N-acetylcysteine: a novel approach to methaemoglobinaemia in normothermic liver machine perfusion

Extended duration of normothermic machine perfusion (NMP) provides opportunities to resuscitate suboptimal donor livers. This intervention requires adequate oxygen delivery typically provided by a blood-based perfusion solution. Methaemoglobin (MetHb) results from the oxidation of iron within haemoglobin and represents a serious problem in perfusions lasting > 24 h. We explored the effects of anti-oxidant, N-acetylcysteine (NAC) on the accumulation of methaemoglobin. NMP was performed on nine human donor livers declined for transplantation: three were perfused without NAC (no-NAC group), and six organs perfused with an initial NAC bolus, followed by continuous infusion (NAC group), with hourly methaemoglobin perfusate measurements. In-vitro experiments examined the impact of NAC (3 mg) on red cells (30 ml) in the absence of liver tissue. The no-NAC group sustained perfusions for an average of 96 (range 87-102) h, universally developing methaemoglobinaemia (≥ 2%) observed after an average of 45 h, with subsequent steep rise. The NAC group was perfused for an average of 148 (range 90-184) h. Only 2 livers developed methaemoglobinaemia (peak MetHb of 6%), with an average onset of 116.5 h. Addition of NAC efficiently limits formation and accumulation of methaemoglobin during NMP, and allows the significant extension of perfusion duration.

Addressing extreme size mismatch in pediatric intestinal transplantation: Outcomes of intestinal length reduction

BACKGROUND

Bench liver reduction, with or without intestinal length reduction (LR) (coupled with delayed closure and abdominal wall prostheses), has been a strategy adopted by our program for small children due to the limited availability of size-matched donors. This report describes the short, medium, and long-term outcomes of this graft reduction strategy.

METHODS

A single-center, retrospective analysis of children that underwent intestinal transplantation (April 1993 to December 2020) was performed. Patients were grouped according to whether they received an intestinal graft of full length (FL) or following LR.

RESULTS

Overall, 105 intestinal transplants were performed. The LR group (n = 10) was younger (14.5 months vs. 40.0 months, p = .012) and smaller (8.7 kg vs. 13.0 kg, p = .032) compared to the FL group (n = 95). Similar abdominal closure rates were achieved after LR, without any increase in abdominal compartment syndrome (1/10 vs. 7/95, p = .806). The 90-day graft and patient survival were similar (9/10, 90% vs. 83/95, 86%; p = .810). Medium and long-term graft survival at 1 year (8/10, 80% vs. 65/90, 71%; p = .599), and 5 years (5/10, 50% vs. 42/84, 50%; p = 1.00) was similar.

CONCLUSION

LR of intestinal grafts appears to be a safe strategy for infants and small children requiring intestinal transplantation. This technique should be considered in the situation of significant size mismatch of intestine containing grafts.

Low C-reactive Protein and Urea Distinguish Primary Nonfunction From Early Allograft Dysfunction Within 48 Hours of Liver Transplantation

Primary nonfunction (PNF) is a life-threatening complication of liver transplantation (LT), but in the early postoperative period, it can be difficult to differentiate from early allograft dysfunction (EAD). The aim of this study was to determine if serum biomarkers can distinguish PNF from EAD in the initial 48 h following LT.

Materials and Methods

A retrospective study of adult patients that underwent LT between January 2010 and April 2020 was performed. Clinical parameters, absolute values and trends of C-reactive protein (CRP), blood urea, creatinine, liver function tests, platelets, and international normalized ratio in the initial 48 h after LT were compared between the EAD and PNF groups.

Results

There were 1937 eligible LTs, with PNF and EAD occurring in 38 (2%) and 503 (26%) patients, respectively. A low serum CRP and urea were associated with PNF. CRP was able to differentiate between the PNF and EAD on postoperative day (POD)1 (20 versus 43 mg/L; P < 0.001) and POD2 (24 versus 77; P < 0.001). The area under the receiver operating characteristic curve (AUROC) of POD2 CRP was 0.770 (95% confidence interval [CI] 0.645-0.895). The urea value on POD2 (5.05 versus 9.0 mmol/L; P = 0.002) and trend of POD2:1 ratio (0.71 versus 1.32 mmol/L; P < 0.001) were significantly different between the groups. The AUROC of the change in urea from POD1 to 2 was 0.765 (95% CI 0.645-0.885). Aspartate transaminase was significantly different between the groups, with an AUROC of 0.884 (95% CI 0.753-1.00) on POD2.

Discussion

The biochemical profile immediately following LT can distinguish PNF from EAD; CRP, urea, and aspartate transaminase are more effective than ALT and bilirubin in distinguishing PNF from EAD in the initial postoperative 48 h. Clinicians should consider the values of these markers when making treatment decisions.

Machine perfusion and the prevention of ischemic type biliary lesions following liver transplant: What is the evidence?

The widespread uptake of different machine perfusion (MP) strategies for liver transplant has been driven by an effort to minimize graft injury. Damage to the cholangiocytes during the liver donation, preservation, or early posttransplant period may result in stricturing of the biliary tree and inadequate biliary drainage. This problem continues to trouble clinicians, and may have catastrophic consequences for the graft and patient. Ischemic injury, as a result of compromised hepatic artery flow, is a well-known cause of biliary strictures, sepsis, and graft failure. However, very similar lesions can appear with a patent hepatic artery and these are known as ischemic type biliary lesions (ITBL) that are attributed to microcirculatory dysfunction rather than main hepatic arterial compromise. Both the warm and cold ischemic period duration appear to influence the onset of ITBL. All of the commonly used MP techniques deliver oxygen to the graft cells, and therefore may minimize the cholangiocyte injury and subsequently reduce the incidence of ITBL. As clinical experience and published evidence grows for these modalities, the impact they have on ITBL rates is important to consider. In this review, the evidence for the three commonly used MP strategies (abdominal normothermic regional perfusion [A-NRP], hypothermic oxygenated perfusion [HOPE], and normothermic machine perfusion [NMP] for ITBL prevention has been critically reviewed. Inconsistencies with ITBL definitions used in trials, coupled with variations in techniques of MP, make interpretation challenging. Overall, the evidence suggests that both HOPE and A-NRP prevent ITBL in donated after circulatory death grafts compared to cold storage. The evidence for ITBL prevention in donor after brain death grafts with any MP technique is weak.

