Biomarkers in osteoarthritis: current status and outlook - the FNIH Biomarkers Consortium PROGRESS OA study

Currently, no disease-modifying therapies are approved for osteoarthritis (OA) use. One obstacle to trial success in this field has been our existing endpoints' limited validity and responsiveness. To overcome this impasse, the Foundation for the NIH OA Biomarkers Consortium is focused on investigating biomarkers for a prognostic context of use for subsequent qualification through regulatory agencies. This narrative review describes this activity and the work underway, focusing on the PROGRESS OA study.

Reverse Engineering of Digital Measures: Inviting Patients to the Conversation

Background

Digital measures offer an unparalleled opportunity to create a more holistic picture of how people who are patients behave in their real-world environments, thereby establishing a better connection between patients, caregivers, and the clinical evidence used to drive drug development and disease management. Reaching this vision will require achieving a new level of co-creation between the stakeholders who design, develop, use, and make decisions using evidence from digital measures.

Summary

In September 2022, the second in a series of meetings hosted by the Swiss Federal Institute of Technology in Zürich, the Foundation for the National Institutes of Health Biomarkers Consortium, and sponsored by Wellcome Trust, entitled "Reverse Engineering of Digital Measures," was held in Zurich, Switzerland, with a broad range of stakeholders sharing their experience across four case studies to examine how patient centricity is essential in shaping development and validation of digital evidence generation tools.

Key Messages

In this paper, we discuss progress and the remaining barriers to widespread use of digital measures for evidence generation in clinical development and care delivery. We also present key discussion points and takeaways in order to continue discourse and provide a basis for dissemination and outreach to the wider community and other stakeholders. The work presented here shows us a blueprint for how and why the patient voice can be thoughtfully integrated into digital measure development and that continued multistakeholder engagement is critical for further progress.

Remote Cardiac Safety Monitoring through the Lens of the FDA Biomarker Qualification Evidentiary Criteria Framework: A Case Study Analysis

Clinical safety findings remain one of the reasons for attrition of drug candidates during clinical development. Cardiovascular liabilities are not consistently detected in early-stage clinical trials and often become apparent when drugs are administered chronically for extended periods of time. Vital sign data collection outside of the clinic offers an opportunity for deeper physiological characterization of drug candidates and earlier safety signal detection. A working group representing expertise from biopharmaceutical and technology sectors, US Food and Drug Administration (FDA) public-private partnerships, academia, and regulators discussed and presented a remote cardiac monitoring case study at the FNIH Biomarkers Consortium Remote Digital Monitoring for Medical Product Development workshop to examine applicability of the biomarker qualification evidentiary framework by the FDA. This use case examined the components of the framework, including the statement of need, the context of use, the state of the evidence, and the benefit/risk profile. Examination of results from 2 clinical trials deploying 510(k)-cleared devices for remote cardiac data collection demonstrated the need for analytical and clinical validity irrespectively of the regulatory status of a device of interest, emphasizing the importance of data collection method assessment in the context of intended use. Additionally, collection of large amounts of ambulatory data also highlighted the need for new statistical methods and contextual information to enable data interpretation. A wider adoption of this approach for drug development purposes will require collaborations across industry, academia, and regulatory agencies to establish methodologies and supportive data sets to enable data interpretation and decision-making.

Biomarkers of Crohn's Disease to Support the Development of New Therapeutic Interventions

BACKGROUND

Currently, 2 coprimary end points are used by health authorities to determine the effectiveness of therapeutic interventions in patients with Crohn's disease (CD): symptomatic remission (patient-reported outcome assessment) and endoscopic remission (ileocolonoscopy). However, there is lack of accepted biomarkers to facilitate regulatory decision-making in the development of novel therapeutics for the treatment of CD.

METHODS

With support from the Helmsley Charitable Trust, Critical Path Institute formed the Crohn's Disease Biomarkers preconsortium (CDBpC) with members from the pharmaceutical industry, academia, and nonprofit organizations to evaluate the CD biomarker landscape. Biomarkers were evaluated based on biological relevance, availability of biomarker assays, and clinical validation data.

RESULTS

The CDBpC identified the most critical need as pharmacodynamic/response biomarkers to monitor disease activity in response to therapeutic intervention. Fecal calprotectin (FC) and serum C-reactive protein (CRP) were identified as biomarkers ready for the regulatory qualification process. A number of exploratory biomarkers and potential panels of these biomarkers was also identified for additional development. Given the different factors involved in CD and disease progression, a combination of biomarkers, including inflammatory, tissue injury, genetic, and microbiome-associated biomarkers, will likely have the most utility.

CONCLUSIONS

The primary focus of the Inflammatory Bowel Disease Regulatory Science Consortium will be development of exploratory biomarkers and the qualification of FC and CRP for IBD. The Inflammatory Bowel Disease Regulatory Science Consortium, focused on tools to support IBD drug development, will operate in the precompetitive space to share data, biological samples for biomarker testing, and assay information for novel biomarkers.

Remote Digital Monitoring for Medical Product Development

The use of digital health products has gained considerable interest as a new way to improve therapeutic research and development. Although these products are being adopted by various industries and stakeholders, their incorporation in clinical trials has been slow due to a disconnect between the promises of digital products and potential risks in using these new technologies in the absence of regulatory support. The Foundation for the National Institutes of Health (FNIH) Biomarkers Consortium hosted a public workshop to address challenges and opportunities in this field. Important characteristics of tool development were addressed in a series of presentations, case studies, and open panel sessions. The workshop participants endorsed the usefulness of an evidentiary criteria framework, highlighted the importance of early patient engagement, and emphasized the potential impact of digital monitoring tools and precompetitive collaborations. Concerns were expressed about the lack of real‐life validation examples and the limitations of legacy standards used as a benchmark for novel tool development and validation. Participants recognized the need for novel analytical and statistical approaches to accommodate analyses of these novel data types. Future directions are to harmonize definitions to build common methodologies and foster multidisciplinary collaborations; to develop approaches toward integrating digital monitoring data with the totality of the data in clinical trials, and to continue an open dialog in the community. There was a consensus that all these efforts combined may create a paradigm shift of how clinical trials are planned, conducted, and results brought to regulatory reviews.

