An update on interventional lung assist devices and their role in acute respiratory distress syndrome.

In recent years, pumpless arteriovenous systems for extracorporeal gas exchange have become a new therapeutic option for the treatment of patients suffering from acute respiratory failure. Experiences with the pumpless extracorporeal membrane lung in animal experiments and in patients with adult respiratory distress syndrome published in the current literature are reviewed. In addition this article presents a case of varicella pneumonia with persistent hypoxemia and hypercapnia under mechanical ventilation that showed a significant improvement with treatment with a pumpless extracorporeal lung assist using an arteriovenous shunt for eight days. The patient made a complete recovery. This is the first report of a patient with a life-threatening varicella pneumonia successfully treated with pumpless extracorporeal lung assist device. This review provides an update on interventional lung assist devices and a critical discussion of their advantages and limitations.

Multipotential nestin and Isl-1 positive mesenchymal stem cells isolated from human pancreatic islets.

Mesenchymal cells in the developing pancreas express the neural stem cell marker nestin and the transcription factor islet-1 (Isl-1). Using defined culture conditions we isolated on a single cell basis nestin producing cells from human pancreatic islets. These cells were immortalized with lentiviral vectors coding for telomerase and mBmi. They are positive for Isl-1 and nestin and have the potential to adopt a pancreatic endocrine phenotype with expression of critical transcription factors including Ipf-1, Isl-1, Ngn-3, Pax4, Pax6, Nkx2.2, and Nkx6.1 as well as the islet hormones insulin, glucagon, and somatostatin. In addition, they can be differentiated into human albumin producing cells in vivo when grafted into a SCID mouse liver. In accordance with a mesenchymal phenotype, the cells were also able to adopt adipocytic or osteocytic phenotypes in vitro. In conclusion, cultured pancreatic islets contain nestin and Isl-1 positive mesenchymal stem cells with multipotential developmental capacity.

Anticoagulation with low-molecular-weight heparin (dalteparin) in plasmapheresis therapy: initial experience.

BACKGROUND: In contrast to other extracorporeal treatments no established regime exists for anticoagulation with low-molecular-weight heparin (LMWH) in plasmapheresis therapy. A study was conducted to investigate whether LMWH (dalteparin-Na) is suitable as an effective anticoagulant in plasmapheresis therapy. STUDY DESIGN AND METHODS: Eleven patients with autoimmune neurological diseases and the necessity for a plasmapheresis therapy were enrolled. A capillary membrane filter was used. A total of 2000 mL of human plasma was isovolumetrically exchanged per plasmapheresis cycle. The anticoagulation was accomplished with a single bolus of LMWH (dalteparin) of 80 to 90 IU per kg of body weight. The system was visually monitored. Anti-factor (F)Xa activity, thrombin-antithrombin III complex (TAT), and prothrombin fragment 1+2 (F 1+2) were determined at regular intervals. Samples were taken from the collected plasma pool to determine the loss of LMWH during the plasmapheresis procedure. RESULTS: All plasmapheresis cycles with LMWH were successful without complications. Approximately 40 percent of the initially administered LMWH bolus was lost by the large porous filter during the plasmapheresis. The anti-FXa values were determined to be 0.5 IU per mL during the entire plasmapheresis. TAT values were elevated (TAT median, 14.3 microg/L). F 1+2 values measured before the filter cartridge remained within the normal range for the entire plasmapheresis cycle (<1.2 nmol/L) and were increasingly elevated after the filter. CONCLUSION: Our initial experiences with LMWH for anticoagulation in plasmapheresis indicate that a body weight adjusted dose of LMWH (dalteparin) is suitable for anticoagulation in plasmapheresis therapy. No complications were observed. The data are encouraging. Further investigations will show if and how the present anticoagulation regime could be further optimized.

Generation of human hepatocytes by stem cell technology: definition of the hepatocyte.

