Stabilization of cell-cell junctions by active vitamin D ameliorates uraemia-induced loss of human endothelial barrier function

Background

Uraemia induces endothelial cell (EC) injury and impaired repair capacity, for which the underlying mechanism remains unclear. Active vitamin D (VD) may promote endothelial repair, however, the mechanism that mediates the effects of VD in chronic kidney disease are poorly understood. Thus, we investigated uraemia-induced endothelial damage and the protection against such damage by active VD.

Methods

We applied electric cell-substrate impedance sensing (ECIS) to study real-time responses of human ECs exposed to pooled uraemic and non-uraemic plasma with or without the addition of active VD. The effects of indoxyl sulphate and p-cresol were tested in non-uraemic plasma. Structural changes for vascular endothelial (VE)-cadherin and F-actin were assessed by immunostaining and quantified.

Results

The exposure of ECs to uraemic media significantly decreased endothelial barrier function after 24 h. Cell migration after electrical wounding and recovery of the barrier after thrombin-induced loss of integrity were significantly impaired in uraemic-medium stimulated cells and cells exposed to indoxyl sulphate and p-cresol. This effect on ECIS was dependent on loss of cell-cell interaction. Mechanistically, we found that EC, exposed to uraemic media, displayed disrupted VE-cadherin interactions and F-actin reorganization. VD supplementation rescued both endothelial barrier function and cell-cell interactions in ECs exposed to uraemic media. These events were associated with an increment of VE-cadherin at intercellular junctions.

Conclusions

Our data demonstrate a potentially clinically relevant mechanism for uraemia-induced endothelial damage. Furthermore, active VD rescued the uraemic medium-induced loss of cell-cell adhesion, revealing a novel role of active VD in preservation of endothelial integrity during uraemia.

Associations between traumatic stress symptoms, pain and bio-active components in burn wounds

OBJECTIVE

Pain and traumatic stress symptoms often co-occur. Evidence suggests that the neuropeptide oxytocine and pro-inflammatory cytokines are associated with both stress and pain. The aim of this pilot study was to explore relations between self-reported pain and traumatic stress, oxytocin and three cytokines in burn wounds.

METHODS

An observational study in three burn centres was performed. Patients were invited to participate in the study when deep dermal injury was suspected. Patients completed the Impact of Event Scale (IES), a self-report questionnaire assessing traumatic stress symptoms, and they rated their pain the day prior to surgery. During surgery, eschar (i.e., burned tissue) was collected and stored at -80 ° C until analysis. When the data collection was complete, oxytocin and cytokine levels were analysed.

RESULTS

Eschar from 53 patients was collected. Pain and stress scores were available from 42 and 36 patients respectively. Spearman correlational analyses showed an association between lower oxytocin levels at wound site and a higher total IES score (r = -0.37) and pain (r = -0.32). Mann-Whitney U tests comparing groups scoring high or low on pain or stress confirmed these associations.

CONCLUSION

These analyses lend support to a hormonal pathway that may explain how psychological distress affects pain at skin level in patients with traumatic stress symptoms.

Early intervention by Captopril does not improve wound healing of partial thickness burn wounds in a rat model

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Inhibition of the Renin Angiotensin System does not influence the inflammatory reaction in the burn wounds.

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Inhibition of the Renin Angiotensin System early during burn wound healing does not improve the process.

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Inhibition of the Renin Angiotensin System early during burn wound healing does not reduce scar formation.

The Renin Angiotensin System is involved in fibrotic pathologies in various organs such as heart, kidney and liver. Inhibition of this system by angiotensin converting enzyme antagonists, such as Captopril, has been shown beneficial effects on these pathologies. Captopril reduced the inflammatory reaction but also directly influenced the fibrotic process.

Prolonged and excessive inflammatory response is a major cause of hypertrophic scar formation in burns. We therefore evaluated the effect of Captopril on the healing of partial thickness burn wounds in a rat model.

Partial thickness contact burns were inflicted on the dorsum of the rats. The rats received either systemic or local treatment with Captopril. The inflammatory reaction and wound healing (scar) parameters were investigated and compared to control animals.

In this study we could not detect positive effects of either administration route with Captopril on the inflammatory reaction, nor on wound healing parameters. The local treatment showed reduced wound closure in comparison to the systemic treatment and the control group.