The Foundation for the National Institutes of Health Biomarkers Consortium: Past Accomplishments and New Strategic Direction

The Foundation for the National Institutes of Health (FNIH) Biomarkers Consortium (BC) is a public–private partnership that aims to facilitate drug development with biomarkers across a range of therapeutic areas. The BC is organized to address specific precompetitive biomarker projects, giving participating stakeholders a role in the design and conduct of projects and making the results freely public. Ultimately, the goals of the BC are to accelerate the development of new medicines, inform regulatory decision making, and improve patient care. Here, we describe how the BC works and briefly highlight its accomplishments. The BC has had many notable successful biomarker projects in the past 12 years, including I‐SPY2, which has improved clinical trials and biomarker use for breast cancer, and an evidentiary framework for biomarker qualification. Recently, the BC has undergone a strategic expansion of its scope to include related drug development tools along the lines of the Biomarkers, Endpoints, and other Tools (BEST) resource.

Predictive validity of biochemical biomarkers in knee osteoarthritis: data from the FNIH OA Biomarkers Consortium

OBJECTIVE

To investigate a targeted set of biochemical biomarkers as predictors of clinically relevant osteoarthritis (OA) progression.

METHODS

Eighteen biomarkers were measured at baseline, 12 months (M) and 24 M in serum (s) and/or urine (u) of cases (n=194) from the OA initiative cohort with knee OA and radiographic and persistent pain worsening from 24 to 48 M and controls (n=406) not meeting both end point criteria. Primary analyses used multivariable regression models to evaluate the association between biomarkers (baseline and time-integrated concentrations (TICs) over 12 and 24 M, transposed to z values) and case status, adjusted for age, sex, body mass index, race, baseline radiographic joint space width, Kellgren-Lawrence grade, pain and pain medication use. For biomarkers with adjusted p<0.1, the c-statistic (area under the curve (AUC)), net reclassification index and the integrated discrimination improvement index were used to further select for hierarchical multivariable discriminative analysis and to determine the most predictive and parsimonious model.

RESULTS

The 24 M TIC of eight biomarkers significantly predicted case status (ORs per 1 SD change in biomarker): sCTXI 1.28, sHA 1.22, sNTXI 1.25, uC2C-HUSA 1.27, uCTXII, 1.37, uNTXI 1.29, uCTXIα 1.32, uCTXIβ 1.27. 24 M TIC of uCTXII (1.47-1.72) and uC2C-Human Urine Sandwich Assay (HUSA) (1.36-1.50) both predicted individual group status (pain worsening, joint space loss and their combination). The most predictive and parsimonious combinatorial model for case status consisted of 24 M TIC uCTXII, sHA and sNTXI (AUC 0.667 adjusted). Baseline uCTXII and uCTXIα both significantly predicted case status (OR 1.29 and 1.20, respectively).

CONCLUSIONS

Several systemic candidate biomarkers hold promise as predictors of pain and structural worsening of OA.

Developing Outcomes Assessments as Endpoints for Registrational Clinical Trials of Antibacterial Drugs: 2015 Update From the Biomarkers Consortium of the Foundation for the National Institutes of Health

One important component in determining the benefits and harms of medical interventions is the use of well-defined and reliable outcome assessments as endpoints in clinical trials. Improving endpoints can better define patient benefits, allowing more accurate assessment of drug efficacy and more informed benefit-vs-risk decisions; another potential plus is facilitating efficient trial design. Since our first report in 2012, 2 Foundation for the National Institutes of Health Biomarkers Consortium Project Teams have continued to develop outcome assessments for potential uses as endpoints in registrational clinical trials of community-acquired bacterial pneumonia and acute bacterial skin and skin structure infections. In addition, the teams have initiated similar work in the indications of hospital-acquired bacterial pneumonia and ventilator-associated bacterial pneumonia. This report provides an update on progress to date in these 4 diseases.

The tetraspanin network modulates MT1-MMP cell surface trafficking

The membrane-type 1 matrix metalloproteinase (MT1-MMP) drives fundamental physiological and pathophysiological processes. Among other substrates, MT1-MMP cleaves components of the extracellular matrix and activates other matrix-cleaving proteases such as MMP-2. Trafficking is a highly effective means to modulate MT1-MMP cell surface expression, and hence regulate its function. Here, we describe the complex interaction of MT1-MMP with tetraspanins, their effects on MT1-MMP intracellular trafficking and proteolytic function. Tetraspanins are credited as membrane organizers that form a network within the membrane to regulate the trafficking of associated proteins. In short, we found MT1-MMP to interact with the tetraspanin-associated EWI-2 protein by a yeast two-hybrid screen. Immunoprecipitation analysis confirmed this interaction and further revealed that MT1-MMP also stably interacts with distinct tetraspanins (CD9, CD37, CD53, CD63, CD81, and CD82) and the tetraspanin-like MAL protein. By using different MT1-MMP truncation constructs and mutants, we observed that all tetraspanins and MAL associated with the hemopexin domain of MT1-MMP. Moreover, this interaction was independent of O-glycosylation of MT1-MMP and exclusively occurred in the endoplasmic reticulum. Here, the respective subcellular compartment was identified by fitting the MT1-MMP interaction pattern to a model for post-translational processing of MT1-MMP. In addition, tetraspanins differentially affected the cell surface localization of MT1-MMP, its capacity to activate pro-MMP-2, and the collagen invasion capacity. Interestingly, the degree of tetraspanin-MT1-MMP association did not correlate with its impact on MT1-MMP function. Tetraspanins thus distinctly affect MT1-MMP subcellular localization and function, and may constitute an effective mechanism to control MT1-MMP-dependent proteolysis at the cell surface.

Neonatal-onset multisystem inflammatory disease responsive to interleukin-1beta inhibition

BACKGROUND

Neonatal-onset multisystem inflammatory disease is characterized by fever, urticarial rash, aseptic meningitis, deforming arthropathy, hearing loss, and mental retardation. Many patients have mutations in the cold-induced autoinflammatory syndrome 1 (CIAS1) gene, encoding cryopyrin, a protein that regulates inflammation.

