Biomedical subjects

Zhenlin Li

Publications and source records attributed to Zhenlin Li.

8 recordsLinked to original sources

PubMed2003

Temporal patterns of bone marrow cell differentiation following transplantation in doxorubicin-induced cardiomyopathy.

OBJECTIVE: Recent studies have suggested benefits of bone marrow cell transplantation for the regeneration of ischemic cardiac tissue. To extend the potential of cell transplantation, we assessed this treatment in a mouse model of acute nonischemic doxorubicin-induced cardiomyopathy. METHODS: To allow detection of engrafted cells, we used transgenic mice expressing the nuclear-located LacZ under the control of either desmin or vimentin promoters, which identify muscle lineage and mesenchymal cells, respectively. All transplanted cells were also labeled with the fluorescent dye DIL. One week after the administration of doxorubicin (15 mg/kg), mice were intramyocardially injected with either allogeneic unpurified bone marrow cells (6 x 10(6) in 30 microl, n=59) or purified sca-1(pos) cells (4 x 10(5) in 30 microl, n=22). In parallel, control normal mice received only unpurified bone marrow cells (n=28). Hearts were harvested at serial intervals until 2 weeks after transplantation and analyzed by immunohistochemistry to assess the degree of engraftment and transplanted cell differentiation. RESULTS: In control mice, no differentiation of bone marrow cells was detected. In contrast, unpurified bone marrow cells grafted into diseased myocardium featured two successive phases of cell differentiation. The first yielded cells with a mesenchymal phenotype (44.1+/-10.1 cells/3 x 10(-2) mm(3) at 2 days), was transient and lasted 1 week. The second phase was characterized by cells with a muscular phenotype detected in a small number of cells (5.6+/-2.3 cells/3 x 10(-2) mm(3) at 7 days). Two weeks after transplantation, some of these cells appeared phenotypically close to cardiomyocytes, as evidenced by morphology and positive staining for myosin binding protein C, vinculin and myosin heavy chain. In sca-1(pos) hematopoietic progenitor grafted mice hearts, no transdifferentiation into cardiac cells was detected at any time point. CONCLUSION: These data support the hypothesis of the potential for a myogenic differentiation of bone marrow cells following engraftment in a nonischemic model of global cardiomyopathy. Bone marrow-derived cells amenable to cardiac differentiation are present in total unpurified bone marrow but not in the sca-1(pos) hematopoietic progenitor cell population. However, the very small number of transdifferentiated cells raises concerns over their functional efficacy.

Animals↗

PubMed2003

Expression of the intermediate filament protein synemin in myofibrillar myopathies and other muscle diseases.

Synemin is a member of the intermediate protein superfamily. Previous studies in avian and rodent skeletal and cardiac muscles have demonstrated that synemin localises at the Z-band, where it associates with desmin and alpha-actinin. In the present study, the distribution of synemin was examined using immunohistochemistry in muscle biopsy specimens from patients suffering from myofibrillar myopathy (MM, n=6), dermatomyositis (DM, n=3), inclusion body myositis (IBM, n=5), oculopharyngeal muscular dystrophy (OPD, n=3) and denervation atrophy (DA, n=3), to investigate the possible participation of this protein in the pathogenesis of various muscular diseases. Of patients affected by MM, two showed the presence of mutations in the desmin gene; none had mutations in the alphaB-crystallin gene; and no mutations were identified in synemin or syncoilin genes of three patients. Synemin immunohistochemistry disclosed a faint staining corresponding to the Z-bands in the cytoplasm of control muscle fibres; in contrast, focal aggregates of synemin were seen in patients with MM. Increased synemin immunoreactivity was identified diffusely or in the subsarcolemmal space of scattered fibres in patients with DM, and in vacuolated fibres of patients with IBM and OPD. Strong synemin immunoreactivity was observed in target formations and atrophic fibres of patients with denervating disorders, as well as in atrophic fibres, regardless of their origin, in all patients studied. Synemin co-localised with desmin, as seen on consecutive serial sections immunostained with anti-synemin or anti-desmin antibodies. These observations demonstrate abnormal accumulations containing both synemin and desmin in muscle fibres in patients with MM, IBM, DM, OPD and DA. Considering the important role of synemin as one of intermediate filaments of skeletal and cardiac muscle, its destruction and accumulation in the intracellular debris suggest that synemin may participate in the pathogenesis of these disorders.