Early Captopril treatment of burn wounds did not show the beneficial effects that were reported for fibrotic disorders in other tissues. To influence the fibrotic response Captopril treatment at a later time point, e.g. during the remodeling phase, might still have beneficial effects.

Differential effects of Losartan and Atorvastatin in partial and full thickness burn wounds

Healing of burn wounds is often associated with scar formation due to excessive inflammation and delayed wound closure. To date, no effective treatment is available to prevent the fibrotic process. The Renin Angiotensin System (RAS) was shown to be involved in fibrosis in various organs. Statins (e.g. Atorvastatin), Angiotensin receptor antagonists (e.g. Losartan) and the combination of these drugs are able to reduce the local RAS activation, and reduced fibrosis in other organs. We investigated whether inhibition of the RAS could improve healing of burn wounds by treatment with Atorvastatin, Losartan or the combination of both drugs. Therefore, full and partial thickness burn wounds were inflicted on both flanks of Yorkshire pigs. Oral administration of Atorvastatin, Losartan or the combination was started at post-burn day 1 and continued for 28 days. Full thickness wounds were excised and transplanted with an autologous meshed split-thickness skin graft at post-burn day 14. Partial thickness wounds received conservative treatment. Atorvastatin treatment resulted in enhanced graft take and wound closure of the full thickness wounds, faster resolution of neutrophils compared to all treatments and reduced alpha-smooth muscle actin positive cells compared to control treatment. Treatment with Losartan and to a lesser extent the combination therapy resulted in diminished graft take, increased wound contraction and poorer scar outcome. In contrast, Losartan treatment in partial thickness wounds decreased the alpha-smooth muscle actin+ fibroblasts and contraction. In conclusion, we showed differential effects of Losartan and Atorvastatin in full and partial thickness wounds. The extensive graft loss seen in Losartan treated wounds is most likely responsible for the poor clinical outcome of these full thickness burn wounds. Therefore, Losartan treatment should not be started before transplantation in order to prevent graft loss. Atorvastatin seems to accelerate the healing process in full thickness wounds possibly by dampening the pro-inflammatory response.

In vitro cultured fetal fibroblasts have myofibroblast-associated characteristics and produce a fibrotic-like environment upon stimulation with TGF-β1: Is there a thin line between fetal scarless healing and fibrosis?

Transforming growth factor-β (TGF-β) is a cytokine occurring in three isoforms with an important function in development and wound healing. In wound healing, prolonged TGF-β signaling results in myofibroblast differentiation and fibrosis. In contrast, the developing second-trimester fetal skin contains high levels of all three TGF-β isoforms but still has the intrinsic capacity to heal without scarring. Insight into TGF-β signal transduction during fetal wound healing might lead to methods to control the signaling pathway during adult wound healing. In this study, we imitated wound healing in vitro by stimulating fibroblasts with TGF-β1 and examining myofibroblast differentiation. The aim was to gain insight into TGF-β signaling in human fibroblasts from fetal and adult dermis. First, TGF-β1 stimulation resulted in similar or even more severe upregulation of myofibroblast-associated genes in fetal fibroblasts compared to adult fibroblasts. Second, fetal fibroblasts also had higher protein levels of myofibroblast-marker α-smooth muscle actin (α-SMA). Third, stimulated fetal fibroblasts in collagen matrices had higher protein levels of α-SMA, produced more of the fibrotic protein fibronectin splice-variant extra domain A (FnEDA), and showed enhanced contraction. Finally, fetal fibroblasts also produced significant higher levels of TGF-β1. Altogether, these data show that in vitro cultured fetal fibroblasts have myofibroblast-associated characteristics and do produce a fibrotic environment. As healthy fetal skin has high levels of TGF-β1, FnEDA, and collagen-III as well, these findings correlate with the in vivo situation. Therefore, our study demonstrates that there are similarities between fetal skin development and fibrosis and shows the necessity to discriminate between these processes.

Currently known risk factors for hypertrophic skin scarring: A review

OBJECTIVE

The study aims to provide an overview of risk factors for hypertrophic scarring.

BACKGROUND

Hypertrophic skin scarring remains a major concern in medicine and causes considerable morbidity. Despite extensive research on this topic, the precise mechanism of excessive scarring is still unknown. In addition, the current literature lacks an overview of the possible risk factors in the development of hypertrophic scars.

METHODS

PubMed searches were performed on risk factors for hypertrophic scar (HTS) formation.

