rejection rates were 7.7% versus 9.4% in the BELA+EVL versus TAC+MMF group. The corresponding 24-mo biopsy-proven acute rejection rates were 19.2% versus 12.5% in the ITT population and 16.0% versus 15.2% in the mITT population; all events were Banff severity grade ≤IIA and similar between groups. One patient in each group experienced graft loss unrelated to acute rejection. The 24-mo mean unadjusted estimated glomerular filtration rates were 71.8 versus 68.7 mL/min/1.73 m2 in the BELA+EVL versus TAC+MMF groups. Posttransplant lymphoproliferative disorder was reported for 1 patient in each group. No deaths or unexpected adverse events were observed. Conclusions: A steroid-free maintenance regimen of BELA+EVL may be associated with biopsy-proven acute rejection rates comparable to TAC+MMF.

Smartphone-microfluidic fluorescence imaging system for studying islet physiology.

Smartphone technology has been recently applied for biomedical image acquisition and data analysis due to its high-quality imaging capability, and flexibility to customize multi-purpose apps. In this work, we developed and characterized a smartphone-microfluidic fluorescence imaging system for studying the physiology of pancreatic islets. We further evaluated the system capability by performing real-time fluorescence imaging on mouse islets labeled with either chemical fluorescence dyes or genetically encoded fluorescent protein indicators (GEFPIs). Our results showed that the system was capable of analyzing key beta-cell insulin stimulator-release coupling factors in response to various stimuli with high-resolution dynamics. Furthermore, the integration of a microfluidics allowed high-resolution detection of insulin secretion at single islet level. When compared to conventional fluorescence microscopes and macro islet perifusion apparatus, the system has the advantages of low cost, portable, and easy to operate. With all of these features, we envision that this smartphone-microfluidic fluorescence imaging system can be applied to study islet physiology and clinical applications.

Consensus recommendations for use of maintenance immunosuppression in solid organ transplantation: Endorsed by the American College of Clinical Pharmacy, American Society of Transplantation, and the International Society for Heart and Lung Transplantation.

Advances in maintenance immunosuppression over the past three decades have improved solid organ transplantation outcomes dramatically. Uninterrupted access to immunosuppression is paramount to minimize rejection and maintain allograft and patient survival. There is no standardized approach to maintenance immunosuppression management. Agents used vary based on transplanted organ, center-specific protocol, provider expertise, insurance formularies, ability to cover co-pays, recipient characteristics and tolerability. Published data reflects this heterogeneity. Despite this limitation, maintenance immunosuppression usage cross pollinates between organ groups with standard of care agents often being used off-label, making medication access a challenge for many transplant recipients. A multidisciplinary panel of American transplant clinicians was formed to review published literature on maintenance immunosuppression with the goal to formulate consensus recommendations for their use in specific organ groups. These consensus recommendations are intended to provide transplant clinicians with a summary of literature on maintenance immunosuppression in the modern era and to support transplant team members working to secure medication access for patients.

Split liver transplantation with extended right grafts on adult recipients: A propensity score matching analysis.

INTRODUCTION: Split liver transplantation (SLT) emerged due to its potential to contribute to the organ pool and reduce organ shortage. However, SLT is technically challenging and has been associated with higher rates of postoperative complications leading to concerns about graft and patient survival. Moreover, there are few studies on matched-pair adult recipients of SLT and whole-liver transplant (WLT), with conflicting results. METHODS: This retrospective study analyze outcomes among adults who underwent SLT at our institution from 2010 to 2019. A 1:1 propensity score matching analysis was performed based on important donor and recipient variables. Baseline characteristics and postoperative outcomes were analyzed and compared between groups. Actuarial graft and patient survival were analyzed by KM curves. RESULTS: Out of 592 adults receiving a LT in our institution, 21 SLT adult recipients were identified and matched with 21 adults undergoing WLT. As expected donor age was significantly lower in SLT recipients (16 (15-22) vs. 32 (17-47), P = .012). Additional donor characteristics, including anthropometrics, and ischemic times were similar between groups. Baseline recipient characteristics and postoperative outcomes, including length of stay, vascular complications, biliary complications, and re-transplantation were comparable between SLT and WLT recipients. Graft (95/95/95 vs. 100/94/94, P = .98) and patient (100/100/100 vs. 100/94/94, P = .30) survival at 1-, 3-, 5-years, were similar between the SLT- and WLT group, respectively. CONCLUSION: Split liver transplantation has the potential to increase the availability of organs for adult recipients without compromising individual outcomes.

