Ex vivo allotransplantation engineering: Delivery of mesenchymal stem cells prolongs rejection‐free allograft survival

Current pharmacologic regimens in transplantation prevent allograft rejection through systemic recipient immunosuppression but are associated with severe morbidity and mortality. The ultimate goal of transplantation is the prevention of allograft rejection while maintaining recipient immunocompetence. We hypothesized that allografts could be engineered ex vivo (after allotransplant procurement but before transplantation) by using mesenchymal stem cell–based therapy to generate localized immunomodulation without affecting systemic recipient immunocompetence. To this end, we evaluated the therapeutic efficacy of bone marrow–derived mesenchymal stem cells in vitro and activated them toward an immunomodulatory fate by priming in inflammatory or hypoxic microenvironments. Using an established rat hindlimb model for allotransplantation, we were able to significantly prolong rejection‐free allograft survival with a single perioperative ex vivo infusion of bone marrow–derived mesenchymal stem cells through the allograft vasculature, in the absence of long‐term pharmacologic immunosuppression. Critically, transplanted rats rejected a second, nonengineered skin graft from the same donor species to the contralateral limb at a later date, demonstrating that recipient systemic immunocompetence remained intact. This study represents a novel approach in transplant immunology and highlights the significant therapeutic opportunity of the ex vivo period in transplant engineering.     

Recipient‐derived angiogenesis with short term immunosuppression increases bone remodeling in bone vascularized composite allotransplantation: A pilot study in a swine tibial defect model

Current vascularized composite allotransplantation (VCA) transplantation protocols rely upon life‐long immune modulation to maintain tissue perfusion. Alternatively, bone‐only VCA viability may be maintained in small animal models using surgical angiogenesis from implanted autogenous vessels to develop a neoangiogenic bone circulation that will not be rejected. This study tests the method's efficacy in a large animal model as a bridge to clinical practice, quantifying the remodeling and mechanical properties of porcine tibial VCAs. A segmental tibial defect was reconstructed in Yucatan miniature swine by transplantation of a matched tibia segment from an immunologically mismatched donor. Microsurgical repair of nutrient vessels was performed in all pigs, with simultaneous intramedullary placement of an autogenous arteriovenous (AV) bundle in Group 2. Group 1 served as a no‐angiogenesis control. All received 2 weeks of immunosuppression. After 16 weeks, micro‐CT and histomorphometric analyses were used to evaluate healing and remodeling. Axial compression and nanoindentation studies evaluated bone mechanical properties. Micro‐CT analysis demonstrated significantly more new bone formation and bone remodeling at the distal allotransplant/recipient junction and on the endosteal surfaces of Group 2 tibias (p = 0.03). Elastic modulus and hardness were not adversely affected by angiogenesis. The combination of 2 weeks of immunosuppression and autogenous AV‐bundle implantation within a microsurgically transplanted tibial allotransplant permitted long‐term allotransplant survival over the study period of 16 weeks in this large animal model. Angiogenesis increased bone formation and remodeling without adverse mechanical effects. The method may allow future composite‐tissue allotransplantation of bone without the risks associated with long‐term immunosuppression. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1242–1249, 2017.

     

Repopulation of vascularized bone allotransplants with recipient‐derived cells: Detection by laser capture microdissection and real‐time PCR