METHODS

We selected 18 patients with neonatal-onset multisystem inflammatory disease (12 with identifiable CIAS1 mutations) to receive anakinra, an interleukin-1-receptor antagonist (1 to 2 mg per kilogram of body weight per day subcutaneously). In 11 patients, anakinra was withdrawn at three months until a flare occurred. The primary end points included changes in scores in a daily diary of symptoms, serum levels of amyloid A and C-reactive protein, and the erythrocyte sedimentation rate from baseline to month 3 and from month 3 until a disease flare.

RESULTS

All 18 patients had a rapid response to anakinra, with disappearance of rash. Diary scores improved (P<0.001) and serum amyloid A (from a median of 174 mg to 8 mg per liter), C-reactive protein (from a median of 5.29 mg to 0.34 mg per deciliter), and the erythrocyte sedimentation rate decreased at month 3 (all P<0.001), and remained low at month 6. Magnetic resonance imaging showed improvement in cochlear and leptomeningeal lesions as compared with baseline. Withdrawal of anakinra uniformly resulted in relapse within days; retreatment led to rapid improvement. There were no drug-related serious adverse events.

CONCLUSIONS

Daily injections of anakinra markedly improved clinical and laboratory manifestations in patients with neonatal-onset multisystem inflammatory disease, with or without CIAS1 mutations. (ClinicalTrials.gov number, NCT00069329 [ClinicalTrials.gov].).

Nitroglycerin reperfusion reduces ischemia-reperfusion injury in non-heart-beating donor lungs

BACKGROUND

Lung transplantation is severely limited by an inadequate supply of lungs from brain-dead donors. A potential solution is use of lungs from non-heart-beating donors (NHBDs) with retrieval at intervals after circulatory arrest and death. A warm ischemic period with concomitant reperfusion injury is a major limiting factor in the transplantation of lungs retrieved from NHBDs. We hypothesized that the administration of the nitric oxide-donor nitroglycerin to lungs from NHBDs would reduce ischemia-reperfusion injury by activation of guanylate cyclase to form guanosine 3',5'-cyclic monophosphate (cGMP).

METHODS

An in situ isolated perfused rat lung model was used. Lungs were retrieved from rats at varying intervals after circulatory arrest and death. Lungs were either ventilated with O(2) in situ or not ventilated. Lungs were reperfused at intervals after death with Earle's solution with or without nitroglycerin (0.1 mg/ml). Lung ischemia-reperfusion injury was assessed by capillary filtration coefficient, wet-to-dry lung weight ratio, and pulmonary hemodynamics. Tissue levels of adenine nucleotides and cGMP concentrations were measured by high-performance liquid chromatography and enzyme immunoassay, respectively.

RESULTS

Reperfusion with nitroglycerin decreased capillary filtration coefficient compared with reperfusion without nitroglycerin at all post-mortem ischemic times, irrespective of pre-harvest ventilation. cGMP levels increased significantly with nitroglycerin-reperfusion and attenuated decreases in high-energy adenine nucleotides.

CONCLUSIONS

Reperfusion of lungs with nitroglycerin may facilitate safe lung transplantation from NHBDs by reducing capillary leak after reperfusion.

Results from a human renal allograft tolerance trial evaluating T-cell depletion with alemtuzumab combined with deoxyspergualin

BACKGROUND

Perioperative lymphocyte depletion induces allograft tolerance in some animal models, but in humans has only been shown to reduce immunosuppressive requirements. Without maintenance immunosuppression, depleted human renal allograft recipients experience rejection characterized by infiltration of the allograft with monocytes and macrophages. T-cell depletion combined with a brief course of deoxyspergualin (DSG), a drug with inhibitory effects on monocytes and macrophages, induces tolerance in nonhuman primates. We therefore performed a trial to determine if lymphocyte depletion with alemtuzumab combined with DSG would induce tolerance in humans.

METHODS

Five recipients of live donor kidneys were treated perioperatively with alemtuzumab and DSG and followed postoperatively without maintenance immunosuppression. Patients were evaluated clinically, by flow cytometry, and by protocol biopsies analyzed immunohistochemically and with real-time polymerase chain reaction. Results were compared to previously studied patients receiving alemtuzumab alone or standard immunosuppression.

RESULTS

Despite profound T-cell depletion and therapeutic DSG dosing, all alemtuzumab/DSG patients developed reversible rejection that was similar in timing, histology, and transcriptional profile to that seen in patients treated with alemtuzumab alone. Chemokine expression was marked prior to and during rejections.

CONCLUSIONS

We conclude that treatment with alemtuzumab and DSG does not induce tolerance in humans. Chemokine production may not be adequately suppressed using this approach.

Molecular evaluation of BK polyomavirus nephropathy

Understanding at a molecular level, the immunologic response of polyomavirus nephropathy (PVN), a critical cause of kidney graft loss, could lead to new targets for treatment and diagnosis. We undertook a transcriptional evaluation of kidney allograft biopsies from recipients with PVN or acute rejection (AR), as well as from recipients with stable allograft function (SF). In both the PVN and AR groups, Banff histologic scores and immunohistochemical analysis of inflammatory infiltrates were similar. Despite their different etiologies, the transcriptional profiles of PVN and AR were remarkably similar. However, transcription of genes previously linked to AR including CD8 (65.9 +/- 18.8) and related molecules IFN-gamma(55.1 +/- 17.0), CXCR3 (49.9 +/- 12.8) and perforin (153.8 +/- 50.4) were significantly higher in PVN compared to AR (30.9 +/- 2.0, 14.0 +/- 7.3, 12.1 +/- 7.3 and 15.6 +/- 3.8-fold, respectively; p < 0.01). Importantly, transcription of molecules associated with graft fibrosis including matrix collagens, TGFbeta, MMP2 and 9, as well as markers of epithelial-mesenchymal transformation (EMT) were significantly higher in PVN than AR. Thus, renal allografts with PVN transcribe proinflammatory genes equal in character and larger in magnitude to that seen during acute cellular rejection. BK infection creates a transcriptional microenvironment that promotes graft fibrosis. These findings provide new insights into the intrarenal inflammation of BK infection that promotes graft loss.