RESULTS

Eleven studies suggesting nine factors associated with HTS formation were found. Studies concerning chemotherapy, age, stretch, infection, and smoking have a moderate to high strength of evidence, but some other factors have not been studied in a convincing manner or are still disputed.

CONCLUSIONS

Risk factors for HTS formation are young age, bacterial colonization, and skin subjected to stretch. Chemotherapy, statins, and smoking seem to play a protective role in HTS formation.

Cell therapy for full-thickness wounds: are fetal dermal cells a potential source?

The application of autologous dermal fibroblasts has been shown to improve burn wound healing. However, a major hurdle is the availability of sufficient healthy skin as a cell source. We investigated fetal dermal cells as an alternative source for cell-based therapy for skin regeneration. Human (hFF), porcine fetal (pFF) or autologous dermal fibroblasts (AF) were seeded in a collagen–elastin substitute (Novomaix, NVM), which was applied in combination with an autologous split thickness skin graft (STSG) to evaluate the effects of these cells on wound healing in a porcine excisional wound model. Transplantation of wounds with NVM+hFF showed an increased influx of inflammatory cells (e.g., neutrophils, macrophages, CD4⁺ and CD8⁺ lymphocytes) compared to STSG, acellular NVM (Acell-NVM) and NVM+AF at post-surgery days 7 and/or 14. Wounds treated with NVM+pFF presented only an increase in CD8⁺ lymphocyte influx. Furthermore, reduced alpha-smooth muscle actin (αSMA) expression in wound areas and reduced contraction of the wounds was observed with NVM+AF compared to Acell-NVM. Xenogeneic transplantation of NVM+hFF increased αSMA expression in wounds compared to NVM+AF. An improved scar quality was observed for wounds treated with NVM+AF compared to Acell-NVM, NVM+hFF and NVM+pFF at day 56. In conclusion, application of autologous fibroblasts improved the overall outcome of wound healing in comparison to fetal dermal cells and Acell-NVM, whereas application of fetal dermal fibroblasts in NVM did not improve wound healing of full-thickness wounds in a porcine model. Although human fetal dermal cells demonstrated an increased immune response, this did not seem to affect scar quality.

The delicate balance of macrophages in colorectal cancer; their role in tumour development and therapeutic potential

Most tumours are heavily infiltrated by immune cells. This has been correlated with either a good or a bad patient prognosis, depending on the (sub) type of immune cells. Macrophages represent one of the most prominent leukocyte populations in the majority of tumours. Functions of macrophages range from cytotoxicity, to stimulation of tumour growth by secretion of cytokines, growth and angiogenic factors, or suppressing immune responses. In most tumours macrophages are described as cells with immune suppressing, and wound healing properties, which aids tumour development. Yet, increasing evidence shows that macrophages are potent inhibitors of tumour growth in colorectal cancer. Macrophages in this respect show high plasticity. The presence of high macrophage numbers in the tumour may therefore become advantageous, if cells can be reprogrammed from tumour promoting macrophages into potent effector cells. Enhancing cytotoxic properties of macrophages by microbial products, pro-inflammatory cytokines or monoclonal antibody therapy are promising possibilities, and are currently tested in clinical trials.

Transforming growth factor-β (TGF-β) signaling in healthy human fetal skin: a descriptive study

BACKGROUND

TGF-β plays an important role in growth and development but is also involved in scarring and fibrosis. Differences for this growth factor are known between scarless fetal wound healing and adult wound healing. Nonetheless, most of the data in this area are from animal studies or in vitro studies and, thus, information about the human situation is incomplete and scarce.

OBJECTIVE

The aim of this study was to compare the canonical TGF-β signaling in unwounded human fetal and adult skin.

METHODS

Q-PCR, immunohistochemistry, Western Blot and Luminex assays were used to determine gene expression, protein levels and protein localization of components of this pathway in healthy skin.

RESULTS

All components of the canonical TGF-β pathway were present in unwounded fetal skin. Compared to adult skin, fetal skin had differential concentrations of the TGF-β isoforms, had high levels of phosphorylated receptor-Smads, especially in the epidermis, and had low expression of several fibrosis-associated target genes. Further, the results indicated that the processes of receptor endocytosis might also differ between fetal and adult skin.

CONCLUSION

This descriptive study showed that there are differences in gene expression, protein concentrations and protein localization for most components of the canonical TGF-β pathway between fetal and adult skin. The findings of this study can be a starting point for further research into the role of TGF-β signaling in scarless healing.

