Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

BACKGROUND

Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres.

METHODS

This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low-middle-income countries.

RESULTS

In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of 'single-use' consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low-middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia.

CONCLUSION

This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high- and low-middle-income countries.

Donor-Recipient Body Surface Area Mismatch and the Outcome of Liver Transplantation in the UK

Introduction: Too small or too big liver grafts for recipient's size has detrimental effects on transplant outcomes. Research Questions: The purpose was to correlate donor-recipient body surface area ratio or body surface area index with recipient survival, graft survival, hepatic artery or portal vein, or vena cava thrombosis. High and low body surface area index cut-off points were determined. Design: There were 11,245 adult recipients of first deceased donor whole liver-only grafts performed in the UK from January 2000 until June 2020. The transplants were grouped according to the body surface area index and compared to complications, graft and recipient survival. Results: The body surface area index ranged from 0.491 to 1.691 with a median of 0.988. The body surface area index > 1.3 was associated with a higher rate of portal vein thrombosis within the first 3 months (5.5%). This risk was higher than size-matched transplants (OR: 2.878, 95% CI: 1.292-6.409, P = 0.01). Overall graft survival was worse in transplants with body surface area index ≤ 0.85 (HR: 1.254, 95% CI: 1.051-1.497, P = 0.012) or body surface area index > 1.4 (HR: 3.704, 95% CI: 2.029-6.762, P < 0.001) than those with intermediate values. The graft survival rates were reduced by 2% for cases with body surface area index ≤ 0.85 but were decreased by 20% for cases with body surface area index > 1.4. These findings were confirmed by bootstrap internal validation. No statistically significant differences were detected for hepatic artery thrombosis, occlusion of hepatic veins/inferior vena cava or recipient survival. Conclusions: Donor-recipient size mismatch affects the rates of portal vein thrombosis within the first 3 months and overall graft survival in deceased-donor liver transplants.

Combining Donor and Recipient Age With Preoperative MELD and UKELD Scores for Predicting Survival After Liver Transplantation

OBJECTIVES

The end-stage liver disease scoring systems MELD, UKELD, and D-MELD (donor age × MELD) have had mediocre results for survival assessment after orthotopic liver transplant. Here, we introduced new indices based on preoperative MELD and UKELDscores and assessed their predictive ability on survival posttransplant.

MATERIALS AND METHODS

We included 1017 deceased donor orthotopic liver transplants that were performed between 2008 (the year UKELD was introduced) and 2019. Donor and recipient characteristics, liver disease scores, transplant characteristics, and outcomes were collected for analyses. D-MELD, D-UKELD (donor age × UKELD),DR-MELD[(donor age + recipient age) × MELD], and DR-UKELD [(donor age + recipient age) × UKELD] were calculated.

RESULTS

No score had predictive value for graft survival. For patient survival,DR-MELD and DR-UKELD provided the best results but with low accuracy. The highest accuracy was observed at 1 year posttransplant (areas under the curve of 0.598 [95% CI, 0.529-0.667] and 0.609 [95% CI, 0.549-0.67]forDR-MELDandDR-UKELD). Addition of donor and recipient age significantly improved the predictive abilities of MELD and UKELD for patient survival, but addition of donor age alone did not. For 1-year mortality (using receiver operating characteristic curves), optimal cut-off points were DR-MELD>2345 and DR-UKELD>5908. Recipients with DR-MELD >2345 (P < .001) and DR-UKELD >5908 (P = .002) had worse patient survival within the first year, but only DR-MELD >2345 remained significant after multivariable analysis (P = .007).

CONCLUSIONS

DR-MELD and DR-UKELD scores provided the best, albeit mediocre, predictive ability among the 6 tested models, especially at 1 year after posttransplant, although only for patient but not for graft survival. A DR-MELD >2345 was considered to be an additional independent risk factor for worse recipient survival within the first postoperative year.