Disruption of CD40/CD40-ligand interactions in a retinal autoimmunity model results in protection without tolerance

We examined the role of CD40/CD40L interactions on the development of experimental autoimmune uveoretinitis (EAU), a cell-mediated, Th1-driven autoimmune disease that serves as a model for autoimmune uveitis in humans. EAU-susceptible B10.RIII mice immunized with the retinal autoantigen interphotoreceptor retinoid binding protein in CFA and treated with anti-CD40L Ab (MR1) had reduced incidence and severity of disease. Real-time PCR analysis revealed that the innate and adaptive responses of protected mice were reduced, without an obvious shift toward a Th2 cytokine profile. In contrast to some other reports, no evidence was found for regulatory cells in adoptive transfer experiments. To determine whether CD40L blockade resulted in long-term tolerance, mice protected by treatment with MR1 Ab were rechallenged for uveitis after circulating MR1 Ab levels dropped below the detection limit of ELISA. MR1-treated mice developed severe EAU and strong cellular responses to interphotoreceptor retinoid binding protein, comparable to those of control mice. These responses were higher than in mice that had not received the primary immunization concurrently with anti-CD40L treatment. We conclude that 1) CD40/CD40L interaction is required for EAU and its disruption prevents disease development; 2) CD40L blockade inhibits the innate response to immunization and reduces priming, but does not result in immune deviation; and 3) protection is dependent on persistence of anti-CD40L Abs, and long-term tolerance is not induced. Furthermore, immunological memory develops under cover of CD40L blockade causing enhanced responses upon rechallenge. Taken together, our data suggest that ongoing CD40/CD40L blockade might be required to maintain a therapeutic effect against uveitis.

Functionally significant renal allograft rejection is defined by transcriptional criteria

Renal allograft acute cellular rejection (ACR) is a T-cell mediated disease that is diagnosed histologically. However, many normally functioning allografts have T-cell infiltrates and histological ACR, and many nonimmune processes cause allograft dysfunction. Thus, neither histological nor functional criteria are sufficient to establish a significant rejection, and the fundamental features of clinical rejection remain undefined. To differentiate allograft lymphocyte infiltration from clinically significant ACR, we compared renal biopsies from patients with ACR to patients with: sub-clinical rejection (SCR, stable function with histological rejection); no rejection; and nontransplanted kidneys. Biopsies were compared histologically and transcriptionally by RT-PCR for 72 relevant immune function genes. Neither the degree nor the composition of the infiltrate defined ACR. However, transcripts up-regulated during effector T(H)1 T-cell activation, most significantly the transcription factor T-bet, the effector receptor Fas ligand and the costimulation molecule CD152 clearly (p = 0.001) distinguished the patient categories. Transcripts from other genes were equivalently elevated in SCR and ACR, indicating their association with infiltration, not dysfunction. Clinically significant ACR is not defined solely by the magnitude nor composition of the infiltrate, but rather by the transcriptional activity of the infiltrating cells. Quantitative analysis of selected gene transcripts may enhance the clinical assessment of allografts.

Immunocompetent T-cells with a memory-like phenotype are the dominant cell type following antibody-mediated T-cell depletion

T-cell depletion facilitates reduced immunosuppression following organ transplantation and has been suggested to be pro-tolerant. However, the characteristics of post-depletional T cells have not been evaluated as they relate to tolerance induction. We therefore studied patients undergoing profound T-cell depletion with alemtuzumab or rabbit anti-thymocyte globulin following renal transplantation, evaluating the phenotype and functional characteristics of their residual cells. Naive T cells and T cells with potential regulatory function (CD4+CD25+) were not prevalent following aggressive depletion. Rather, post-depletion T cells were of a single phenotype (CD3+CD4+CD45RA-CD62L-CCR7-) consistent with depletion-resistant effector memory T cells that expanded in the first month and were uniquely prevalent at the time of rejection. These cells were resistant to steroids, deoxyspergualin or sirolimus in vitro, but were calcineurin-inhibitor sensitive. These data demonstrate that therapeutic depletion begets a limited population of functional memory-like T cells that are easily suppressed with certain immunosuppressants, but cannot be considered uniquely pro-tolerant.

Insulinomas and expression of an insulin splice variant

BACKGROUND

Insulinomas are beta-cell tumours characterised by uncontrolled insulin secretion even in the presence of hypoglycaemia. However, the mechanisms allowing such excessive insulin secretion are not known. Insulin secretion can occur only when the beta-cell insulin stores have been replenished by insulin biosynthesis, which is mainly controlled by translation. Such specific translational regulation often involves the 5' untranslated region. We have identified an insulin splice variant in isolated human pancreatic islets of non-diabetic donors that retains 26 bp of intron 1 and thereby changes the 5' untranslated region, but leaves the coding region unchanged. This splice variant has increased translation efficiency in vitro and in vivo compared with native insulin mRNA. However, splice variant expression is less than 1% of native insulin mRNA in normal islets.

METHODS

To test whether this splice variant is involved in insulin production by human insulinomas, we extracted RNA from nine laser-captured surgical insulinoma samples and from isolated islets of nine donors who did not have diabetes. We then determined the ratio of splice variant to native insulin mRNA by quantitative real-time RT-PCR.

FINDINGS

The mean ratio of the splice variant to native insulin mRNA was increased more than 50-fold in insulinomas compared with normal islets, and this difference was present in all nine human insulinomas. Overexpression of the splice variant therefore seems to be a general characteristic of insulinomas and is estimated to contribute about 90% to insulin synthesis by these tumours.

INTERPRETATION

Overexpression of the insulin splice variant with increased translation efficiency in insulinomas might explain how these tumours maintain high levels of insulin synthesis and secretion leading to hyperinsulinaemia-the hallmark of this disease.

