Tacrolimus for the prevention and treatment of rejection of solid organ transplants

Impact of Switching From Immediate- or Prolonged-Release to Once-Daily Extended-Release Tacrolimus (LCPT) on Tremor in Stable Kidney Transplant Recipients: The Observational ELIT Study

Once-daily extended-release tacrolimus (LCPT) exhibits increased bioavailability versus immediate-release (IR-TAC) and prolonged release (PR-TAC) tacrolimus. Improvements in tremor were previously reported in a limited number of kidney transplant patients who switched to LCPT. We conducted a non-interventional, non-randomized, uncontrolled, longitudinal, prospective, multicenter study to assess the impact of switching to LCPT on tremor and quality of life (QoL) in a larger population of stable kidney transplant patients. The primary endpoint was change in The Essential Tremor Rating Assessment Scale (TETRAS) score; secondary endpoints included 12-item Short Form Survey (SF-12) scores, tacrolimus trough concentrations, neurologic symptoms, and safety assessments. Subgroup analyses were conducted to assess change in TETRAS score and tacrolimus trough concentration/dose (C0/D) ratio by prior tacrolimus formulation and tacrolimus metabolizer status. Among 221 patients, the mean decrease of TETRAS score after switch to LCPT was statistically significant (p < 0.0001 vs. baseline). There was no statistically significant difference in change in TETRAS score after switch to LCPT between patients who had received IR-TAC and those who had received PR-TAC before switch, or between fast and slow metabolizers of tacrolimus. The overall increase of C0/D ratio post-switch to LCPT was statistically significant (p < 0.0001) and from baseline to either M1 or M3 (both p < 0.0001) in the mITT population and in all subgroups. In the fast metabolizers group, the C0/D ratio crossed over the threshold of 1.05 ng/mL/mg after the switch to LCPT. Other neurologic symptoms tended to improve, and the SF-12 mental component summary score improved significantly. No new safety concerns were evident. In this observational study, all patients had a significant improvement of tremor, QoL and C0/D ratio post-switch to LCPT irrespective of the previous tacrolimus formulation administered (IR-TAC or PR-TAC) and irrespective from their metabolism status (fast or slow metabolizers).

Tacrolimus Drug Exposure Level and Smoking Are Modifiable Risk Factors for Early De Novo Malignancy After Liver Transplantation for Alcohol-Related Liver Disease

De novo malignancy (DNM) is the primary cause of mortality after liver transplantation (LT) for alcohol-related liver disease (ALD). However, data on risk factors for DNM development after LT are limited, specifically in patients with ALD. Therefore, we retrospectively analyzed all patients transplanted for ALD at our center before October 2016. Patients with a post-LT follow-up of <12 months, DNM within 12 months after LT, patients not on tacrolimus in the 1st year post-LT, and unknown smoking habits were excluded. Tacrolimus drug exposure level (TDEL) was calculated by area under the curve of trough levels in the 1st year post-LT. 174 patients received tacrolimus of which 19 (10.9%) patients developed a DNM between 12 and 60 months post-LT. Multivariate cox regression analysis identified TDEL [HR: 1.710 (1.211-2.414); p = 0.002], age [1.158 (1.076-1.246); p < 0.001], number of pack years pre-LT [HR: 1.021 (1.004-1.038); p = 0.014] and active smoking at LT [HR: 3.056 (1.072-8.715); p = 0.037] as independent risk factors for DNM. Tacrolimus dose minimization in the 1st year after LT and smoking cessation before LT might lower DNM risk in patients transplanted for ALD.

Population pharmacokinetic models of tacrolimus in paediatric solid organ transplant recipients: A systematic review

AIMS

This study aimed to provide up-to-date information on paediatric population pharmacokinetic models of tacrolimus and to identify factors influencing tacrolimus pharmacokinetic variability.

METHODS

Systematic searches in the Web of Science, PubMed, Scopus, Science Direct, Cochrane, EMBASE databases and reference lists of articles were conducted from inception to March 2023. All population pharmacokinetic studies of tacrolimus using nonlinear mixed-effect modelling in paediatric solid organ transplant patients were included.

RESULTS

Of the 21 studies reviewed, 62% developed from liver transplant recipients and 33% from kidney transplant recipients. Most studies used a 1-compartment model to describe tacrolimus pharmacokinetics. Body weight was a significant predictor for tacrolimus volume of distribution (Vd/F). The estimated Vd/F for 1-compartment models ranged from 20 to 1890 L, whereas the peripheral volume of distribution (Vp/F) for 2-compartment models was between 290 and 1520 L. Body weight, days post-transplant, CYP3A5 genotype or haematocrit were frequently reported as significant predictors of tacrolimus clearance. The estimated apparent clearance values range between 0.12 and 2.18 L/h/kg, with inter-individual variability from 13.5 to 110.0%. Only 29% of the studies assessed the generalizability of the models with external validation.

CONCLUSION

This review highlights the potential factors, modelling approaches and validation methods that impact tacrolimus pharmacokinetics in a paediatric population. The clinician could predict tacrolimus clearance based on body weight, CYP3A5 genotype, days post-transplant or haematocrit. Further research is required to determine the relationship between pharmacogenetics and tacrolimus pharmacodynamics in paediatric patients and confirm the applicability of nonlinear kinetics in this population.

Protein kinases: drug targets for immunological disorders

Protein kinases play a major role in cellular activation processes, including signal transduction by diverse immunoreceptors. Given their roles in cell growth and death and in the production of inflammatory mediators, targeting kinases has proven to be an effective treatment strategy, initially as anticancer therapies, but shortly thereafter in immune-mediated diseases. Herein, we provide an overview of the status of small molecule inhibitors specifically generated to target protein kinases relevant to immune cell function, with an emphasis on those approved for the treatment of immune-mediated diseases. The development of inhibitors of Janus kinases that target cytokine receptor signalling has been a particularly active area, with Janus kinase inhibitors being approved for the treatment of multiple autoimmune and allergic diseases as well as COVID-19. In addition, TEC family kinase inhibitors (including Bruton's tyrosine kinase inhibitors) targeting antigen receptor signalling have been approved for haematological malignancies and graft versus host disease. This experience provides multiple important lessons regarding the importance (or not) of selectivity and the limits to which genetic information informs efficacy and safety. Many new agents are being generated, along with new approaches for targeting kinases.

