Biomedical subjects

Masaru Okabe

Publications and source records attributed to Masaru Okabe.

62 records · Page 4Linked to original sources

PubMed2002

Mechanism of host cell protection from complement in murine cytomegalovirus (CMV) infection: identification of a CMV-responsive element in the CD46 promoter region.

Mouse cells ubiquitously express CRRY, which is a functional orthologue of human decay-accelerating factor (DAF; CD55) and membrane cofactor protein (MCP; CD46), and thus protects cells from homologous complement. NIH3T3 cells expressed minute levels of mouse CD46 (mCD46) mRNA but barely produced mCD46 protein. mCD46 message and protein levels were markedly increased during mouse cytomegalovirus (mCMV) infection. Consistently, mCD46-expressing cells became resistant to mouse complement; primary-cultured fibroblasts from mCD46 gene-disrupted mice showed no increase in protection, resulting in complement-dependent cytolysis. Thus, the marked up-regulation of mCD46 in mouse fibroblast cells/cell lines by mCMV infection participates in host cell protection from complement. By mCD46 promoter deletion assay, the region necessary for induction of the promoter activity by mCMV infection was shown to be restricted to a sequence of 19 bp, which was homologous to the corresponding portion in human CD46, and the promoter regions of early-inducible human CMV UL36 and human herpesvirus 6 UL29. The results were confirmed by mutation analysis of this 19-bp region. We designated this sequence as the CMV-responsive element (CMVRE). Electrophoretic mobility shift assay demonstrated the existence of a CMVRE-binding factor, expression of which was significantly increased after mCMV infection. Thus, mCMV up-regulates the gene expression of mCD46 via CMVRE and CMVRE-binding factor, resulting in mCD46 protein expression on mCMV-infected cells. Since both the membrane and soluble mCD46retained complement regulatory activity, mCD46 induced by mCMV infection may act as a regulator of systemic complement activation. This represents a unique strategy of mCMV survival in host cells with sufficient replication by circumventing host complement attack.

3T3 Cells↗

PubMed2002

Transgenic pigs expressing human decay-accelerating factor regulated by porcine MCP gene promoter.

Porcine membrane cofactor protein (pMCP) is abundantly expressed throughout the body with particularly strong expression on the vascular endothelia. Previous studies demonstrated that the promoter of the pMCP gene induced efficient expression of a human complement regulatory protein, decay-accelerating factor (DAF; CD55), in transgenic mice. In the present study, we tried to produce transgenic pigs with two hybrid genes, 0.9/hDAF and 5.4/hDAF, which were composed of human DAF (hDAF) gene regulated under pMCP promoters of different lengths (0.9 and 5.4 kb). Five live founder transgenic pigs were obtained only with the 0.9/hDAF construct. Although, four founder pigs transmitted the transgene to the second generation, the transmission rates varied among founders. We examined the expression of hDAF in tissues of descendants of two lines (Dm1 and Dm4). Human DAF specific RNAs were confirmed by an RT-PCR analysis in all organs examined. Levels of hDAF protein in the organs from the descendants of Dm1 line were higher than those in the corresponding human organs as determined by enzyme-linked immunosorbent assay. Immunohistochemical studies showed that the tissue distribution of hDAF in the descendants of both lines was similar to that of endogenous pMCP. The expression level of hDAF on the vascular endothelial cells in Dm1 line was twice that on the corresponding human cells. We tested whether proinflammatory cytokines upregulate an efficiency of pMCP promoter on hDAF expression in transgenic pigs. Although the expression of hDAF on the human endothelial cells increased with a combination of cytokines, tumor necrosis factor alpha and interferon-gamma, no cytokine-induced upregulation was seen in the cells of transgenic pigs. The endothelial cells from transgenic pigs exhibited high resistance to the human serum-mediated cytolysis.

Animals↗

PubMed2002

FISH analysis of 142 EGFP transgene integration sites into the mouse genome.

