Henri Haapanen

Safety and biodistribution study of bone marrow–derived mesenchymal stromal cells and mononuclear cells and the impact of the administration route in an intact porcine model

BACKGROUND AIMS Bone marrow mononuclear cells (BM-MNCs) and bone marrow-derived mesenchymal stem stromal cells (BM-MSCs) could have therapeutic potential for numerous conditions, including ischemia-related injury. Cells transplanted intravascularly may become entrapped in the lungs, which potentially decreases their therapeutic effect and increases the risk for embolism. METHODS Twelve pigs were divided into groups of 3 and received (99m)Tc- hydroxymethyl-propylene-amine-oxime-labeled autologous BM-MNCs or allogeneic BM-MSCs by either intravenous (IV) or intra-arterial (IA) transplantation. A whole body scan and single photon emission computed tomography/computed tomography (SPECT/CT) were performed 8 h later, and tissue biopsies were collected for gamma counting. A helical CT scan was also performed on 4 pigs to detect possible pulmonary embolism, 2 after IV BM-MSC injection and 2 after saline injection. RESULTS The transplantation route had a greater impact on the biodistribution of the BM-MSCs than the BM-MNCs. The BM-MNCs accumulated in the spleen and bones, irrespective of the administration route. The BM-MSCs had relatively higher uptake in the kidneys. The IA transplantation decreased the deposition of BM-MSCs in the lungs and increased uptake in other organs, especially in the liver. Lung atelectases were frequent due to mechanical ventilation and attracted transplanted cells. CT did not reveal any pulmonary embolism. CONCLUSIONS Both administration routes were found to be safe, but iatrogenic atelectasis might be an issue when cells accumulate in the lungs. The IA administration is effective in avoiding pulmonary entrapment of BM-MSCs. The cell type and administration method both have a major impact on the acute homing.

Remote ischemic preconditioning protects the spinal cord against ischemic insult: An experimental study in a porcine model

OBJECTIVE Surgical repair of thoracoabdominal aneurysm jeopardizes the vascularization of the spinal cord, and therefore, despite improvement in surgical techniques, still carries the risk of paraplegia. This study aimed to demonstrate the possible protective effects of remote ischemic preconditioning (RIPC) on the preservation of spinal cord function after segmental artery (SA) occlusion. METHODS Twenty piglets were randomized into the RIPC group (n = 10) and the control group (n = 10). The RIPC group underwent transient left hind limb ischemia before systematic left subclavian artery and SA occlusion at the level of the diaphragm. Motor-evoked potential (MEP) monitoring was performed from the hind limbs. Afterward, the thoracic and lumbar spinal cords were harvested and analyzed. RESULTS The elevation of the MEP amplitude after RIPC was statistically significant, whereas amplitude was consistently decreased in the control group. Additionally, the onset latency was significantly shorter after RIPC during SA occlusion. The control group reached a 50% decrease of MEP amplitude in the right hind limb sooner than did the experimental group. CONCLUSIONS Remote ischemic preconditioning preserves spinal cord function after left subclavian artery and SA occlusion, as indicated by the MEP amplitudes.

Review of remote ischemic preconditioning: from laboratory studies to clinical trials

Abstract In remote ischemic preconditioning (RIPC) short periods of non-lethal ischemia followed by reperfusion of tissue or organ prepare remote tissue or organ to resist a subsequent more severe ischemia-reperfusion injury. The signaling mechanism of RIPC can be humoral communication, neuronal stimulation, systemic modification of circulating immune cells, and activation of hypoxia inducible genes. Despite promising evidence from experimental studies, the clinical effects of RIPC have been controversial. Heterogeneity of inclusion and exclusion criteria and confounding factors such as comedication, anesthesia, comorbidities, and other risk factors may have influenced the efficacy of RIPC. Although the cardioprotective pathways of RIPC are more widely studied, there is also evidence of benefits in CNS, kidney and liver protection. Future research should explore the potential of RIPC, not only in cardiac protection, but also in patients with threatening ischemia of the brain, organ transplantation of the heart, liver and kidney and extensive cardiovascular surgery. RIPC is generally well-tolerated, safe, effective, and easily feasible. It has a great prospect for ischemic protection of the heart and other organs.