Mechanisms underlying successful composite tissue transplantation must include an analysis of transplant chimerism, which is little studied, particularly in calcified tissue. We have developed a new method enabling determination of lineage of selected cells in our model of vascularized bone allotransplantation. Vascularized femoral allotransplantation was performed from female Dark Agouti (DA) donor rats to male Piebald Virol Glaxo (PVG) recipients, representing a major histocompatibility mismatch. Four groups differed in use of immunosuppression (±2 weeks Tacrolimus) and surgical revascularization, by implantation of either a patent or a ligated saphenous arteriovenous (AV) bundle. Results were assessed at 18 weeks. Bone blood flow was measured by the hydrogen washout technique and transverse specimens were prepared for histology. Real‐time PCR was performed on DNA from laser capture microdissected cortical bone regions to determine the extent of chimerism. To do so, we analyzed the relative expression ratio of the sex‐determining region Y (Sry) gene, specific only for recipient male rat DNA, to the cyclophilin housekeeper gene. Substantial transplant chimerism was seen in cortical bone of all groups (range 77–97%). Rats without immunosuppression and with a patent AV bundle revealed significantly higher chimerism than those with immunosuppression and a ligated AV bundle, which maintained transplant cell viability. We describe a new method to study the extent of chimerism in rat vascularized bone allotransplants, including a sex‐mismatched transplantation model, laser capture microdissection of selected bone regions, and calculation of the relative expression ratio. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1514–1520, 2009     

Donor‐derived infections and infectious risk in xenotransplantation and allotransplantation

Post‐transplantation infections are common in allograft recipients and should be expected in all immunocompromised hosts. Based on the need for immunosuppression in xenotransplantation, procedures developed to enhance safety in allotransplantation can be applied in future xenotransplantation clinical trials. Standardized approaches can be developed to guide the evaluation of common infectious syndromes in xenograft recipients. The opportunity created by screening of swine intended as xenograft donors has equal applicability to allotransplantation—notably broader screening strategies for allograft donors such as use of advanced sequencing modalities including broad‐range molecular probes, microarrays, and high‐throughput pyrosequencing. Considerations in management of allotransplant‐ and xenotransplant‐associated infections are largely the same. Experience in xenotransplantation will continue to inform thinking regarding donor‐derived infections in allotransplantation. We expect that experience in managing complex allotransplant recipients will similarly inform clinical trials in xenotransplantation.     

Neo-Angiogenesis,Transplant Viability,and Molecular Analyses of Vascularized Bone Allotransplantation Surgery in a Large Animal Model

Vascularized composite allotransplantation of bone is a possible alternative treatment for large osseous defects but requires life-long immunosuppression. Surgical induction of autogenous neo-angiogenic circulation maintains transplant viability without this requirement, providing encouraging results in small animal models [1–3]. A preliminary feasibility study in a swine tibia model demonstrated similar findings [4, 5]. This study in swine tibial allotransplantation tests its applicability in a pre-clinical large animal model. Previously, we have demonstrated bone vascularized composite allotransplantation (VCA) survival was not the result of induction of tolerance nor an incompetent immune system [1]. Fourteen tibia vascularized bone allotransplants were microsurgically transplanted orthotopically to reconstruct size-matched tibial defects in Yucatan miniature swine. Two weeks of immunosuppression was used to maintain allotransplant pedicle patency during angiogenesis from a simultaneously implanted autogenous arteriovenous bundle. The implanted arteriovenous bundle was patent in group 1 and ligated in group 2 (a neo-angiogenesis control). At twenty weeks, we quantified the neo-angiogenesis and correlated it with transplant viability, bone remodeling, and gene expression. All patent arteriovenous bundles maintained patency throughout the survival period. Micro-angiographic, osteocyte cell count and bone remodeling parameters were significantly higher than controls due to the formation of a neo-angiogenic autogenous circulation. Analysis of gene expression found maintained osteoblastic and osteoclastic activity as well as a significant increase in expression of endothelial growth factor-like 6 (EGFL-6) in the patent arteriovenous bundle group. Vascularized composite allotransplants of swine tibia maintained viability and actively remodeled over 20 weeks when short-term immunosuppression is combined with simultaneous autogenous neo-angiogenesis. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:288-296, 2020     

