In vitro characteristics of rat mesangial cells in comparison with aortic smooth muscle cells and dermal fibroblasts

Platelet-derived growth factor plays a critical role to convert bone marrow cells into glomerular mesangial-like cells

BACKGROUND

Despite increasing interest in bone marrow-derived stem cells, little is known about critical factors that determine their fates both in vitro and in vivo. Recently, we have reported that bone marrow is a reservoir for glomerular mesangial cells in rats. To find a key factor responsible for the differentiation of bone marrow-derived cells into mesangial cells, we established a new culture system of rat bone marrow, which is based on serial replating and differential attachment to collagen types I and IV.

METHODS

Bone marrow cells that did not adhere to collagen type I within 24 hours were transferred to collagen type IV-coated dishes. Then, the cells attached to collagen type IV in the following 24 hours were maintained in the presence of 2% horse serum, 200 ng/mL of platelet-derived growth factor (PDGF)-BB, and 1 micromol/L of all-trans retinoic acid. In vivo effect of PDGF-B was also examined by introducing human PDGF-B gene into glomeruli.

RESULTS

After cultivation under the above condition for 7 days, approximately 14% of cells expressed Thy-1 and desmin, both of which are markers for rat mesangial cells. Thy-1++/desmin+ cells were stellate-shaped, and contracted in response to angiotensin II. When human PDGF-B gene was overexpressed in the glomeruli of chimeric rats whose bone marrow was transplanted from enhanced green florescent protein (EGFP) transgenic rats, the number of EGFP+ mesangial cells increased. This effect was canceled by prior introduction of a neutralizing molecule that is composed of PDGF receptor-beta ligand binding site and IgG-Fc.

CONCLUSION

These results indicate that PDGF-B plays a critical role to direct bone marrow-derived cells toward mesangial-like cells both in vitro and in vivo.

Localization and expression of the aquaporin-1 water channel in mesangial cells in the human glomerulus

The expression and localization of the aquaporin-1 (AQP1) water channel were examined in the glomeruli of the human kidney. A ribonuclease protection assay showed the expression of AQP1 mRNA in human glomeruli but not in rat glomeruli. Western blot analysis revealed 28 kDa and 35 kDa bands corresponding to unglycosylated and glycosylated AQP1 proteins in human glomeruli. Immunoreactive AQP1 was demonstrated almost exclusively in the mesangium in the human glomeruli by immunohistochemistry. The endothelium of glomerular capillaries was only partly immunostained while podocytes and Bowman's capsule epithelia were not immunolabeled. Immunoelectron microscopy localized the immunoreactive AQP1 on the plasma membrane of mesangial cells in human glomeruli. The immouno-gold labeling was dense on the projections of mesangial cells protruding to the glomerular capillary lumen or to endothelial cells, but was sparse on other parts of the mesangial cell surface. No immunoreactivity for AQP1 was demonstrated in rat glomeruli. This study showed the distinct localization of AQP1 in the mesangial cells of human glomeruli, suggesting its role in water movement through these cells.

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.

Roles of prostaglandin E receptors in mesangial cells under high-glucose conditions

BACKGROUND

High glucose reportedly stimulates prostaglandin (PG) E2 production and DNA synthesis in mesangial cells (MCs). However, the pathophysiological significance of PGE2 in MCs has remained unclear.

METHODS

The effects of prostanoids on [3H]-thymidine uptake and cAMP production in rat MCs cultured with 5.6 mM glucose, 25 mM glucose, or 5.6 mM glucose supplemented with 19.4 mM mannitol were examined. The gene expression of PGE2 receptor (EP) subtypes in MCs was analyzed with Northern blotting techniques.

RESULTS

Northern blotting indicated EP1 and EP4 gene expression in MCs. EP1 agonists and PGE2 stimulated [3H]-thymidine uptake in MCs. EP1 antagonists dose dependently attenuated high-glucose-induced [3H]-thymidine uptake, which suggests EP1 involvement, by an increase in intracellular Ca2+, in DNA synthesis of MCs. On the other hand, forskolin, db-cAMP, and 11-deoxy-PGE1, an EP4/EP3/EP2 agonist, significantly decreased DNA synthesis in MCs. These inhibitory effects are thought to be mediated via EP4 as a result of an increase in cAMP synthesis. The effects via EP4 seem to be particularly important because PGE2-induced cAMP synthesis was significantly attenuated in the high-glucose group compared with the mannitol group, in which [3H]-thymidine uptake did not increase in spite of augmented PGE2 production.