Tacrolimus Maintains the Balance of Neutrophil Extracellular Traps by Inducing DNA Methylation of Neutrophils to Reduce Immune Rejection

Immune rejection is a significant concern in organ transplantation, as it can lead to damage to and failure of the transplanted organ. To prevent or treat immune rejection, transplant recipients are commonly administered immunosuppressive drugs. Tacrolimus (FK506) is a widely used immunosuppressive drug in organ transplantation. The excessive formation of neutrophil extracellular traps (NETs) can contribute to inflammation and tissue damage. Although NETs play an antimicrobial role, their overproduction can be harmful. To investigate the mechanism by which FK506 suppresses immune rejection, we utilized HL-60 cells, which were differentiated into neutrophils using DMSO and induced to form NETs with phorbol myristate acetate (PMA), a very efficient and frequently used drug for inducing NET formation. By comparing pre- and post-treatment with FK506, we examined whether FK506 affects the formation of NETs. Various experimental techniques were employed, including confocal imaging for visualizing cell NETs, qPCR and Western blotting for gene and protein expression analyses, ELISAs for protein content detection, and LC-MS/MS for methylation detection. In our study, we discovered that FK506 can enhance DNA methylation, which likely contributes to the reduction in NETs. Genes and proteins related to methylation, namely, DNMT3B and TET3, exhibited significant correlations with methylation. Consistent changes in both genes and proteins suggest that DNMT3B and TET3 are key factors that are influenced by FK506, resulting in enhanced DNA methylation and the potential inhibition of PMA-induced NET production. In summary, we have identified a novel mechanism by which FK506 inhibits NET production through the enhancement of DNA methylation. This finding highlights a new aspect of FK506's immunosuppressive effect. Our results provide valuable insights for clinical research, immunosuppression, and organ preservation strategies.

Case report: Supratherapeutic tacrolimus concentrations with nirmatrelvir/ritonavir in a lung transplant patient: a case report using Rifampin for reversal

Paxlovid (nirmatrelvir/ritonavir) is an antiviral drug used to treat COVID-19, nirmatrelvir, a SARS-CoV-2 main protease inhibitor, works by inhibiting viral replication in the early stages, and ritonavir is a strong cytochrome P450 (CYP) 3A inhibitor that helps the nirmatrelvir reach and maintain the therapeutic concentrations. Paxlovid has a potential risk of drug interaction by elevating the plasma concentration of other drugs metabolized by CYP3A, like tacrolimus. This report examines the case of a 57-year-old female lung transplant patient self-administered Paxlovid for 5 days without discontinuing tacrolimus. She presented to the hospital with symptoms of headache, dizziness, palpitations, abdominal distension, nausea, vomiting, and diarrhea. The patient presented with tacrolimus toxicity and the blood concentration of tacrolimus was measured at 106 ng/mL. Urgent medical intervention was initiated, and Rifampin was administered to induce enzyme activity and rapidly decrease the concentration of tacrolimus. By adjusting the tacrolimus dosage, the final concentration was brought within the appropriate range. Clinical pharmacists should prioritize medication education for transplant patients to prevent severe drug interactions and minimize the impact on the patient's overall well-being.

Long-term normalization of calcineurin activity in model mice rescues Pin1 and attenuates Alzheimer's phenotypes without blocking peripheral T cell IL-2 response

BACKGROUND

Current treatments for Alzheimer's disease (AD) have largely failed to yield significant therapeutic benefits. Novel approaches are desperately needed to help address this immense public health issue. Data suggests that early intervention at the first stages of mild cognitive impairment may have a greater chance for success. The calcineurin (CN)-Pin1 signaling cascade can be selectively targeted with tacrolimus (FK506), a highly specific, FDA-approved CN inhibitor used safely for > 20 years in solid organ transplant recipients. AD prevalence was significantly reduced in solid organ recipients treated with FK506.

METHODS

Time release pellets were used to deliver constant FK506 dosage to APP/PS1 mice without deleterious manipulation or handling. Immunofluorescence, histology, molecular biology, and behavior were used to evaluate changes in AD pathology.

RESULTS

FK506 can be safely and consistently delivered into juvenile APP/PS1 mice via time-release pellets to levels roughly seen in transplant patients, leading to the normalization of CN activity and reduction or elimination of AD pathologies including synapse loss, neuroinflammation, and cognitive impairment. Pin1 activity and function were rescued despite the continuing presence of high levels of transgenic Aβ42. Indicators of neuroinflammation including Iba1 positivity and IL-6 production were also reduced to normal levels. Peripheral blood mononuclear cells (PBMC) obtained during treatment or splenocytes isolated at euthanasia activated normally after mitogens.

CONCLUSIONS

Low-dose, constant FK506 can normalize CNS CN and Pin1 activity, suppress neuroinflammation, and attenuate AD-associated pathology without blocking peripheral IL-2 responses making repurposed FK506 a viable option for early, therapeutic intervention in AD.

Initial exploration of a novel fusion protein, IL-4/IL-34/IL-10, which promotes cardiac allograft survival mice through alloregulation

Immune mediated graft loss still represents a major risk to transplant recipients. Creative approaches to immunosuppression that exploit the recipient's own alloregulatory mechanisms could reduce the need for pharmacologic immunosuppression and potentially induce immune tolerance. In the process of studying recipient derived myeloid derived suppressor cells (MDSCs), we identified key alloregulatory MDSC mechanisms, mediated by isolatable proteins IL-4, IL-34, and IL-10. We sought to purify these proteins and fuse them for subsequent infusion into transplant recipients as a means of inducing an alloregulatory response. In this introductory investigation, we leveraged molecular engineering technology to create a fusion protein (FP) of three cytokine coding sequences of IL-4, IL-34, and IL-10 and demonstrated their expressions by Western Blot analysis. Following purification, we tested whether FP IL-4/IL-34/IL-10 (FP1) can protect heart transplant allografts. Injection of FP1 significantly prolonged allogeneic cardiac graft survival in a dose-dependent fashion and the increase of graft survival time exceeded survival attributable to IL-34 alone. In vitro, MDSCs cells were expanded by FP1 treatment. However, FP1 did not directly inhibit T cell proliferation in vitro. In conclusion, newly developed FP1 improves the graft survival in cardiac transplantation mouse model. Significant additional work to optimize FP1 or include other novel proteins could supplement current treatment options for transplant patients.

Population Pharmacokinetic Analysis for Model-Based Therapeutic Drug Monitoring of Tacrolimus in Chinese Han Heart Transplant Patients

BACKGROUND AND OBJECTIVE

Tacrolimus has become the first-line immunosuppressant for preventing rejection after heart transplantation. The present study aimed to investigate genetic variants and clinical factors affecting the variability of tacrolimus in Chinese Han heart transplant patients using a population pharmacokinetic approach.