A modified vascularized whole knee joint allotransplantation model in the rat

Previous papers have shown surgical neoangiogenesis to allow long‐term bone allotransplant survival without immunosuppression. Whole joint composite tissue allotransplants (CTA) might be treated similarly. A novel rat knee CTA model is described for further study of the roles of neoangiogensis in joint allotransplant survival and adjustment of immunosuppression. Microvascular knee CTA was performed in nine rats across a major histocompatibility barrier with both pedicle repair and implantation of host‐derived arteriovenous (“a/v”) bundles. In the control group (N = 3), the pedicle was ligated. Immunosuppression was given daily. Joint mobility, weight‐bearing, pedicle patency, bone blood flow, and sprouting from a/v bundles were assessed at 3 weeks. All but the nonrevascularized control knees had full passive motion and full weight bearing. One nutrient pedicle thrombosed prematurely. Blood flow was measurable in transplants with patent nutrient pedicles. Implanted a/v bundles produced new vascular networks on angiography. This new rat microsurgical model permits further study of joint allotransplantation. Patency of both pedicles and implanted a/v bundles was maintained, laying a foundation for future studies. © 2010 Wiley‐Liss, Inc. Microsurgery, 2010.     

The effects of early and delayed immunosuppression in experimental tracheal transplantation with omentopexy.

BACKGROUND/PURPOSE: Best results in experimental tracheal allotransplantation are obtained when metachronous revascularization by omentopexy and immunosuppression are used. Nevertheless, this method of revascularization implies in a 4-day period of ischemia to the graft. The aim of this study was to assess the influence of the 4-day period of ischemia on host sensitization as well as the effect of early or delayed immunosuppression on the outcome of the grafts. METHODS: Thirty rabbits were submitted to tracheal allotransplantation and divided according to position of the graft (orthotopic or heterotopic transplants) and the initiation of immunosuppression (early or delayed). The quality of the revascularization was evaluated by the identification of Indian ink, perfused through the abdominal aorta, inside the submucosal vessels. The outcome of the grafts was evaluated by histological analysis according to a semiquantitative scale of alterations. RESULTS: Grafts were better revascularized in heterotopic position. Grafts with late immunosuppression presented good outcome only when heterotopically positioned. No significant differences were observed in grafts placed heterotopically or orthotopically when immunosuppression was initiated early after the transplant. CONCLUSIONS: Transient ischemia produced by metachronous revascularization is not the single factor responsible for the histological alterations observed in tracheal allografts. These alterations probably also are produced by the activation of immune responses. This activation is more intense in more ischemic grafts, but can be suppressed by early administration of immunosuppression.     

Clinical factors associated with graft fibrosis in kidney-transplant recipients on steroid-avoidance immunosuppression

Abstract: Background: Recent studies have documented good patient and graft outcomes and a low risk of acute rejection with steroid‐avoidance immunosuppression in kidney‐transplant recipients, but the risk of progressive graft fibrosis is not well studied. Methods: All adult primary kidney transplant or combined kidney and pancreas transplant recipients on steroid avoidance immunosuppression were eligible for study. All recipients received induction with antithymocyte globulin or basiliximab. Corticosteroids were stopped after day 4 post‐transplantation. Patients were maintained with tacrolimus and mycophenolate mofetil. Protocol biopsies were done at reperfusion and at one, four, and 12 months after transplantation. Results: Eighty one‐yr protocol biopsies with adequate specimens were obtained from 132 kidney or kidney–pancreas transplant recipients. Fifteen (19%) of the biopsies showed moderate to severe graft interstitial fibrosis (GIF) (Banff ci score ≥2). Recipients with GIF were older, had lower body mass index, greater human lymphocyte antigen (HLA) mismatch, older donors, serum creatinine ≥1.6 mg/dL at one month, a Banff ci score >0 on one‐month biopsy, BK nephropathy, and interstitial cellular infiltrates on the one‐yr biopsy. In the unadjusted logistic regression analysis, BK nephropathy, serum creatinine ≥1.6 mg/dL at one month, recipient age, Banff ci score >0 on one‐month biopsy, and donor age were the only variables associated with a higher risk of GIF on the one‐year biopsy. In the multivariate logistic regression model adjusted for these variables, BK nephropathy, serum creatinine ≥1.6 mg/dL at one month after transplantation, and recipient age were independently associated with the risk of GIF on the one‐year biopsy. Conclusion: In this small study of primary kidney or combined kidney–pancreas transplant recipients on steroid‐avoidance immunosuppression, we found that 19% had GIF on a one‐year protocol biopsy. BK nephropathy, serum creatinine ≥1.6 mg/dL one month after transplantation, and recipient age correlated with an increased risk for GIF on the one‐yr biopsy.     

