Prolonged Myocardial Regenerative Capacity in Neonatal Opossum.

BACKGROUND: Early neonates of both large and small mammals are able to regenerate the myocardium through cardiomyocyte proliferation for only a short period after birth. This myocardial regenerative capacity declines in parallel with withdrawal of cardiomyocytes from the cell cycle in the first few postnatal days. No mammalian species examined to date has been found capable of a meaningful regenerative response to myocardial injury later than 1 week after birth. METHODS: We examined cardiomyocyte proliferation in neonates of the marsupial opossum (Monodelphis domestica) by immunostaining at various times after birth. The regenerative capacity of the postnatal opossum myocardium was assessed after either apex resection or induction of myocardial infarction at postnatal day 14 or 29, whereas that of the postnatal mouse myocardium was assessed after myocardial infarction at postnatal day 7. Bioinformatics data analysis, immunofluorescence staining, and pharmacological and genetic intervention were applied to determine the role of AMPK (5'-AMP-activated protein kinase) signaling in regulation of the mammalian cardiomyocyte cell cycle. RESULTS: Opossum neonates were found to manifest cardiomyocyte proliferation for at least 2 weeks after birth at a frequency similar to that apparent in early neonatal mice. Moreover, the opossum heart at postnatal day 14 showed substantial regenerative capacity both after apex resection and after myocardial infarction injury, whereas this capacity had diminished by postnatal day 29. Transcriptomic and immunofluorescence analyses indicated that AMPK signaling is activated in postnatal cardiomyocytes of both opossum and mouse. Pharmacological or genetic inhibition of AMPK signaling was sufficient to extend the postnatal window of cardiomyocyte proliferation in both mouse and opossum neonates as well as of cardiac regeneration in neonatal mice. CONCLUSIONS: The marsupial opossum maintains cardiomyocyte proliferation and a capacity for myocardial regeneration for at least 2 weeks after birth. As far as we are aware, this is the longest postnatal duration of such a capacity among mammals examined to date. AMPK signaling was implicated as an evolutionarily conserved regulator of mammalian postnatal cardiomyocyte proliferation.

Metabolic regulation of cardiac regeneration: roles of hypoxia, energy homeostasis, and mitochondrial dynamics.

The adult mammalian heart cannot regenerate after myocardial injury because most cardiomyocytes lack the ability to proliferate. In contrast, cardiomyocytes of vertebrates such as zebrafish and urodele amphibians, but also those of fetal and early neonatal mammals, maintain the ability to proliferate and therefore support regeneration of injured tissue and recovery of cardiac function. Whether evolutionarily conserved regulatory mechanisms of cardiomyocyte proliferation exist and, if so, whether they are modifiable to allow cardiac regeneration in adult mammals are questions of great scientific and medical interest. Environmental hypoxia, hypoxia-induced cellular signaling, and mitochondrial metabolism have recently emerged as key regulators of the cardiomyocyte cell cycle and cardiac regeneration in vertebrates. In this review, we address the cardiac regenerative capacity of several model animals and discuss potential strategies related to hypoxia and mitochondrial metabolism for induction of therapeutic heart regeneration.

Cardiac regeneration as an environmental adaptation.

Heart failure is a devastating disease that affects more than 26 million individuals worldwide and has a 5-year survival rate of less than 50%, with its development in part reflecting the inability of the adult mammalian heart to regenerate damaged myocardium. In contrast, certain vertebrate species including fish and amphibians, as well as neonatal mammals, are capable of complete cardiac regeneration after various types of myocardial injury such as resection of the ventricular apex or myocardial infarction, with this regeneration being mediated by the proliferation of cardiomyocytes, dissolution of temporary fibrosis, and revascularization of damaged tissue. In an effort to identify regulators of cardiac regeneration and to develop novel therapeutic strategies for induction of myocardial regeneration in the adult human heart, recent studies have adopted an approach based on comparative biology. These studies have pointed to cellular or tissue responses to environmental cues-including activation of the immune system, the reaction to mechanical stress, and the adoption of oxidative metabolism-as key determinants of whether the heart undergoes regeneration or nonregenerative scar formation after injury. We here summarize recent insight into the molecular mechanisms as well as environmental and systemic factors underlying cardiac regeneration based on the findings of inter- or intraspecific comparisons between regenerative and nonregenerative responses to heart injury. We also discuss how recent progress in understanding the molecular, systemic, and environmental basis of cardiac regeneration in a variety of organisms may relate to multiple scientific fields including ecology, evolutionary as well as developmental biology.