Resistin is expressed in pancreatic islets

Resistin, a recently described adipocyte factor, is regulated by peroxisome proliferator-activated receptor gamma (PPARgamma) agonists. While resistin has been proposed to mediate insulin resistance in rodents, little is known about human resistin and its expression in pancreatic islets has not been tested. The goal of the present study was therefore to analyze whether resistin, like PPARgamma, is expressed in islets. Human islets from seven donors were analyzed by quantitative RT-PCR revealing resistin expression in all samples. Immunohistochemistry using a resistin-specific antibody on human pancreatic sections localized resistin protein to the islets. Mouse resistin was also detected in the Min6 beta cell line. Interestingly, we found a 4-fold increase in islet resistin expression in insulin resistant A-ZIP transgenic compared to wild-type mice. Our results demonstrate that resistin is expressed in islets and up-regulated in insulin resistance and thereby shed new light on the role of resistin in mice and humans.

Immune profiling: molecular monitoring in renal transplantation

Molecular techniques have become a mainstay for most biomedical research. In particular, sensitive methods for gene transcript detection and advanced flow cytometry have been crucial in fostering our understanding of the basic mechanisms promoting allosensitization and adaptive immune regulation. These technologies have been validated in vitro, and in pre-clinical settings, and as such their clinical application is now clearly appropriate. It is becoming increasingly clear that these robust techniques hold much promise to better elucidate human transplant biology, and more importantly, guide clinical decision making with mechanistically-based information. This article will discuss our laboratory's use of several novel technologies, including gene polymorphism analysis, real-time polymerase chain reaction transcript quantification, and multi-color flow cytometry in clinical human renal transplantation. Specific technical methodology will be presented outlining keys for effective clinical application. Clinical correlations will be presented as examples of how these techniques may have clinical relevance. Suggestions for the adaptation of these methods for therapeutic intervention will be given. We propose that clinical transplantation should proceed in close step with modern molecular diagnostics.

Results from a human renal allograft tolerance trial evaluating the humanized CD52-specific monoclonal antibody alemtuzumab (CAMPATH-1H)

BACKGROUND

Profound T-cell depletion before allotransplantation with gradual posttransplant T-cell repopulation induces a state of donor-specific immune hyporesponsiveness or tolerance in some animal models. Alemtuzumab (Campath-1H, Millennium Pharmaceuticals, Cambridge, MA) is a humanized CD52-specific monoclonal antibody that produces profound T-cell depletion in humans and reduces the need for maintenance immunosuppression after renal transplantation. We therefore performed a study to determine if pretransplant T-cell depletion with alemtuzumab would induce tolerance in human renal allografts and to evaluate the nature of the alloimmune response in the setting of T-cell depletion.

METHODS

Seven nonsensitized recipients of living-donor kidneys were treated perioperatively with alemtuzumab and followed postoperatively without maintenance immunosuppression. Patients were evaluated clinically by peripheral flow cytometry, protocol biopsies evaluated immunohistochemically, and real-time polymerase chain reaction-based transcriptional analysis.

RESULTS

Lymphocyte depletion was profound in the periphery and secondary lymphoid tissues. All patients developed reversible rejection episodes within the first month that were characterized by predominantly monocytic (not lymphocytic) infiltrates with only rare T cells in the peripheral blood or allograft. These episodes were responsive to treatment with steroids or sirolimus or both. After therapy, patients remained rejection-free on reduced immunosuppression, generally monotherapy sirolimus, despite the recovery of lymphocytes to normal levels.

CONCLUSIONS

T-cell depletion alone does not induce tolerance in humans. These data underscore a prominent role for early responding monocytes in human allograft rejection.

Pulmonary preservation studies: effects on endothelial function and pulmonary adenine nucleotides

BACKGROUND

Lung transplantation is an effective therapy plagued by a high incidence of early graft dysfunction, in part because of reperfusion injury. The optimal preservation solution for lung transplantation is unknown. We performed experiments using an isolated perfused rat lung model to test the effect of lung preservation with three solutions commonly used in clinical practice.

METHODS

Lungs were retrieved from Sprague-Dawley rats and flushed with one of three solutions: modified Euro-Collins (MEC), University of Wisconsin (UW), or low potassium dextran and glucose (LPDG), then stored cold for varying periods before reperfusion with Earle's balanced salt solution using the isolated perfused rat lung model. Outcome measures were capillary filtration coefficient (Kfc), wet-to-dry weight ratio, and lung tissue levels of adenine nucleotides and cyclic AMP.

RESULTS

All lungs functioned well after 4 hr of storage. By 6 hr, UW-flushed lungs had a lower Kfc than LPDG-flushed lungs. After 8 hr of storage, only UW-flushed lungs had a measurable Kfc. Adenine nucleotide levels were higher in UW-flushed lungs after prolonged storage. Cyclic AMP levels correlated with Kfc in all groups.

CONCLUSIONS

Early changes in endothelial permeability seemed to be better attenuated in lungs flushed with UW compared with LPDG or MEC; this was associated with higher amounts of adenine nucleotides. MEC-flushed lungs failed earlier than LPDG-flushed or UW-flushed lungs. The content of the solution may be more important for lung preservation than whether the ionic composition is intracellular or extracellular.

Molecular and immunohistochemical characterization of the onset and resolution of human renal allograft ischemia-reperfusion injury

BACKGROUND Following allotransplantation, renal ischemia-reperfusion (I/R) injury initiates a series of events that provokes counter-adaptive immunity. Though T cells clearly mediate allospecific immunity, the manner in which reperfusion events augment their activation has not been established. In addition, comprehensive analysis of I/R injury in humans has been limited. METHODS To evaluate the earliest events occurring following allograft reperfusion and gain insight into those factors linking reperfusion to alloimmunity, we examined human renal allografts 30 to 60 minutes postreperfusion (n=10) and compared them with allografts with normal function that had resolved their I/R injury insult (>1 month posttransplant, n=6) and to normal kidneys (living donor kidneys before procurement, n=8). Biopsies were processed both for immunohistochemical analysis as well as for transcript analysis by real-time quantitative polymerase chain reaction (RT-PCR). RESULTS Reperfusion injury was characterized by increased levels of gene transcripts known to be involved in cellular adhesion, chemotaxis, apoptosis, and monocyte recruitment and activation. T-cell-associated transcripts were generally absent. However, recovered allografts exhibited increased levels of T-cell and costimulation-related gene transcripts despite normal allograft function. Consistent with these findings, the immediate postreperfusion state was characterized histologically by tubular injury and monocyte infiltration, while the stable posttransplant state was notable for T-cell infiltration. CONCLUSIONS These data suggest that monocytes and transcripts related to their recruitment dominate the immediate postreperfusion state. This gives way to a T-cell dominant milieu even in grafts selected for their stable function and absence of rejection. These data have implications for understanding the fundamental link between I/R injury and alloimmunity.