A7 OPPORTUNISTIC PATHOGEN MODULATION OF GLUTEN-REACTIVE CD4+ T CELL ACTIVATION BY DQ2-EXPRESSING ORGANOID MONOLAYERS

Background

Bacteria have recently emerged as additional modulators of inflammation in CeD. We have shown that the elastase-like producing opportunistic pathogen, Pseudomonas (P) aeruginosa, partially metabolizes gluten into peptides that translocate the mucosal barrier and retain their immunogenicity. We previously demonstrated that organoid monolayers derived from DR3-DQ2 mice carrying the CeD risk gene HLA-DQ2 express MHC class II (HLA-DQ2) and co-stimulatory molecules under induced inflammatory conditions, priming the monolayers for gluten antigen presentation. Here we investigate the activation of human (h)CD4⁺ T cell co-cultured with DQ2 monolayers stimulated with gluten pre-digested, or not, by bacterial elastase.

Purpose

To investigate whether organoid monolayers expressing DQ2 activate T cell differentially in the presence of gluten metabolized by elastase-like producing Pseudomonas aeruginosa.

Method

Organoid monolayers were derived from the duodenum and proximal jejunum of gluten-sensitized DR3-DQ2 mice, following the gluten sensitization protocol previously described¹. Monolayers were then stimulated with IFN-γ for 24h to induce MHC-II and co-stimulatory molecules expression. Splenic T-cell expressing hCD4 from gluten-sensitized DR3-DQ2-hCD4 mice were then co-cultured with monolayers in the presence of deamidated pepsin-trypsin-digested (DAPT)-gluten or Pseudomonas aeruginosa PA14 (WT)-digested DAPT-gluten. As a control, DAPT-gluten was incubated with a P. aeruginosa lasB mutant strain that lacks elastase-like activity (lasB^△/△). Co-cultures stimulated with DAPT-gluten alone or WT-media were used as additional controls.

Result(s)

Increased hCD4⁺ T-cell proliferation was observed in co-cultures stimulated with WT-digested gluten compared with lasB^△/△-digested gluten (p<0.0001), gluten alone (p=0.0002) or WT-media (p<0.0001). hCD4⁺ T cell co-cultured with organoid monolayers stimulated with WT-digested gluten, had an activated phenotype with increased expression of CD69, CD44 and CD25 versus those stimulated with gluten, lasB^△/△-digested gluten, or WT-media. Increased levels of pro-inflammatory and T helper type 1 (Th1)-associated cytokines were detected in the supernatant of the co-cultures stimulated with WT-digested gluten, including IL-2, IFN-γ, IL-6, TNF-α, IL-1α, IL-β, and IL-15.

Conclusion(s)

Using a novel HLA-DQ2-expressing organoid monolayer, we demonstrate elastase-like producing P. aeruginosa, enhanced activation and proliferation of hCD4⁺ T cell through gluten metabolism. This in vitro model constitutes a relevant tool for studying microbial triggers and drivers of intestinal epithelial dysfunction in CeD.

1. Galipeau, H. J. et al. 1. Galipeau, H. J. et al. Sensitization to Gliadin Induces Moderate Enteropathy and Insulitis in Nonobese Diabetic-DQ8 Mice. J. Immunol.187, 4338–4346 (2011).

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CIHR, Other

Please indicate your source of funding;

Canadian Celiac Disease Association (CCA)

Disclosure of Interest

None Declared

A32 PHAGE TREATMENT DELAYS ONSET OF CROHN’S-ASSOCIATED E. COLI DRIVEN COLITIS IN MICE COLONIZED WITH A DEFINED MICROBIOTA

Background

Opportunistic pathogens have been postulated to drive dysregulated inflammation in inflammatory bowel disease (IBD). Indeed, adherent-invasive Escherichia coli (AIEC) isolated from IBD patients have pathobiont and pro-inflammatory characteristics. Current treatments for IBD suppress the immune response and do not target key microbial drivers, therefore novel strategies are required.

Purpose

Our aim was to determine whether bacteriophage therapy targeted against AIEC could reduce the severity of E. coli-driven colitis in gnotobiotic mice.

Method

Adult germ-free C57BL/6 mice were colonized with altered Schaedler-like flora (ASF) and E. coli NRG857c, a Crohn’s disease-associated bacterial isolate. Three weeks later, mice were treated with daily phage (selected by killing curves bioassays against E. coli NRG857c) or PBS for 2 weeks (n=6/group). Mice were then exposed to low-dose dextran sulfate sodium (2%; DSS) in drinking water for 5 days, followed by 2 days of water. PBS-treated mice (n=6) that received no DSS were used as additional negative controls. Mice were monitored daily for weight, stool consistency, and occult blood. At sacrifice, colon tissue was collected for histological analysis and fecal contents were cultured to determine bacterial load. In separate experiments, C57BL/6NTac-Il10^em8Tac (IL-10^-/-) mice were colonized with ASF-like microbiota and E. coli NRG857c. Three weeks later, mice (n=5) were treated with weekly phage or PBS (n=5) for 7 weeks. Mice were monitored weekly as described above.

Result(s)

Daily phage treatment reduced the severity of clinical symptoms induced by acute DSS administration (p < 0.001 vs. DSS-PBS treated mice). At endpoint, phage treatment was associated with lower histological scores as compared with DSS-PBS controls (p < 0.0001). A 1-log reduction in AIEC bacterial load was observed in phage treated mice as compared with DSS-PBS controls (p < 0.001). In IL-10^-/- mice, weekly phage treatment delayed the spontaneous onset of colitis (p < 0.0001 vs. PBS-treated mice). At endpoint, mice treated with phage had lower colitis scores. Reduced weekly AIEC bacterial load was observed in phage-treated mice.

Conclusion(s)

Lytic phages, targeting a known AIEC pathobiont isolated from Crohn’s disease patients, ameliorate acute intestinal injury and delay onset of spontaneous colitis. Future work will investigate the mechanisms by which phage therapy prevents and treats colitis, to better inform clinical trial design.

Disclosure of Interest

None Declared

A3 CROHN’S DISEASE PROTEOLYTIC MICROBIOTA ENHANCES INFLAMMATION THROUGH PAR2 PATHWAY IN GNOTOBIOTIC MICE

Background

An imbalance in host proteases has been implicated in inflammatory bowel disease (IBD). Recent evidence implicates microbial proteolytic activity (PA) in ulcerative colitis but whether it also plays a role in Crohn’s disease (CD) remains unclear.

Purpose

We therefore investigated the colitogenic potential and underlying pathways of proteolytic CD microbiota.