Allotransplantation of Cryopreserved Parathyroid Tissue for Severe Hypocalcemia in a Renal Transplant Recipient

We report the successful allotransplantation of cryopreserved parathyroid tissue to reverse hypocalcemia in a kidney transplant recipient. A 36‐year‐old male received a second deceased donor kidney transplant, and 6 weeks later developed severe bilateral leg numbness and weakness, inability to walk, acute pain in the left knee and wrist tetany. His total calcium was 2.6 mg/dL and parathormone level 5 pg/mL (normal 10–60 pg/mL). He underwent allotransplantation of parathyroid tissue cryopreserved for 8 months into his left brachioradialis muscle. Immunosuppression included tacrolimus (target C₀ 10–12 ng/mL), mycophenolate mofetil and steroids. Within 2 weeks, the left knee pain, leg weakness and numbness resolved, and by 1 month he could walk normally. After a peak at month 2, his parathyroid hormone (PTH) level fell to <10 pg/mL; therefore at month 3 he received a second parathyroid transplant from the same donor. Eight months later (11 months after initial graft) he has a total calcium of 9.3 mg/dL, PTH level 15 pg/mL and is clinically asymptomatic. The amount of parathyroid tissue needed to render a patient normocalcemic is not known. In our case, the need for second transplant suggests that the amount of tissue transferred for an allograft may need to be substantially greater than for an autograft.     

Host-derived angiogenesis maintains bone blood flow after withdrawal of immunosuppression

A novel method of living bone allotransplantation combining microvascular repair of the nutrient circulation, implantation of host-derived arteriovenous (AV) bundles, and short-term immunosuppression is described. We hypothesized that neoangiogenesis from the implanted vessels would maintain graft viability and circulation after withdrawal of FK506 (Tacrolimus) immunosuppression. Vascularized femoral transplantation was performed between DA and PVG rats. In addition to microsurgical pedicle anastomoses, a saphenous AV bundle from the recipient animal was implanted in the medullary space. Ninety-seven rats were randomly allocated to groups differing in immunosuppression and AV bundle patency. Implanted vessels significantly improved capillary density and bone blood flow in nonimmunosuppressed and immmunosuppressed groups, respectively. A lower incidence of spontaneous AV bundle thrombosis was found with Tacrolimus treatment. More viable osteocytes were seen at 4 weeks when the AV bundle was patent. Further investigations may confirm host-derived neoangiogenesis as an alternative to tolerance induction or immunosuppression in bone allotransplantation.     

Successful allotransplantation of cryopreserved tracheal grafts with preservation of the pars membranacea in nonhuman primates.

OBJECTIVE: This study was performed to confirm the feasibility of cryopreserved tracheal allotransplantation in primates, the anatomy and immunology of which are considered to be more closely related to those of humans than those of other animals. METHODS: Cryopreserved tracheal allotransplantations were performed in 3 recipient primates. In the control group fresh tracheal allotransplantations were performed in 2 primates (control A), and a tracheal allotransplantation with a simply frozen tracheal graft was performed in 1 primate (control B). Monthly bronchoscopic examinations, histologic examinations, electron microscopic examinations, and immunohistochemical investigations were performed in each of the primates. RESULTS: In the cryopreserved tracheal allotransplantation group, 3 recipient monkeys were killed on the 35th, 144th, and 387th postoperative days, respectively. All grafts were incorporated by the recipient trachea without stenosis in the cryopreserved group. In the control group 2 recipient monkeys were killed on the 93rd postoperative day (control A), and one was killed on the 84th postoperative day (control B). Severe stenosis was observed after the transplantation in all of the control monkeys. Immunologic reactions appeared to be attenuated by the cryopreservation, whereas T cell-mediated immunologic rejection (control A) and loss of cartilage viability (control B) were considered to be the causes of graft failure in the control group. CONCLUSION: The immunogenicity of the tracheal allografts was reduced by cryopreservation, and cryopreserved tracheal allotransplantation was successful in our primate model. Further investigation of cryopreserved tracheal allotransplantation with regard to proper clinical applications and the limitations of the procedure should be performed.     