CONCLUSION

The increase in DNA synthesis in MCs under high-glucose conditions can be explained, at least in part, by the high-glucose-induced inhibition of cAMP production via EP4, which augments EP1 function in conjunction with the overproduction of PGE2.

Effects of cytosolic Ca2+ on membrane voltage and conductance of cultured mesangial cells from stroke-prone spontaneously hypertensive rats and WKY rats

Mesangial cells (MC) are considered to play an important role in the development of hypertension. The purpose of this study was to characterize the effects of cytosolic Ca2+ on membrane voltage and conductance of MC using stroke-prone spontaneously hypertensive rats (SHRSP) and Wistar Kyoto rats (WKY). We applied the patch-clamp technique in the whole-cell configuration to measure membrane potential (Vm) and ion currents. There was no significant difference in resting Vm values between MC from WKY and SHRSP. The cytosolic Ca2+ increase induced membrane depolarization and the increase of Cl- currents in MC from WKY but not in MC from SHRSP. On the other hand, the Ca2+ increase induced membrane hyperpolarization and the increase of K+ currents in MC from SHRSP but not in MC from WKY. Such differences between MC from two rat strains may play an important role in the alterations in renal hemodynamics observed in hypertension.

Autocrine/paracrine role of adrenomedullin in cultured endothelial and mesangial cells

Adrenomedullin (AM), a potent vasorelaxant and natriuretic peptide isolated from human pheochromocytoma, is present in the kidney and secreted from endothelial cells (EC) and vascular smooth muscle cells (VSMC), but the functional role of AM is still unclear. To clarify the significance of AM as a local regulator, we investigated its secretion and action in cultured cells, and examined the effects of neutralization using a specific monoclonal antibody against AM. The prepared antibody directed against the ring structure showed a high affinity for human and rat AM. Using radioimmunoassay with this antibody, we found significant secretion from cultured rat mesangial cells (MC) of a 6-kDa mature form of AM as seen from EC and VSMC. The addition of AM into cultured cells dose-dependently increased cAMP production and potently inhibited PDGF-stimulated thymidine incorporation. Pretreatment with the monoclonal antibody completely abolished cAMP increase induced by exogenous AM. Moreover, antibody neutralization of endogenously secreted AM in cultured EC, but not in MC or VSMC, markedly (by approximately 70%) reduced basal cAMP production and significantly (1.7-fold) enhanced DNA synthesis. These results indicate that AM, acting as an autocrine/paracrine regulator, exerts an antiproliferative action on EC and MC, and suggest its role as a local modulator of endothelial and mesangial function.

Growth-dependent induction of angiotensin II type 2 receptor in rat mesangial cells

Angiotensin II acts on at least two receptor subtypes, AT1 and AT2. Although the physiological role of the AT2 receptor is still poorly defined, it may be implicated in inhibition of cell growth, vasorelaxation, and apoptosis. In the present study, to investigate the role of the AT2 receptor in the kidney and its implication in hypertensive states, we examined its expression using cultured mesangial cells (MC) from normotensive Wistar-Kyoto rats (WKY) and from stroke-prone spontaneously hypertensive rats (SHRSP). Receptor binding assays were performed using a nonselective ligand, [Sar1,Ile8]angiotensin II, or AT2-selective CGP42112A. Binding assays revealed that MC from WKY exhibited both AT1 and AT2 receptors, the ratio of which was confluence-dependent. In contrast, MC from SHRSP, whose proliferation activity was much higher than those from WKY, showed only the AT1 subtype. In receptor binding and Northern blot analyses, expression of the AT2 receptor of WKY-MC was low in the growing state but significantly induced upon confluence to become abundant in the post-confluent state, whereas that of SHRSP-MC was undetectable in either state. Gene expressions of AT1A and AT1B receptors were not significantly altered in either strain during the time in culture. These results indicate that the mesangial AT2-receptor expression is growth-dependent and suggest a role in the inhibition of MC growth in WKY. Much lower expression of the AT2 receptor in MC from SHRSP may suggest involvement in their higher proliferation activity and possibly in consequent renal disorders.

