Fateh Entabi

Liver-assist device with a microfluidics-based vascular bed in an animal model.

Objective:This study evaluates a novel liver-assist device platform with a microfluidics-modeled vascular network in a femoral arteriovenous shunt in rats. Summary of Background Data:Liver-assist devices in clinical trials that use pumps to force separated plasma through packed beds of parenchymal cells exhibited significant necrosis with a negative impact on function. Methods:Microelectromechanical systems technology was used to design and fabricate a liver-assist device with a vascular network that supports a hepatic parenchymal compartment through a nanoporous membrane. Sixteen devices with rat primary hepatocytes and 12 with human HepG2/C3A cells were tested in athymic rats in a femoral arteriovenous shunt model. Several parenchymal tube configurations were evaluated for pressure profile and cell survival. The blood flow pattern and perfusion status of the devices was examined by laser Doppler scanning. Cell viability and serum protein secretion functions were assessed. Results:Femoral arteriovenous shunt was successfully established in all animals. Blood flow was homogeneous through the vascular bed and replicated native flow patterns. Survival of seeded liver cells was highly dependent on parenchymal chamber pressures. The tube configuration that generated the lowest pressure supported excellent cell survival and function. Conclusions:This device is the first to incorporate a microfluidics network in the systemic circulatory system. The microvascular network supported viability and function of liver cells in a short-term ex vivo model. Parenchymal chamber pressure generated in an arteriovenous shunt model is a critical parameter that affects viability and must be considered in future designs. The microfluidics-based vascular network is a promising platform for generating a large-scale medical device capable of augmenting liver function in a clinical setting.

Effect of PJ34 on Spinal Cord Tissue Viability and Gene Expression in a Murine Model of Thoracic Aortic Reperfusion Injury

Introduction: These studies were designed to determine whether PJ34, a novel Poly-ADP Ribose Polymerase Inhibitor, modulates expression of markers of stress and inflammation in the spinal cord following ischemia/ reperfusion(TAR). Methods: 129S1/SvImj mice were subjected to thoracic aortic occlusion and 48 hours of reperfusion (n = 38). Experimental Groups included: Untreated Control (UC, n = 21); PJ34 (PJ34, n = 11) and sham (S, n = 6). At 48 hours, mice were euthanized for mRNA analysis and assessment of spinal cord viability. Results: PJ34 improved spinal cord tissue viability following TAR (UC:53.1 ± 6.3, PJ34:73.5 ± 4.1% sham, p < 0.01). mRNA analysis revealed significant expression of stress response genes in UC and PJ34 treated mice. Conclusions: PJ34 enhanced mitochondrial activity and preserved neurologic function following TAR despite the expression of stress and pro-inflammatory markers within the spinal cord. The ongoing cord stress response in neurologically intact PJ34 treated mice may indicate the potential to develop delayed neurologic dysfunction.

PJ34, a poly-ADP-ribose polymerase inhibitor, modulates visceral mitochondrial activity and CD14 expression following thoracic aortic ischemia-reperfusion

BACKGROUND Visceral ischemia-reperfusion injury (VI) contributes to adverse outcomes following the repair of thoracoabdominal aneurysms. Experiments were designed to determine whether a poly-adenosine diphosphate-ribose polymerase (PARP) inhibitor modulates indexes of metabolic function (mitochondrial activity), inflammatory cell activation, and tissue inflammation (lipopolysaccharide receptor CD14 messenger ribonucleic acid) following VI. METHODS 129S1/SvImj mice were subjected to thoracic aortic occlusion followed by 48 hours of reperfusion. Normal saline was administered to 25 untreated control mice and PJ34 to 21 mice before and immediately after thoracic aortic ischemia-reperfusion. Sham mice (n = 13) underwent median sternotomy alone. At 48 hours, all animals were euthanized and tissues harvested for quantitative analysis. RESULTS PJ34 improved intestinal (P < .05) but not hepatic mitochondrial activity following reperfusion. CD14 messenger ribonucleic acid levels in liver (P < .004), kidney (P < .003), and spinal cord (P < .03) tissue were less in PJ34-treated mice. CONCLUSIONS PJ34 preserved the metabolic function of intestinal but not hepatic tissue during reperfusion. PJ34 uniformly decreased the expression of an important marker of inflammatory cell activation and tissue inflammation in visceral tissue following VI. PARP inhibitors may serve as a therapeutic modality to abrogate the stress response to VI.

Effects of Acute Global Venous Obstruction and Unfractionated Heparin on Muscle Cytokine Synthesis

Phlegmasia cerulea dolens is a devastating complication of massive deep venous thrombosis, which is clinically characterized by massive lower extremity tissue edema and subsequent arterial insufficiency. These experiments evaluated the local tissue effects of acute global venous obstruction combined with partial arterial ischemia. Experiments were performed to assess the effects of heparin on the cytokine response to simultaneous venous and partial arterial obstruction. Murine hind limbs were subjected to conditions of unilateral venous occlusion and partial tourniquet limb ischemia, which was confirmed by laser Doppler imaging (LDI). Mice underwent either hind limb venous obstruction with intravenous unfractionated heparin (200IU/kg) or intravenous saline 5min before venous occlusion. Sham-treated mice were subjected to anesthesia alone without venous occlusion. After 3hr, the mice were killed and tissue was harvested for measurement of edema (wet to dry weight ratio, W/D), muscle viability, indices of local thrombosis (thrombin-antithrombin complex [TAT]), and cytokine analysis for growth-related oncogene-1 (GRO-1) and interleukin-6 (IL-6, protein via enzyme-linked immunoassay and mRNA via reverse transcriptase polymerase chain reaction). Bleeding time and volume were documented in saline- and heparin-treated mice to confirm systemic anticoagulation. Administration of intravenous heparin resulted in a marked increase in bleeding time and volume. LDI confirmed venous obstruction and ongoing arterial inflow. Venous obstruction resulted in severe visible edema that correlated with a significantly higher W/D ratio but was not associated with a significant decrease in muscle viability. GRO-1 and IL-6 protein and mRNA levels were significantly elevated in the venous occlusion group compared to sham. Heparin therapy significantly decreased TAT3 levels but did not alter the profile of GRO-1 or IL-6 protein levels seen with venous occlusion. Venous occlusion with partial ischemia induces a unique and potent local cytokine expression. Heparin therapy did not ameliorate the cytokine response. These data indicate that heparin therapy does not modulate the cytokine response to venous obstruction.