Method

Adult germ-free (GF) C57BL/6 mice were colonized with CD microbiota selected based on high (CD-HPA) or low fecal proteolytic activity (CD-LPA), and from healthy controls with LPA (HC-LPA), after which total fecal proteolytic, elastolytic and mucolytic activity were analyzed in the mice. Microbial community was assessed by 16S rRNA gene sequencing. Immune function and colonic injury were investigated by inflammatory gene expression (NanoString) and histology. Colitis severity and underlying pathways were investigated in C57BL/6, Nucleotide-binding Oligomerization Domain-2 knock-out (Nod2^-/-), and Protease-Activated Receptor 2 (PAR2) cleavage resistant mice (R38E-PAR2) subjected to 2% dextran sodium sulfate in drinking water for 5 days followed by 2 days on water.

Result(s)

Colonization with HC-LPA or CD-LPA lowered baseline fecal proteolytic activity compared with GF mice, which was paralleled by lower acute inflammatory cell infiltrate. CD-HPA further increased proteolytic activity compared with GF mice. Fecal supernatants from CD-LPA or HC-LPA colonized mice had lower in vitro PAR2 cleavage compared to supernatants from GF and CD-HPA colonized mice. Several genes, such as Map kinases, Rhoa, Myd88, and Tollip, were increased in GF mice compared to colonized mice. 18 genes related to inflammation and barrier function (e.g., Mapk2k6, Tnf, Claudin1) were differentially expressed between CD-LPA and CD-HPA. CD-HPA mice had lower alpha diversity, distinct microbial profiles, and higher fecal proteolytic activity compared with CD-LPA. Abundance of several beneficial species (e.g., Akkermansia muciniphilia) was decreased while other taxa were increased (e.g., Hungattella hathewayi) in CD-HPA compared to CD-LPA. H. hathewayi as well as the serine protease K04772 were transcriptionally increased in fecal samples from CD-HPA colonized mice. C57BL/6 and Nod2^-/- mice, but not R38E-PAR2 mice, colonized with CD-HPA developed earlier and more severe colitis compared with mice colonized with CD-LPA.

Conclusion(s)

CD proteolytic microbiota is proinflammatory through a PAR2 pathway. H. hathewayi correlates with the proinflammatory phenotype through the serine protease K04772 in this model. The results support a role of microbial PA in CD, which could constitute a biomarker for identifying patients who would benefit from anti-proteolytic therapies.

Disclosure of Interest

None Declared

Normothermic Machine Perfusion—Improving the Supply of Transplantable Livers for High-Risk Recipients

The effectiveness of liver transplantation to cure numerous diseases, alleviate suffering, and improve patient survival has led to an ever increasing demand. Improvements in preoperative management, surgical technique, and postoperative care have allowed increasingly complicated and high-risk patients to be safely transplanted. As a result, many patients are safely transplanted in the modern era that would have been considered untransplantable in times gone by. Despite this, more gains are possible as the science behind transplantation is increasingly understood. Normothermic machine perfusion of liver grafts builds on these gains further by increasing the safe use of grafts with suboptimal features, through objective assessment of both hepatocyte and cholangiocyte function. This technology can minimize cold ischemia, but prolong total preservation time, with particular benefits for suboptimal grafts and surgically challenging recipients. In addition to more physiological and favorable preservation conditions for grafts with risk factors for poor outcome, the extended preservation time benefits operative logistics by allowing a careful explant and complicated vascular reconstruction when presented with challenging surgical scenarios. This technology represents a significant advancement in graft preservation techniques and the transplant community must continue to incorporate this technology to ensure the benefits of liver transplant are maximized.

A5 GLUTEN-SPECIFIC T CELL ACTIVATION BY MHC CLASS II EXPRESSING ORGANOID MONOLAYERS

NOT PUBLISHED AT AUTHOR’S REQUEST

Funding Agencies: CIHR

A200 CROHN’S-ASSOCIATED E. COLI WORSEN COLITIS SEVERITY IN MICE COLONIZED WITH DEFINED MICROBIOTA

Background

Bacterial infections have been postulated to drive the dysregulated inflammation found in inflammatory bowel disease (IBD). In particular, adherent-invasive Escherichia coli (AIEC) isolated from patients with IBD have pathobiont characteristics and have been implicated in IBD pathogenesis.

Aims

Our aim was to characterize and compare the level of intestinal inflammation and potential microbiota shifts induced by E. coli clinical isolates using a gnotobiotic mouse model of colitis.

Methods

Adult germ-free C57BL/6 mice were transferred to ISO positive cages in a gnotobiotic facility and colonized with altered Schaedler flora-like (ASF) microbiota and one of three clinical E. coli isolates: E. coli C0004 (n = 5), E. coli LF82 (n = 9), E. coli NRG857c (n = 6), or ASF alone (n = 6). Three weeks later, mice were treated for 5 days with low dose dextran sodium sulphate in drinking water (2%; DSS), followed by 2 days of water. Mice were monitored daily for clinical symptoms (weight, stool consistency, and occult blood). At sacrifice, colon tissue was collected for histological analysis. Cecum contents were cultured to determine bacterial load. Fecal samples were collected for 16S rRNA gene sequencing analysis before and after DSS treatment.

Results

All mice colonized with an E. coli isolate displayed significantly greater clinical and microscopic scores of colitis compared to ASF alone, but the severity was dependent on the colonized E. coli strain. E. coli NRG857c-colonized mice exhibited more severe symptoms (p &lt; 0.001) two days earlier than mice colonized with other E. coli isolates. Mice colonized with E. coli LF82 or E. coli NRG857c had higher histological scores of colitis compared to mice colonized with E. coli C0004, which were also significantly greater than ASF alone (p &lt; 0.0001). 16S rRNA gene sequencing revealed that ASF-alone-colonized mice lacked Proteobacteria. All E. coli-colonized mice had comparable bacterial loads, which were verified by 16S rRNA analysis. Following DSS, E. coli LF82 and E. coli NRG857c relative abundance remained stable, whereas the relative abundance of Roseburia/ASF 492 declined significantly in all E. coli colonized mice.

Conclusions

The presence of E. coli pathobionts in mice drive the severity of chemically induced colitis, with AIEC NRG857c inducing the greatest severity. This gnotobiotic mouse model enables us to control the severity of colitis in a well-defined microbiota that is dependent on the colonized E. coli isolate. Using this model, we will be able to assess therapeutic candidates that aim to treat colitis at varying stages of its disease progression.