Woodchuck hepatocytes remain permissive for hepadnavirus infection and mouse liver repopulation after cryopreservation

Isolated hepatocytes represent a relevant model of the liver and are highly required both for research and therapeutic applications. However, sources of primary liver cells from human beings and from some animal species are limited. Therefore, cryopreservation of hepatocytes could greatly facilitate advances in various research areas. The aim of this study was to evaluate whether cryopreserved primary woodchuck hepatocytes could be used for woodchuck hepatitis B virus (WHV) infection studies, and whether they could maintain their regenerative potential in vivo after thawing. Critical steps for good quality of cryopreserved hepatocytes included the use of University of Wisconsin (UW) solution as a main component of the freezing medium, stepwise reduction of dimethylsulfoxide (DMSO) to avoid osmotic shock, and maintenance of low concentrations of DMSO in the culture medium. After cryopreservation, cell viability was still high (70% to 80%), and 50% to 60% of thawed cells attached to the plates. The appearance of covalently closed circular (ccc)DNA and of WHV-replicative forms a few days after in vitro infection demonstrated that thawed woodchuck hepatocytes were still susceptible to viral infection, thus proving maintenance of a very high hepatocyte-specific differentiation status. Furthermore, transplantation of woodchuck hepatocytes into the liver of urokinase-type plasminogen activator (uPA)/recombination activation gene-2 (RAG-2) mice, a model of liver regeneration, demonstrated that cryopreserved cells retained the ability to divide and to extensively repopulate a xenogenic liver. Notably, in vivo susceptibility to infection with WHV and proliferative capacity of frozen/thawed woodchuck hepatocytes in recipient mice were identical to those observed by transplanting fresh hepatocytes.

In vitro function of islets of Langerhans encapsulated with a membrane of porcine chondrocytes for immunoisolation

BACKGROUND/AIMS

Widespread clinical application of islet transplantation remains restricted, because of insufficient methods to prevent rejection and autoimmune destruction of islet grafts. In this study we demonstrate long-term function of islets of Langerhans within a capsule of porcine chondrocytes which may serve as an immunoisolation barrier utilizing the immunoprivileged properties of the chondrocyte matrix.

METHODS

Islets of Langerhans were isolated from Lewis rats, seeded on biodegradable polyglycolic acid polymer, and encapsulated with a monolayer of porcine chondrocytes. The encapsulated constructs and controls were kept in culture for 5 weeks. One group was exposed to a glucose challenge every 5th day. The insulin concentration of the culture medium was measured. Histological and insulin-immunohistochemical studies were performed.

RESULTS

Hematoxylin and eosin histology demonstrated viability of the islets of Langerhans. The intact morphology was demonstrated by Heidenhain staining. Toluidine blue showed viability of surrounding chondrocyte layers. Immunohistochemistry was positive for insulin within the beta cells of the islets. Both encapsulated constructs and nonencapsulated controls showed increasing insulin levels after glucose challenge.

CONCLUSIONS

We can tissue engineer a chondrocyte encapsulation membrane which permits diffusion of glucose and insulin. Islets of Langerhans survive within the chondrocyte capsule, and the glucose/insulin feedback mechanism remains intact.

Hepatic tissue engineering on 3-dimensional biodegradable polymers within a pulsatile flow bioreactor

BACKGROUND

An optimal method for hepatocyte transplantation is not yet determined. With the principles of tissue engineering in vitro conditioning of hepatocytes on biodegradable polymer in a flow bioreactor before implantation forming spheroids may achieve increased cell mass and function to replace lost organ function in vivo.

METHODS

Biodegradable poly-L-lactic (PLLA) polymer discs were seeded with rat hepatocytes in a concentration of 10 x 10(6) cells per ml and exposed to a medium flow of 24 ml/min for 1, 2, 4 and 6 days. The number and diameter of spheroidal aggregates was measured by phase-contrast microscopy. H&E histology was performed. Albumin production as hepatocyte specific function was determined by ELISA.

RESULTS

Spheroids of viable hepatocytes of 50-200 microm in diameter were formed. Both the number and diameter of the spheroids increased during the first 2 days and then remained constant until day 6. Albumin production was maintained throughout the culture period.