Group II phospholipase A2 as an autocrine growth factor mediating interleukin-1 action on mesangial cells

The proliferation of mesangial cells plays a central role in the progression of glomerulonephritis. We studied the role of group II phospholipase A2 in interleukin-1-stimulated proliferation of mesangial cells. Cultured rat mesangial cells secreted 5.3 units group II phospholipase A2/24 h per 10(5) cells in response to stimulation of 200 U/ml of interleukin-1. Northern hybridization analysis showed that mRNA for group II phospholipase A2 was induced by exogenously added group II phospholipase A2 (15 U/ml) as well as interleukin-1. The pretreatment of quiescent mesangial cells with interleukin-1 augmented [3H]thymidine incorporation caused by platelet derived growth factor. Exogenous group II phospholipase A2 (5-36 U/ml) purified homogeneously from rat spleen also increased [3H]thymidine incorporation by platelet derived growth factor-stimulated mesangial cells in a dose dependent manner (36 U/ml phospholipase A2; 1.9-fold). The stimulatory effect of interleukin-1 on DNA synthesis of mesangial cells was specifically blunted by immunoglobulin raised against group II phospholipase A2. Group II phospholipase A2 (16 U/ml) amplified a platelet derived growth factor-stimulated increase in the mesangial cell number by 1.5-fold. Among the products of the phospholipase A2-catalyzed reaction, lysophospholipids including lysophosphatidylcholine, lysophosphatidylethanolamine and lysophosphatidic acid, but not fatty acids, mimicked the stimulatory effect of interleukin-1 and phospholipase A2. These results suggest that group II phospholipase A2 acts as a signaling molecule that mediates interleukin-1-induced growth of rat mesangial cells through yielding lysophospholipids.

Altered gene expression of natriuretic peptide receptor subtypes in the kidney of stroke-prone spontaneously hypertensive rats

1. To elucidate the physiological and pathophysiological role of the natriuretic peptide system in the progression of hypertensive renal disease, we examined the gene expression of natriuretic peptide receptor subtypes, guanylate cyclase-A (GC-A), guanylate cyclase-B (GC-B) and clearance receptor (C receptor), in the kidney of stroke-prone spontaneously hypertensive rats (SHRSP) at 8 and 20 weeks of age, and compared them with their gene expression in age-matched Wistar-Kyoto (WKY) rats. 2. Northern blot analyses revealed that messages for three natriuretic peptide receptor subtypes were expressed in the kidney, and their expressions were higher in the glomeruli than in the whole kidney in each strain. 3. In 20 week old rats with established hypertension, the glomerular concentration of GC-A mRNA was significantly higher in SHRSP than in WKY. The concentrations of GC-B and C receptor mRNA in the glomeruli tended to increase and decrease, respectively, but they were not statistically significant in SHRSP. 4. In 8 week old rats, the glomerular concentrations of GC-A, GC-B and C receptor mRNA were not significantly different between SHRSP and WKY. 5. This study demonstrates that in the progression of hypertension, the expression of GC-A, which mediates biological actions of natriuretic peptides, is enhanced in the kidney of SHRSP compared to that of WKY. Together with the augmented secretion of the ligands previously revealed, altered expression of natriuretic peptide receptor subtypes in SHRSP may have a deterrent role in the development of hypertension and its renal complications.

Na+/myo-inositol cotransport is regulated by tonicity in cultured rat mesangial cells

Mesangial cells are considered to be faced with osmotic stress under physiological (such as extraglomerular mesangial cells) and pathophysiological (for example, diabetes mellitus) conditions. To see if mesangial cells have an osmoregulatory mechanism, like renal medullary cells, we measured the intracellular contents of organic osmolytes in isotonic and hypertonic conditions. Cultured rat mesangial cells are well tolerant of acute increase in osmolality up to 500 mOsm/kg. The myo-inositol content increased in hypertonic cells more than six-fold the value in isotonic cells. The contents of glycerophosphorylcholine and sorbitol also increased but were less than that of myo-inositol. The Na(+)-dependent myo-inositol uptake in hypertonic cells was a 12-fold uptake in isotonic cells, reaching a maximum 24 hours after the switch to a hypertonic medium. The uptake rate increased as medium osmolality increased from 300 to 500 mOsm/kg. Raffinose is the most effective solute to increase the myo-inositol uptake. NaCl, glucose and mannitol also increased the uptake rate (NaCl > glucose > mannitol). The increased uptake by hypertonicity was the result of an increase in Vmax without change in Km and was dependent on RNA and protein synthesis. These results indicate that mesangial cells respond to extracellular hypertonicity by increasing myo-inositol transport activity and accumulating myo-inositol into the cells, suggesting that myo-inositol functions as an organic osmolyte in mesangial cells.

