Evidence for fusion between cardiac and skeletal muscle cells

Cardiomyoplasty with skeletal myoblasts may benefit cardiac function after infarction. Recent reports indicate that adult stem cells can fuse with other cell types. Because myoblasts are "fusigenic" cells by nature, we hypothesized they might be particularly likely to fuse with cardiomyocytes. To test this, neonatal rat cardiomyocytes labeled with LacZ and green fluorescent protein (GFP) were cocultured with unlabeled C2C12 myoblasts. After 3 days, we observed a small population of skeletal myotubes that expressed LacZ and GFP, indicating cell fusion. To test whether such fusion occurred in vivo, LacZ-expressing C2C12 myoblasts were grafted into normal nude mouse hearts. At 2 weeks after grafting, cells at the graft-host interface expressed both LacZ and cardiac-specific myosin light chain 2v (MLC2v). To test more definitively whether fusion between skeletal and cardiac muscle could occur, we used a Cre/lox reporter system that activated LacZ only upon cell fusion. When neonatal cardiomyocytes from -myosin heavy chain promoter (-MHC)-Cre mice were cocultured with myoblasts from floxed-lacZ reporter mice, LacZ was activated in a subset of cells, indicating cell fusion occurred in vitro. Finally, we grafted the floxed-lacZ myoblasts into normal hearts of -MHC-Cre+ and -MHC-Cre- mice (n=5 each). Hearts analyzed at 4 days and 1 week after transplantation demonstrated activation of LacZ when the skeletal muscle cells were implanted into hearts of -MHC-Cre+ mice, but not after implantation into -MHC-Cre- mice. These data indicate that skeletal muscle cell grafting gives rise to a subpopulation of skeletal-cardiac hybrid cells with a currently unknown phenotype. The full text of this article is available online at http://circres.ahajournals.org.     

A new site-specific integration system for mycobacteria

Site-specific integration into the mycobacterial chromosome can produce stable transformants useful for understanding pathogenesis. However, gene expression can be problematic at certain sites of integration. We have used the Streptomyces phiC31 integration system to integrate vector DNA into Mycobacterium smegmatis, M. bovis BCG, and M. tuberculosis through site-specific recombination. A single dominant insertion site was found in M. smegmatis, as previously reported. Three different insertion sites were found in M. bovis BCG. In M. smegmatis, integrated vectors appear to be far more stable than episomal plasmids during unselected passage in vitro, although excision products are detectable. Plasmids based on the phiC31 integration system could make useful tools for the study of mycobacterial genetics.     

Interleukin-10 promoter polymorphisms in rheumatoid arthritis and Felty's syndrome

OBJECTIVE: To examine whether promoter polymorphisms associated with variation in interleukin-10 (IL-10) production are relevant to the development of rheumatoid arthritis (RA) or Felty's syndrome (FS). METHODS: DNA was obtained from 44 FS patients, 117 RA patients and 295 controls. The promoter region between -533 and - 1120 was amplified by polymerase chain reaction, and polymorphisms detected by restriction enzyme digest or sequence-specific oligonucleotide probing. RESULTS: We found no significant difference in allele or haplotype frequencies between the groups. CONCLUSION: There is no association between FS or RA and these recently identified IL-10 promoter polymorphisms. Other genetic or environmental factors could explain the alterations in IL-10 levels seen in these conditions.      

Skeletal muscle stem cells do not transdifferentiate into cardiomyocytes after cardiac grafting

Skeletal muscle cell-derived grafts in the heart may benefit myocardial performance after infarction. Several studies have suggested that skeletal muscle stem cells (satellite cells) from adult muscle undergo transdifferentiation into cardiomyocytes after grafting into the heart, but expression of cardiac markers in graft cells has not been rigorously confirmed. To determine the fate of satellite cell-derived grafts in the heart, adult rat satellite cells were tagged in vitro with bromodeoxyuridine (BrdU) and grafted into normal hearts of syngeneic rats. At 4 and 12 weeks the graft cells formed multinucleated, cross-striated myofibers that expressed fast skeletal myosin heavy chain (MHC), thus indicating a mature skeletal muscle phenotype. Double staining for the BrdU tag and cardiac-specific markers was employed to identify transdifferentiation. Aside from four questionable cells, none of the 11 grafts examined expressed alpha-MHC, cardiac troponin I, or atrial natriuretic peptide. At 4 weeks, grafts expressed beta -MHC, a hallmark of slow twitch myofibers. By 12 weeks, however, the myofibers had atrophied and downregulated beta-MHC. Grafts never expressed the intercalated disk proteins N-cadherin or connexin43, hence electromechanical coupling did not occur. In conclusion, satellite cells differentiate into mature skeletal muscle and do not express cardiac-specific genes after grafting into the heart. Thus, transdifferentiation into cardiomyocytes did not occur.     