CONCLUSION

Short (2- 3 days) pre-transplant conditioning of hepatocytes in a flow bioreactor on biodegradable PLLA resulted in formation of spheroids with a liver-like morphology and preserved specific metabolic function. Tissue engineered hepatocyte spheroids on polymer may represent a functionally active and easy transplantable neotissue and may serve as an in vivo substitute for lost liver function.

Optimization of hepatocyte spheroid formation for hepatic tissue engineering on three-dimensional biodegradable polymer within a flow bioreactor prior to implantation

We hypothesize that in vitro conditioning of hepatocytes within biodegradable poly-L-lactic acid (PLLA) polymer matrices prior to implantation may increase hepatocyte survival and function after transplantation. The purpose of this study was to optimize the culture conditions of hepatocytes in a pulsatile flow bioreactor. PLLA discs were seeded with rat hepatocytes in a concentration of 2.5, 5, 10, 20 and 40 x 10(6) cells/ml. Seeded discs were exposed to recirculated perpendicular flow of 0, 7, 15, 24, 32, 52 ml/min of supplemented Williams' Medium E and harvested after 6 days in flow culture. Only under flow conditions the hepatocytes formed spheroidal aggregates (SphA) of 50-260 microm in diameter with a liver-like morphology and active metabolic function. The number of SphA was examined by phase contrast microscopy and the reductive enzyme function of the hepatocytes was tested using MTT. Hematoxylin and eosin histology showed vital hepatocytes within the SphA less than 200 microm in diameter but central necrosis in the SphA exceeding this size. Immunohistochemical staining confirmed albumin production of hepatocytes within the SphA. The optimal cell seeding concentration was 10 x 10(6) cells/ml with a flow speed of 24 ml/min. SphA of hepatocytes cultured with this flow bioreactor method may prove useful as a functional unit for tissue engineering of an in vivo liver substitute.

Hepatocyte transplantation using biodegradable matrices in ascorbic acid-deficient rats: comparison with heterotopically transplanted liver grafts

BACKGROUND

Hepatocyte transplantation using polymeric matrices is under investigation as an alternative therapy for metabolic liver diseases. Long-term engraftment of hepatocytes in polymers has been demonstrated. However, the metabolic activity of hepatocytes in such devices has never been assessed in direct comparison with liver grafts.

METHODS

Hepatocyte and partial liver transplantation were evaluated in the scurvy-prone osteogenic disorder Shionogi rat model. Biodegradable poly glycolic acid matrices seeded with hepatocytes equivalent to 20% of the recipient's liver mass, or 20% liver grafts were heterotopically transplanted into ascorbic acid- (AsA) deficient recipients. Recipients of cell-free matrices or AsA-deficient liver grafts served as controls. Recipients were set on AsA-free diet after transplantation. Plasma AsA levels, AsA concentrations in liver and adrenal gland tissue, and body weight ratios were assessed and H&E histology was performed.

RESULTS

Recipients from the control groups showed symptoms of scurvy at 1 month after cessation of AsA supply. Hepatocyte transplantation and auxiliary liver transplantation prevented symptoms of scurvy and increased plasma and tissue AsA levels and body weight ratios. AsA levels in recipients of 20% liver grafts were comparable to normal control animals.

CONCLUSIONS

Hepatocytes transplanted in polymeric matrices are able to compensate for liver-based metabolic deficiencies. Hepatocyte transplantation improves plasma AsA levels in AsA-deficient recipients. However, auxiliary liver grafts are superior to hepatocyte grafts in improving metabolic parameters. Further research work is needed to increase the efficiency of liver cell transplantation with regard to a clinical application.