Leg ischaemia before circulatory arrest alters brain leucocyte count and respiratory chain redox state

OBJECTIVES Remote ischaemic preconditioning and its neuroprotective abilities are currently under investigation and the method has shown significant effects in several small and large animal studies. In our previous studies, leucocyte filtration during cardiopulmonary bypass reduced cerebrocortical adherent leucocyte count and mitigated cerebral damage after hypothermic circulatory arrest (HCA) in piglets. This study aimed to obtain and assess direct visual data of leucocyte behaviour in cerebral vessels after hypothermic circulatory arrest following remote ischaemic preconditioning. METHODS Twelve native stock piglets were randomized into a remote ischaemic preconditioning group (n = 6) and a control group (n = 6). The intervention group underwent hind-leg ischaemia, whereas the control group received a sham-treatment before a 60-min period of hypothermic circulatory arrest. An intravital microscope was used to obtain measurements from the cerebrocortical vessel in vivo. It included three sets of filters: a violet filter to visualize microvascular perfusion and vessel diameter, a green filter for visualization of rhodamine-labelled leucocytes and an ultraviolet filter for reduced nicotinamide adenine dinucleotide (NADH) analysis. The final magnification on the microscope was 400. After the experiment, cerebral and cerebellar biopsies were collected and analysed with transmission electron microscope by a blinded analyst. RESULTS In the transmission electron microscope analysis, the entire intervention group had normal, unaffected rough endoplasmic reticulums in their cerebellar tissue, whereas the control group had a mean score of 1.06 (standard deviation 0.41) (P = 0.026). The measured amount of adherent leucocytes was lower in the remote ischaemic preconditioning group. The difference was statistically significant at 5, 15 and 45 min after circulatory arrest. Statistically significant differences were seen also in the recovery phase at 90 and 120 min after reperfusion. Nicotinamide adenine dinucleotide autofluorescence had statistically significant differences at 10 min after cooling and at 120 and 180 min after hypothermic circulatory arrest. CONCLUSIONS Remote ischaemic preconditioning seems to provide better mitochondrial respiratory chain function as indicated by the higher NADH content. It simultaneously provides a reduction of adherent leucocytes in cerebral vessels after hypothermic circulatory arrest. Additionally, it might provide some degree of cellular organ preservation as implied by the electron microscopy results.

Remote ischemic precondition preserves cerebral oxygen tension during hypothermic circulatory arrest

Abstract Objectives. Remote ischemic preconditioning (RIPC) is a novel and promising method of mitigating neurological injury. In previous animal studies, RIPC has provided substantial neuroprotective effects. We hypothesized that the promising neuroprotective properties were a consequence of a better oxygen consumption profile during hypothermic circulatory arrest (HCA). Design. Six 7-week-old female pigs were randomly assigned to undergo the 60 minutes of HCA with the right hind leg receiving transient RIPC preoperatively and six animals were assigned to a control group that underwent 60 minutes of HCA without any preconditioning. A combined temperature/oxygen-tension probe was inserted into the parietal cortex of each animal to monitor cerebral oxygen tension during experiments. Results. The RIPC group had significantly higher cerebral oxygen tension readings throughout the HCA. Statistically significant differences were measured from the 20 minute time point onwards in every time point up to the 60 minute time point. Conclusions. This study shows that RIPC performed before HCA conserves the cerebral oxygen tension during a circulatory arrest. RIPC could possibly prolong the safe operating time during HCA as cerebral oxygen content is preserved throughout circulatory arrest.

Remote Ischemic Preconditioning Attenuates Oxidative Stress during Cardiopulmonary Bypass

BACKGROUND Deep hypothermic circulatory arrest (DHCA) is used to overcome the threat of cerebral ischemia during complex surgical operations of the heart and the aortic arch. Remote ischemic preconditioning (RIPC) has been shown to mitigate neurological damage. METHODS We analyzed blood samples in a consecutive series of 52 piglets that underwent a 60-min period of DHCA with RIPC (the RIPC group) or without (the control group), to reveal whether the protective effect to oxidative stress could be seen by measuring serum 8-hydroxydeoxyguanosine (8-OHdG). The piglets were cannulated and cooled to 18°C using a heart-lung machine, for the DHCA. The piglets were then rewarmed to normothermic temperature. Blood sampling was taken at baseline, after 30 minutes of cooling, 2 hours postoperatively, and 8 hours postoperatively, and analyzed. 8-hydroxydeoxyguanosine (8-OHdG) from blood samples was analyzed by using Enzyme Linked Immunosorbent Assay (ELISA). RESULTS The serum 8-OHdG concentration was lower in the RIPC group after the cooling phase, 1.84 (1.44-2.17) ng/mL, and at 8 hours after HCA 1.48 (1.39-1.69) ng/mL, when compared with the control group, where the values were 2.14 (1.81-2.56) and 1.84 (1.62-2.44) ng/mL, respectively (P = .025) and (P = .004). CONCLUSION Remote ischemic preconditioning lowers oxidative stress during cardiopulmonary bypass.