Early changes in scores of chronic damage on transplant kidney protocol biopsies reflect donor characteristics,but not future graft function

The amount of irreversible injury on renal allograft biopsy predicts function, but little is known about the early evolution of this damage. In a single‐center cohort, we examined the relationship between donor‐, recipient‐, and transplantation‐associated factors and change in a morphometric index of chronic damage (ICD) between protocol biopsies performed at implantation and at 2–3 months. We then investigated whether early delta ICD predicted subsequent biochemical outcomes. We found little evidence to support differences between the study group, who had undergone serial biopsies, and a contemporaneous control group, who had not. In allografts with serial biopsies (n = 162), there was an increase in ICD between implantation (median: 2%, IQR:0–8) and 2–3 months post‐transplant (median 8% IQR:4–15; p < 0.0001). Donation from younger or live donors was independently associated with smaller early post‐transplant increases in ICD. There was no evidence for a difference in delta ICD between donation after cardiac death vs. donation after brain death, nor association with length of cold ischemia. After adjustment for GFR at the time of the second biopsy, delta ICD after three months did not predict allograft function at one yr. These findings suggest that graft damage develops shortly after transplantation and reflects donor factors, but does not predict future biochemical outcomes.     

Transformation of Face Transplants: Volumetric and Morphologic Graft Changes Resemble Aging After Facial Allotransplantation

Facial allotransplantation restores normal anatomy to severely disfigured faces. Although >30 such operations performed worldwide have yielded promising short‐term results, data on long‐term outcomes remain scarce. Three full‐face transplant recipients were followed for 40 months. Severe changes in volume and composition of the facial allografts were noted. Data from computed tomography performed 6, 18 and 36 months after transplantation were processed to separate allograft from recipient tissues and further into bone, fat and nonfat soft tissues. Skin and muscle biopsies underwent diagnostic evaluation. All three facial allografts sustained significant volume loss (mean 19.55%) between 6 and 36 months after transplant. Bone and nonfat soft tissue volumes decreased significantly over time (17.22% between months 6 and 18 and 25.56% between months 6 and 36, respectively), whereas fat did not. Histological evaluations showed atrophy of muscle fibers. Volumetric and morphometric changes in facial allografts have not been reported previously. The transformation of facial allografts in this study resembled aging through volume loss but differed substantially from regular aging. These findings have implications for risk–benefit assessment, donor selection and measures counteracting muscle and bone atrophy. Superior long‐term outcomes of facial allotransplantation will be crucial to advance toward future clinical routine.     

Short-course immunosuppression using FK506 for rat tracheal allografts

BACKGROUND: A minimizing immunosuppression after a tracheal allotransplantation is desirable. METHODS: We examined the usefulness of a short-course of immunosuppression after tracheal allotransplantation in rat. Each transplant consisting of a 5-ring segment was heterotopically implanted into the omentum. Four animals underwent a syngeneic transplantation and thus served as controls (Group A). Thirty animals underwent an allogeneic transplantation and were randomly classified into 4 groups as follows: No immunosuppression (Group B, n=6), treatment with 0.5 mg/kg of Tacrolims (FK506) (Group C, n=8), 1.0 mg/kg of FK506 (Group D, n=8), and 1.5 mg/kg of FK506 (Group E, n=8). Different doses of FK506 were administered intramuscularly for only three consecutive days after heterotopic tracheal allotransplantation. The serum levels of FK506 were then investigated 3, 7, 14, 21, and 28 days after transplantation in groups C, D, and E. All rats were killed 28 days after transplantation and then the implanted tracheae were harvested, and evaluated histologically. RESULTS: All animals survived for the protocol period. The graft morphology of Group E was significantly better than that of groups B, C, and D regarding both macro- and microscopy, and also showed the same findings as that of Group A, except for low-grade mononuclear cell infiltration. Only in Group E, the FK506 blood level was maintained at over 0.5 ng/ml, which is the lowest detectable limit in this assay, until 21 days after transplantation. CONCLUSIONS: We thus conclude that 1.5 mg/kg of FK506 which was administered for only three consecutive days after surgery may be used to maintain the morphology of tracheal allografts in rats for 28 days after transplantation.     