The Evaluation of Fibrin-Related Markers for Diagnosing or Predicting Acute or Subclinical Venous Thromboembolism in Patients Undergoing Major Orthopedic Surgery.

OBJECTIVE: The cutoff values of fibrin-related markers (FRMs) diagnosing or predicting the occurrence of a venous thromboembolism (VTE) were evaluated. MATERIALS AND METHODS: Fibrin-related markers such as fibrin monomer complex (FMC), D-dimer, and fibrinogen and fibrin degradation products (FDPs) before surgery were measured in 326 patients undergoing orthopedic surgery to diagnose subclinical VTE or predict postoperative VTE. RESULTS: Although the FMC, D-dimer, and FDP levels were all useful for the diagnosis of acute VTE, the FDP level was not useful for diagnosing subclinical VTE or predicting postoperative VTE. The results of several D-dimer assays closely correlated with other D-dimer assays. There were various cutoff ranges for diagnosing or predicting VTE. Some D-dimer assays were useful for diagnosing low levels of D-dimer and others were useful for diagnosing moderate to high D-dimer levels. Increased D-dimer levels were useful for diagnosing acute (cutoff values: 2.0-5.9 µg/mL) or about 10% of subclinical VTE (cutoff values: 3.4-5.3 µg/mL), for predicting about 10% of postoperative VTE (cutoff values: 3.4-5.3 µg/mL), and for excluding VTE. CONCLUSION: Although increased D-dimer levels were useful for diagnosing subclinical VTE and predicting the risk of VTE, there were various cutoff values for the diagnosis or prediction of VTE.

Sfrp5 identifies murine cardiac progenitors for all myocardial structures except for the right ventricle.

Upon acquirement of pulmonary circulation, the ancestral heart may have been remodelled coincidently with, or accompanied by, the production and rearrangement of progenitor cells. However, the progenitor populations that give rise to the left ventricle (LV) and sinus venosus (SV) are still ambiguous. Here we show that the expression of Secreted frizzled-related protein Sfrp5 in the mouse identifies common progenitors for the outflow tract (OFT), LV, atrium and SV but not the right ventricle (RV). Sfrp5 expression begins at the lateral sides of the cardiac crescent, excluding early differentiating regions, and continues in the venous pole, which gives rise to the SV. Lineage-tracing analysis revealed that descendants of Sfrp5-expressing cells at E7.5 contribute not only to the SV but also to the LV, atria and OFT and are found also in the dorsal splanchnic mesoderm accompanied by the expression of the secondary heart field marker, Islet1. These findings provide insight into the arrangement of cardiac progenitors for systemic circulation.

Comparison of three different anti-Xa assays in major orthopedic surgery patients treated with fondaparinux.

Anti-Xa assays are useful for monitoring the effects of selective anti-Xa drugs, such as fondaparinux, in the prophylaxis of deep vein thrombosis. In the present study, anti-Xa activity was measured using three different assays, Testzym(®) Heparin S, STA(®)-Liquid Anti-Xa and HemosIL(®) Liquid Heparin. Anti-Xa activity in each assay gradually increased from day one after administration to day eight, and still remained on day 15. Although there were significant differences in anti-Xa activity among the three assays, the activity showed significant correlation across assays. There were no significant differences in the anti-Xa activity between patients with and without DVT or between patients with and without massive bleeding on day one before and after administration, day four, day eight and day 15. Anti-Xa activity in each assay was weakly correlated with antithrombin (AT) activity. The AT activity in patients were significantly higher on days four, eight and 15 compared with day one before and after administration, suggesting that AT activity increases following the administration of fondaparinux. The three anti-Xa assay kits tested are useful for monitoring fondaparinux treatment in orthopedic surgery patients.