Pharmacologic targets and peritoneal membrane remodeling

Peritoneal dialysis (PD) is associated with functional and structural changes of the peritoneal membrane, also known as peritoneal remodeling. The peritoneal membrane is affected by many endogenous and exogenous factors such as cytokines, PD fluids, and therapeutic interventions. Here, we present an overview of various studies that have investigated pharmacologic interventions aimed at regression of peritoneal damage and prolongation of PD treatment.

Minimal extracorporeal circulation (MECC) does not result in less hypertrophic scar formation as compared to conventional extracorporeal circulation (CECC) with dexamethasone

INTRODUCTION

Cardiopulmonary bypass surgery is associated with a systemic inflammatory response through the interaction of air, blood and synthetic components in the bypass system and the physical trauma of surgery. An alternative cardiopulmonary bypass system, minimal extracorporeal circulation (MECC), has shown promising results in terms of reducing the inflammatory response. We hypothesized that this system may reduce pathological excessive scarring. To study this assumption, the effects of MECC and the effects of conventional extracorporeal circulation (CECC) with dexamethasone on skin scarring were compared in a standardized wound-healing model.

METHODS AND RESULTS

Pre-sternal scars were evaluated prospectively at four and 12 months postoperatively. The height and width of the scars were measured, using a slide caliper and sonography. The scars were scored using the validated Patient and Observer Scar Assessment Scale. Additional risk factors for hypertrophic scar formation were identified by means of a questionnaire. During surgery, MECC was used in 45 patients and CECC/dexamethasone in 42 patients. Four months postoperatively, 22 patients of the MECC group (49%) and 18 patients in the CECC/dexamethasone group (43%) had developed hypertrophic scars. Twelve months postoperatively, the hypertrophic scars in four patients of the MECC group and in two patients of the CECC/dexamethasone group had become normotrophic. In 18 patients of the MECC group (38%) and 16 patients of the CECC group (41%) the scars remained hypertrophic at 12 months. These differences between the two groups were not statistically significant.

CONCLUSION

MECC does not reduce hypertrophic scar formation compared with CECC with dexamethasone, but its use is more beneficial than the use of CECC/dexamethasone because of the circulatory and immunological advantages and because treatment with dexamethasone can be omitted.

Altered TGF-β signaling in fetal fibroblasts: what is known about the underlying mechanisms?

Scarless wound healing is a unique and intrinsic capacity of the fetal skin that is not fully understood. Further insight into the underlying mechanisms of fetal wound healing may lead to new therapeutic approaches promoting adult scarless wound healing. Differences between fetal and adult wound healing are found in the extracellular matrix, the inflammatory reaction and the levels of growth factors present in the wound. This review focuses specifically on transforming growth factor β (TGF-β), as this growth factor is prominently involved in wound healing and fibroblast-to-myofibroblast differentiation. Although fetal fibroblasts do respond to TGF-β, they lack a proliferative and a contractile response and display short-lived myofibroblast differentiation, autocrine response, and collagen up-regulation in comparison with adult fibroblasts. Curiously, prolonged TGF-β activation is associated with fibrosis, and therefore, this short-lived response in fetal fibroblasts might contribute to scarless healing. This review gives an overview of the current knowledge on TGF-β signaling and the intracellular TGF-β signaling pathway in fetal fibroblasts. Furthermore, this review also describes the various components that regulate the cellular TGF-β response and hypothesizes about the possible roles these components might play in the altered response of fetal fibroblasts to TGF-β.

Angiogenesis in peritoneal dialysis

Long-term exposure to peritoneal dialysis fluid induces morphological alterations, including angiogenesis, leading to a loss of ultrafiltration (UF) capacity. We discuss the effect of different factors in peritoneal dialysis (PD) on angiogenesis. In addition, we describe the process of angiogenesis and the possible role of different cell types in the peritoneum upon PD contributing to new blood vessel formation. Furthermore, we review several interventions used in our rat PD exposure model to decrease angiogenesis in PD. Moreover, we show new data on the use of sunitinib to inhibit angiogenesis in this rat model. Although various interventions seem to be promising, well-randomised clinical trials showing absolute prevention of angiogenesis and UF failure are, yet, still missing. To make real progress in PD treatment, the aim should be to prevent angiogenesis as well as peritoneal fibrosis and PD-induced inflammation.