Repopulation of mouse liver with human hepatocytes and in vivo infection with hepatitis B virus

Mice containing livers repopulated with human hepatocytes would provide excellent in vivo models for studies on human liver diseases and hepatotropic viruses, for which no permissive cell lines exist. Here, we report partial repopulation of the liver of immunodeficient urokinase-type plasminogen activator (uPA)/recombinant activation gene-2 (RAG-2) mice with normal human hepatocytes isolated from the adult liver. In the transplanted mice, the production of human albumin was demonstrated, indicating that human hepatocytes remained functional in the mouse liver for at least 2 months after transplantation. Inoculation of transplanted mice with human hepatitis B virus (HBV) led to the establishment of productive HBV infection. According to human-specific genomic DNA analysis and immunostaining of cryostat liver sections, human hepatocytes were estimated to constitute up to 15% of the uPA/RAG-2 mouse liver. This is proof that normal human hepatocytes can integrate into the mouse hepatic parenchyma, undergo multiple cell divisions, and remain permissive for a human hepatotropic virus in a xenogenic liver. This system will provide new opportunities for studies on etiology and therapy of viral and nonviral human liver diseases, as well as on hepatocyte biology and hepatocellular transplantation.

Long-term differentiated function of heterotopically transplanted hepatocytes on three-dimensional polymer matrices

Hepatocyte transplantation using porous matrices is under investigation as an alternative therapy for certain liver diseases. For this purpose, long-term function of transplanted hepatocytes is mandatory. This problem has not been sufficiently investigated yet. In this study Lewis rats were used as donors and recipients. Stimulated (group A, portocaval shunt) or unstimulated (group B) hepatocytes were transplanted into prevascularized polyvinyl-alcohol matrices. Cell-free matrices served as controls (group C). Matrices were harvested between 1 h and 1 year after implantation and analyzed by morphometry; albumin RNA in situ hybridization; and cytokeratin-, actin-, desmin-, and macrophage-specific antigen immunohistology. The hepatocyte number significantly decreased within the first week following implantation. Between 1 month and 1 year after transplantation a significant increase in hepatocyte number was noted in groups A and B. Albumin transcripts of transplanted hepatocytes were at normal levels at all times except for group B after 1 year. The immunohistology suggested engraftment of nonparenchymal liver cells. We conclude that 3-dimensional matrices provide a sufficient environment for long-term engraftment of transplanted liver cells. The hepatocytes are able, despite suboptimal initial engraftment, to repopulate the scaffold for at least half of the recipient's life span and maintain cell-specific function after sufficient stimulation.

Influence of pancreatic islets on growth and differentiation of hepatocytes in co-culture

Improvement of cell culture conditions in hepatic tissue engineering may permit cell/tissue banking and the generation of liver tissue equivalents for transplantation. In these systems, continuous hepatotrophic stimulation is still necessary. We investigated the stimulatory effects of pancreatic islets on hepatocytes in co-culture and characterized the stimulatory mechanisms. Hepatocytes and pancreatic islets were harvested from Lewis rats. Cells were cultured on collagen dishes either with nonstimulated media (controls and co-cultures with low or high islet rate) or stimulated media (controls and co-cultures). To characterize stimulatory mechanisms, additional co-cultures with membrane separation, with antiinsulin, antiglucagon, and with both antibodies were examined. Hepatocyte numbers, albumin secretion rate by enzyme-linked immunoadsorbent assay, and monoethylglycinxylidid biotransformation values by fluorescence polarization immunoassay were assessed. A radioimmunoassay measured insulin and glucagon concentrations. In groups with nonstimulated media, cell number was higher in co-cultures with low islet rate, and albumin secretion rate was increased in co-cultures with high islet rate compared to controls. MEGX biotransformation was decreased in co-cultures. In groups with stimulated media, co-culture had no impact on cell number or albumin secretion rate. Hepatocyte numbers and albumin secretion rates were not changed in co-cultures after membrane separation. Islet effects on hepatocytes were reduced in co-cultures with antiinsulin, antiglucagon, or both antibodies. Pancreatic islets provide stimulation for hepatocytes in vitro. Islet effects were mediated by soluble factors, and are dependent on insulin and glucagon. These results permit further investigations towards three-dimensional transplantable hepatocyte-islet devices for continuous in vitro and in vivo stimulation.