METHODS

The retrospective study included 53 hospitalized patients with 547 tacrolimus concentrations for analysis. Nonlinear mixed-effects modeling was used to develop the population pharmacokinetics model for tacrolimus in patients with heart transplants, followed by Monte Carlo simulations to design initial dosing regimens.

RESULTS

In our study, the mutation rate of CYP3A4*18B (C>T) was 27.36%. An oral one-compartment model with first-order absorption and elimination was used to describe the pharmacokinetics of tacrolimus in heart transplant patients. In the final model, the estimated apparent clearance (CL/F) and volume of distribution (V/F) were 532.5 L/h [12.20% interindividual variability, IIV] and 16.87 L (23.16% IIV), respectively. Albumin, postoperative time, and rs2242480 (CYP3A4*18B) gene polymorphisms were the significant covariates affecting CL/F, and creatinine clearance had significant effects on the V/F.

CONCLUSION

The population pharmacokinetic model of tacrolimus in heart transplant patients can better estimate the population and individual pharmacokinetic parameters of patients and can provide a reference for the design of individualized dosing regimens.

The Effect of Voriconazole on Tacrolimus in Kidney Transplantation Recipients: A Real-World Study

Tacrolimus is an immunosuppressant with a narrow therapeutic window. Tacrolimus exposure increased significantly during voriconazole co-therapy. The magnitude of this interaction is highly variable, but it is hard to predict quantitatively. We conducted a study on 91 kidney transplantation recipients with voriconazole co-therapy. Furthermore, 1701 tacrolimus concentration data were collected. Standard concentration adjusted by tacrolimus daily dose (C/D) and weight-adjusted standard concentration (CDW) increased to 6 times higher during voriconazole co-therapy. C/D and CDW increased with voriconazole concentration. Patients with the genotype of CYP3A5 *3/*3 and CYP2C19 *2/*2 or *2/*3 were more variable at the same voriconazole concentration level. The final prediction model could explain 54.27% of the variation in C/D and 51.11% of the variation in CDW. In conclusion, voriconazole was the main factor causing C/D and CDW variation, and the effect intensity should be quantitative by its concentration. Kidney transplant recipients with CYP3A5 genotype of *3/*3 and CYP2C19 genotype of *2/*2 and *2/*3 should be given more attention during voriconazole co-therapy. The prediction model established in this study may help to reduce the occurrence of rejection.

Genetic factors underlying tacrolimus intolerance after liver transplantation

Background

Tacrolimus (FK506) is the cornerstone of immunosuppression after liver transplantation (LT), however, clinically, switching from FK506 to cyclosporine (SFTC) is common in LT patients with tacrolimus intolerance. The aim of this study was to investigate the genetic risk of patients with tacrolimus intolerance.

Methods

A total of 114 LT patients were enrolled in this retrospective study. SNPs were genotyped using Infinium Human Exome-12 v1.2 BeadChip, and genome-wide gene expression levels were profiled using Agilent G4112F array.

Results

SFTC was a potential risk factor of dyslipidemia (OR=4.774[1.122-20.311], p = 0.034) and insulin resistance (IR) (OR=6.25[1.451-26.916], p = 0.014), but did not affect the survival of LT patients. Differential expression analysis showed donor CYP3A5, CYP2C9, CFTR, and GSTP1, four important pharmacogenetic genes were significantly up-regulated in the tacrolimus intolerance group. Twelve SNPs of these four genes were screened to investigate the effects on tacrolimus intolerance. Regression analysis showed donor rs4646450 (OR=3.23 [1.22-8.60] per each A allele, p = 0.01), donor rs6977165 (OR=6.44 [1.09-37.87] per each C allele, p = 0.02), and donor rs776746 (OR=3.31 [1.25-8.81] per each A allele, p = 0.01) were independent risk factors of tacrolimus intolerance.

Conclusions

These results suggested that SFTC was a potential risk factor for dyslipidemia and IR after LT. Besides, rs4646450, rs6977165, and rs776746 of CYP3A5 might be the underlying genetic risks of tacrolimus intolerance. This might help transplant surgeons make earlier clinical decisions about the use of immunosuppression.

Recent advances and limitations of mTOR inhibitors in the treatment of cancer

The PI3K-Akt-mechanistic (formerly mammalian) target of the rapamycin (mTOR) signaling pathway is important in a variety of biological activities, including cellular proliferation, survival, metabolism, autophagy, and immunity. Abnormal PI3K-Akt-mTOR signalling activation can promote transformation by creating a cellular environment conducive to it. Deregulation of such a system in terms of genetic mutations and amplification has been related to several human cancers. Consequently, mTOR has been recognized as a key target for the treatment of cancer, especially for treating cancers with elevated mTOR signaling due to genetic or metabolic disorders. In vitro and in vivo, rapamycin which is an immunosuppressant agent actively suppresses the activity of mTOR and reduces cancer cell growth. As a result, various sirolimus-derived compounds have now been established as therapies for cancer, and now these medications are being investigated in clinical studies. In this updated review, we discuss the usage of sirolimus-derived compounds and other drugs in several preclinical or clinical studies as well as explain some of the challenges involved in targeting mTOR for treating various human cancers.

Tacrolimus (FK506) for induction of remission in corticosteroid-refractory ulcerative colitis

BACKGROUND

There are a limited number of treatment options for people with corticosteroid-refractory ulcerative colitis. Animal models of inflammatory bowel disease and uncontrolled studies in humans suggest that tacrolimus may be an effective treatment for ulcerative colitis.

OBJECTIVES

To evaluate the efficacy and safety of tacrolimus for induction of remission in people with corticosteroid-refractory ulcerative colitis.

SEARCH METHODS

We searched the Cochrane Gut group specialised register, CENTRAL, MEDLINE (PubMed), Embase, Clinicaltrials.gov and WHO ICTRP from inception to October 2021 to identify relevant randomised controlled trials (RCT).

SELECTION CRITERIA

Two review authors independently selected potentially relevant studies to determine eligibility based on the prespecified criteria.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and analysed them using Review Manager Web. The primary outcomes were induction of remission and clinical improvement, as defined by the studies and expressed as a percentage of the participants randomised (intention-to-treat analysis).