Since 1999, numerous articles have reported the generation of hepatocytes from different types of extrahepatic stem or precursor cells. This opens exciting new possibilities for pharmacology and toxicology, as well as for cell therapy. Hepatocyte marker expression, including albumin, cytokeratin 18, c-met, alpha-fetoprotein and cytochrome P450 3A4 and -2B6, has been observed after transplantation of different types of human stem cells into the liver of laboratory animals or in vitro after incubation with cytokines. These intriguing observations have prompted scientists to classify stem cell-derived cell populations as hepatocytes. However, this conclusion may be premature. It has been shown that factors of the liver microenvironment can induce expression of a limited number of hepatocyte marker genes in nonhepatic cell types. To conclude on the grounds of a limited number of markers that these cells are true hepatocytes is not indicated. In this case one should carefully evaluate crucial hepatocyte-defining enzymatic properties. The present article: i) reviews studies describing the fate of extrahepatic human stem and precursor cells in livers of laboratory animals, including the possibility of cell fusion; and ii) critically discusses the phenotype of stem cells after application of various differentiation protocols aimed at generating human hepatocytes. In addition, the necessary criteria needed for defining a true hepatocyte are suggested. Establishing the necessary properties for stem cell-derived hepatocytes is timely and reasonable, and thus avoids further misleading semantic confusion. Finally, it is essential to understand that the definition of a bona fide hepatocyte should not be limited to qualitative assays, such as reverse transcriptase polymerase chain reaction and immunohistochemistry, but has to include a quantitative analysis of enzymatic activities, which allows direct comparison with primary hepatocytes. Although the stem cell-derived-hepatocyte does not yet exist there is a good chance that this aim may be achieved in the future.

In vitro cultured islet-derived progenitor cells of human origin express human albumin in severe combined immunodeficiency mouse liver in vivo.

Studies in rodents suggest the presence of a hepatopancreatic stem cell in adult pancreas that may give rise to liver cells in vivo. The aim of the present study was to determine the ability of human islet-derived cells to adopt a hepatic phenotype in vivo. Cultured human islet-derived progenitor cells that did not express albumin in vitro were stained with the red fluorescent dye PKH26 and injected into the liver of severe combined immunodeficiency mice. After 3 or 12 weeks, red fluorescent cells were detected in 11 of 15 livers and were mostly single cells that were well integrated into the liver tissue. Human albumin was found in 8 of 11 animals by immunohistochemistry, and human albumin mRNA was detected in 4 of 10 host livers. The mechanism underlying this phenomenon seems to be transdifferentiation, because human and mouse albumin were found to be expressed in distinct cells in the host liver.

Intraportal transplantation of allogenic pancreatic islets encapsulated in barium alginate beads in diabetic rats.

The survival of microencapsulated islets transplanted into the unmodified peritoneal cavity is limited, even if capsular overgrowth is restricted to a minimum, due to an insufficient oxygen supply to the islets. Therefore, research efforts should focus on finding or creating a transplantation site, which permits a closer contact between the encapsulated islets and the blood. For this reason, the liver could be an interesting candidate. The aim of the present study was to test the hypothesis that the intraportal transplantation of allogenic islets encapsulated in small-sized barium alginate beads is safe and succeeds to induce normoglycemia in diabetic rats. The intraportal transplantation of 1,500 islets encapsulated in barium alginate beads leads within 10 h and up to 24 h to blood sugar concentrations below 40 mg/dL, most likely due to an acute cell lysis of the graft. Afterwards, the reappearance of the diabetic state could be detected in these animals. Most likely these findings are induced by a sudden hypoxia to the islets. We believe that the occlusion of small- and medium-sized portal venules by the alginate beads is responsible for this effect. Therefore, in forthcoming studies, barium alginate beads, with a diameter below 350 micro m, stabilized with medical approved additives should be used.

Plasticity of synaptic ribbons of the rat pineal gland in vitro--minor effects of electrical stimulation.

Synaptic ribbons (SRs) of mammalian pinealocytes exhibit day/night changes in number and size, changes that are apparently regulated by the suprachiasmatic nucleus via postganglionic sympathetic nerve fibres. Since the neural control of SR changes is far from clear and as pinealocytes produce action potentials, we undertook to investigate whether electrical stimulation affects SR changes. Isolated rat pineal glands removed during the daytime were kept in vitro for 0, 30, 60, 90 or 120 min, with or without continuous electrical stimulation (1 mA, 1 Hz), followed by the quantification of SR profiles (SRPs) by transmission electron microscopy. SRs were categorised as to whether they lay less than 100 nm away from the pinealocyte plasmalemma (SRPs(near)) or more distant from it (SRPs(dist)) and the lengths of the profiles were measured. Cultured pineal organs showed a significant numerical depression of SRPs(near), irrespective of whether the organs had been electrically stimulated or not. SRPs(near) length revealed a significant increase at 60 min in unstimulated control tissue and at 30 min in electrically stimulated glands. SRPs(dist) length decreased significantly at 30 min in control glands and after 60 min in electrically stimulated glands. Thus, action potentials inside the pineal gland appear to be minor factors regulating SR numbers. In future pineal studies, SRPs(near) and SRPs(dist) should be considered separately as they differ in plasticity.