Interaction of hepatocytes and pancreatic islets cotransplanted in polymeric matrices

Heterotopic hepatocyte transplantation (HcTx) in polymeric matrices may become an alternative to liver transplantation for metabolic disorders. Hepatotrophic stimulation by means of a portocaval shunt operation is an established, but invasive, procedure used to optimize hepatocyte engraftment in matrices. We evaluated hepatocyte and pancreatic islet cotransplantation (ICT) as an alternative noninvasive approach to hepatotrophic stimulation. Lewis rats served as donors and recipients. Hepatocytes and islets were isolated using collagenase digestion and seeded into polyvinylalcohol matrices. HcTx and ICT were compared with HcTx plus portocaval shunt and HcTx without stimulation. Matrices were investigated at 1, 3, and 6 months after implantation: the test methods applied were trichrome staining, PAS, immunohistochemistry for insulin, glucagon and incorporated BrdU, and in situ hybridization for albumin RNA. Hepatocytes expressed albumin RNA and formed conglomerates without atypias in all animals. ICT and portocaval shunting increased the number of hepatocytes and BrdU uptake. Alpha cells migrated into the islet-surrounding hepatocytes, whereas beta cells remained immobile. It is concluded that ICT and portocaval shunting supported engraftment of hepatocytes in polymeric matrices equally well. ICT did not interfere with recipient glucose metabolism and did not induce hyperproliferative premalignant foci within the transplanted hepatocytes. The technique is an attractive approach to hepatotrophic stimulation of bioartificial liver equivalents.

Is there an optimal concentration of cotransplanted islets of Langerhans for stimulation of hepatocytes in three dimensional matrices?

BACKGROUND

Hepatocyte transplantation using three-dimensional matrices is under investigation as an alternative therapy for several liver diseases. For sufficient transplantation results hepatotrophic stimulation is necessary. We investigated the stimulatory effect of cotransplanted pancreatic islets in different ratios.

METHODS

Lewis rats were used as donors and recipients. A portocaval shunt (group A) or sham operation (groups B-G) was performed 1 week before hepatocyte transplantation. Four polyvinyl-alcohol matrices each containing 1.25 x 10(7) hepatocytes (groups A and B) or 1.25 x 10(7) hepatocytes and 125 (C), 250 (D), 500 (E), or 750 (F) islets were implanted between small bowel mesenteric leaves. In group G, medium soaked matrices were implanted. One month after implantation, specimens were harvested and investigated using albumin-RNA in situ hybridization, and insulin, glucagon, and bromodesoxy uridine immunohistochemistry. The hepatocyte area was assessed using image analysis.

RESULTS

Hepatocyte area and proliferation ratio increased depending on the number of cotransplanted islets with a peak at 40 islets per 1 million hepatocytes (group E). Cotransplantation of islets in higher concentrations did not further increase hepatocyte area or proliferation ratio. Hepatocytes in all groups expressed albumin RNA at normal transcription levels as compared to standard liver sections. Islets displayed insulin and glucagon in physiological distribution.

DISCUSSION

Three-dimensional matrices provide a sufficient environment for transplanted hepatocytes and islets. The hepatotrophic effect of cotransplanted islets is comparable to portocaval shunting and has a saturation limit at 40 islets per 1 million hepatocytes. For further application of islet cotransplantation, this ratio seems to be preferable.

Long-term insulin-secretory function of islets of Langerhans encapsulated with a layer of confluent chondrocytes for immunoisolation

Islet transplantation is a potential cure for diabetes mellitus. The major problem for broad clinical application remains the prevention of transplant rejection without major side effects. Immunoisolation is an experimental strategy to prevent rejection by separating the transplanted cells from the host immune system using a barrier device. Current methods use artificial, not completely inert materials as barrier devices and induce an unwanted foreign-body (FB) reaction. Using the recipients of own cells for encapsulation, the FB reaction could be prevented. This study describes a new method of encapsulation of islets of Langerhans within a capsule of chondrocytes, which may serve as an immunoisolation barrier utilizing the immunoprivileged properties of the chrondrocyte matrix, and demonstrates the functional survival of the encapsulated islets in vitro.