MAIN RESULTS

This review included five RCTs with 347 participants who had active ulcerative colitis or ulcerative proctitis. The duration of intervention varied between two weeks and eight weeks. Tacrolimus versus placebo Tacrolimus (oral and rectal) may be superior in achieving clinical remission compared to placebo (oral and rectal) (14/87 participants with tacrolimus versus 1/61 participants with placebo; risk ratio (RR) 3.76, 95% confidence interval (CI) 1.03 to 13.73; 3 studies). These results are of low certainty due to imprecision and risk of bias. Tacrolimus (oral and rectal) may be superior for clinical improvement compared to placebo (oral and rectal) (45/87 participants with tacrolimus versus 7/61 participants with placebo; RR 4.47, 95% CI 2.15 to 9.29; 3 studies). These results are of low certainty due to imprecision and risk of bias. The evidence is very uncertain about the effects of tacrolimus (oral and rectal) on serious adverse events compared to placebo (oral and rectal) (2/87 participants with tacrolimus versus 0/61 participants with placebo; RR 2.44, 95% CI 0.12 to 48.77; 3 studies). These results are of very low certainty due to high imprecision and risk of bias. Tacrolimus versus ciclosporin One study compared oral tacrolimus to intravenous ciclosporin, with an intervention lasting two weeks and 113 randomised participants. The evidence is very uncertain about the effect of tacrolimus on achievement of clinical remission compared to ciclosporin (15/33 participants with tacrolimus versus 24/80 participants with ciclosporin; RR 1.52, 95% CI 0.92 to 2.50). The results are of very low certainty due to risk of bias and high imprecision. The evidence is very uncertain about the effect of tacrolimus on clinical improvement compared to intravenous ciclosporin (23/33 participants with tacrolimus versus 62/80 participants with ciclosporin; RR 0.90, 95% CI 0.70 to 1.16). The results are of very low certainty due to risk of bias and imprecision. Tacrolimus versus beclometasone One study compared tacrolimus suppositories with beclometasone suppositories in an intervention lasting four weeks with 88 randomised participants. There may be little to no difference in achievement of clinical remission (16/44 participants with tacrolimus versus 15/44 participants with beclometasone; RR 1.07, 95% CI 0.60 to 1.88). The results are of low certainty due to high imprecision. There may be little to no difference in clinical improvement when comparing tacrolimus suppositories to beclometasone suppositories (22/44 participants with tacrolimus versus 22/44 with beclometasone; RR 1.00, 95% CI 0.66 to 1.52). The results are of low certainty due to high imprecision. There may be little to no difference in serious adverse events when comparing tacrolimus suppositories to beclometasone suppositories (1/44 participants with tacrolimus versus 0/44 with beclometasone; RR 3.00, 95% CI 0.13 to 71.70). These results are of low certainty due to high imprecision. There may be little to no difference in total adverse events when comparing tacrolimus suppositories to beclometasone suppositories (21/44 participants with tacrolimus versus 14/44 participants with beclometasone; RR 1.50, 95% CI 0.88 to 2.55). These results are of low certainty due to high imprecision. No secondary outcomes were reported for people requiring rescue medication or to undergo surgery.

AUTHORS' CONCLUSIONS

There is low-certainty evidence that tacrolimus may be superior to placebo for achievement of clinical remission and clinical improvement in corticosteroid-refractory colitis or corticosteroid-refractory proctitis. The evidence is very uncertain about the effect of tacrolimus compared to ciclosporin for achievement of clinical remission or clinical improvement. There may be no difference between tacrolimus and beclometasone for inducing clinical remission or clinical improvement. The cohorts studied to date were small, with missing data sets, offered short follow-up and the clinical endpoints used were not in line with those suggested by regulatory bodies. Therefore, no clinical practice conclusions can be made. This review highlights the need for further research that targets the relevant clinical questions, uses appropriate trial methodology and reports key findings in a systematic manner that facilitates future integration of findings with current evidence to better inform clinicians and patients. Future studies need to be adequately powered and of pertinent duration so as to capture the efficacy and effectiveness of tacrolimus in the medium to long term. Well-structured efficacy studies need to be followed up by long-term phase 4 extensions to provide key outputs and inform in a real-world setting.

Development and Validation of A Liquid Chromatography-Tandem Mass Spectrometry Method to Simultaneously Measure Tacrolimus and Everolimus Concentrations in Kidney Allograft Biopsies After Kidney Transplantation

BACKGROUND

Therapeutic drug monitoring is necessary for immunosuppressive therapy with tacrolimus and everolimus after kidney transplantation. Several studies have suggested that the concentrations of immunosuppressive agents in allografts may better reflect clinical outcomes than whole blood concentrations. This study aimed to develop a method for the simultaneous quantification of tacrolimus and everolimus concentrations in clinical biopsy samples and investigate their correlation with histopathological findings in kidney transplant recipients.

METHODS

Fourteen biopsy samples were obtained from kidney transplant recipients at 3 months after transplantation. Kidney allograft concentrations (Ctissue) of tacrolimus and everolimus were measured by liquid chromatography-tandem mass spectrometry, and the corresponding whole blood trough concentrations (C0) were obtained from clinical records.

RESULTS

The developed method was validated over a concentration range of 0.02-2.0 ng/mL for tacrolimus and 0.04-4.0 ng/mL for everolimus in kidney tissue homogenate. The Ctissue of tacrolimus and everolimus in kidney biopsies ranged from 21.0 to 86.7 pg/mg tissue and 33.5-105.0 pg/mg tissue, respectively. Dose-adjusted Ctissue of tacrolimus and everolimus was significantly correlated with the dose-adjusted C0 (P < 0.0001 and P = 0.0479, respectively). No significant association was observed between the Ctissue of tacrolimus and everolimus and the histopathologic outcomes at 3 months after transplantation.

CONCLUSIONS

This method could support further investigation of the clinical relevance of tacrolimus and everolimus allograft concentrations after kidney transplantation.

Impact of COVID-19 Infection on Liver Transplant Recipients: Does It Make Any Difference?

The first case of coronavirus disease 2019 (COVID-19) was diagnosed in December 2019 in Wuhan, China. Since then, this novel infectious disease, caused by the severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), has grown into a pandemic with over 330 million infected individuals worldwide, many of them with innate or acquired immunosuppression.

Liver transplantation (LT) is offered as a curative therapy for end-stage liver disease as well as for acute liver failure cases. Advances in immunosuppressive therapy decreased the rates of acute and chronic graft rejection, significantly improving the quality of life.