Funding Agencies

CCC, CIHRNSERC

A144 CHRONIC DSS LEADS TO ALTERED EXPRESSION OF IRAK4/TPL2 PATHWAYS IN UC-COLONIZED MICE

Background

Ulcerative colitis (UC) is one of two forms of inflammatory bowel disease (IBD). The exact cause of IBD is unknown but altered host-microbe interactions and genetic susceptibility are involved in its pathogenesis. Many patients with IBD do not respond to biological therapies targeting single cytokines, therefore new therapies that target common immune pathways are being developed and need to be tested in relevant preclinical models. Previously we have shown that mice colonized with UC microbiota upregulated genes related to inflammation without induction of colitis compared to healthy volunteer-colonized mice. We thus investigated whether IRAK4 and TPL2-induced pathways, new therapeutic targets in development upstream of inflammatory cytokine gene activation, are upregulated in mice colonized with UC microbiota and chronic colitis.

Aims

Our aim was to characterize TPL2 and IRAK4 signalling pathways and T cell phenotypes in UC-colonized mice following chronic low-dose dextran sodium sulfate (DSS) colitis.

Methods

10-16-week-old germ-free C57BL/6 mice were colonized with fecal microbiota from a patient with UC experiencing a flare (n=16). Mice were housed in a gnotobiotic facility during the experiment. Three weeks following colonization, colitis was induced in half of the mice by three cycles (5 d each; 2.0%, 1.5% and 1.5%, respectively) of DSS in drinking water with a 5-d wash-out period between cycles. All mice were fed a control diet (7004, Teklad). Fecal samples were collected weekly. At sacrifice, disease activity (colon length, occult blood in feces, stool consistency, and spleen weight) was measured and colon tissue was collected for histological analysis and RNA sequencing. Mesenteric lymph nodes (MLNs) were acquired for flow cytometry to analyze T cell phenotypes.

Results

In UC-colonized mice, chronic low-dose DSS induced softer feces (p<0.0001), shorter colon length (p<0.0001), and increased spleen weight (p<0.0001), compared with water treated mice. This was paralleled by detectable blood in stool, development of moderate colitis (DSS: 1.9+/-1.4 vs H₂O: 0.5+/-0.2; p<0.02) and higher proportion of IL-17 (p=0.003) and IFN-γ-producing T cells (p=0.06) in MLNs compared with water treated mice. RNA sequencing revealed that inflammatory genes, mainly related to the IRAK4/TPL2 pathway (e.g., Gadd45b, Socs3, Il1b), were significantly increased (p≤0.05) in the colon of mice treated with DSS compared with water.

Conclusions

When challenged with a chronic low-dose chemical injury agent, mice colonized with UC microbiota develop clinical and histological signs of colitis and upregulation of genes involved in inflammation like Gadd45b, Socs3, and Il1b. Thus, this model represents a new valuable tool for preclinical testing of new drug candidates, such as those related to the modulation of IRAK4/TPL2 pathways.

Funding Agencies

CCC

Primary Nonfunction of the Liver Allograft

Severe allograft dysfunction, as opposed to the expected immediate function, following liver transplantation is a major complication, and the clinical manifestations of such that lead to either immediate retransplant or death are the catastrophic end of the spectrum. Primary nonfunction (PNF) has declined in incidence over the years, yet the impact on patient and healthcare teams, and the burden on the organ pool in case of the need for retransplant should not be underestimated. There is no universal test to define the diagnosis of PNF, and current criteria are based on various biochemical parameters surrogate of liver function; moreover, a disparity remains within different healthcare systems on selecting candidates eligible for urgent retransplantation. The impact on PNF from traditionally accepted risk factors has changed somewhat, mainly driven by the rising demand for organs, combined with the concerted approach by clinicians on the in-depth understanding of PNF, optimal graft recipient selection, mitigation of the clinical environment in which a marginal graft is reperfused, and postoperative management. Regardless of the mode, available data suggest machine perfusion strategies help reduce the incidence further but do not completely avert the risk of PNF. The mainstay of management relies on identifying severe allograft dysfunction at a very early stage and aggressive management, while excluding other identifiable causes that mimic severe organ dysfunction. This approach may help salvage some grafts by preventing total graft failure and also maintaining a patient in an optimal physiological state if retransplantation is considered the ultimate patient salvage strategy.

Regulatory T-Cell Therapy in Liver Transplantation and Chronic Liver Disease

The constant exposure of the liver to gut derived foreign antigens has resulted in this organ attaining unique immunological characteristics, however it remains susceptible to immune mediated injury. Our understanding of this type of injury, in both the native and transplanted liver, has improved significantly in recent decades. This includes a greater awareness of the tolerance inducing CD4+ CD25+ CD127low T-cell lineage with the transcription factor FoxP3, known as regulatory T-Cells (Tregs). These cells comprise 5-10% of CD4+ T cells and are known to function as an immunological "braking" mechanism, thereby preventing immune mediated tissue damage. Therapies that aim to increase Treg frequency and function have proved beneficial in the setting of both autoimmune diseases and solid organ transplantations. The safety and efficacy of Treg therapy in liver disease is an area of intense research at present and has huge potential. Due to these cells possessing significant plasticity, and the potential for conversion towards a T-helper 1 (Th1) and 17 (Th17) subsets in the hepatic microenvironment, it is pre-requisite to modify the microenvironment to a Treg favourable atmosphere to maintain these cells' function. In addition, implementation of therapies that effectively increase Treg functional activity in the liver may result in the suppression of immune responses and will hinder those that destroy tumour cells. Thus, fine adjustment is crucial to achieve this immunological balance. This review will describe the hepatic microenvironment with relevance to Treg function, and the role these cells have in both native diseased and transplanted livers.

COVID-19 in liver transplant candidates: pretransplant and post-transplant outcomes - an ELITA/ELTR multicentre cohort study

OBJECTIVE

Explore the impact of COVID-19 on patients on the waiting list for liver transplantation (LT) and on their post-LT course.

DESIGN

Data from consecutive adult LT candidates with COVID-19 were collected across Europe in a dedicated registry and were analysed.