Fibrin-related markers for diagnosing acute-, subclinical-, and pre-venous thromboembolism in patients with major orthopedic surgery.

Venous thromboembolism (VTE) is a common complication in patients who have undergone major orthopedic surgery, but there are few predictors of VTE after major orthopedic surgery treated with an anticoagulant. We measured levels of fibrin-related markers (FRMs), such as D-dimer, soluble fibrin (SF), and fibrinogen and fibrin degradation products (FDPs) in 66 patients with acute-phase VTE, and 367 patients undergoing major orthopedic surgery. Plasma FDP, D-dimer, and SF levels were significantly higher in patients with acute VTE, but only FDP and D-dimer levels were significantly higher in subclinical VTE. Adequate cut-off levels of D-dimer were 2.2 µg/ml for diagnosing acute VTE and 1.5 µg/ml for diagnosing subclinical VTE. D-dimer of less than 1.9 or 0.7 µg/ml ruled out acute VTE or subclinical VTE. D-dimer of more than 1.3 µg/ml preoperatively showed a moderate risk for postoperative VTE. Measurement of FRMs is useful for evaluating the risk of subclinical or postoperative VTE in patients with major orthopedic surgery. In particular, FDP is the most valuable marker for diagnosing acute VTE, whereas D-dimer is the most valuable for diagnosing subclinical VTE or predicting VTE.

Substrate specificity engineering of Escherichia coli derived fructosamine 6-kinase.

A three-dimensional structural model of Escherichia coli fructosamine 6-kinase (FN6K), an enzyme that phosphorylates fructosamines at C6 and catalyzes the production of the fructosamine 6-phosphate stable intermediate, was generated using the crystal structure of 2-keto-3-deoxygluconate kinase isolated from Thermus thermophilus as template. The putative active site region was then investigated by site-directed mutagenesis to reveal several amino acid residues that likely play important roles in the enzyme reaction. Met220 was identified as a residue that plays a role in substrate recognition when compared to Bacillus subtilis derived FN6K, which shows different substrate specificity from the E. coli FN6K. Among the various Met220-substituted mutant enzymes, Met220Leu, which corresponded to the B. subtilis residue, resulted in an increased activity of fructosyl-valine and decreased activity of fructosyl-lysine, thus increasing the specificity for fructosyl-valine by 40-fold.

[Analysis of platelet production following liver transplantation using the immature platelet fraction (IPF) parameter].

Although liver transplantation (LT) is frequently associated with thrombocytopenia, thrombopoiesis following LT remains to be evaluated. We analyzed platelet counts (PLT), immature Platelet Fraction (IPF), and thrombopoietin (TPO) in 8 patients with LT. PLT and IPF were measured using Sysmex XE-2100. TPO was measured with Human TPO ELISA Kit. In 7 of 8 patients with LT, IPF increased prior to the elevation of platelet counts. In 5 of 7 patients with increased IPF, TPO levels increased simultaneously with IPF, suggesting that IPF may reflect the production of platelets in patients with LT. IPF and TPO might be useful to monitor the platelet production in patients following LT.

Elevated levels of prothrombin fragment 1 + 2 indicate high risk of thrombosis.

Prothrombin fragment 1 + 2 (F1 + 2) is considered to be useful for diagnosis of thrombosis. However, the evidence for a diagnosis of thrombosis by F1 + 2 is still not well established. The plasma concentrations of F1 + 2, soluble fibrin, D-dimer, and thrombin-antithrombin complex were measured in 694 patients suspected of having thrombosis and then were correlated with thrombosis. Plasma concentrations of F1 + 2, soluble fibrin, D-dimer, and thrombin-antithrombin complex were significantly higher in patients with thrombosis, compared with patients without thrombosis. When cutoff values of more than 300 pmol/L for F1 + 2 were used for the diagnosis, more than 50% of the patients were thus found to have thrombosis. The findings showed that F1 + 2, soluble fibrin, D-dimer, and thrombin-antithrombin complex have similar diagnostic ability. The plasma concentration of F1 + 2 closely was well correlated with thrombin-antithrombin complex, soluble fibrin, and D-dimer. Finally, F1 + 2 is one of the most useful parameters for the diagnosis of thrombosis.