Exploring effects of remote ischemic preconditioning in a pig model of hypothermic circulatory arrest

Abstract Objectives. During aortic and cardiac surgery, risks for mortality and morbidity are inevitable. Surgical setups involving deep hypothermic circulatory arrest (DHCA) are effective to achieve organ protection against ischemic injury. The aim of this study was to identify humoural factors mediating additive protective effects of remote ischemic preconditioning (RIPC) in a porcine model of DHCA. Design. Twenty-two pigs were randomized into the RIPC group (n = 11) and the control group (n = 11). The RIPC group underwent four 5-minute hind limb ischemia-reperfusion cycles prior to cardiopulmonary bypass and DHCA. All animals underwent identical surgical procedures including 60 min DHCA at 18 °C. Blood samples were collected from vena cava and sagittal sinus at several time points. After the 8-hour follow-up period, the brain, heart, and kidney tissue samples were collected for tissue analyses. Results. Serum levels of brain damage marker S100B recovered faster in the RIPC group, after 4 hours of the arrest, (p < .05). Systemic lactate levels were lower and cardiac index was higher in the RIPC group postoperatively. Immunohistochemical cerebellum regional scores of antioxidant response regulator Nrf2 were better in the RIPC group (mean: 1.1, IQR: 0.0–2.5) compared with the control group (mean: 0.0, IQR: 0.0–0.0), reaching borderline statistical significance (p = .064). RIPC induced detectable modulations of plasma proteome and metabolites. Conclusions. The faster recovery of S100B, lower systemic lactate levels and favourable regional antioxidant response suggest possible neuronal cellular and mitochondrial protection by RIPC, whereas better cardiac index underlines functional effects of RIPC. The exact humoural factor remains unclear.

Diazoxide Attenuates Ischemic Myocardial Injury in a Porcine Model

BACKGROUND We hypothesized that diazoxide, a mitochondrial ATP-sensitive potassium channel opener, has cardioprotective effects during acute myocardial ischemia. Diazoxide is suggested to act through protein kinase Cε (PKCε) activation. METHODS Twelve piglets were randomly assigned to receive intravenous infusion of diazoxide (3.5 mg/kg) with solvent or only solvent (6 animals per group) before cardiac ischemia. Myocardial ischemia was induced by occluding the left circumflex artery (LCX) for 40 minutes. The reperfusion and follow-up period lasted for three hours. Throughout the experiment hemodynamic measurements and blood samples were collected, and after the follow-up period the hearts were harvested for transmission electron microscopy (TEM) as well as histopathological and immunohistochemical analyses. RESULTS TEM showed less ischemic damage on a cellular level in the diazoxide group (P = .004) than in the control group. Creatinine kinase MB levels (Pt*g = .030) were lower, and oxygen consumption (Pt*g = .037) and delivery (Pg = .038) were higher in the diazoxide group compared to the controls. CONCLUSION Diazoxide preserves myocardial cellular structure and cellular function, and thus it may have benefits in treating ischemic myocardial injury.

Remote Ischemic Preconditioning Reduces Cerebral Oxidative Stress Following Hypothermic Circulatory Arrest in a Porcine Model

Remote ischemic precondition has become prominent as one of the most promising methods to mitigate neurological damage following ischemic insult. The purpose of this study was to investigate whether the effects of remote ischemic preconditioning can be seen in the markers of oxidative stress or in redox-regulating enzymes in a porcine model. A total of 12 female piglets were randomly assigned to 2 groups. The study group underwent an intervention of 4 cycles of 5-minute ischemic preconditioning on the right hind leg. All piglets underwent 60-minute hypothermic circulatory arrest. Oxidative stress marker 8-hydroxydeoxyguanosine (8-OHdG) was measured from blood samples with enzyme-linked immunosorbent assay. After 7 days of follow-up, samples from the brain, heart, kidney, and ovary were harvested for histopathologic examination. The immunohistochemical stainings of hypoxia marker hypoxia-inducible factor-1-α, oxidative stress marker 8-OHdG, DNA repair enzyme 8-oxoguanine glycosylase, and antioxidant response regulators nuclear factor erythroid 2-related factor 2 and protein deglycase were analyzed. The level of 8-OHdG referred to baseline was decreased in the sagittal sinus׳ blood samples in the study group after a prolonged deep hypothermic circulatory arrest at 360 minutes after reperfusion. Total histopathologic score was 3.8 (1.8-6.0) in the study group and was 4.4 (2.5-6.5) in the control group (P = 0.72), demonstrating no statistically significant difference in cerebral injury. Our findings demonstrate that the positive effects of remote ischemic preconditioning can be seen in cellular oxidative balance regulators in an animal model after 7 days of preconditioned ischemic insult.