Adult↗

PubMed2003

On noxious desmin: functional effects of a novel heterozygous desmin insertion mutation on the extrasarcomeric desmin cytoskeleton and mitochondria.

Recent studies in desmin (-/-) mice have shown that the targeted ablation of desmin leads to pathological changes of the extrasarcomeric intermediate filament cytoskeleton, as well as structural and functional abnormalities of mitochondria in striated muscle. Here, we report on a novel heterozygous single adenine insertion mutation (c.5141_5143insA) in a 40-year-old patient with a distal myopathy. The insertion mutation leads to a frameshift and a truncated desmin (K239fs242). Using transfection studies in SW13 and BHK21 cells, we show that the K239fsX242 desmin mutant is incapable of forming a desmin intermediate filament network. Furthermore, it induces the collapse of a pre-existing desmin cytoskeleton, alters the subcellular distribution of mitochondria and leads to abnormal cytoplasmic protein aggregates reminiscent of desmin-immunoreactive granulofilamentous material seen in the ultrastructural analysis of the patient's muscle. Analysis of mitochondrial function in isolated saponin-permeablized skeletal muscle fibres from our patient showed decreased maximal rates of respiration with the NAD-dependent substrate combination glutamate and malate, as well as a higher amytal sensitivity of respiration, indicating an in vivo inhibition of complex I activity. Our findings suggest that the heterozygous K239fsX242 desmin insertion mutation has a dominant negative effect on the polymerization process of desmin intermediate filaments and affects not only the subcellular distribution, but also biochemical properties of mitochondria in diseased human skeletal muscle. As a consequence, the intermediate filament pathology-induced mitochondrial dysfunction may contribute to the degeneration/regeneration process leading to progressive muscle dysfunction in human desminopathies.

Adenine↗

PubMed2003

Spontaneous muscular dystrophy caused by a retrotransposal insertion in the mouse laminin alpha2 chain gene.

We identified a novel spontaneous mouse model of human congenital muscular dystrophy with laminin alpha2 chain deficiency, named dy(Pas)/dy(Pas). Homozygous animals rapidly developed a progressive muscular dystrophy leading to premature death. Immunohistological and biochemical analyses demonstrated the absence of laminin alpha2 chain expression in skeletal muscle. Analysis of the laminin alpha2 chain cDNA showed the insertion of the long terminal repeat of an intracisternal A-particle gene. In addition, a 6.1 kb insertion composed of retrotransposon elements was identified in the Lama2 sequence. The dy(Pas)/dy(Pas) mouse is thus the first spontaneous mutant with a complete laminin alpha2 chain deficiency in which the mutation has been identified.

Animals↗

PubMed2002

Excessive microvascular adaptation to changes in blood flow in mice lacking gene encoding for desmin.

OBJECTIVE: Desmin, an intermediate filament, has a key role in the integrity of myocytes, and its absence induces cardiomyopathies. Mice lacking desmin (Des-/- group) exhibit microvascular dysfunction leading to smooth muscle hyporeactivity. We investigated the effect of the absence of desmin in mice (Des-/- mice versus Des+/+ mice) on the adaptation of mesenteric arteries to changes in blood flow. METHODS AND RESULTS: With the use of selective ligations of second-order mesenteric arteries, blood flow was either diminished (low flow [LF]) or elevated (high flow [HF]); respective LF to HF values were 136+/-18 to 206+/-29 microL/min for Des+/+ mice and 119+/-14 to 189+/-24 microL/min for Des-/-mice in daughter arteries. Two weeks after ligation, arteries were mounted in an arteriograph, allowing the measurement of diameter under controlled conditions of pressure and flow. In HF arteries, diameter changes in response to increases in pressure were higher in Des-/- mice than in Des+/+ mice. Conversely, in LF arteries, diameter was lower in Des-/- mice. Flow-dependent dilation was higher in HF arteries and lower in LF arteries than in control arteries. This adaptation was lower in Des-/- mice than in Des+/+ mice (11.6+/-3.1% versus 25.5+/-4.8% dilation, respectively). Endothelial NO synthase expression increased in HF arteries in both strains. CONCLUSIONS: These findings provide a demonstration of the role of the intermediate filament desmin in microvascular remodeling. This dysfunction might take place in desmin-related myopathies.