Reduced calcium levels and accumulation of abnormal insulin granules in stem cell models of HNF1A deficiency.

Mutations in HNF1A cause Maturity Onset Diabetes of the Young (HNF1A-MODY). To understand mechanisms of ß-cell dysfunction, we generated stem cell-derived pancreatic endocrine cells with hypomorphic mutations in HNF1A. HNF1A-deficient ß-cells display impaired basal and glucose stimulated-insulin secretion, reduced intracellular calcium levels in association with a reduction in CACNA1A expression, and accumulation of abnormal insulin granules in association with SYT13 down-regulation. Knockout of CACNA1A and SYT13 reproduce the relevant phenotypes. In HNF1A deficient ß-cells, glibenclamide, a sulfonylurea drug used in the treatment of HNF1A-MODY patients, increases intracellular calcium, and restores insulin secretion. While insulin secretion defects are constitutive in ß-cells null for HNF1A, ß-cells heterozygous for hypomorphic HNF1A (R200Q) mutations lose the ability to secrete insulin gradually; this phenotype is prevented by correction of the mutation. Our studies illuminate the molecular basis for the efficacy of treatment of HNF1A-MODY with sulfonylureas, and suggest promise for the use of cell therapies.

Consensus recommendations for use of maintenance immunosuppression in solid organ transplantation: Endorsed by the American College of Clinical Pharmacy, American Society of Transplantation, and International Society for Heart and Lung Transplantation: An executive summary.

Advances in maintenance immunosuppression over the past three decades have improved solid organ transplantation outcomes dramatically. Uninterrupted access to immunosuppression is paramount to minimize rejection and maintain allograft and patient survival. Agents used vary based on transplanted organ, center-specific protocol, provider expertise, insurance formularies, ability to cover co-pays, recipient characteristics and tolerability. Published data reflects this heterogeneity. Despite these obstacles, the information about maintenance immunosuppression use cross pollinates between organ groups with standard of care agents often being used off-label, making medication access a challenge for many transplant recipients. A multidisciplinary panel of American transplant clinicians was formed to review published literature on maintenance immunosuppression with the goal to formulate consensus recommendations for their use in specific organ groups. These consensus recommendations are intended to provide transplant clinicians with a summary of literature on maintenance immunosuppression in the modern era, and to support transplant team members working to secure medication access for patients.

Outcomes in Adult Liver Transplant Recipients Using Pediatric Deceased Donor Liver Grafts.

Background: The use of pediatric grafts for liver transplantation (LT) into adult recipients is rare, and reported outcomes are conflicting. The aim of this study is to evaluate the outcomes in adult recipients following LT with grafts from deceased pediatric donors. Methods: A retrospective study identifying adult LT between 2010 and 2020 using pediatric deceased donor liver grafts was conducted. Adults undergoing LT with deceased donor pediatric grafts (age ≤ 12) were identified and matched 1:2 with adults receiving adult grafts (age ≥ 18) based on recipient age (±10 y), model for end-stage liver disease (MELD) score at transplant (±5 points) and etiology of liver disease. To assess real liver size differences between the pediatric-donor and adult-donor groups, patients receiving a graft from a donor between 13 and 17 y were excluded from the main analysis and studied independently. Outcomes between the groups were compared. Complication rates were identified and graded using Clavien-Dindo classification. Graft and patient survival were assessed by Kaplan-Meier curves. Results: Twelve adult LT recipients with whole liver grafts from deceased pediatric donors were matched with 24 adult recipients of adult donors. Recipient age and MELD score were similar between groups. Recipients of pediatric grafts were more likely to be female (66.7% versus 16.7%, P = 0.007) and leaner (body mass index = 24.4 versus 29.9, P = 0.013). Alcohol-related cirrhosis was the most prevalent liver disease etiology in both groups (P = 0.96). There was no significant difference in length of stay, readmissions, early complications, or major complications between groups. Vascular and biliary complication rates were similar. Actuarial graft and patient survival at 1, 3, and 5 y were 100/100/100 versus 96/96/96 (P = 0.48). Conclusions: Excellent patient and graft survival is achievable with LT using young pediatric deceased donor grafts in smaller adult recipients. Outcomes are comparable with recipients of age and MELD-matched adult donors. Careful donor MELD-score recipient matching and close monitoring for potential biliary and vascular complications are crucial to achieve acceptable outcomes.

Living Donor Liver Transplantation vs. Split Liver Transplantation Using Left Lateral Segment Grafts in Pediatric Recipients: An Analysis of the UNOS Database.