Species incompatibilities in the pig-to-macaque islet xenotransplant model affect transplant outcome: a comparison with allotransplantation

Graham ML, Bellin MD, Papas KK, Hering BJ, Schuurman H‐J. Species incompatibilities in the pig‐to‐macaque islet xenotransplant model affect transplant outcome: a comparison with allotransplantation. Xenotransplantation 2011; 18: 328–342. © 2011 John Wiley & Sons A/S. Abstract: Background: Porcine islet transplantation into diabetic non‐human primates is considered most relevant in translational research supporting a clinical application. Most studies have focused on immunosuppressive protocols, while metabolic aspects have mainly been utilized in graft monitoring. We evaluated data from our group regarding human and non‐human primate (NHP) allotransplantation and pig‐to‐NHP xenotransplantation to identify incompatibilities in metabolic factors and their consequences for transplant outcomes. Methods: Basic gluco‐metabolic parameters (fasting blood glucose, C‐peptide, and response to stimulation with arginine or glucose) were derived from literature (humans), 72 macaques, and 47 adult Landrace pigs. Islet preparations from 15 human deceased donors, 61 macaques, and 23 adult pigs were compared with respect to yield, fractional viability assessed by oxygen consumption normalized for DNA, and in vitro glucose‐induced insulin release. Metabolic parameters at day 75 after a single islet transplantation in the liver were compared for 19 patients and 9 macaques receiving an allotransplant and 11 macaques receiving a porcine xenotransplant: recipients received chronic immunosuppression. Results: Pigs differ from NHPs and humans by a much lower C‐peptide level (0.42 vs. 1.3 to 2.0 ng/ml, respectively) and a 2‐ to 7‐fold lower C‐peptide response to arginine stimulation. In contrast, NHPs have the highest metabolic demand as evidenced by a high C‐peptide and high C‐peptide response to arginine stimulation; values are about twice higher than in humans. For manufactured islet preparations, these differences are reflected by glucose‐stimulated insulin release (the stimulation index for pigs is 1.5, for humans 3.8, and for macaques 7.7), but not by fractional viability, which was in the same range. The day 75 outcome after transplantation assessed by C‐peptide was similar for allotransplanted humans and NHPs (80 to 90% good graft function) and lower in xenografted NHPs (36% good graft function); gluco‐metabolic parameters were in accordance with graft function, albeit different between species because normoglycemia under exogenous insulin is maintained more aggressively in patients than in NHPs. In xenografted NHPs, the shift in glycemic control with respect to normal values, combined with low values of circulating porcine C‐peptide, resembled more the normal condition in a pig than that in a macaque. Conclusions: The substantially lower glucose‐induced insulin response in adult porcine islet preparations as opposed to islets manufactured from humans or macaques combined with the much higher need for insulin in macaques than in humans creates an imbalance between the metabolic demand and the engrafted islet mass in the pig‐to‐NHP xenograft recipient. Engrafted islet mass is affected by dose, suggesting that a much higher dose level of islets is necessary in the xenogeneic setting than in human or NHP allotransplantation, and pig islets need to be given at a higher dose in macaques than the anticipated effective dose in humans. To cope with differences in metabolic demand and presumably also metabolic dynamics, a liberal regime in supportive exogenous insulin might be essential to achieve long‐term survival. These intrinsic characteristics of the NHP model deserve consideration to optimally design experimental studies with the perspective of translational value of results.     