Novel fluorescent sensing system for alpha-fructosyl amino acids based on engineered fructosyl amino acid binding protein.

A novel fluorescent sensing system for alpha-glycated amino acids was created based on fructosyl amino acid binding protein (FABP) from Agrobacterium tumefaciens. The protein was found to bind specifically to the alpha-glycated amino acids fructosyl glutamine (Fru-Gln) and fructosyl valine (Fru-Val) while not binding to epsilon-fructosyl lysine. An Ile166Cys mutant of FABP was created by genetic engineering and modified with the environmentally sensitive fluorophore acrylodan. The acrylodan-conjugated mutant FABP showed eight-fold greater sensitivity to Fru-Val than the unconjugated protein and could detect concentrations as low as 17 nM, making it over 100-fold more sensitive than enzyme-based detection systems. Its high sensitivity and specificity for alpha-substituted fructosyl amino acids makes the new sensing system ideally suited for the measurement of hemoglobin A1c (HbA1c), a major marker of diabetes.

Hemostatic abnormalities and leukocyte activation caused by infection in patients with malignant lymphoma during chemotherapy.

Hemostatic parameters were examined before and during 102 courses of chemotherapy in 42 patients with malignant lymphoma with high risk for infection. The white blood cell count was significantly reduced in all patients at days 1 and 3, but significantly increased at days 7 and 9, compared to before chemotherapy. At day 7 of chemotherapy, tissue factor (TF) mRNA levels in leukocytes were significantly increased in all patients, especially those with infection. Plasma concentrations of granulocyte elastase derived-XDP (GE-XDP) levels correlated with D-dimer levels during chemotherapy in patients with malignant lymphoma, suggesting that the elevated D-dimer is fibrin products degraded by granulocyte elastase. GE-XDP, C-reactive protein (CRP), GE-XDP and D-dimer were significantly higher in patients with infection, disseminated intravascular coagulation (DIC) and acute respiratory distress syndrome (ARDS) than those without. In patients with DIC or ARDS, TF mRNA correlated with D-dimer, and GE-XDP correlated with leukocyte count, CRP and D-dimer, suggesting that inflammatory changes due to thrombosis may cause the activation of leukocytes in patients with malignant lymphoma during chemotherapy. Activated leukocytes and granulocyte elastase may elicit a hypercoagulable state and ARDS in patients with malignant lymphoma during chemotherapy.

A simple technique to determine thrombopoiesis level using immature platelet fraction (IPF).

Immature platelet fraction (IPF) has been measured by fully automated analyzer (XE-2100) as reticulated platelet (RP) which is reflected with thrombopoiesis in bone marrow. IPF value in the healthy volunteers was 3.3% (1.0-10.3) and upper 95% confidential interval (95% CI) of IPF was determined as 7.7%. IPF was significantly high in the patients with idiopathic thrombocytopenic purpura (ITP; 17.4%, 1.2-53.2%) and recovery phase of post-chemotherapy, and significantly low in nadir phase of post-chemotherapy, and within normal range in the patients with ITP in complete remission (CR) and with aplastic anemia (AA). Total count of IPF was significantly low in patients with ITP, AA or post-chemotherapy. Mean platelet volume (MPV) was significantly high in only patients with ITP. IPF 7.7% is best point for highest sensitivity (86.8%) and specificity (92.6%) in diagnosis of ITP and recovery phase of post-chemotherapy. In receiver operating characteristic curve for diagnosis of ITP and recovery phase of post-chemotherapy, IPF was significantly more useful than MPV. These results show that IPF reflects the pathology of thrombocytopenic disorders, and that measurement of IPF is useful for the differential diagnosis and analysis of platelet kinetics.