RESULTS

From 21 February to 20 November 2020, 136 adult cases with laboratory-confirmed SARS-CoV-2 infection from 33 centres in 11 European countries were collected, with 113 having COVID-19. Thirty-seven (37/113, 32.7%) patients died after a median of 18 (10-30) days, with respiratory failure being the major cause (33/37, 89.2%). The 60-day mortality risk did not significantly change between first (35.3%, 95% CI 23.9% to 50.0%) and second (26.0%, 95% CI 16.2% to 40.2%) waves. Multivariable Cox regression analysis showed Laboratory Model for End-stage Liver Disease (Lab-MELD) score of ≥15 (Model for End-stage Liver Disease (MELD) score 15-19, HR 5.46, 95% CI 1.81 to 16.50; MELD score≥20, HR 5.24, 95% CI 1.77 to 15.55) and dyspnoea on presentation (HR 3.89, 95% CI 2.02 to 7.51) being the two negative independent factors for mortality. Twenty-six patients underwent an LT after a median time of 78.5 (IQR 44-102) days, and 25 (96%) were alive after a median follow-up of 118 days (IQR 31-170).

CONCLUSIONS

Increased mortality in LT candidates with COVID-19 (32.7%), reaching 45% in those with decompensated cirrhosis (DC) and Lab-MELD score of ≥15, was observed, with no significant difference between first and second waves of the pandemic. Respiratory failure was the major cause of death. The dismal prognosis of patients with DC supports the adoption of strict preventative measures and the urgent testing of vaccination efficacy in this population. Prior SARS-CoV-2 symptomatic infection did not affect early post-transplant survival (96%).

Health-related quality of life, uncertainty and coping strategies in solid organ transplant recipients during shielding for the COVID-19 pandemic

Strict isolation of vulnerable individuals has been a strategy implemented by authorities to protect people from COVID‐19. Our objective was to investigate health‐related quality of life (HRQoL), uncertainty and coping behaviours in solid organ transplant (SOT) recipients during the COVID‐19 pandemic. A cross‐sectional survey of adult SOT recipients undergoing follow‐up at our institution was performed. Perceived health status, uncertainty and coping strategies were assessed using the EQ‐5D‐5L, Short‐form Mishel Uncertainty in Illness Scale (SF‐MUIS) and Brief Cope, respectively. Interactions with COVID‐19 risk perception, access to health care, demographic and clinical variables were assessed. The survey was completed by 826 of 3839 (21.5%) invited participants. Overall, low levels of uncertainty in illness were reported, and acceptance was the major coping strategy (92%). Coping by acceptance, feeling protected, self‐perceived susceptibility to COVID‐19 were associated with lower levels of uncertainty. Health status index scores were significantly lower for those with mental health illness, compromised access to health care, a perceived high risk of severe COVID‐19 infection and higher levels of uncertainty. A history of mental health illness, risk perceptions, restricted healthcare access, uncertainty and coping strategies was associated with poorer HRQoL in SOT recipients during strict isolation. These findings may allow identification of strategies to improve HRQoL in SOT recipients during the pandemic.

A13 A HIGH SALT DIET SYNERGIZES WITH UC MICROBIOTA TO INDUCE A PROINFLAMMATORY IMMUNE TONE IN IMMUNOCOMPETENT GNOTOBIOTIC MICE

Background

The exact cause for inflammatory bowel disease (IBD) is unknown, however, there is consensus that a combination of genetic, environmental, and immune factors, participate in its pathogenesis. Recently, high salt diet (HSD) has been shown to increase the severity of experimental colitis through depletion of lactobacilli in specific pathogen-free mice. However, whether HSD-microbiota interaction occurs in mice colonized with microbiota from patients with IBD, is unknown.

Aims

Our aim was to determine whether mice colonized with microbiota from patients with active ulcerative colitis (UC), one of two forms of IBD, develop more severe inflammation when fed a HSD.

Methods

10–15 week-old germ-free C57BL/6 mice were colonized with fecal microbiota from a healthy control (HC, n=13) or from a patient with UC experiencing a flare (UC, n=13). Colonized mice were housed in ISO positive cages (Techniplast) in a gnotobiotic facility during the experiment. For each group, half of the mice were kept on a control diet (7004, Teklad) and the other half were fed a HSD (7004 supplemented with 4% NaCl) plus 1% NaCl in drinking water for 3 weeks. At sacrifice, colon tissue was collected for histological analysis, RNA sequencing, and flow cytometry. Fecal samples were collected for lipocalin-2 determination.

Results

Colonic polymorphonuclear (PMN) cells were higher in UC compared with HC mice, regardless of diet (p&lt;0.01). In mice fed HSD, UC mice also had higher PMN cell counts than HC mice (p&lt;0.001). Administration of HSD to UC, but not to HC mice, also increased the proportion of α4+IFNg-producing T cells in the colonic lamina propria, compared with UC mice fed control diet (p&lt;0.01). This was paralleled by higher fecal lipocalin-2 in UC mice fed HSD compared with control diet (p&lt;0.05). Targeted analysis of RNA sequencing data revealed that 7 genes, mainly related to the JAK/STAT pathway (i.e., Stat2, Tyk2, Tlr7) were differentially expressed (p≤0.05) between HC and UC mice fed the control diet. A different gene expression signature was found in mice fed HSD compared with control diet, with an increase in proinflammatory genes in UC colonized mice compared to HC colonized mice, such as Il12a and Il6 (p&lt;0.05).

Conclusions

Immunocompetent mice colonized with microbiota from a UC patient in flare spontaneously developed a proinflammatory immune tone, which was exacerbated by HSD. The different pattern of gene induction observed in mice colonized with the microbiota from the same UC donor, but fed HSD, suggests independent and synergistic pathways conducive to inflammation. Future studies will explore the preclinical therapeutic effect of novel drug candidates for the inhibition of such pathways.

Funding Agencies

CCC

Severe Sepsis Mimicking Primary Nonfunction Following Liver Transplantation: Normothermic Machine Perfusion Is a Potential Environment for Bacterial Overgrowth and Transmission From Donor to Recipient. A Case Report

Primary nonfunction (PNF) in the early postoperative period following liver transplantation is fatal if not managed appropriately with early retransplantation. Severe early allograft dysfunction can mimic PNF. The identification of treatable causative factors such as sepsis, hepatic artery, or portal vein thrombosis is essential to distinguish it from PNF, and their early management may avoid the need for retransplantation. In this article, we describe a case of sepsis-induced severe liver dysfunction from a contaminated graft perfused with normothermic machine perfusion (NMP), which presented in a manner similar to PNF. The implications of graft contamination are poorly described. To our knowledge, this is the first report of bacterial contamination of a graft that underwent NMP and subsequently caused severe sepsis in the recipient. The conditions created with NMP may be optimal for certain micro-organisms to thrive. The role of the liver in the immune system is complex as it provides an essential barrier to enterically derived portal venous pathogens and produces numerous acute phase proteins that augment the systemic immune response. Additionally, the liver is also known to restrain harmful and excessive systemic immune responses such as those that occur with the sepsis syndrome. The relationship between bacterial graft contamination, sepsis, and graft dysfunction may be multidirectional.