Liver transplant recipients are considered at particularly high risk for developing critical COVID-19 infection because of their chronic immunosuppressed state. Available data are heterogeneous, and the mortality rate is variably reported in the literature. There is controversy regarding whether their immunosuppressive status is a risk or a protective factor for developing severe respiratory disease. Moreover, the mechanism of action is still unclear.

We report the clinical outcome of three liver transplant recipients who had COVID-19 pneumonia at different moments following liver transplantation. All patients received a standard immunosuppression regimen and specific antiviral therapy, requiring no invasive mechanical ventilation. They were discharged from the hospital with no long-term COVID-19 complications.

Mechanism of Action and Efficacy of Immunosupressors in Lupus Nephritis

Approximately 70% of the patients with systemic lupus erythematosus will have clinical evidence of kidney damage during their evolution. Patients with impaired renal function at onset and those with recurrent flares have a poor prognosis. Understanding the mechanism of action of immunosuppressants is essential for proper prescription. Steroids inhibit the DNA sequence that promotes the release of inflammatory cytokines. Phosphoramide mustard, metabolite of cyclophosphamide, cross-link with the DNA, causing the aggregation of an alkyl group, causing cell death. Mycophenolate inhibits inosine monophosphate dehydrogenase, prevents de novo synthesis of guanine, inducing cell arrest in S phase. Azathioprine blocks the synthesis of purines and induces apoptosis. Calcineurin inhibitors prevent the dephosphorylation of NFAT and reduce the production of interleukin 2. Antimalarials alter the enzymatic release of lysosomes by increasing intravesicular pH. The mechanism of action of rituximab is related to complement-dependent cytotoxicity and the elimination of anti-CD20-labeled B cells. Progress in the knowledge and management of low doses of steroids may change the current paradigm and reduce the frequency of related adverse events. Mycophenolate seems to be a better choice than cyclophosphamide for induction, it is also preferred over azathioprine as a maintenance immunosuppressive agent, although azathioprine is preferred in women with a desire for conception, those pregnant, or with low resources. For treatment-resistant cases, tacrolimus, rituximab or belimumab may be effective. Ongoing clinical trials with new drugs offer promising results.

Exosomes Secreted by Adipose-Derived Stem Cells Following FK506 Stimulation Reduce Autophagy of Macrophages in Spine after Nerve Crush Injury

Macrophages emerge in the milieu around innervated neurons after nerve injuries. Following nerve injury, autophagy is induced in macrophages and affects the regulation of inflammatory responses. It is closely linked to neuroinflammation, while the immunosuppressive drug tacrolimus (FK506) enhances nerve regeneration following nerve crush injury and nerve allotransplantation with additional neuroprotective and neurotrophic functions. The combined use of FK506 and adipose-derived stem cells (ADSCs) was employed in cell therapy for organ transplantation and vascularized composite allotransplantation. This study aimed to investigate the topical application of exosomes secreted by ADSCs following FK506 treatment (ADSC-F-exo) to the injured nerve in a mouse model of sciatic nerve crush injury. Furthermore, isobaric tags for relative and absolute quantitation (iTRAQ) were used to profile the potential exosomal proteins involved in autophagy. Immunohistochemical analysis revealed that nerve crush injuries significantly induced autophagy in the dorsal root ganglia and dorsal horn of the spinal segments. Locally applied ADSC-F-exo significantly reduced autophagy of macrophages in the spinal segments after nerve crush injury. Proteomic analysis showed that of the 22 abundant exosomal proteins detected in ADSC-F-exo, heat shock protein family A member 8 (HSPA8) and eukaryotic translation elongation factor 1 alpha 1 (EEF1A1) are involved in exosome-mediated autophagy reduction.

FK506 induces lung lymphatic endothelial cell senescence and downregulates LYVE-1 expression, with associated decreased hyaluronan uptake

BACKGROUND

Therapeutic lymphangiogenesis in an orthotopic lung transplant model has been shown to improve acute allograft rejection that is mediated at least in part through hyaluronan drainage. Lymphatic vessel endothelial hyaluronan receptor (LYVE-1) expressed on the surface of lymphatic endothelial cells plays important roles in hyaluronan uptake. The impact of current immunosuppressive therapies on lung lymphatic endothelial cells is largely unknown. We tested the hypothesis that FK506, the most commonly used immunosuppressant after lung transplantation, induces lung lymphatic endothelial cell dysfunction.

METHODS

Lung lymphatic endothelial cells were cultured in vitro and treated with FK506. Telomerase activity was measured using the TRAP assay. Protein expression of LYVE-1 and senescence markers p21 and β-galactosidase was assessed with western blotting. Matrigel tubulation assay were used to investigate the effects of FK506 on TNF-α-induced lymphangiogenesis. Dual luciferase reporter assay was used to confirm NFAT-dependent transcriptional regulation of LYVE-1. Flow cytometry was used to examine the effects of FK506 on LYVE-1 in precision-cut-lung-slices ex vivo and on hyaluronan uptake in vitro.

RESULTS

In vitro, FK506 downregulated telomerase reverse transcriptase expression, resulting in decreased telomerase activity and subsequent induction of p21 expression and cell senescence. Treatment with FK506 decreased LYVE-1 mRNA and protein levels and resulted in decreased LEC HA uptake. Similar result showing reduction of LYVE-1 expression when treated with FK506 was observed ex vivo. We identified a putative NFAT binding site on the LYVE-1 promoter and cloned this region of the promoter in a luciferase-based reporter construct. We showed that this NFAT binding site regulates LYVE-1 transcription, and mutation of this binding site blunted FK506-dependent downregulation of LYVE-1 promoter-dependent transcription. Finally, FK506-treated lymphatic endothelial cells show a blunted response to TNF-α-mediated lymphangiogenesis.

CONCLUSION

FK506 alters lymphatic endothelial cell molecular characteristics and causes lymphatic endothelial cell dysfunction in vitro and ex vivo. These effects of FK506 on lymphatic endothelial cell may impair the ability of the transplanted lung to drain hyaluronan macromolecules in vivo. The implications of our findings on the long-term health of lung allografts merit more investigation.

Long-term outcome of a randomised controlled trial comparing tacrolimus with mycophenolate mofetil as induction therapy for active lupus nephritis

OBJECTIVES

To report the 10-year outcome of lupus nephritis (LN) treated with mycophenolate mofetil (MMF) or tacrolimus (TAC) induction in a randomised controlled trial.