A review of cervical spine injury associated with maxillofacial trauma at a UK tertiary referral centre

IntroductionThe aim of this study was to determine the incidence and patterns of cervical spine injury (CSI) associated with maxillofacial fractures at a UK trauma centre.MethodsA retrospective analysis was conducted of 714 maxillofacial fracture patients presenting to a single trauma centre between 2006 and 2012.ResultsOf the 714 maxillofacial fracture patients, 2.2% had associated CSI including a fracture, cord contusion or disc herniation. In comparison, 1.0% of patients without maxillofacial trauma sustained a CSI (odds ratio: 2.2, p=0.01). The majority (88%) of CSI cases of were caused by a road traffic accident (RTA) with the remainder due to falls. While 8.8% of RTA related maxillofacial trauma patients sustained a CSI, only 2.0% of fall related patients did (p=0.03, not significant). Most (70%) of the CSIs occurred at C1/C2 or C6/C7 levels. Overall, 455, 220 and 39 patients suffered non-mandibular, isolated mandibular and mixed mandibular/non-mandibular fractures respectively. Their respective incidences of CSI were 1.5%, 1.8% and 12.8% (p=0.005, significant). Twelve patients with concomitant CSI had their maxillofacial fractures treated within twenty-four hours and all were treated within four days.ConclusionsThe presence of maxillofacial trauma mandates exclusion and prompt management of cervical spine injury, particularly in RTA and trauma cases involving combined facial fracture patterns. This approach will facilitate management of maxillofacial fractures within an optimum time period.     

Alloimmunization to platelets in heavily transfused patients with sickle cell disease

Bone marrow transplantation (BMT) is now an option for some patients with sickle cell disease (SCD). Many SCD patients are multiply transfused with red blood cells (RBCs), and may be immunized to alloantigens other than erythrocyte antigens. Because platelet refractoriness is a significant complication during BMT, we wished to determine the prevalence of alloimmunization to platelets in transfused SCD patients. Sera collected from 47 transfused and 14 untransfused SCD patients were screened for HLA and platelet-specific antibodies. Transfusion and RBC antibody histories were reviewed. A subset of the patients were rescreened 1 year later. Eighty-five percent of patients with at least 50 RBC transfusions (22 of 26), 48% of patients with less than 50 transfusions (10 of 21), and none of 14 untransfused patients demonstrated platelet alloimmunization (P < .05). Platelet alloimmunization was more prevalent than RBC alloimmunization (20% to 30%). Half of the platelet reactivity was chloroquine-elutable. Eighteen of 22 patients (82%) on chronic RBC transfusion remained platelet-alloimmunized 11 to 22 months after initial testing. In summary, 85% of heavily transfused SCD patients are alloimmunized to HLA and/or platelet-specific antigens. These patients may be refractory to platelet transfusion, a condition that would increase their risk during BMT. Leukodepletion in the transfusion support of SCD patients should be considered to prevent platelet alloimmunization.     

The effect of lithium on growth factor production in long-term bone marrow cultures

We have previously reported that lithium chloride (LiCl) stimulates the production of granulocyte-macrophage colony-forming cells (GM-CFC), pluripotent stem cells (CFU-S), and differentiated granulocytes, macrophages and megakaryocytes in murine Dexter marrow cultures and that this effect appears to be mediated indirectly by a radioresistant adherent marrow cell. In this study we have established that exposure of murine Dexter cultures to LiCl (4 mEq/L) causes an increase of colony-forming cell megakaryocytes (CFU-meg) over 1 to 6 weeks of culture in both supernatant (188% to 611%) and stromal phases (123% to 246%). Moreover, we have shown that lithium treatment of either irradiated (1,100 rad) or unirradiated stromal cells increased production of activities stimulating formation of megakaryocyte, granulocyte, macrophage, and mixed lineage colonies and proliferation of the factor-dependent cell line, FDC-P1. This FDC-P1 stimulatory activity was completely blocked by an antibody to purified recombinant granulocyte-macrophage colony stimulating factor (rGM-CSF). The baseline or lithium-induced--stromal-derived bone marrow colony stimulating activity was partially blocked by the antibody to rGM-CSF and by an antibody to purified colony stimulating factor I (CSF-1); the two antibodies combined resulted in greater than 90% inhibition of the lithium-induced marrow stimulatory activity. In addition, radioimmunoassay (RIA) showed that although CSF-1 was detectable in supernatants of these cultures, exposure to lithium did not increase CSF-1 levels. These data indicate that Dexter stromal cells produce CSF- 1 and GM-CSF and that lithium appears to exert its stimulatory effects on in vitro myelopoiesis by inducing production of GM-CSF.     

Immunologic status of hemophilia patients treated with cryoprecipitate or lyophilized concentrate

We evaluated 37 patients with moderate or severe hemophilia A and six patients with severe factor IX deficiency for clinical or laboratory evidence of immune abnormalities. Patients were assigned to one of four groups according to the type of clotting factor replacement. Twenty patients had received only cryoprecipitate during the two years preceding the evaluation (group I); 11 additional patients were treated predominantly with cryoprecipitate but had also received up to nine bottles of factor VIII concentrate (group II); six patients received factor VIII concentrate (group III); six patients received factor IX concentrate (group IV). There was no clinical or laboratory evidence of immunodeficiency among the 43 patients. The mean absolute number of Th cells was normal in all patient groups, but the mean absolute number of Ts cells was increased compared with controls, both in patients treated with cryoprecipitate and in patients treated with factor VIII or factor IX concentrate. There was no correlation between the Th/Ts ratio and patient age, alanine aminotransferase level, hepatitis serology, in vitro lymphocyte function, or amount of clotting factor administered. Our observations demonstrate that the volunteer or commercial origin of clotting factor replacement cannot fully explain the alterations in lymphocyte subset distribution previously described in patients with hemophilia A.