Heterotopic hepatocyte transplantation utilizing pancreatic islet cotransplantation for hepatotrophic stimulation: morphologic and morphometric evaluation

Hepatocyte transplantation using three-dimensional (3D) matrices is under evaluation as an alternative therapy for liver diseases. It is known that hepatotropic stimulation optimizes hepatocyte engraftment. We investigated hepatotrophic stimulation by portocaval shunt operation (PCS) or pancreatic islet cotransplantation (ICT) over a period of 6 months. Lewis rats served as donors and recipients, respectively. One week prior to hepatocyte implantation PCS (group A) or a sham operation (groups B-D) was performed. Four polyvinyl-alcohol matrices, each containing 1.25 x 10(7) hepatocytes (groups A and C), 1.25 x 10(7) hepatocytes and 500 islets (group B), or cell-free culture medium (group D, control) were implanted between recipients' small-bowel mesenteric leaves. One, 3, and 6 months after implantation eight polymers from each group were harvested and analyzed by morphometry, PAS reaction, and immunohistochemistry for insulin, glucagon, and bromodesoxyuridine. Morphologically healthy-appearing hepatocytes were found in all cell transplantation groups at all times. Stimulation by either PCS or ICT significantly increased hepatocyte area at 1 and 6 months compared to unstimulated specimens (group C). Over time, an increase in hepatocyte area was noted in all groups. There were no significant differences in proliferation ratios between the three experimental groups. The initially reduced PAS reaction became normal after 3 months. 3D matrices provided a sufficient environment for transplanted hepatocytes and islets. Hepatocytes proliferated and maintained differentiation independent of hepatotrophic stimulation for at least 6 months when 3D matrices were utilized. ICT efficiently stimulated transplanted hepatocytes by means of hepatocyte area. These results justify further research on hepatocyte transplantation and ICT with regard to clinical application.

[Immuno-isolation of xenogenic islands of Langerhans in a tissue engineered autologous cartilage capsule]

Islet transplantation is a potential cure for diabetes mellitus. The major problem for clinical application remains the prevention of transplant rejection without major side effects. Broad application in early disease will make the usage of xenogeneic tissue necessary. Immunoisolation is an experimental strategy to prevent rejection, by separating the transplanted allogeneic or xenogeneic cells from the host immune system using a barrier device. Current methods of immunoisolation use artificial, not completely inert materials as barrier devices and induce an unwanted foreign body reaction. Using recipient own cells for encapsulation the foreign body reaction could be prevented. This study describes a new method of encapsulation of islets of Langerhans within a capsule of chondrocytes, which may serve as an immunoisolation barrier utilizing the immunoprivileged properties of the chondrocyte matrix and demonstrates the functional survival of the encapsulated islets in vivo.

Formation of spheroidal aggregates of hepatocytes on biodegradable polymers under continuous-flow bioreactor conditions

Our laboratory has investigated heterotopic hepatocyte transplantation on biodegradable polymer matrices as an experimental treatment for end-stage liver disease. One of the limitations has been survival of sufficient cell mass after transplantation. We hypothesize that in vitro conditioning of cells within polymer matrices prior to implantation may increase hepatocyte survival and function. In this preliminary study we investigated the effect of continuous flow on hepatocytes and sinusoidal endothelial cells on poly-L-lactic acid (PLLA) discs in vitro. Highly porous PLLA discs were manufactured measuring 18 mm diameter by 1 mm thickness using previously described techniques. Hepatocytes were isolated from adult, male Lewis rats (200-300 g) using a two-step collagenase digestion. Sinusoidal endothelial cells were isolated using a two-step collagenase digestion, differential sedimentation, Percoll gradient centrifugation, and selective adherence. PLLA discs were seeded with hepatocytes alone or with co-cultures of hepatocytes and sinusoidal endothelial cells. Seeded discs were then secured within a flow bioreactor chamber and exposed to continuous flow of culture media at a rate of 20 ml/minute through the chamber. Seeded discs placed in static culture conditions served as controls. Specimens seeded with only hepatocytes were harvested at 24 hours, 48 hours, and 168 hours after seeding. Co-culture specimens were harvested after 168 hours. Specimens were viewed under phase-contrast microscopy and then formalin-fixed and prepared for histologic sectioning. Sections were stained with Hematoxylin and Eosin and then analyzed with light microscopy. Hepatocytes under flow conditions formed spheroidal aggregates of cells of 50 to 200 microns in diameter by 24 hours in culture. Hepatocytes in static conditions showed decreased aggregation of cells and spheroid formation was absent. Co-cultured specimens under flow also showed spheroid formation with endothelial cells lining the outside of hepatocyte spheroids. Co-cultured specimens in static culture showed no spheroid formation and no organization between sinusoidal endothelial cells and hepatocytes. These results suggest that continuous flow increases organization of hepatocytes cultured within biodegradable polymer matrices.