Adaptation, Physiological↗

PubMed2002

Comparative study of immune responses induced after immunization with plasmids encoding the HIV-1 Nef protein under the control of the CMV-IE or the muscle-specific desmin promoter.

The objective of this study was to compare immune responses induced against HIV-1 Nef after DNA immunization with Nef encoding plasmids under the control of an ubiquitous or a muscle-specific promoter. To this end, plasmids containing HIV-1 nef under the control of the Cytomegalovirus or the human desmin promoters, specifically expressed in muscle cells, were constructed. Different groups of BALB/c mice were immunized with 10 or 100 microg of both constructs, controls were the pcDNA3 vector or the Nef protein in Freund's adjuvant (Nef-CFA). Our data showed that both plasmids stimulated anti-Nef humoral responses in a dose-dependent manner. The anti-Nef antibody response, however, was earlier and higher with the CMV-IE promoter than with the desmin promoter. We also showed that Nef expressing plasmids induced high titers of anti-Nef antibodies (10(4)), comparable to those obtained in the Nef-CFA group (4x10(4)). Analysis of the specificity of anti-Nef antibodies revealed no influence of the promoter, and in contrast to Nef-CFA, plasmid immunization elicited anti-Nef antibodies directed principally against conformational-dependent epitopes. Data on the lymphoproliferative response showed that the specificity of expression, or the plasmid dose, did not affect the onset-time or the intensity of the response. The predominant IgG2a isotype of anti-Nef antibodies and the cytokine profile, mostly IL-2 and IFN-gamma, produced by Nef-stimulated spleen cells indicated a Th1 response in plasmid-immunized mice, in contrast to mice immunized with Nef-CFA, where a Th2 response was induced. In conclusion, these data indicate that antigen expression by muscle cells is sufficient to stimulate a Th1 immune response.

AIDS Vaccines↗

PubMed2002

Mechanical function of intermediate filaments in arteries of different size examined using desmin deficient mice.

Protein composition and mechanical function of intermediate filaments were examined in arteries of different sizes using desmin deficient mice (Des-/-) and their wild-type controls (Des+/+). Using SDS-PAGE gels and Western blots we found a gradient in desmin expression in the arterial tree; the desmin content increased from the elastic artery aorta, via the muscular mesenteric artery to the resistance-sized mesenteric microarteries approximately 150 microm in diameter in Des+/+ mice. Mechanical experiments were performed on the aorta, the mesenteric artery and resistance-sized arteries using wire myographs. For aorta and mesenteric artery, no differences in passive or active circumference- stress relations were found between Des-/- and Des+/+ mice. In microarteries, both passive and active stress were lower in the Des-/- group. In conclusion, large elastic and muscular arteries contain a relatively low amount of desmin, and the desmin intermediate filaments do not seem to play a major role in the mechanical properties of these larger arterial vessels. In the microarteries, where expression of desmin is high, desmin plays a role in supporting both passive and active tension.

Animals↗

PubMed2001

Selective microvascular dysfunction in mice lacking the gene encoding for desmin.

The intermediate filament desmin has a key role in the integrity and contractility of skeletal and cardiac myocytes. Its absence or aggregation leads to cardiomyopathies. In arteries desmin is distributed heterogeneously; vascular disorders might also occur in its absence. We studied endothelial and muscular functions in arteries from mice lacking desmin (des-/-), compared with control (des+/+). Carotid and mesenteric resistance arteries were mounted in vitro in arteriographs. Desmin was located exclusively in smooth muscle cells. In arteries from des-/- mice, pressure-induced (myogenic) tone was unchanged, but agonist-induced tone decreased in resistance arteries (no change in large arteries). Flow (shear stress)- and acetylcholine-induced, endothelium-dependent dilation, as well as endothelium-independent dilation, were also decreased in resistance arteries. To our knowledge, this is the first study of vascular contractile and dilatory functions in arteries lacking desmin. Although vascular reactivity was normal in large arteries, it decreased strongly in small resistance arteries. Thus, desmin is required in vascular smooth muscle cells and in resistance arteries, for efficient control of vascular tone and consequently for an optimal blood flow supply. This microvascular defect found in the absence of desmin might play a major role in myopathies seen in desmin-related diseases.

Animals↗