Tubulointerstitial heparan sulfate proteoglycan changes in human renal diseases correlate with leukocyte influx and proteinuria

Heparan sulfate proteoglycans (HSPGs) are well known for their proposed role in glomerular filtration. In addition, HSPGs can bind the leukocyte adhesion molecule l-selectin and chemokines, suggesting a role in inflammation. We examined a panel of biopsies representing different human primary kidney diseases for l-selectin and monocyte chemoattractant protein-1 (MCP-1) binding. In various renal diseases, l-selectin and MCP-1 binding to interstitial perivascular matrix HSPGs is increased, which is significantly associated with leukocyte influx. In proteinuric diseases, including membranous glomerulopathy, minimal change disease, but also IgA nephropathy and lupus nephritis, increased binding of l-selectin and MCP-1 to tubular epithelial cell (TEC) HSPGs is observed, which colocalizes with increased basolateral syndecan-1 and anti-heparan sulfate 10E4 staining. Short-hairpin RNA-mediated silencing demonstrates that syndecan-1 on TECs indeed mediates l-Selectin binding. Increased TEC expression of IL-8 in biopsies of proteinuric patients suggests that the increase in luminal protein may activate TECs to increase expression of l-selectin and MCP-1 binding syndecan-1. Strikingly, urinary syndecan-1 from proteinuric patients is less capable of binding l-selectin compared with urinary syndecan-1 from healthy controls, although syndecan-1 concentrations are similar in both groups. Together, our data show pronounced tubulointerstitial HSPG alterations in primary kidney disease, which may affect the inflammatory response.

Perioperative IFN-alpha to avoid surgically induced immune suppression in colorectal cancer patients

Surgical treatment of colorectal cancer is associated with postoperative immunosuppression, which might facilitate dissemination of tumor cells and outgrowth of minimal residual disease/(micro) metastases. Minimal residual disease has been shown to be of prognostic relevance in colorectal cancer. Therefore, stimulation of (anti-tumor) immune responses may be beneficial in the prevention of metastases formation. Important anti-tumor effector cells, which serve this function, are natural killer (NK) cells, CD8+ lymphocytes (CTL), dendritic cells (DC) and macrophages. In this review the immunomodulating properties of IFN-alpha are discussed, with a particular focus on perioperative stimulation of immune function in cancer patients. IFN-alpha is known to enhance innate immune functions such as stimulation of NK cells, transition from innate to adaptive responses (activation of DC) and regulating of CD8+ CTL activity and memory. Moreover, it exerts direct antitumor effects by regulating apoptosis and cell cycle. In several clinical trials, perioperative administration of IFN-alpha has indeed been shown to improve T cell responsiveness, prevent impairment of NK cell cytotoxicity and increase expression of activation markers on NK, T and NKT cells. In a clinical pilot study we showed in colorectal cancer patients that received perioperative IFN-alpha enhanced activation markers on T cells and NK cells, combined with better-preserved T cell function as indicated by phytohemaggluttinin skin tests. In the liver of these patients significantly more CD8+ T cells were found. In conclusion, IFN-alpha provides an effective adjuvant in several forms of cancer and improves several postoperative immune functions in perioperative administration. However, larger clinical trials are necessary to investigate effects on disease-free and overall survival.

Effect of fixation protocols on in situ detection of L-selectin ligands

In situ binding of (chimeric) proteins to tissue sections is a widely used method to identify ligands and their localization. Many different protocols for the fixation of frozen tissue sections are used for in situ binding studies. We report the effects of different fixation protocols on the binding pattern observed using in situ binding of an L-selectin-IgM chimeric protein to both rat lymph node and kidney tissue sections. L-selectin is a C-type lectin, expressed on leukocytes and is involved in both lymphocyte homing and migration upon inflammation. We show that different in situ binding patterns in rat kidney are observed using different fixation protocols, including glutaraldehyde, methanol, formaldehyde and acetone fixation. The observed staining is specific, as it can be blocked in the presence of EGTA, an L-selectin blocking antibody or by ligand competition. Enzymatic pre-treatment of the tissue sections using sialidase, heparitinase I or chondroitinase ABC has differential effects on in situ binding depending on tissue type and fixation protocol. These data indicate that special attention should be paid in choosing a fixation protocol for in situ binding studies, especially when using lectins. This could prevent biologically relevant ligands remaining undetected or wrong conclusions being drawn based on the localization of observed binding.