Split and LDLT in pediatric patients have the potential to decrease wait times and waitlist mortality. Using UNOS-STAR data, we compared outcomes of pediatric patients undergoing LDLT and SLT using LLS grafts. The baseline characteristics and post-operative outcomes were compared between groups. Actuarial graft and patient survival were analyzed with Kaplan-Meier curves. Between 2010 and 2019, 911 pediatric LT were included in the analysis (LD graft group, n = 508, split graft group, n = 403). LD graft recipients spent more time on the waitlist vs. the split graft group (60 (22-138) days vs. 46 (16-108) days; p = 0.007). LD recipients had a lower rate of graft failure, found in 9.8% of patients compared with 14.6% in the split graft group (p = 0.02). HAT was the most common graft failure cause, with similar rates. Graft and patient survival at 1-, 3-, and 5-years was comparable between LDLT and SLT. In subgroup analyses, patients with biliary atresia, those ≤10 kg or ≤10 years old receiving an LD graft showed improved graft survival. In conclusion, LDLT is associated with a lower rate of graft failure in pediatric patients. The use of LLS regardless of the type of donor is a safe way to facilitate access to transplantation to pediatric patients with acceptable short and long-term outcomes.

Clinically translatable cytokine delivery platform for eradication of intraperitoneal tumors.

Proinflammatory cytokines have been approved by the Food and Drug Administration for the treatment of metastatic melanoma and renal carcinoma. However, effective cytokine therapy requires high-dose infusions that can result in antidrug antibodies and/or systemic side effects that limit long-term benefits. To overcome these limitations, we developed a clinically translatable cytokine delivery platform composed of polymer-encapsulated human ARPE-19 (RPE) cells that produce natural cytokines. Tumor-adjacent administration of these capsules demonstrated predictable dose modulation with spatial and temporal control and enabled peritoneal cancer immunotherapy without systemic toxicities. Interleukin-2 (IL2)-producing cytokine factory treatment eradicated peritoneal tumors in ovarian and colorectal mouse models. Furthermore, computational pharmacokinetic modeling predicts clinical translatability to humans. Notably, this platform elicited T cell responses in NHPs, consistent with reported biomarkers of treatment efficacy without toxicity. Combined, our findings demonstrate the safety and efficacy of IL2 cytokine factories in preclinical animal models and provide rationale for future clinical testing in humans.

Pericapsular fibrotic overgrowth mitigated in immunocompetent mice through microbead formulations based on sulfated or intermediate G alginates.

Cell encapsulation in alginate microbeads is a promising approach to provide immune isolation in cell therapy without immunosuppression. However, the efficacy is hampered by pericapsular fibrotic overgrowth (PFO), causing encapsulated cells to lose function. Stability of the microbeads is important to maintain immune isolation in the long-term. Here, we report alginate microbeads with minimal PFO in immunocompetent C57BL/6JRj mice. Microbead formulations included either alginate with an intermediate (47 %) guluronate (G) content (IntG) or sulfated alginate (SA), gelled in Ca2+/Ba2+ or Sr2+. A screening panel of eleven microbead formulations were evaluated for PFO, yielding multiple promising microbeads. Two candidate formulations were evaluated for 112 days in vivo, exhibiting maintained stability and minimal PFO. Microbeads investigated in a human whole blood assay revealed low cytokine and complement responses, while SA microbeads activated coagulation. Protein deposition on microbeads explanted from mice investigated by confocal laser scanning microscopy (CLSM) showed minimal deposition of complement C3. Fibrinogen was positively associated with PFO, with a high deposition on microbeads of high G (68 %) alginate compared to IntG and SA microbeads. Overall, stable microbeads containing IntG or SA may serve in long-term therapeutic applications of cell encapsulation. STATEMENT OF SIGNIFICANCE: Alginate-based hydrogels in the format of micrometer size beads is a promising approach for the immunoisolation of cells in cell therapy. Clinical trials in type 1 diabetes have so far had limited success due to fibrotic responses that hinder the diffusion of nutrients and oxygen to the encapsulated cells, resulting in graft failure. In this study, minimal fibrotic response towards micrometer size alginate beads was achieved by chemical modification of alginate with sulfate groups. Also, the use of alginate with intermediate guluronic acid content resulted in minimally fibrotic microbeads. Fibrinogen deposition was revealed to be a good indicator of fibrosis. This study points to both new microsphere developments and novel insight in the mechanisms behind the fibrotic responses.