The Human Immune Response to Cadaveric and Living Donor Liver Allografts

The liver is an important contributor to the human immune system and it plays a pivotal role in the creation of both immunoreactive and tolerogenic conditions. Liver transplantation provides the best chance of survival for both children and adults with liver failure or cancer. With current demand exceeding the number of transplantable livers from donors following brain death, improved knowledge, technical advances and the desire to prevent avoidable deaths has led to the transplantation of organs from living, ABO incompatible (ABOi), cardiac death donors and machine based organ preservation with acceptable results. The liver graft is the most well-tolerated, from an immunological perspective, of all solid organ transplants. Evidence suggests successful cessation of immunosuppression is possible in ~20–40% of liver transplant recipients without immune mediated graft injury, a state known as “operational tolerance.” An immunosuppression free future following liver transplantation is an ambitious but perhaps not unachievable goal. The initial immune response following transplantation is a sterile inflammatory process mediated by the innate system and the mechanisms relate to the preservation-reperfusion process. The severity of this injury is influenced by graft factors and can have significant consequences. There are minimal experimental studies that delineate the differences in the adaptive immune response to the various forms of liver allograft. Apart from ABOi transplants, antibody mediated hyperacute rejection is rare following liver transplant. T-cell mediated rejection is common following liver transplantation and its incidence does not differ between living or deceased donor grafts. Transplantation in the first year of life results in a higher rate of operational tolerance, possibly due to a bias toward Th2 cytokines (IL4, IL10) during this period. This review further describes the current understanding of the immunological response toward liver allografts and highlight the areas of this topic yet to be fully understood.

Serum amylase and lipase and urinary trypsinogen and amylase for diagnosis of acute pancreatitis

BACKGROUND

The treatment of people with acute abdominal pain differs if they have acute pancreatitis. It is important to know the diagnostic accuracy of serum amylase, serum lipase, urinary trypsinogen-2, and urinary amylase for the diagnosis of acute pancreatitis, so that an informed decision can be made as to whether the person with abdominal pain has acute pancreatitis. There is currently no Cochrane review of the diagnostic test accuracy of serum amylase, serum lipase, urinary trypsinogen-2, and urinary amylase for the diagnosis of acute pancreatitis.

OBJECTIVES

To compare the diagnostic accuracy of serum amylase, serum lipase, urinary trypsinogen-2, and urinary amylase, either alone or in combination, in the diagnosis of acute pancreatitis in people with acute onset of a persistent, severe epigastric pain or diffuse abdominal pain.

SEARCH METHODS

We searched MEDLINE, Embase, Science Citation Index Expanded, National Institute for Health Research (NIHR HTA and DARE), and other databases until March 2017. We searched the references of the included studies to identify additional studies. We did not restrict studies based on language or publication status, or whether data were collected prospectively or retrospectively. We also performed a 'related search' and 'citing reference' search in MEDLINE and Embase.

SELECTION CRITERIA

We included all studies that evaluated the diagnostic test accuracy of serum amylase, serum lipase, urinary trypsinogen-2, and urinary amylase for the diagnosis of acute pancreatitis. We excluded case-control studies because these studies are prone to bias. We accepted any of the following reference standards: biopsy, consensus conference definition, radiological features of acute pancreatitis, diagnosis of acute pancreatitis during laparotomy or autopsy, and organ failure. At least two review authors independently searched and screened the references located by the search to identify relevant studies.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data from the included studies. The thresholds used for the diagnosis of acute pancreatitis varied in the trials, resulting in sparse data for each index test. Because of sparse data, we used -2 log likelihood values to determine which model to use for meta-analysis. We calculated and reported the sensitivity, specificity, post-test probability of a positive and negative index test along with 95% confidence interval (CI) for each cutoff, but have reported only the results of the recommended cutoff of three times normal for serum amylase and serum lipase, and the manufacturer-recommended cutoff of 50 mg/mL for urinary trypsinogen-2 in the abstract.

MAIN RESULTS

Ten studies including 5056 participants met the inclusion criteria for this review and assessed the diagnostic accuracy of the index tests in people presenting to the emergency department with acute abdominal pain. The risk of bias was unclear or high for all of the included studies. The study that contributed approximately two-thirds of the participants included in this review was excluded from the results of the analysis presented below due to major concerns about the participants included in the study. We have presented only the results where at least two studies were included in the analysis.Serum amylase, serum lipase, and urinary trypsinogen-2 at the standard threshold levels of more than three times normal for serum amylase and serum lipase, and a threshold of 50 ng/mL for urinary trypsinogen-2 appear to have similar sensitivities (0.72 (95% CI 0.59 to 0.82); 0.79 (95% CI 0.54 to 0.92); and 0.72 (95% CI 0.56 to 0.84), respectively) and specificities (0.93 (95% CI 0.66 to 0.99); 0.89 (95% CI 0.46 to 0.99); and 0.90 (95% CI 0.85 to 0.93), respectively). At the median prevalence of 22.6% of acute pancreatitis in the studies, out of 100 people with positive test, serum amylase (more than three times normal), serum lipase (more than three times normal), and urinary trypsinogen (more than 50 ng/mL), 74 (95% CI 33 to 94); 68 (95% CI 21 to 94); and 67 (95% CI 57 to 76) people have acute pancreatitis, respectively; out of 100 people with negative test, serum amylase (more than three times normal), serum lipase (more than three times normal), and urinary trypsinogen (more than 50 ng/mL), 8 (95% CI 5 to 12); 7 (95% CI 3 to 15); and 8 (95% CI 5 to 13) people have acute pancreatitis, respectively. We were not able to compare these tests formally because of sparse data.

AUTHORS' CONCLUSIONS

As about a quarter of people with acute pancreatitis fail to be diagnosed as having acute pancreatitis with the evaluated tests, one should have a low threshold to admit the patient and treat them for acute pancreatitis if the symptoms are suggestive of acute pancreatitis, even if these tests are normal. About 1 in 10 patients without acute pancreatitis may be wrongly diagnosed as having acute pancreatitis with these tests, therefore it is important to consider other conditions that require urgent surgical intervention, such as perforated viscus, even if these tests are abnormal.The diagnostic performance of these tests decreases even further with the progression of time, and one should have an even lower threshold to perform additional investigations if the symptoms are suggestive of acute pancreatitis.