De novo belatacept in clinical vascularized composite allotransplantation

Most immunosuppressive regimens used in clinical vascularized composite allotransplantation (VCA) have been calcineurin inhibitor (CNI)‐based. As such, most recipients have experienced CNI‐related side effects. Costimulation blockade, specifically CD28/B7 inhibition with belatacept, has emerged as a clinical replacement for CNI‐based immunosuppression in kidney transplantation. We have previously shown that belatacept can be used as a centerpiece immunosuppressant for VCA in nonhuman primates, and subsequently reported successful conversion from a CNI‐based regimen to a belatacept‐based regimen after clinical hand transplantation. We now report on the case of a hand transplant recipient, whom we have successfully treated with a de novo belatacept‐based regimen, transitioned to a CNI–free regimen. This case demonstrates that belatacept can provide sufficient prophylaxis from rejection without chronic CNI‐associated side effects, a particularly important goal in nonlifesaving solid organ transplants such as VCA.     

Removal of cartilage rings prevents graft stenosis in extended tracheal allotransplantation with omentopexy and immunosuppression: an experimental study.

BACKGROUND: One of the serious problems in longer size tracheal transplantation is severe stenosis of the graft, probably caused by an inadequate blood supply. We have previously reported that removal of some cartilage rings of the graft and omentopexy helps to provide sufficient blood flow to the graft mucosal tissue and results in satisfactory survival and non-significant graft stenosis in extended tracheal autotransplantation. However, it is unclear whether this method can be applied to extended tracheal allotransplantation that requires immunosuppression. In this report, we describe midterm results of extended tracheal allotransplantation with the technique. METHODS: Twenty-four adult mongrel dogs were used. In 18 dogs, a nine-cartilage-ring length of the trachea was allotransplanted when five cartilage rings of the graft were removed, leaving two rings intact at both ends of the graft for simple fixing to the recipient. Two artificial tracheal rings outside the graft and a stent inside the graft were used for maintaining the lumen width. Omentopexy was done for sufficient blood supply to the graft. FK 506 (0.1 mg/kg) was given on each day after the operation in Group A (n = 10), but was not given at all in Group B (n = 8). In Group C (n = 6), a nine-cartilage-ring length of the trachea, without removal of any cartilage ring, was transplanted into the recipient dog and covered with an omental pedicle flap. The same dose of FK 506 as that used in Group A dogs was given to Group C dogs. RESULTS: In Group A, 2 dogs died of graft stenosis within 9 weeks after surgery and 1 died of emaciation without tracheal stenosis. Seven dogs (70%) survived until time of killing. Among the 8 dogs in Group B, 6 died of graft stenosis within 9 weeks after surgery, with 1 dying of pneumonia and only 1 (13%) surviving for >1 year until killing. In Group C, all 6 dogs died of graft stenosis within 6 weeks after surgery. Survival at 16 weeks after surgery was 70% in Group A, 13% in Group B and 0% in Group C (p < 0.01, A vs B and C). No significant graft stenosis was found in 6 dogs and mild stenosis was found in 2 dogs at the time of death or killing in Group A (80%), whereas mild stenosis was found in only 2 dogs in Group B (25%) (p < 0.05). Mucosal blood flow of the graft in Group A was higher than that in Group C and was the same as that in Group B within 4 weeks after surgery; however, it remained unchanged to ultimately be higher than in Group B at 6 and 8 weeks after surgery. CONCLUSIONS: Removal of some cartilage rings, omentopexy and immunosuppression improved blood supply to the graft and resulted in good survival and non-significant tracheal stenosis in extended tracheal allotransplantation.     