METHODS

Patients with active LN were treated with MMF or TAC combined with high-dose prednisolone. Responders were switched to azathioprine (AZA) at month 6. Clinical outcomes at 10 years (renal flares, renal function decline and mortality) were assessed. Factors affecting prognosis were studied by Cox regression. Urine protein-to-creatinine ratio (uPCr) and estimated glomerular filtration rate (eGFR) at different time points were evaluated for their prediction of a poor prognosis by receiver operating characteristic (ROC) analysis.

RESULTS

150 patients were studied (age 35.5±12.8 years). Complete renal response rate was similar between MMF (59%) and TAC-treated patients (62%; p=0.71). AZA maintenance was given to 79% patients. After 118.2±42 months, proteinuric and nephritic renal flares occurred in 34% and 37% of the MMF, and 53% and 30% of the TAC groups of patients, respectively (p=0.49). The cumulative incidence of a composite outcome of ↓eGFR ≥30%, chronic kidney disease stage 4/5 or death at 10 years was 33% in both groups (p=0.90). Factors independently associated with a poor renal prognosis were first-time LN (HR 0.12 (0.031 to 0.39); p=0.01), eGFR (HR 0.98 (0.96 to 0.99); p=0.008) and no response at month 6 (HR 5.18 (1.40 to 19.1); p=0.01). ROC analysis revealed an uPCr >0.75 and eGFR of <80 mL/min at month 18 best predicted a poor renal prognosis.

CONCLUSIONS

Long-term data confirmed non-inferiority of TAC to MMF as induction therapy of LN. An uPCr≤0.75 and eGFR of ≥80 mL/min at month 18 best predicted a favourable 10-year outcome and may be suitable targets for induction/consolidation therapy.

TRIAL REGISTRATION NUMBER

NCT00371319.

Tacrolimus induces short-term but not long-term clinical response in inflammatory bowel disease

BACKGROUND

Tacrolimus is a calcineurin inhibitor commonly used for prophylaxis of rejection in renal and liver transplantation. There are limited but favourable data regarding its possible use in patients with inflammatory bowel disease (IBD).

AIMS

To evaluate the efficacy and safety of tacrolimus in patients with IBD in clinical practice.

METHODS

We performed a retrospective, multicentre study in 22 centres in Spain. All adult patients who received oral tacrolimus for luminal or perianal IBD were included. Clinical response was assessed by Harvey-Bradshaw index and partial Mayo score after 3 months. Perianal disease was evaluated by fistula drainage assessment.

RESULTS

One hundred and forty-three patients were included (mean age 38 years; 51% male; median disease duration 110 months). In ulcerative colitis (UC) (n = 58), the partial Mayo score decreased after 3 months from median 6 to 3 (P = 0.0001), whereas in Crohn's disease (CD) (n = 85), the Harvey-Bradshaw index decreased after 3 months from median 9 to 7 (P = 0.011). In CD patients, blood tacrolimus concentrations during induction (>10 ng/mL vs <10 ng/mL; odds ratio 0.23, 95% CI 0.05-0.87) and the concomitant use of thiopurines (odds ratio 0.18, 95% CI 0.04-0.81) were associated with lower clinical disease activity at 3 months. Of 62 patients with perianal disease, complete closure was observed in 8% (n = 5) of patients with perianal fistulas, with 34% (n = 21) showing partial response. Treatment was maintained for a median of 6 months (IQR, 2-16). After a median clinical follow-up of 24 months (IQR, 15-57), the rate of treatment-related adverse events was 34%, correlating with blood drug concentrations (P = 0.021). Finally, 120 patients (84%) discontinued tacrolimus, usually due to absence or loss of response. Three patients (2%) were subsequently diagnosed with cancer. The overall rate of surgery was 39%, with a 33% colectomy rate in UC.

CONCLUSIONS

Tacrolimus shows a clinical benefit in both CD and UC after 3 months of treatment, but its long-term effectiveness and frequent adverse events remain relevant issues in clinical practice.

Toward a robust tool for pharmacokinetic-based personalization of treatment with tacrolimus in solid organ transplantation: A model-based meta-analysis approach

AIMS

The objective of this study is to develop a generic model for tacrolimus pharmacokinetics modelling using a meta-analysis approach, that could serve as a first step towards a prediction tool to inform pharmacokinetics-based optimal dosing of tacrolimus in different populations and indications.

METHODS

A systematic literature review was performed and a meta-model developed with NONMEM software using a top-down approach. Historical (previously published) data were used for model development and qualification. In-house individual rich and sparse tacrolimus blood concentration profiles from adult and paediatric kidney, liver, lung and heart transplant patients were used for model validation. Model validation was based on successful numerical convergence, adequate precision in parameter estimation, acceptable goodness of fit with respect to measured blood concentrations with no indication of bias, and acceptable performance of visual predictive checks. External validation was performed by fitting the model to independent data from 3 external cohorts and remaining previously published studies.

RESULTS

A total of 76 models were found relevant for meta-model building from the literature and the related parameters recorded. The meta-model developed using patient level data was structurally a 2-compartment model with first-order absorption, absorption lag time and first-time varying elimination. Population values for clearance, intercompartmental clearance, central and peripheral volume were 22.5 L/h, 24.2 L/h, 246.2 L and 109.9 L, respectively. The absorption first-order rate and the lag time were fixed to 3.37/h and 0.33 hours, respectively. Transplanted organ and time after transplantation were found to influence drug apparent clearance whereas body weight influenced both the apparent volume of distribution and the apparent clearance. The model displayed good results as regards the internal and external validation.

CONCLUSION

A meta-model was successfully developed for tacrolimus in solid organ transplantation that can be used as a basis for the prediction of concentrations in different groups of patients, and eventually for effective dose individualization in different subgroups of the population.

Validation and evaluation of four sample preparation methods for the quantification of intracellular tacrolimus in peripheral blood mononuclear cells by UHPLC-MS/MS

Rejection and toxicity occur despite monitoring of tacrolimus blood levels during clinical routine. The intracellular concentration in lymphocytes could be a better reflection of the tacrolimus exposure. Four extraction methods for tacrolimus in peripheral blood mononuclear cells were validated and evaluated with UHPLC-MS/MS. Methods based on protein precipitation (method 1), solid phase extraction (method 2), phospholipids and proteins removal (method 3) and liquid-liquid extraction (method 4) were evaluated on linearity, lower limit of quantification (LLOQ), imprecision and bias. Validation was completed for the methods within these requirements, adding matrix effect and recovery. Linearity was 0.126 (LLOQ)-15 µg/L, 0.504 (LLOQ)-15 µg/L and 0.298 (LLOQ)-15 µg/L with method 1, 2 and 3, respectively. With method 4 non-linearity and a LLOQ higher than 0.504 µg/L were observed. Inter-day imprecision and bias were ≤4.6%, ≤10.9%; ≤6.8%, ≤-11.2%; ≤9.4%, ≤10.3% and ≤44.6%, ≤23.1%, respectively, with methods 1, 2, 3 and 4. Validation was completed for method 1 and 3 adding matrix effect (7.6%; 15.0%) and recovery (8.9%; 10.8%), respectively. The most suitable UHPLC-MS/MS method for quantification of intracellular tacrolimus was protein precipitation due to the best performance characteristics and the least time-consuming rate and complexity.