[Complicated amebic liver abscess--course and therapy]

We report on a case of an amoebic liver abscess acquired during a holiday in Bali. Transdiaphragmatic migration and consecutive atelectasis of the right lung caused respiratory insufficiency, requiring immediate surgical intervention. Complications consisted of massive bleeding into the colon concomitant with a reactivated CMV-infection. In addition, toxins of Clostridium difficile and enterohaemorrhagic E. coli were seen in the faeces. In contrast to the majority of uncomplicated cases of amoebic liver abscess, usually treated with amoebicidal drugs only, surgical intervention was clearly indicated in our patient.

The effect of donor and recipient age on engraftment of tissue-engineered liver

A novel treatment for end-stage liver disease using heterotopic hepatocyte transplantation on biodegradable polymers has been investigated. Survival and repopulation of adequate cell mass to replace hepatic function has been the principal difficulty of this method. Hence the authors have begun to investigate the role of donor and recipient age on the efficiency of hepatocyte transplantation. Lewis rats were used as donors and recipients. Hepatocytes were isolated with a collagenase digestion, both for the adult and fetal livers (17 days estimated gestational age). After digestion, the hepatocytes were seeded onto 95% porous poly-(L)-lactic acid matrices. The polymer-cell constructs with adult or fetal cells were then implanted between mesenteric leaves of three different recipient groups: adults (approximately 200 g), 2-week, and 4-week neonates (two to five animals per group, depending on litter size). The specimens were harvested at 4 weeks, stained with Hematoxylin and Eosin (H&E), and the cell area of each specimen (24 sections per group) was quantitated using morphometric analysis. Results were statistically analyzed using an unpaired, two-tailed Student's t test. At 4 weeks, all specimens showed survival of groups of hepatocytes, especially along the periphery of the polymers and near blood vessels. The hepatocyte cell area for the six groups was calculated in square micrometers: the adult cells transplanted into adult recipients, 0.16 x 10(5) microns2; fetal cells into adults, 0.47 x 10(5) microns2; adult into 4-week neonates, 1.17 x 10(5) microns2; fetal into 4-week neonates, 4.54 x 10(5) microns2; adult into 2-week neonates, 2.98 x 10(5) microns2, and fetal into 2-week neonates, 5.81 x 10(5) microns2. In all three recipient groups, the area of fetal hepatocytes was approximately two to three times the area of the adult hepatocytes (P < .05 for 2-week and 4-week neonatal recipients, P = .06 for adult recipients). Also, as the recipient age decreased, there was an increase in the hepatocyte cell area (P < .05 for fetal or adult groups). The authors conclude that fetal hepatocytes heterotopically transplanted have a significant survival advantage over adult hepatocytes, independent of recipient age. The authors further conclude that the neonatal environment is more favorable than the adult environment for implantation of hepatocytes.

Tissue engineering

The loss or failure of an organ or tissue is one of the most frequent, devastating, and costly problems in health care. Current treatment modalities include transplantation of organs, surgical reconstruction, use of mechanical devices, or supplementation of metabolic products. Tissue engineering is the application of the principles and methods of engineering and the life sciences to the fundamental understanding of structure/function relationships in normal and pathological tissues and the development of biological substitutes to restore, maintain, or improve function. This article discusses the challenges of this interdisciplinary field and its attempts to provide solutions to tissue creation and repair.