Production of transgenic animals is an important technique for studying various biological processes. However, whether the integration of a particular transgene occurs randomly in the mouse genome has not been determined. Analysis by fluorescence in situ hybridization of the integration sites of the 142 EGFP (a mutant of green fluorescent protein) transgenic lines that we produced showed that the transgenes had become incorporated into every mouse chromosome. A single integration site was observed in 82.4% of the lines. The concomitant integrations of transgene into two different loci were observed in 15 cases (10.6%). In 3 cases, the transgenic founder mice showed chimerism in integration sites (2.1%). Chromosomal translocation was observed in 7 cases (4.9%). Moreover, when we statistically analyzed the transgene integration sites of these mouse lines, they were shown to distribute unevenly throughout the genome. This is the first report to analyze the transgene integration sites by producing more than 100 transgenic mouse lines.

Animals↗

PubMed2002

Rapid compensation for glycosylphosphatidylinositol anchor deficient keratinocytes after birth: visualization of glycosylphosphatidylinositol-anchored proteins in situ.

Pig-a, an X-linked gene, is a key component of glycosylphosphatidylinositol (GPI) anchor biosynthesis based on the fact that lack of this gene causes deficiencies of hundreds of GPI-anchored proteins. We previously demonstrated an essential role for the GPI-anchor in keratinocyte differentiation using male Pig-a knockout mice (K5-Cre:Pig-a flox). Here we analyzed keratinocytes of the female K5-Cre: Pig-a flox/+ mice with heterozygous knockout of Pig-a. These cells exhibited the mosaic pattern of GPI-anchor positive and negative expression typical of random inactivation of the X chromosome. The female K5-Cre:Pig-a flox/+ mice appeared slightly wrinkled with dry skin at birth and white scales starting from 4 d after birth without any histologic abnormality. This phenotype was temporary and milder than that seen in the male knockout mice. To characterize the fate of GPI-anchor-positive cells more clearly, we introduced a transgenic mouse line that expresses enhanced green fluorescent protein in GPI-anchored form into female K5-Cre:Pig-a flox/+ mice and monitored GPI-anchor-positive keratinocytes in situ. Within 36 h after birth, the upper layer of the GPI-anchor-negative zone in epidermis was replaced by the GPI-anchor-positive counterpart. This tissue replacement was accompanied by recovery in trans-epidermal water loss over a similar time course. These observations suggest that the GPI-anchoring is associated with the barrier function as well as with organized differentiation of the epidermis after birth.

Animals↗

PubMed2002

Restoration of spermatogenesis and fertility in azoospermic mutant mice by suppression and reelevation of testosterone followed by intracytoplasmic sperm injection.

Advances in assisted reproduction techniques such as in vitro fertilization and intracytoplasmic sperm injection have made paternity possible for many patients with male infertility. However, at least some sperm or spermatids are required for these techniques to be successful, and patients incapable of producing spermatids cannot be helped. Male mice homozygous for the mutant juvenile spermatogonial depletion (jsd) gene show spermatogonial arrest and an elevated intratesticular testosterone level like many other experimental infertility models such as those with iradiation- or chemotherapy-induced testicular damage. In this category of infertile males, suppression of the testosterone level induces spermatogonial differentiation to the stage of spermatocytes but no further. In the present study with jsd mutant mice, we induced spermatogenesis first to spermatocytes and then to elongated spermatids by suppression of testosterone levels with a GnRH antagonist, Nal-Glu, at a dose of 2500 microg kg(-1) day(-1) for 4 wk and then withdrawal of Nal-Glu. Spermatids were seen in the cross-sections of seminiferous tubules in all mice treated by administration and subsequent withdrawal of Nal-Glu. Four weeks after withdrawal of Nal-Glu, some of the germ cells differentiated into elongated spermatids. Supplementation with testosterone and Nal-Glu after 4 wk of treatment with Nal-Glu alone also induced spermatogenesis similar to the induction by withdrawal of Nal-Glu. Thus, we ascribe the restoration of the differentiation of spermatocytes to spermatids to reelevation of the testosterone level. Furthermore, we successfully rescued male sterility in jsd mice by subsequent intracytoplasmic sperm injection using the elongated spermatids induced by the programmed hormone therapy.

Animals↗

PubMed2001

Cardiac-specific activation of signal transducer and activator of transcription 3 promotes vascular formation in the heart.