Indications and efficacy of conversion from tacrolimus- to sirolimus-based immunosuppression in pediatric patients who underwent liver transplantation for unresectable hepatoblastoma

SRL-based immunosuppressive strategies in pediatric liver transplantation are not clearly defined, especially within the first year after liver transplant. TAC is the more common, traditional immunosuppressant used. However, SRL may modulate TAC-associated kidney injury and may also have antiproliferative properties that are valuable in the management of patients following liver transplantation for HB. We sought to determine whether early conversion from TAC to SRL was safe, effective, and beneficial in a subset of liver transplant recipients with unresectable HB exposed to CDDP-based chemotherapy. Between 2008 and 2013, six patients were transplanted for unresectable HB. All patients received at least one cycle of CDDP-based chemotherapy prior to transplant. All patients were switched from TAC- to SRL-based immunosuppression within 1 year of transplant. Five patients had improvement in their mGFR, while one patient had a slight decline. The improvement in mGFR was statistically significant. No adverse events were identified. Three patients had BPAR that responded to pulsed steroids. Historical controls showed similar rates of BPAR within the first year after transplant. There were no identified HB recurrences in the follow-up time period. Conversion from TAC to SRL appears to be safe and effective in this selected group of pediatric liver transplant recipients without adverse reaction or HB recurrences.

[Clinical effect of tacrolimus combined with glucocorticoid in the treatment of IgA nephropathy in children]

OBJECTIVE

To study the clinical effect and safety of tacrolimus (TAC) combined with glucocorticoid (GC) versus mycophenolate mofetil (MMF) combined with GC in the treatment of primary IgA nephropathy (IgAN) in children.

METHODS

A retrospective analysis was performed for the clinical data of children with primary IgAN confirmed by renal pathology between January 2012 and December 2017. These children were divided into TAC group and MMF group according to the treatment regimen. Their clinical data before treatment and at 1, 3, and 6 months of treatment were collected, and the remission status of IgAN and adverse reactions were compared between the two groups.

RESULTS

A total of 43 children who met the inclusion criteria were enrolled, with 15 children in the TAC group and 28 children in the MMF group. At 1 month of treatment, there was no significant difference in the remission status between the two groups (P>0.05). At 3 and 6 months of treatment, the TAC group had a significantly better remission status than the MMF group (P<0.05). At 1 month of treatment, the TAC group had higher serum albumin levels than the MMF group (P<0.05). Both groups had a significant increase in serum albumin levels at each time point after treatment (P<0.0083) and a significant increase in the glomerular filtration rate (GFR) at 3 and 6 months of treatment (P<0.0083). There was no significant difference in the overall incidence rate of adverse reactions between the two groups (P>0.05), but fungal infection was observed in one child from the TAC group.

CONCLUSIONS

TAC combined with GC can effectively reduce urinary protein in children with primary IgAN, and it has a better short-term clinical effect than MMF combined with GC, with good safety.

Dual regulation between the two-component system PhoRP and AdpA regulates antibiotic production in Streptomyces

Antibiotic production during secondary metabolism in Streptomyces spp. is elaborately controlled by multiple environmental signals and intracellular cascades. These include the two-component system PhoRP responding to phosphate starvation and a conserved signaling pathway mediated by the pleiotropic regulator AdpA. However, little information exists about how these two pathways work together for secondary metabolite production of Streptomyces. Herein, we report the dual regulation from the phosphate starvation-responsive regulator PhoP and AdpA on atrA promoter (atrAp) for the production of daptomycin, an antibiotic produced by Streptomyces roseosporus. We found that PhoP directly binds to atrAp, positively regulates atrA expression and thus daptomycin production. We also observed positive auto-regulation of phoRP expression during fermentation for daptomycin production. Moreover, partial overlap between PhoP- and AdpA-binding sites on atrAp was observed, which results in partial competitive binding between these two regulators. This partial overlapping and competition between PhoP and AdpA was further confirmed by mutations and binding assays. In summary, our findings have revealed dual regulation of PhoP and AdpA on the same promoter for antibiotic production in Streptomyces. This mechanism would be beneficial to further environment-responsive fermentation optimization for antibiotic production.

Drug-Drug Interaction Study of Apixaban with Cyclosporine and Tacrolimus in Healthy Volunteers

Apixaban is metabolized by cytochrome P450 (CYP) 3A4 in the liver and intestine, undergoes direct intestinal excretion, and is a substrate to permeability glycoprotein (P-gp) and breast cancer resistance protein (BCRP) transporters. We examined the drug interactions between cyclosporine and tacrolimus (combined inhibitors of CYP3A4, P-gp, and BCRP) with apixaban in 12 healthy adult male volunteers. Apixaban 10 mg was administered orally alone, in combination with 100 mg cyclosporine or 5 mg tacrolimus. Co-administration with cyclosporine resulted in increase in apixaban maximum plasma concentration (Cmax ) and area under the plasma concentration-time curve from time zero to the last quantifiable concentration (AUC(0-tlast) ) with associated geometric mean ratios (GMRs) and 90% confidence intervals (CIs) of 143% (112, 183) and 120% (97, 148), respectively. Co-administration with tacrolimus resulted in reduction in apixaban Cmax and AUC(0-tlast) with associated GMRs (90% CI) of 87% (69, 112) and 78% (63, 97), respectively. The observed changes in apixaban exposure margins with cyclosporine or tacrolimus are within the range of the historical clinical development program, therefore, apixaban dose adjustments are not warranted.

Long-lasting immunosuppressive effects of tacrolimus-loaded micelle NK61060 in preclinical arthritis and colitis models

AIM

Tacrolimus (TAC) is an important drug for inflammatory diseases. However, TAC has several limitations, such as variable trough concentrations among individuals and a high medication frequency. In this study, we created NK61060, a novel micellar TAC formulation, to circumvent these disadvantages.