Oligonucleotide microarray analysis of intact human pancreatic islets: identification of glucose-responsive genes and a highly regulated TGFbeta signaling pathway

Human pancreatic islets are a major focus of diabetes research due to their key role in glucose homeostasis and their potential for transplantation in the treatment of type 1 diabetes. Currently, no comprehensive analysis of baseline or glucose-stimulated islet gene expression is available. Using oligonucleotide microarrays we analyzed isolated intact human islets incubated at low and high glucose. We identified approximately 6000 islet genes, several with clinical implications, as well as a number of glucose-regulated genes. Interestingly, two transforming growth factor beta (TGFbeta) superfamily members were highly regulated by glucose. One of them, PDF, was found to have a very high expression level compared to other TGFbeta superfamily members. Quantitative reverse transcriptase polymerase chain reaction confirmed these results and demonstrated that the highly expressed PDF was approximately 10-fold down- regulated by glucose while other TGFbeta superfamily members and target genes were up-regulated. These results suggest that a highly regulated TGFbeta signaling cascade exists in human islets, and that PDF may play a central role in islet biology. Since TGFbeta is involved in differentiation and immune modulation, this novel pathway may link glucose metabolism, immune response and development of human islets. We report here the first gene expression profile of intact human islets. These and similar analyses will provide better understanding of human islet biology and enhance the development of novel diabetes therapies.

A proinsulin gene splice variant with increased translation efficiency is expressed in human pancreatic islets

As glucose-induced insulin expression is mainly regulated at the translational level, and such regulation often involves the 5'-untranslated region (5'UTR), we examined the human proinsulin gene 5'UTR. RT-PCR and sequencing demonstrated that a proinsulin splice variant (SPV) generated from a cryptic 5'-splice site and retaining the first 26 bp of intron 1 was present in human pancreatic islets from normal donors. The expression of this SPV was metabolically regulated, as shown by quantitative real-time RT-PCR, revealing a more than 10-fold increase in the SPV in isolated human islets incubated at 16.7 mM compared with 1.67 mM glucose. In vitro wheat-germ translation and in vivom transfection studies demonstrated that the altered 5'UTR of the SPV increased translation. The SPV yielded 4-fold more in vitro translated preproinsulin protein than the native proinsulin mRNA, and the SPV 5'UTR inserted upstream from a luciferase reporter gene resulted in a more than 6-fold higher luciferase activity, suggesting enhanced translation in vivo. Retention of the 26 bp changed the proposed secondary RNA structure of the SPV, which may facilitate ribosomal binding and explain the increase in translation efficiency. These results suggest a novel mechanism by which metabolic changes can modulate the expression of 5'UTR SPVs and thereby regulate translation efficiency.

Ethnicity greatly influences cytokine gene polymorphism distribution

Polymorphisms in the regulatory regions of cytokine genes are associated with high and low cytokine production and may modulate the magnitude of alloimmune responses following transplantation. Ethnicity influences allograft half-life and the incidence of acute and chronic rejection. We have questioned whether ethnic-based differences in renal allograft survival could be due in part to inheritance of cytokine polymorphisms. To address that question, we studied the inheritance patterns for polymorphisms in several cytokine genes (IL-2, IL-6, IL-10, TNF-alpha, TGF-beta, and IFN-gamma) within an ethnically diverse study population comprised of 216 Whites, 58 Blacks, 25 Hispanics, and 31 Asians. Polymorphisms were determined by allele-specific polymerase chain reaction and restriction fragment length analysis. We found striking differences in the distribution of cytokine polymorphisms among ethnic populations. Specifically, significant differences existed between Blacks and both Whites and Asians in the distribution of the polymorphic alleles for IL-2. Blacks, Hispanics and Asians demonstrated marked differences in the inheritance of IL-6 alleles and IL-10 genotypes that result in high expression when compared with Whites. Those of Asian descent exhibited an increase in IFN-gamma genotypes that result in low expression as compared to Whites. In contrast, we did not find significant ethnic-based differences in the inheritance of polymorphic alleles for TNF-alpha. Our results show that the inheritance of certain cytokine gene polymorphisms is strongly associated with ethnicity. These differences may contribute to the apparent influence of ethnicity on allograft outcome.

Association of cytokine polymorphic inheritance and in vitro cytokine production in anti-CD3/CD28-stimulated peripheral blood lymphocytes

BACKGROUND

Genetic variations in cytokine genes are thought to regulate cytokine protein production. However, studies using T cell mitogens have not always demonstrated a significant relationship between cytokine polymorphisms and in vitro protein production. Furthermore, the functional consequence of a polymorphism at position -330 in the IL-2 gene has not been described. We associated in vitro protein production with cytokine gene polymorphic genotypes after costimulation of cultured peripheral blood lymphocytes.

METHODS

PBL were isolated from forty healthy volunteers. Cytokine protein production was assessed by enzyme-linked immunosorbent assay. Polymorphisms in interleukin- (IL) 2, IL-6, IL-10, tumor necrosis factor (TNF-alpha), tumor growth factor (TGF-beta), and interferon (IFN-gamma) were determined by polymerase chain reaction (PCR).