Surgery promotes implantation of disseminated tumor cells, but does not increase growth of tumor cell clusters

INTRODUCTION

Local recurrence and peritoneal dissemination is common after intentionally curative resection of colorectal carcinoma. It is not yet clear which mechanisms stimulate post-operative intra-abdominal tumor development. Enhanced adhesion or growth of tumor cells and/or post-operative immuno suppression may influence tumor recurrence.

AIMS OF THE STUDY

In the present study, we evaluated effects of local and remote surgery on intra-abdominal tumor development.

MATERIALS AND METHODS

A standardized intra-abdominal trauma was inflicted by rubbing both uterus horns in laparotomy groups, while a dorsolateral thoracotomy was performed in thoracotomy groups (on day -1, 0, or +3). To induce tumor development rats were injected intra-peritoneally with the coloncarcinoma cell line CC531s on day 0 and evaluated after 21 days.

RESULTS

Rats undergoing laparotomy and injection on day 0 showed significantly higher tumorload than control rats (195 +/- 20 vs. 47 +/- 29, P < 0.001). When a laparotomy was performed, the day before tumor inoculation even higher tumorload was seen (245 +/- 37 vs. 195 +/- 20, P < 0.01). Strikingly, performing a thoracotomy on the day before or on the same day as tumor inoculation resulted in enhanced tumorload compared to controls as well (135 +/- 84 vs. 47 +/- 29; P < 0.001 and 88 +/- 38 vs. 47 +/- 29; P < 0.02, respectively). Either laparotomy or thoracotomy 3 days after tumor cell inoculation did not affect growth of pre-existing tumor cell clusters.

CONCLUSIONS

The (post) surgical intra-peritoneal microenvironment enhances successful implantation of spilled tumor cells, whereas growth of adhered tumor cell clusters is not affected. The inflammatory response as a result of remote surgery promotes successful tumor development as well.

The effects of surgery, with or without rhGM-CSF, on the angiogenic profile of patients treated for colorectal carcinoma

Wound healing is a process with immunological and angiogenic aspects. rhGM-CSF is known to stimulate the immune system and angiogenesis via multiple pathways. In this study we investigated the combined effects of surgery, with or without rhGM-CSF, on angiogenic parameters in patients with a colorectal carcinoma. In this phase II randomized, placebo-controlled trial, 16 patients were assigned to perioperative rhGM-CSF (2.8 microg/kg body weight) treatment or saline. Patients received subcutaneous injections from three days before surgery until four days after. IL-6, VEGF, endostatin and angiostatin levels were measured perioperatively. rhGM-CSF enhanced the production of IL-6 and VEGF, but had no effect on the antiangiogenic agents endostatin and angiostatin. Surgery induced a transient decrease of endostatin. Two types of angiostatin (kringle 1-3 and kringle 1-4) became visible postoperatively. We conclude that this study demonstrated the immediate initiation of angiogenesis postoperatively, reflected by the increase of VEGF and a transient decrease of endostatin, followed by the appearance of two angiostatin bands, which confirms physiological wound healing in these cancer patients.

The application of animal models to study the biocompatibility of bicarbonate-buffered peritoneal dialysis solutions

The application of animal models to study the biocompatibility of bicarbonate-buffered peritoneal dialysis solutions. Patients treated with peritoneal dialysis (PD) are at risk for development of ultrafiltration failure and peritonitis. These two significant complications can result in the termination of PD treatment. The relative unphysiologic composition of the currently used standard peritoneal dialysis fluids (PDF) is considered to be a major cause for the development of morphologic changes of the peritoneal membrane, ultimately resulting in ultrafiltration failure and probably contributing to changes in local defense mechanisms with the associated increased risk of peritonitis. In recent years, a major research focus has become the development of new and improved PD solutions. This has resulted in the development of an amino-acid-based PDF, a glucose polymer-based PDF, and several bicarbonate-buffered PDF. Typically, the first phase of biocompatibility testing of new PD solutions involves in vitro testing, employing isolated cells such as peritoneal macrophages or cell culture systems using human peritoneal mesothelial cells. The results of such evaluations are useful in providing insights into the biocompatibility performance of any given formulation, but suffer from several disadvantages, which can be better addressed using animal models. In vivo studies using animals permit the analysis of biocompatibility under conditions that allow for cell-to-cell interactions and dynamic changes in solution composition that more closely mimic the clinical situation. In this paper, we will review the use of animal models for the study of PDF biocompatibility and their application to the assessment of bicarbonate-buffered PDF.