Case report: successful open resection of a symptomatic giant liver haemangioma during the second trimester of pregnancy

Liver haemangiomas are consistently reported to be the commonest benign liver tumours and are most often incidental findings in asymptomatic individuals. Large lesions can become symptomatic, spontaneously rupture or result in a consumptive coagulopathy known as Kasabach–Merrit Syndrome. It is believed that the female sex hormones, particularly oestrogen, have an influence on haemangioma development and growth. The optimal management of large haemangiomas during the hyperoestrogenic state of pregnancy is poorly described in the current literature. To our knowledge, we describe only the second case of a giant hepatic haemangioma resection during pregnancy.

Improvement in advanced pancreatic cancer survival with novel chemotherapeutic strategies - experience of a community based hospital

Background: New chemotherapeutic strategies for locally advanced or metastatic pancreatic ductal adenocarcinoma (PDAC) have been shown to improve survival in randomized clinical trials. Little is known about the use of such chemotherapies and their benefit in community-based hospitals. This retrospective study analyzes the overall survival of these patients under "real life conditions" before and after the introduction of FOLFIRINOX in 2011. Methods: We retrospectively identified consecutive patients with PDAC who were treated at our hospital from 2011 to June 2014 (2011+ cohort) and 2004 to 2010 (historical cohort). Patients were included if PDAC was diagnosed in a locally advanced or metastatic state and at least 1 cycle of chemotherapy was given. Survival was assessed until April 2016. Patients with FOLFIRINOX were further analyzed regarding drug administration and side effects. Results: 128 patients met the inclusion criteria. Of the 74 patients in the historical cohort, 62 patients received Gemcitabine. Of the 54 patients diagnosed between 2011 and June 2014, 28 patients received FOLFIRINOX and 22 Gemcitabine as the first-line chemotherapy. Only 34 % of the patients in the historical cohort received a second-line chemotherapy in comparison to 69 % in the 2011+ cohort. Median overall survival (OS) showed a survival of 13.1 months (95 % CI; 11.6 - 14.5) for the 2011+ cohort compared to 9.6 months (95 % CI; 6.1 - 13.1) in the historical group. Conclusion: This study shows a marked improvement in survival of patients diagnosed with locally advanced or metastatic PDAC in a community-based hospital during the past 4 years. The most likely reasons are the use of new polychemotherapies like FOLFIRINOX and the use of second-line chemotherapy.

Training in General Surgery Ward Call: A Resident-Student Buddy System

There is a paucity of literature regarding medical student experiences of after hours hospital ward call. It was observed at our institution that medical students had minimal experience in ward call, yet were required to undertake such shifts as interns after graduation. We implemented a buddy system in which a medical student shadowed a general surgery resident for a ward call shift. Final year medical students were recruited from the local university at a tertiary teaching hospital after institutional approval. Each student attended a 4 hour evening shift on a general surgery ward with a supervising resident. A survey detailing attitudes and expectations of ward call was completed before and after the experience. Nine students enrolled in the project. Familiarity of expectations of what is required of an intern on a ward call shift improved significantly after the experience (3.1/5 to 4.1/5, p = 0.002). After hours work experience was reported as useful both before and after the study (4.5/5 to 4.7/5, p = 0.47). Students and doctors involved unanimously felt the experience was worthwhile. After hours ward call experience is useful for a final year medical student. More studies are required to further define the role of after hours ward call experiences during medical training.

Benefit of cerebrospinal fluid spectrophotometry in the assessment of CT scan negative suspected subarachnoid haemorrhage: a diagnostic accuracy study

This study aimed to determine if performing cerebrospinal fluid spectrophotometry in addition to visual inspection detects more ruptured cerebral aneurysms than performing cerebrospinal fluid visual inspection alone in patients with a normal head CT scan but suspected of suffering an aneurysmal subarachnoid haemorrhage (SAH). We performed a single-centre retrospective study of patients presenting to the emergency department of a tertiary hospital who underwent both head CT scan and lumbar puncture to exclude SAH. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of an approach utilising both spectrophotometry and visual inspection (combined approach) was compared to visual inspection alone. A total of 409 patients (mean age 37.8 years, 56.2% female) were recruited and six (1.5%) had a cerebral aneurysm on angiography. The sensitivity of visual inspection was 50% (95% confidence interval [CI]: 12.4-82.6%), specificity was 99% (95% CI: 97.5-99.7%), PPV was 42.9% (95% CI: 10.4-81.3%) and NPV was 99.2% (95% CI: 97.8-99.8%). The combined approach had a sensitivity of 100% (95% CI: 54.1-100%), specificity of 79.7% (95% CI: 75.4-83.5%), PPV of 6.8% (95% CI: 2.6-14.3%) and a NPV of 100% (95% CI: 98.8-100%). The sensitivity of the combined approach was not significantly different to that of visual inspection alone (p=0.25). Visual inspection had a significantly higher specificity than the combined approach (p<0.01). The combined approach detected more cases of aneurysmal SAH than visual inspection alone, however the difference in sensitivity was not statistically significant. Visual xanthochromia should prompt angiography because of a superior specificity and PPV. Due to its reduced sensitivity, caution should be applied when using only visual inspection of the supernatant.

A randomised controlled trial of the effect of continuous electronic physiological monitoring on the adverse event rate in high risk medical and surgical patients

We conducted a randomised controlled trial of mandated five-channel physiological monitoring vs standard care, in acute medical and surgical wards in a single UK teaching hospital. In all, 402 high-risk medical and surgical patients were studied. The primary outcome was the proportion of patients experiencing one or more major adverse events, including urgent staff calls, changes to higher care levels, cardiac arrests or death, in 96 h following randomisation. Secondary outcomes were the proportion of patients requiring acute treatment changes, and the 30-day and hospital mortality. In the 96 h following randomisation, 113 (56%) patients in the monitored arm and 116 (58%) in the control arm (OR 0.94, 95% CI 0.63-1.40, p = 0.76) had a major event. An acute change in treatment was necessary in 107 (53%) monitored patients and 101 (50%) control patients (OR 0.55, 95% CI 0.87-1.29). Thirty-four (17%) monitored patients and 35 (17%) control patients died within 30 days. Thirteen patients in the control group received full five-channel monitoring at the request of the ward staff. We conclude that mandated electronic vital signs monitoring in high risk medical and surgical patients has no effect on adverse events or mortality.