RESULTS

Statistical difference between protein production and cytokine polymorphic variants in the IL-10, IFN-gamma, and TNF-alpha genes was not evident after 48-hour stimulation with concanavalin-A. In contrast, after anti-CD3/CD28 stimulation significant differences (P<0.05) were found among high and low producers for IL-2, IL-6, and among high, intermediate, and low producers for IFN-gamma, and IL-10. Augmented levels of IL-2 in individuals that were homozygous for the polymorphic IL-2 allele were due to an early and sustained enhancement of IL-2 production. No association was found among TNF-alpha and TGF-beta genotypes and protein production.

CONCLUSION

Polymorphisms in IL-2, IL-6, IL-10, and IFN-gamma genes are associated with their protein production after anti-CD3/CD28 stimulation. The profound effect of the IL-2 gene polymorphism in homozygous individuals may serve as a marker for those that could mount the most vigorous allo- or autoimmune responses, or perhaps become tolerant more easily.

Cytokine polymorphic analyses indicate ethnic differences in the allelic distribution of interleukin-2 and interleukin-6

BACKGROUND

Polymorphisms in the regulatory regions of cytokine genes affect protein production and are associated with allograft outcome. Ethnic origin has been identified as a significant prognostic factor for several immune-mediated diseases and for outcome after allotransplantation. A clear relationship between cytokine polymorphisms and ethnicity has not been shown.

METHODS

One hundred sixty subjects including 102 whites and 43 African-Americans were studied. Using polymerase chain reaction-based assays and, in some cases, restriction enzyme digestion, we determined genetic polymorphisms for the cytokines interleukin (IL) -2, IL-6, IL-10, tumor necrosis factor-alpha, transforming growth factor-beta, and interferon-gamma (IFN-gamma). Genetic polymorphism frequencies were then compared to ethnicity using chi-square analysis and Fisher's exact two-tailed tests.

RESULTS

For both the IL-2 and IL-6 genes, we found that whites and African-Americans differed significantly (P <0.05) in their allelic distribution and genotype frequency. A trend toward ethnic distribution was noted among the alleles and genotypes for the IL-10 and IFN-gamma genes. We found no correlation between ethnicity and either allelic distribution or genotype frequency for the tumor necrosis factor-alpha or transforming growth factor-beta genes. When comparisons were made between patients with or without a history of kidney failure, the allelic or genotypic distributions for the IL-6 and IFN-gamma genes were found to significantly differ.

CONCLUSIONS

Our work demonstrates a correlation between ethnicity and polymorphisms in several cytokine genes. In addition, we found that patients requiring renal transplantation differ from the general population with regard to certain cytokine gene polymorphisms. These findings may have relevance in making prognostic determinations or tailoring immunomodulatory regimens after renal transplantation.

Lung retrieval from non-heart beating cadavers with the use of a rat lung transplant model

BACKGROUND

Lungs retrieved from cadavers after death and circulatory arrest may alleviate the critical shortage of lungs for transplant. We report a rat lung transplantation model that allows serial measurement of arterial blood gases after left single lung transplantation from non-heart beating donors.

METHODS

Twelve Sprague-Dawley rats underwent left lung transplantation with a vascular cuff technique. Donor rats were anesthetized with intraperitoneal injection of pentobarbital, heparinized, intubated via tracheotomy, and then killed with pentobarbital. Lungs were retrieved immediately or after 2 hours of oxygen ventilation after death (tidal volume 1 mL/100 g, rate 40/min FIO2 = 1.0, positive end-expiratory pressure 5 cm H2O). Recipient rats were anesthetized, intubated, and ventilated. The carotid artery and jugular vein were cannulated for arterial blood gases and infusion of Ringer's lactate (4 mL/h). Anesthesia was maintained with halothane 0.2%, and recipient arterial blood gases were measured at 4 and 6 hours after lung transplantation after snaring the right pulmonary artery for 5 minutes. Animals were put to death 6 hours after lung transplantation, and portions of transplanted lungs were frozen in liquid nitrogen and assayed for wet/dry ratio, myeloperoxidase as a measure of neutrophil infiltration, and conjugated dienes as a measure of free radical-mediated lipid peroxidation.

RESULTS

Arterial PO2 and wet/dry ratio were not significantly different in recipients of non-heart beating donor lungs retrieved immediately after death or after 2 hours of oxygen ventilation. Significant neutrophil infiltration was observed in recipients of non-heart beating donor lungs retrieved 2 hours after death from oxygen-ventilated donors.

CONCLUSIONS

Strategies to ameliorate reperfusion injury may allow for successful lung transplantation from non-heart beating donors.

Maintenance of cAMP in non-heart-beating donor lungs reduces ischemia-reperfusion injury

Studies suggest that pulmonary vascular ischemia-reperfusion injury (IRI) can be attenuated by increasing intracellular cAMP concentrations. The purpose of this study was to determine the effect of IRI on capillary permeability, assessed by capillary filtration coeficient (Kfc), in lungs retrieved from non-heart-beating donors (NHBDs) and reperfused with the addition of the beta(2)-adrenergic receptor agonist isoproterenol (iso), and rolipram (roli), a phosphodiesterase (type IV) inhibitor. Using an in situ isolated perfused lung model, lungs were retrieved from NHBD rats at varying intervals after death and either ventilated with O(2) or not ventilated. The lungs were reperfused with Earle's solution with or without a combination of iso (10 microM) and roli (2 microM). Kfc, lung viability, and pulmonary hemodynamics were measured. Lung tissue levels of adenine nucleotides and cAMP were measured by HPLC. Combined iso and roli (iso/roli) reperfusion decreased Kfc significantly (p < 0.05) compared with non-iso/roli-reperfused groups after 2 h of postmortem ischemia. Total adenine nucleotide (TAN) levels correlated with Kfc in non-iso/roli-reperfused (r = 0.89) and iso/roli-reperfused (r = 0.97) lungs. cAMP levels correlated with Kfc (r = 0.93) in iso/roli-reperfused lungs. Pharmacologic augmentation of tissue TAN and cAMP levels might ameliorate the increased capillary permeability observed in lungs retrieved from NHBDs.

