Subject(s)
Graft Rejection/prevention & control , Membrane Glycoproteins/genetics , Transplantation, Homologous/immunology , Animals , CD4-Positive T-Lymphocytes/immunology , Cardiomegaly/immunology , Fas Ligand Protein , Graft Rejection/immunology , Immunosuppression Therapy , Mice , Mice, Inbred Strains , Mice, Transgenic , Myocardium/immunology , Myosin Heavy Chains/genetics , Promoter Regions, Genetic , T-Lymphocytes/immunologyABSTRACT
Mutations in cardiac motor protein genes are associated with familial hypertrophic cardiomyopathy. Mutations in both the regulatory (Glu22Lys) and essential light chains (Met149Val) result in an unusual pattern of hypertrophy, leading to obstruction of the midventricular cavity. When a human genomic fragment containing the Met149Val essential myosin light chain was used to generate transgenic mice, the phenotype was recapitulated. To unambiguously establish a causal relationship for the regulatory and essential light chain mutations in hypertrophic cardiomyopathy, we generated mice that expressed either the wild-type or mutated forms, using cDNA clones encompassing only the coding regions of the gene loci. Expression of the proteins did not lead to a hypertrophic response, even in senescent animals. Changes did occur at the myofilament and cellular levels, with the myofibrils showing increased Ca(2+) sensitivity and significant deficits in relaxation in a transgene dose-dependent manner. Clearly, mice do not always recapitulate important aspects of human hypertrophy. However, because of the discordance of these data with data obtained in transgenic mice containing the human genomic fragment, we believe that the concept that these point mutations by themselves can cause hypertrophic cardiomyopathy should be revisited.
Subject(s)
Cardiomyopathy, Hypertrophic/genetics , Cardiomyopathy, Hypertrophic/pathology , Myocardial Contraction/genetics , Myosin Light Chains/genetics , Point Mutation , Animals , Cardiomyopathy, Hypertrophic/physiopathology , Female , Fibrosis , Gene Expression/physiology , Humans , Male , Mice , Mice, Transgenic , Microscopy, Electron , Molecular Sequence Data , Muscle Fibers, Skeletal/pathology , Muscle Fibers, Skeletal/ultrastructure , Muscle Proteins/analysis , Mutagenesis/physiology , Myocardium/chemistry , Myocardium/pathology , Organ Size , Sequence Homology, Amino AcidABSTRACT
Expression of Fas ligand (FasL) renders certain tissues immune privileged, but its expression in other tissues can result in severe neutrophil infiltration and tissue destruction. The consequences of enforced FasL expression in striated muscle is particularly controversial. To create a stable reproducible pattern of cardiomyocyte-specific FasL expression, transgenic (Tg) mice were generated that express murine FasL specifically in the heart, where it is not normally expressed. Tg animals are healthy and indistinguishable from nontransgenic littermates. FasL expression in the heart does result in mild leukocyte infiltration, but despite coexpression of Fas and FasL in Tg hearts, neither myocardial tissue apoptosis nor necrosis accompanies the leukocyte infiltration. Instead of tissue destruction, FasL Tg hearts develop mild interstitial fibrosis, functional changes, and cardiac hypertrophy, with corresponding molecular changes in gene expression. Induced expression of the cytokines TNF-alpha, IL-1beta, IL-6, and TGF-beta accompanies these proinflammatory changes. The histologic, functional, and molecular proinflammatory consequences of cardiac FasL expression are transgene-dose dependent. Thus, coexpression of Fas and FasL in the heart results in leukocyte infiltration and hypertrophy, but without the severe tissue destruction observed in other examples of FasL-directed proinflammation. The data suggest that the FasL expression level and other tissue-specific microenvironmental factors can modulate the proinflammatory consequences of FasL.
Subject(s)
Membrane Glycoproteins/genetics , Myocarditis/pathology , Age Factors , Animals , Apoptosis , Cardiomegaly/pathology , Cell Size , Cytokines/biosynthesis , Fas Ligand Protein , Gene Dosage , Membrane Glycoproteins/analysis , Mice , Mice, Transgenic , Transforming Growth Factor beta/analysis , fas Receptor/analysisABSTRACT
Splenic salvage in cases of traumatic or iatrogenic injuries may require autotransplantation of splenic fragments when splenorrhaphy or partial splenectomy is not possible. There are no studies which address the issue concerning the optimal amount of spleen to be transplanted in order to yield maximal survival in a model of pneumococcal sepsis. This study uses a Sprague-Dawley rat model to attempt to clarify this issue. Animals were divided into seven groups: control, total splenectomy, 25, 40, 60, 80, and 100% omental pouch autotransplantation. These animals were challenged with intravenous Streptococcus pneumonia Type I after 24 weeks, and mortality and blood culture results were monitored. Transplants were recovered and weights were compared with the weights originally transplanted. Survival and blood culture results were seen to improve in a linear quantitative fashion as the amount of spleen autotransplanted increased up to 80%, after which no further improvement was seen. This data supports the autotransplantation of 80% of the spleen in the Sprague-Dawley rat as the optimum amount to achieve maximal survival in a model of pneumococcal sepsis.