Integrated monitoring and analysis for early warning of patient deterioration

Recently there has been an upsurge of interest in strategies for detecting at-risk patients in order to trigger the timely intervention of a Medical Emergency Team (MET), also known as a Rapid Response Team (RRT). We review a real-time automated system, BioSign, which tracks patient status by combining information from vital signs monitored non-invasively on the general ward. BioSign fuses the vital signs in order to produce a single-parameter representation of patient status, the Patient Status Index. The data fusion method adopted in BioSign is a probabilistic model of normality in five dimensions, previously learnt from the vital sign data acquired from a representative sample of patients. BioSign alerts occur either when a single vital sign deviates by close to +/-3 standard deviations from its normal value or when two or more vital signs depart from normality, but by a smaller amount. In a trial with high-risk elective/emergency surgery or medical patients, BioSign alerts were generated, on average, every 8 hours; 95% of these were classified as 'True' by clinical experts. Retrospective analysis has also shown that the data fusion algorithm in BioSign is capable of detecting critical events in advance of single-channel alerts.

Microfabricated silicon microneedles for nonviral cutaneous gene delivery

BACKGROUND

The skin represents an accessible somatic tissue for therapeutic gene transfer. The superficial lipophilic layer of the skin, the stratum corneum, however, constitutes a major obstacle to the cutaneous delivery of charged macromolecules such as DNA.

OBJECTIVES

To determine whether silicon-based microneedles, microfabricated via a novel isotropic etching/BOSCH reaction process, could generate microchannels in the skin of sufficient dimensions to facilitate access of lipid : polycation : pDNA (LPD) nonviral gene therapy vectors.

METHODS

Scanning electron microscopy was used to visualize the microconduits created in heat-separated human epidermal sheets after application of the microneedles. Following confirmation of particle size and particle surface charge by photon correlation spectrocopy and microelectrophoresis, respectively, the diffusion of fluorescent polystyrene nanospheres and LPD complexes through heat-separated human epidermal sheets was determined in vitro using a Franz-type diffusion cell. In-vitro cell culture with quantification by flow cytometry was used to determine gene expression in human keratinocytes (HaCaT cells).

RESULTS

The diffusion of 100 nm diameter fluorescent polystyrene nanospheres, used as a readily quantifiable predictive model for LPD complexes, through epidermal sheets was significantly enhanced following membrane treatment with microneedles. The delivery of LPD complexes either into or through the membrane microchannels was also demonstrated. In both cases considerable interaction between the particles and the epidermal sheet was observed. In-vitro cell culture was used to confirm that LPD complexes mediated efficient reporter gene expression in human keratinocytes in culture when formulated at the appropriate surface charge.

CONCLUSIONS

These studies demonstrate the utility of silicon microneedles in cutaneous gene delivery. Further studies are required to elucidate fully the influence of the physicochemical characteristics of gene therapy vectors, e.g. particle diameter and surface charge, on their diffusion through microchannels and to quantify gene expression in vivo.

Apoptosis in the connective tissues of the periodontal ligament and gingivae of rat incisor and molar teeth at various stages of development

Apoptosis in the periodontal connective tissues was studied using the TUNEL technique, supported by electron microscopy. For 16 rats (aged 3, 8, or 104 weeks), nuclear fragmentation was assessed using the TUNEL technique (for 4 of the animals aged 8 weeks, incisor eruption was experimentally increased by trimming of teeth to the gingival margin--unimpeded eruption). A further 8 rats (aged 8 and 104 weeks) were employed for electron microscopy. For the incisor, prior to aging, and regardless of eruptive behavior (i.e., for both impeded and unimpeded incisors), there was little evidence of apoptosis in the periodontal ligament or gingival connective tissues. For the molar, apoptosis was also not usually detected when the teeth were erupting or in the mature, erupted state. In the aged animals, however, there was a marked increase in apoptosis (as assessed by the TUNEL technique) within the periodontal ligament and gingivae of both the molars and incisors (where eruption rates also increased). Nevertheless, electron microscopy indicated that significant numbers of apoptotic cells were only in the incisor periodontium. These findings are not consistent with the view that the periodontal fibroblasts provide a component of the force(s) responsible for eruption.

Megakaryopoiesis in vitro in myelodysplastic syndromes and acute myeloid leukaemia: effect of pegylated recombinant human megakaryocyte growth and development factor in combination with other growth factors

Pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF) can stimulate megakaryopoiesis in vitro in some myelodysplastic syndrome (MDS) and acute myeloid leukaemia (AML) patients. We assessed PEG-rHuMGDF combined with granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage CSF (GM-CSF), interleukin 3 (IL-3), IL6, stem cell factor (SCF) or erythropoietin in 40 MDS, 33 AML and 16 normal bone marrow samples. CD61-positive cells in suspension cultures increased with PEG-rHuMGDF alone in 20/25 RA + RAS, 11/14 RAEB + RAEBt and 29/33 AML cases. Further increases when IL-3 and/or SCF were added to PEG-rHuMGDF occurred in 14/20 RA + RAS, 8/13 RAEB + RAEBt and 18/26 AML cases. CFU-Mk growth was poor overall, but could be enhanced by PEG-rHuMGDF combinations in some patients. Stimulation of megakaryopoiesis by PEG-rHuMGDF can be augmented by IL-3 and SCF in many MDS and AML patients.

The reactions of articular cartilage to experimental wounding: role of apoptosis

OBJECTIVE

To determine the cellular and matrix responses to experimental wounding of articular cartilage.

METHODS

Immature and mature bovine articular cartilage was used as an in vitro model system to study the cellular responses to cartilage wounding. Explant cultures were wounded centrally with a trephine and maintained for up to 10 days. TUNEL labeling together with ultrastructural analyses were used to assess the nature of the observed cell death. In vitro labeling with 3H-thymidine was used to detect cell proliferation, and 2 antibodies (COL2-3/4M and BC-13) were used to detect changes in matrix turnover.

RESULTS

Cell death was observed as a response to wounding and was considered to be a combination of necrosis and apoptosis. In immature tissue, cell death was more pronounced, particularly in the articular surface region. Within the area of cell death, many cells that did not die subsequently underwent proliferation. The collagenous network showed evidence of denaturation in the area of the wound, but "aggrecanase" activity was not detected.

CONCLUSION

There are 2 contrasting, but related, responses to cartilage wounding--apoptosis and proliferation. In order to improve cartilage repair, future studies need to elucidate the regulatory mechanisms that determine these responses.