MATERIALS & METHODS

Immunosuppressive activity of NK61060 was determined in the collagen-induced arthritis rat model, mannan-induced arthritis mouse model and dextran sodium sulfate-induced colitis mouse model. The pharmacokinetics and toxicology of NK61060 were evaluated in those models.

RESULTS

In arthritis and colitis models, NK61060 exhibited superior immunosuppressive activity compared with that of TAC. Pharmacokinetic and toxicological analyses indicated that NK61060 had a wider safety margin and could be administered at a reduced medication frequency.

CONCLUSION

NK61060 mitigates the trough concentration variability and the medication frequency and it may be a safer and more effective option for use in clinical settings. Further studies are needed to determine its clinical usefulness.

Evaluation of Flexible Tacrolimus Drug Concentration Monitoring Approach in Patients Receiving Extended-Release Once-Daily Tacrolimus Tablets

The majority of United States kidney transplant patients are treated with tacrolimus, a drug effective in preventing graft rejection, but with a narrow therapeutic range, necessitating close monitoring to avoid increased risks of transplant rejection or toxicity if the tacrolimus concentration is too low or too high, respectively. The trough drug concentration tests are time sensitive; patients treated on a twice-daily basis have blood draws exactly 12 hours after their previous dose. The schedule's rigidity causes problems for both patients and health care providers. Novel once-daily tacrolimus formulations such as LCPT (an extended-release tablet by Veloxis Pharmaceuticals, Inc., Cary, North Carolina) have allowed for blood draws on a once-daily basis; however, even that schedule can be restrictive. Results from tests taken either before or after that 24-hour target time may be discarded, or worse, may lead to inappropriate dose changes. Data from ASTCOFF, a phase 3B pharmacokinetic clinical trial (NCT02339246), demonstrated that the unique pharmacokinetic curve of LCPT may allow for a therapeutic monitoring window that extends for 3 hours before or after the 24-hour monitoring target. Furthermore, important tools to help clinicians interpret these levels, such as formulas to estimate the 24-hour trough level if an alternative monitoring time is used, were constructed from these data. These study results give treating clinicians access to data that allow them to safely use and monitor LCPT in their patients and expand the body of evidence surrounding differentiation and practical application of the novel LCPT tacrolimus formulation.

Calcineurin inhibitors in systemic lupus erythematosus

The calcineurin inhibitors (CNIs) belong to a group of immunosuppressive agents that block T-cell activation through the suppression of the calcium/calcimodulin-dependent phosphatase calcineurin. Agents such as cyclosporine A (CSA) and tacrolimus (TAC) have long been used in patients with systemic lupus erythematosus (SLE). TAC is preferred to CSA in SLE because of the lower frequency of cosmetic, hypertensive and dyslipidemic adverse effects. Recent randomised controlled trials have demonstrated noninferiority of TAC to mycophenolate mofetil (MMF) or cyclophosphamide (CYC) for induction therapy of lupus nephritis. Low-dose combination of TAC and MMF has also been shown to outperform CYC pulses in inducing remission of lupus nephritis in Chinese patients. TAC does not affect fertility and is relatively safe in pregnancy. In SLE patients who are intolerant or refractory to conventional immunosuppressives, or where contraindications to other immunosuppressive agents exist, TAC is an alternative option. However, the therapeutic window of TAC is narrow, and drug level monitoring is required to ensure drug exposure and minimise toxicities. Current evidence of TAC in lupus nephritis is limited to 6 months, and its long-term safety as maintenance therapy of SLE is yet to be determined. Newer chemical analogues of CNIs, such as voclosporin, with less variable plasma concentration are being tested in lupus nephritis.

Tacrolimus Eye Drops as Adjunct Therapy in Severe Corneal Endothelial Rejection Refractory to Corticosteroids

PURPOSE

To evaluate the safety and efficacy of tacrolimus eye drops as adjunctive therapy in the treatment of severe corneal endothelial rejection after penetrating keratoplasty refractory to corticosteroids.

METHODS

In this prospective interventional case series, 11 eyes of 11 patients assessed for severe corneal endothelial rejection, with an inadequate response to topical, local, and systemic corticosteroids, were treated with either 0.01% or 0.05% tacrolimus eye drops 4 times daily. Improvement in signs of rejection, visual function, and development of complications were monitored.

RESULTS

The duration of steroid treatment before intervention was 8.1 ± 1.4 days (range = 7-11). Patients were subsequently administered topical tacrolimus 0.01% or 0.05% qid. The time to clinical improvement was 10.3 ± 3.4 days (range = 3-17). The time to rejection reversal was 27.8 ± 16.3 days (range = 7-52). After 3 months, 10 patients (90.8%) demonstrated clinical improvement, and complete restoration of graft clarity was achieved in 5 patients (45.4%). In responsive cases, steroid therapy was successfully tapered off after 60.2 ± 19.7 days (range = 36-93). The best spectacle-corrected visual acuity improved from 1.7 ± 0.9 to 0.8 ± 0.5 logMAR (P = 0.0016). Reported side effects included stinging on drop instillation and punctate epithelial keratopathy.

CONCLUSIONS

Tacrolimus eye drops may be able to play an adjunctive therapeutic role in patients with severe corneal endothelial rejection refractory to conventional steroid treatment. Controlled studies are needed to further investigate the role of tacrolimus in this setting.

Assessment of the synergic effect of immunomodulation on nerve repair using multiparametric magnetic resonance imaging

INTRODUCTION

The immune system plays a pivotal role in nerve injury. The aim of this study was to determine the role of multiparametric magnetic resonance imaging (MRI) in evaluation of the synergic effect of immunomodulation on nerve regeneration in neurotmesis.

METHODS

Rats with sciatic nerve neurotmesis and surgical repair underwent serial multiparametric MR examinations over an 8-week period after subepineurial microinjection of lipopolysaccharide (LPS) and subsequent subcutaneous injection of FK506 or subepineurial microinjection of LPS or phosphate-buffered saline (PBS) alone.

RESULTS

Nerves treated with immunomodulation showed more prominent regeneration than those treated with LPS or PBS alone and more rapid restoration toward normal T2, fractional anisotropy (FA), and radial diffusivity (RD) values than nerves injected with LPS or PBS.

DISCUSSION

Nerves treated with immunomodulation exert synergic beneficial effects on nerve regeneration that can be predicted by T2 measurements and FA and RD values. Muscle Nerve 57: E38-E45, 2018.