Differences between the CD34+ and CD34- blast compartments in apoptosis resistance in acute myeloid leukemia

BACKGROUND AND OBJECTIVES

Altered expression of members of the Bcl-2 family might account for the observed apoptosis resistance to chemotherapy in acute myeloid leukemia (AML). Given the poor prognosis associated with CD34+ expression in AML, we studied the role of spontaneous apoptosis and apoptosis regulatory proteins in sorted CD34+ and CD34- primary AML fractions.

DESIGN AND METHODS

The expression levels of apoptosis regulatory proteins and spontaneous apoptosis were measured in primary AML samples by Western blot analysis and flow cytometry. To determine the role of CD34+ cells in apoptosis resistance, spontaneous apoptosis in serum-free conditions and apoptosis regulatory protein levels were measured in CD34+ and CD34- sorted cells from CD34+ primary AML samples.

RESULTS

We show that CD34+ AML fractions are more resistant to apoptosis than are corresponding CD34- AML fractions, and that this is paralleled by higher Bcl-2, Bcl-xL, Mcl-1, Pgp and lower Bax expression levels. Interestingly, as the percentage of CD34 cells increased in the primary AML sample, so too did the apoptosis resistance in the corresponding CD34- fraction, which was reflected by an increasing anti-apoptosis protein profile.

INTERPRETATION AND CONCLUSIONS

The data show that the CD34+ fraction is more resistant to apoptosis than is the corresponding CD34- fraction and secondly that the AML as a whole is more apoptosis resistant with increasing CD34 percentage.

Rat monocyte-derived dendritic cells function and migrate in the same way as isolated tissue dendritic cells

Dendritic cells (DC) are the most potent antigen-presenting cells and are therefore useful to induce immune responses against tumor cells in patients. DC can be generated in vitro from monocytes using GM-CSF and IL-4, the so-called monocyte-derived DC (MoDC). To achieve antitumor responses, MoDC must be able to migrate to the draining lymph nodes after injection to induce cytotoxic T cells. Therefore, we studied migration of MoDC in a rat model. Functional rat MoDC were generated from PVG-RT7B rats and injected subcutaneously into PVG rats. These rat strains differ only at one epitope of the leukocyte-common antigen, which can be recognized by the antibody His 41. The advantage is that migrated cells can be detected in the draining lymph nodes by staining sections with His 41+; thus, migration is not influenced by labeling procedures. Rat MoDC migrated to the T-cell areas of the draining lymph nodes, just as isolated Langerhans cells or spleen DC do. In contrast, monocytes also migrated to the B-cell areas and the medulla.

The influence of CO2 versus helium insufflation or the abdominal wall lifting technique on the systemic immune response

BACKGROUND

Both laparoscopic and conventional surgery result in activation of the systemic immune response; however, the influence of the laparoscopic approach, using CO2 insufflation, is significantly less. Little is known about the influence of alternative methods for performing laparoscopy, such as helium insufflation and the abdominal wall lifting technique (AWLT), and the systemic immune response.

METHODS

Thirty-three patients scheduled for elective cholecystectomy were randomly assigned to undergo laparoscopy using either CO2 or helium for abdominal insufflation or laparoscopy using only the AWLT. The postoperative inflammatory response was assessed by measuring the white blood cell count, C-reactive protein (CRP) and interleukin-6 (IL-6). The postoperative immune response was assessed by measuring monocyte HLA-DR expression.

RESULTS

CRP levels were significantly higher 1 day after helium insufflation when compared with CO2 insufflation; however, no differences were observed 2 days after surgery. The AWLT resulted in significantly higher levels of CRP both 1 and 2 days after surgery when compared with either CO2 or helium insufflation. A small increase in postoperative IL-6 levels was observed in all groups, but no significant differences were seen between the groups. After both helium insufflation and AWLT a significant decrease in HLA-DR expression was observed, in contrast to the CO2 group.

CONCLUSION

Carbon dioxide used for abdominal insufflation seems to limit the postoperative inflammatory response and to preserve parameters reflecting the immune status. These findings may be of importance in determining the preferred method of laparoscopy in oncologic surgery.