[Diagnosis of DIC based on evidence].

The diagnosis of disseminate intravascular coagulation (DIC) was first based on the detection of microthrombi, but it currently involves analysis of hemostatic abnormalities by various laboratory tests and further studies are needed to simplify diagnosis of DIC. There are three diagnostic criteria for DIC developed by the International Society of Thrombosis Haemostasis (ISTH), the Japanese Association for Acute Medicine (JAAM) and the Japanese Ministry Health and Welfare. These diagnostic criteria consist of the scoring system by the same global coagulation tests. From ROC analysis, the ability for diagnosis of DIC is similar among three diagnostic criteria. ISTH diagnostic criteria has high specificity and low sensitivity, but JAAM criteria has low specificity and high sensitivity. Several molecular hemostatic markers such as thrombin antithrombin complex, D-dimer, soluble fibrine (SF) and plasmin-plasmin inhibitor complex have to be adopted for further improvement of diagnostic criteria for DIC. Finally, prospective study for new diagnostic criteria for DIC should be carried out in infectious diseases by molecular hemostatic markers.

SocA is a novel periplasmic binding protein for fructosyl amino acid.

Bacterial periplasmic proteins (bPBPs) undergo drastic conformational changes upon binding substrate, making them appealing as novel molecular recognition tools for biosensing. A putative bPBP-encoding gene, socA, belongs to the soc operon responsible for santhopine (fructosyl glutamine, FQ) catabolism of Agrobacterium tumefaciens. The socA gene was isolated and expressed in Escherichia coli as a soluble 28.8kDa periplasmic protein to investigate its properties as a potential bPBP for fructosyl amino acid (FA). The autofluorescence of SocA was used to monitor the protein's conformational change resulting from substrate binding. The fluorescence intensity changed upon binding FQ in a concentration dependent manner with a calculated K(d) of 2.1muM, but was unaffected by the presence of sugars or amino acid. Our results demonstrate that SocA is a novel FA bPBP that can be utilized as a novel molecular recognition element for the monitoring of FA.

Diagnosis of deep vein thrombosis by plasma-soluble fibrin or D-dimer.

The present study was designed to determine the cutoff values of D-dimer and soluble fibrin (SF) for the diagnosis of deep venous thrombosis (DVT) and pulmonary embolism (PE) in Japanese patients. Plasma levels of these molecules were measured in 243 patients suspected of having DVT and 100 healthy volunteers (controls). Out of 243 patients, 20 patients were diagnosed with DVT. In the control group, plasma levels of D-dimer and SF did not show normal distribution, and the 95% confidence intervals (CI) of D-dimer and SF were 2.45 microg/mL and 6.92 microg/mL, respectively. Plasma levels of D-dimer and SF of patients with DVT were significantly higher than of those without DVT. In patients with DVT, the minimum values of D-dimer and SF were 1.71 and 1.44 microg/mL, respectively. When the cutoff value was set at the average+1 SD of those of the control (D-dimer, about 1.8 microg/mL; SF, about 1.4 microg/mL), 1 and 0 patient with DVT was overlooked, respectively. The sensitivity and specificity of D-dimer and SF for DVT were 95% and 100%, and 61.9% and 53.8%, respectively. When the cutoff value was set at 95% CI of the control (D-dimer, 2.5 microg/mL; SF, 6.9 microg/mL), 2 and 9 patients with DVT were overlooked, respectively. The sensitivity and specificity of D-dimer and SF were 90% and 50%, and 77.6% and 88.3%, respectively. When the cutoff values set at 2.5 microg/mL of D-dimer or 6.9 microg/mL of SF, 1 DVT patient was overlooked, with sensitivity and specificity of 95% and 69.5%. Our data suggest that both D-dimer and SF are useful markers for the diagnosis of DVT and that measurement of both D-dimer and SF increases the sensitivity and specificity for the diagnosis of DVT/PE.

[Markedly increased red cell fragmentations counted as platelets in a patient with thrombotic microangiopathy].