CD40 ligand (CD154) triggers a short-term CD4(+) T cell activation response that results in secretion of immunomodulatory cytokines and apoptosis

Signals generated through CD28-B7 and CD40 ligand (CD40L)-CD40 interactions have been shown to be crucial for the induction of long-term allograft survivability. We have recently demonstrated that humanized anti-CD40L (hu5C8) prevents rejection of mismatched renal allografts in primates. To investigate potential mechanisms of CD40L-induced allograft acceptance, we coimmobilized hu5C8 with suboptimal amounts of anti-CD3 to stimulate CD4(+) T cells. We now report that anti-CD3/CD40L costimulation results in CD28-independent activation and subsequent deletion of resting T cells. Coligation of CD3 and CD40L increased expression of CD69, CD25, and CD54 on CD4(+) T cells. We also found that costimulation with anti-CD3/CD40L resulted in enhanced production of interleukin (IL)-10, interferon gamma, and tumor necrosis factor alpha but not IL-2 or IL-6. Interestingly, after several days, anti-CD3/CD40L-mediated activation was followed by apoptosis in a significant population of cells. Consistent with that observation, anti-CD3/CD40L did not enhance the antiapoptotic proteins Bcl-2 and Bcl-xL. Further, the addition of CD28 at 24 h failed to rescue those cells induced to die after costimulation with anti-CD3/CD40L. Together, these data suggest that the graft-sparing effect of hu5C8 in vivo may result in part from early and direct effects on CD4(+) T cells, including a vigorous induction of immunomodulatory cytokines and/or apoptosis of allograft-specific T cells.

Reduced ischemia-reperfusion injury with rolipram in rat cadaver lung donors: effect of cyclic adenosine monophosphate

BACKGROUND

The perfusion of rat lungs retrieved from cadavers with a solution containing isoproterenol has been shown to ameliorate the ischemia-reperfusion injury seen in lungs retrieved after death, and this protective effect parallels increases in tissue cyclic adenosine monophosphate levels. In this study, we investigated the effect of rolipram, a phosphodiesterase inhibitor, on capillary permeability and lung cyclic adenosine monophosphate levels in lungs retrieved from circulation-arrested rats.

METHODS

Using an isolated perfused lung circuit, we retrieved lungs from circulation-arrested donor rats either ventilated with 100% oxygen or not ventilated for varying postmortem times. The lungs were reperfused with or without rolipram (2 micromol/L). The capillary filtration coefficient and wet to dry weight ratio, indicators of pulmonary vascular integrity, were determined, and tissue levels of adenine nucleotides and cyclic adenosine monophosphate were measured by high-performance liquid chromatography.

RESULTS

The capillary filtration coefficient was significantly reduced in nonventilated cadaver lungs reperfused with rolipram 120 minutes after death (p<0.05). Oxygen ventilation or reperfusion with rolipram had a similar effect on the capillary filtration coefficient. Cyclic adenosine monophosphate levels were significantly higher in rolipram-reperfused lungs retrieved 120 minutes after death in both oxygen-ventilated (p<0.01) and nonventilated (p<0.01) lungs.

CONCLUSIONS

In lungs from nonventilated, circulation-arrested donors, reperfusion with rolipram reduces the ischemia-reperfusion injury that may be due to intracellular cyclic adenosine monophosphate. Alteration of perfusate may have an impact on capillary leak caused by antecedent ischemia. Thus, rolipram may be a useful adjunct in the preservation of donor lungs retrieved after death.

When does the lung die? Kfc, cell viability, and adenine nucleotide changes in the circulation-arrested rat lung

Lungs harvested from cadaveric circulation-arrested donors may increase the donor pool for lung transplantation. To determine the degree and time course of ischemia-reperfusion injury, we evaluated the effect of O2 ventilation on capillary permeability [capillary filtration coefficient (Kfc)], cell viability, and total adenine nucleotide (TAN) levels in in situ circulation-arrested rat lungs. Kfc increased with increasing postmortem ischemic time (r = 0.88). Lungs ventilated with O2 1 h postmortem had similar Kfc and wet-to-dry ratios as controls. Nonventilated lungs had threefold (P < 0.05) and sevenfold (P < 0.0001) increases in Kfc at 30 and 60 min postmortem compared with controls. Cell viability decreased in all groups except for 30-min postmortem O2-ventilated lungs. TAN levels decreased with increasing ischemic time, particularly in nonventilated lungs. Loss of adenine nucleotides correlated with increasing Kfc values (r = 0.76). This study indicates that lungs retrieved 1 h postmortem may have normal Kfc with preharvest O2 ventilation. The relationship between Kfc and TAN suggests that vascular permeability may be related to lung TAN levels.

Reduced ischemia-reperfusion injury with isoproterenol in non-heart-beating donor lungs

Transplantation of lungs retrieved from non-heart-beating donors could expand the donor pool. Recent studies suggest that the ischemia-reperfusion injury (IRI) to the lung can be attenuated by increasing intracellular cAMP concentrations. The purpose of this study was to determine the effect of IRI on capillary permeability, as measured by Kfc, in lungs retrieved from non-heart-beating donors and reperfused with or without isoproterenol (iso). Using an in situ isolated perfused lung model, lungs were retrieved from non-heart-beating donor rats ventilated with O2 or not at varying intervals after death. The lungs were reperfused with or without iso (10 microM). Kfc, lung viability, and pulmonary hemodynamics were measured, and tissue levels of adenine nucleotides and cAMP were measured by HPLC. Iso-reperfusion decreased Kfc significantly (P < 0.05) compared to non-iso-reperfused groups at all postmortem ischemic times, irrespective of preharvest ventilation status. Pulmonary arterial pressures and resistances increased and venous resistances decreased with iso-reperfusion. Total adenine nucleotide (TAN) levels correlated with Kfc in non-iso-reperfused (r = 0.65) and iso-perfused (r = 0.84) lungs. cAMP levels increased significantly with iso-reperfusion. cAMP levels correlated with Kfc (r = 0.87) in iso-reperfused lungs. Iso-reperfusion of lungs retrieved from non-heart-beating donor rats results in decreased capillary permeability and increased lung tissue cAMP levels. Pharmacologic augmentation of tissue TAN and cAMP levels may further ameliorate the increased capillary permeability seen in lungs retrieved from non-heart-beating donors.