Parathyroid allotransplantation to treat post-thyroidectomy hypoparathyroidism: A review of case studies

ObjectiveSymptomatic long-term hypoparathyroidism following thyroid surgery requires an alternative and permanent therapy that would effectively restore parathyroid function and eliminate the need for substitution drug therapy. The aim of this study was to systematically review the literature on the efficacy and safety of parathyroid allotransplantation to treat post-operative hypoparathyroidism.MethodsMEDLINE, Embase, BIOSIS and the Cochrane Library were searched for published articles (from inception of each database to September 30, 2018). A total of 9 studies comprising 146 patients (177 allotransplantations) with post thyroidectomy hypoparathyroidism were identified.ResultsParathyroid tissues used for allotransplant were cultured parathyroid cells, cryopreserved parathyroid cells and encapsulated microspheres. Post-transplant immunosuppression was only reported in three studies, mainly with oral prednisolone for 2 weeks to 6 months. Mean graft survival following allotransplantation was 47% (95% CI 24%–71%) when patients were followed-up to 6 months and 41% (95% CI 2.3%–80%) at 12 months. There was significant unexplained heterogeneity observed between studies in both these groups (I² > 50%). Parathyroid hormone (PTH) levels, and serum calcium levels post intervention was not reported in all studies, but available evidence suggests the levels remains higher (PTH level around 12 pg/ml; Ca level around 8 mg/dl) post-allotransplantation for up to 24 months.ConclusionsLong-term benefit and harms of allotransplantation is still unclear due to the clinical and statistical heterogeneity observed among the studies. Therefore, conduct of a well-designed controlled clinical trial in the immediate future on allotransplantation is of paramount importance.     

Allogenic Hair Transplant in a Bone Marrow Transplant Recipient

BACKGROUND: Autotransplantation of hair normally provides satisfactory correction of baldness. The authors suggest that the allotransplantation of hair can aid patients who have undergone bone marrow transplantation as to correct hematologic disorders. In such patients, autotransplantation of hair may be unsatisfactory because of insufficient donor hair. OBJECTIVE: To determine whether allogeneic hair grafts from bone marrow donors can grow in the bone marrow transplant recipient. METHODS: The authors performed a standard hair transplant using minigrafts. The patient, who presented a large bald area, had undergone bone marrow transplant due to acute lymphoblastic leukemia. The authors transplanted the patient with hair taken from the same bone marrow donor. RESULTS: The hair had very good growth and the results, according to the authors, are comparable to those of hair autotransplantation. CONCLUSION: Chemotherapy and radiation treatments can often lead to widespread, permanent hair loss. Allotransplantation of hair usually proves unsatisfactory, because skin is strongly antigenic. Bone marrow transplant patients can undergo an allotransplant of hair from the same bone marrow donor if their own donor area is inadequate.     

Tacrolimus trough levels after month 3 as a predictor of acute rejection following kidney transplantation: a lesson learned from DeKAF Genomics

Most calcineurin inhibitor (CNI)‐based protocols reduce blood trough goals approximately 2–3 months post‐transplant in clinically stable kidney transplant recipients. The CNI target trough level to prevent rejection, after reduction, is unknown. Using a multivariate Cox proportional hazards model, we determined the association of time‐varying tacrolimus (TAC) trough levels with acute rejection (AR) occurring in the first 6 months post‐transplant, but specifically we assessed this association after 3 months. A total of 1930 patients received TAC‐based immunosuppression prior to AR in a prospective study. Of the 151 (7.8%) who developed AR, 47 developed AR after 3 months post‐transplant. In an adjusted time‐varying multivariate model, each 1 ng/ml decrease in TAC trough levels was associated with a 7.2% increased risk of AR [hazards ratio (HR) = 1.07, 95% confidence interval (CI) (1.01, 1.14) P = 0.03] in the first 6 months. There was an additional 23% increased risk of AR with each 1 ng/ml decrease in the TAC trough levels in months 3–6 [HR = 1.23, 95% CI (1.06, 1.43) P = 0.008]. In conclusion, lower TAC trough levels were significantly associated with increased risk of AR in the first 6 months post‐transplant with additional risk of AR between months 3 and 6 post‐transplant. The timing and practice of TAC dose reduction should be personalized based on the individual's risk factors.