A patient with acute lymphocytic leukemia (ALL) experienced severe thrombotic microangiopathy (TMA) after allo-bone marrow transplantation (BMT). She had high risk for TMA; due to total body irradiation (TBI), intensive chemotherapy, treatment with Ciclosporin and association with veno-occlusive disease (VOD). Markedly increased fragmentations of red blood cells were observed in this case, and were incorrectly counted as platelets by a fully automated blood cells counter. Careful evaluation of the platelet count is necessary in patients with red cell fragmentations.

Isolation and characterization of a fructosyl-amine oxidase from an Arthrobacter sp.

An Arthrobacter sp. was isolated that, when induced by fructosyl-valine, expressed a fructosyl-amine oxidase (FAOD) that was specific for alpha-glycated amino acids. The N-terminal amino acid sequence of the purified oxidase was determined and used to design oligonucleotides to amplify the gene by inverse PCR. Expression of the gene in Escherichia coli produced 0.23 units FAOD per mg protein, over 30-fold greater than native expression levels, with properties almost indistinguishable from the native enzyme. The presence of FAOD was confirmed in other Arthrobacter ssp.

Effects of atorvastatin on serum lipids, lipoproteins, and hemostasis.

Serum levels of lipids and lipoproteins were examined in individuals with hyperlipidemia treated with atorvastatin or colestimide and in healthy volunteers. Modified low-density lipoprotein (LDL) was measured by its faster electrophoretic mobility and expressed as charge modification frequency (CMF). Serum levels of total cholesterol (t-chol), triglyceride (TG), very low-density lipoprotein (VLDL)-chol, low-density lipoprotein (LDL)-chol, and CMF were significantly higher in hyperlipidemia, but there was no significant difference in serum high-density lipoprotein (HDL)-chol levels between hyperlipidemic and healthy subjects. Treatment with atorvastatin resulted in significant decreases of serum t-chol, TG, and LDL-chol levels but not serum HDL-chol and VLDL-chol. Treatment with colestimide significantly reduced serum t-chol, HDL-chol, and LDL-chol levels but not those of TG and VLDL-chol. CMF was significantly reduced by treatment with atorvastatin but not by colestimide. Atorvastatin significantly reduced plasma levels of thrombomodulin, thrombin antithrombin complex (TAT) and tissue type plasminogen activator-plasminogen activator inhibitor-I complex. Colestimide moderately prolonged activated partial thromboplastin time and reduction of TAT. Based on its actions of lowering modified LDL and improving hemostatic abnormalities, we postulate that atorvastatin might inhibit the onset of ischemic diseases.

Cloning and expression of fructosyl-amine oxidase from marine yeast Pichia species N1-1.

The gene encoding the fructosyl-amine oxidase (FAOD) from the marine yeast Pichia sp. N1-1 was cloned and expressed in Escherichia coli. Partial amino acid sequence analysis of the Pichia sp. N1-1 FAOD allowed the design of oligonucleotide primers for the amplification of the gene by inverse polymerase chain reaction. The FAOD gene was found to be devoid of introns and to encode a 48-kDa protein composed of 429 amino acid residues. The FAD-binding consensus sequence GXGXXG: and the FAD covalent attachment-site cysteine residue have been identified within the predicted amino acid sequence. Comparisons with the amino acid sequences of other eukaryotic FAODs showed only 30% to 40% identities, establishing that the isolated Pichia N1-1 gene encodes a unique FAOD. Recombinant FAOD expression levels in E. coli reached 0.48 U/mg of soluble protein, which is considerably greater than native expression levels by inducing Pichia sp. N1-1 with fructosyl-valine (f-Val). The kinetic properties of the recombinant enzyme were almost indistinguishable from those of the native enzyme. We previously reported on the construction of a number of effective Pichia sp. N1-1 FAOD-based biosensors for measuring f-Val, a model compound for glycated hemoglobin. The further development of these biosensor systems can now greatly benefit from protein engineering and recombinant expression of the FAOD from Pichia N1-1.