Signal transducer and activator of transcription 3 (STAT3) functions in cell proliferation, differentiation, and cell survival. Previously, we have demonstrated that the activation of STAT3 is required for glycoprotein 130-mediated induction of VEGF in cardiac myocytes, but the functional importance of STAT3 as an angiogenic mediator remains to be determined. To address this issue, we first generated the adenoviral vector expressing constitutively active STAT3 (caSTAT3). Adenoviral gene transfer of caSTAT3 induced an increase in the expression of VEGF in cultured cardiomyocytes. The conditioned medium from caSTAT3-transfected cardiomyocyte culture promoted endothelial tubule formation, which was inhibited by anti-VEGF antibody. Next, we generated the transgenic (TG) mice with cardiac-specific overexpression of caSTAT3 and demonstrated that caSTAT3 TG mice showed evidence of VEGF induction in the hearts. The caSTAT3 TG hearts also demonstrated increased capillary density accompanied by an increase in the expression of VE-cadherin, an endothelial-specific component. These data indicate that caSTAT3 TG hearts exhibit an enriched vascular structure compared with non-transgenic hearts. The study presented here provides the first evidence that activation of STAT3 controls vessel growth in vivo and suggests that STAT3 contributes to cardiac adaptation by regulating vascular function under the conditions of stress.

Acute-Phase Proteins↗

PubMed2001

Bone marrow is a reservoir of repopulating mesangial cells during glomerular remodeling.

The renal glomerulus, whose cellular components are developmentally derived from the mesenchyme, plays a pivotal role in filtratating plasma. Irretrievable changes of glomerular components are responsible for the initiation and progression of impaired renal function. Recently, it has been shown that functional stem cells exist in the bone marrow of adult bodies and that they can reconstitute damaged tissues of the mesenchymal origin. To examine whether the bone marrow provides stem cells to damaged glomeruli, transgenic rats carrying enhanced green fluorescence protein (EGFP rat) were established in a systemic and constitutive manner. After transplanting the bone marrow of EGFP rats into wild-type rats, the progeny of the transplanted marrow cells were tracked with a tag of EGFP. Recruitment of bone marrow-derived cells into glomeruli was dramatically facilitated in response to mesangiolysis evoked in anti-Thy1 antibody-mediated glomerulonephritis. In the restored glomeruli, 11% to 12% of glomerular cells were derived from the transplanted bone marrow. The number of bone marrow-derived CD45(+) cells transiently increased during the disease process, and CD45-negative cells constantly accounted for more than half of the bone marrow-derived population in glomeruli. Bone marrow-derived Thy1(+) cells kept increasing in number until the remodeling ceased and finally made up 7% to 8% of glomerular cells. Laser scanning microscopy displayed that the bone marrow-derived Thy1(+) cells provide structural support for glomerular capillaries, which indicates that they are mesangial cells. Although CD45(-)Thy1(-) bone marrow-derived cells exist during the remodeling of glomeruli, none of them expressed endothelial markers such as Factor VIII and RECA1 as long as they were tested. The results indicate that the bone marrow can give rise to mesangial cells in vivo.

Animals↗

PubMed2001

The potential of bone marrow-derived cells to differentiate to glomerular mesangial cells.

Bone marrow stem cells (BMC) develop into hematopoietic and mesenchymal lineages but have not been known to differentiate into glomerular cells. To investigate whether such differentiation is possible, a search was made for donor glomerular cells in lethally irradiated C57BL/6j (B6) mice given transplants of BMC from syngeneic mice transgenic for green fluorescence protein (GFP) ([GFP-->B6] mice). After the recipients of donor BMC manifested GFP-positive cells in their glomeruli, the numbers of such cells increased markedly, in a time-dependent manner, from 2 wk to 24 wk after bone marrow transplantation. Immunohistochemical analyses revealed that most GFP-positive cells in the glomeruli were neither macrophages nor T cells. With the use of a laser-scanning confocal microscope, GFP-positive cells were observed within the mesangium of [GFP-->B6] mice. Furthermore, indirect immunofluorescence assays demonstrated that desmin-positive cells in the glomeruli of these chimeric mice were also positive for GFP. Among glomerular cells isolated from [GFP-->B6] mice 24 wk after bone marrow transplantation and then cultured, the majority of cells (approximately 84%) stained for desmin and approximately 60% of the desmin-positive cells expressed GFP. In addition, these GFP-positive cells in the cultures contracted in response to angiotensin II stimulation. These results suggest that bone marrow-derived cells may have the potential to differentiate into glomerular mesangial cells.

Angiotensin II↗