Response to osmotic stimuli in mesangial cells: role of system A transporter

It has been suggested that mesangial cells have an osmoregulatory mechanism like that of renal medullary cells, such as intracellular accumulation of polyols in response to hypertonicity. We examined osmoregulatory role of neutral amino acids transported by system A in cultured mesangial cells. The contents of almost all amino acids increased under hypertonic conditions to more than twice the value in isotonic cells. In hypertonic cells, the system A transport activity, measured by Na(+)-dependent 2-(methylamino)isobutyric acid (MeAIB) uptake, was 3.8-fold the uptake in isotonic cells, reaching a maximum 16 h after the switch to hypertonic medium. The response to hypertonicity was the result of an increase in maximal velocity without change in Michaelis constant and was dependent on RNA and protein synthesis. When medium osmolality decreased from hypertonic to isotonic, MeAIB uptake reverted to the isotonic level within 16 h and a large transient efflux of L-proline occurred within 10 min. These results suggest that mesangial cells respond to extracellular hypertonicity by increasing system A transport activity and neutral amino acids can function as compatible osmolytes in mesangial cells.

Effects of tumour necrosis factor alpha and interleukin 1 beta on the proliferation of cultured glomerular epithelial cells

Rat glomerular epithelial cells were cultured with human monocyte supernatant or with recombinant cytokines. A primary glomerular culture and a glomerular epithelial cell culture were made; supernatant from monocyte cultures derived from healthy humans, and recombinant tumour necrosis factor alpha (TNF alpha) or recombinant interleukin 1 beta (IL-1 beta) were added. Cell proliferation rates were assayed by the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay. In serum-free media, consistent proliferation of glomerular epithelial cells (GEC) was observed throughout the 3 week culture period. Significant growth-stimulatory effects were induced by lipopolysaccharide-treated monocyte conditioned medium and by 1-50 ng/ml of TNF alpha, growth being up to 400% more than in the control culture. The effect of TNF alpha depended mainly on its interaction with epidermal growth factor (EGF). In contrast to TNF alpha, IL-1 beta inhibited GEC proliferation; this was due to the early appearance and proliferation of mesangial cells, despite the culture being serum-free. This study showed that activated monocytes secrete growth factors for GEC in vitro, and that interaction between both TNF alpha and IL-1 beta and between TNF alpha and EGF can modulate GEC proliferation. These findings suggest that, under pathological conditions, monocytes or macrophages affect GEC proliferation, probably being involved in crescent formation.

Immunohistochemical identification and characterization of a special type of desmin-producing stromal cells in human placenta and other fetal tissues

An unusual type of stromal cells has been found to be abundantly present in chorionic villi of human placenta of gestational weeks 6, 17, 35-42 and in tissues of early stages of fetal development (gestational weeks 16-21). These mesenchymal cells are loosely arranged throughout the villous interior and contain the intermediate filament (IF) proteins vimentin and desmin; however the smooth muscle (sm) markers sm-alpha-actin and sm-myosin are absent. Typical myoid stromal cells that are positive for both desmin and sm-alpha-actin also occur in this tissue but are restricted to certain dispersed cell clusters associated with blood vessels. Similar disperse desmin-positive, sm-alpha-actin-negative stromal cells have also been identified, although more sparsely, in the chorionic plate of the placenta and in other diverse fetal tissues such as the interstitium of the kidney, of testis and epididymis, and in cells surrounding Hassall bodies of thymus. The biological nature of these desmin-containing but sm-alpha-actin-negative stromal cells is discussed in relation to myoid cell differentiation. It is emphasized that despite their synthesis of considerable amounts of desmin they cannot be considered myogenic as the occurrence of desmin in the cells may represent an isolated expression of an individual IF protein gene, independent of the synthesis of other muscle proteins.

Immunofluorescent study of heterogeneity in smooth muscle cells of human fetal vessels using antibodies to myosin, desmin, and vimentin

Immunofluorescence-microscopy was applied to study the distribution of desmin, vimentin, and smooth muscle myosin in smooth muscle of human fetal vessels. Serial cryostat sections of the vessels examined all reacted positively with myosin and vimentin antibodies. However, heterogeneous staining of the vessels with desmin antibodies was observed. Thus, 2 types of smooth muscle staining were documented--desmin-negative and desmin-positive. Elastic and muscular arteries of the fetus (aorta, femoral and branchial artery) were desmin-negative while femoral and branchial veins were desmin-positive. In umbilical cord arteries and veins, the distribution of desmin-positive cells was largely localized to the outer layer of media, but not to the inner layer. In placenta, both desmin-positive and desmin-negative vessels were also revealed. Thus, differences in desmin expression by human vascular smooth muscle cells already exists during early stages of ontogeny.

Biochemical characterization of contractile proteins of rat cultured mesangial cells

We examined characteristics of contractile proteins of rat cultured mesangial cells. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that actomyosin was a major protein component in the extract of mesangial cells. By Western blot, tropomyosin, caldesmon, alpha-actinin, and vinculin were recognized in mesangial cells. The molecular masses of alpha-actinin and vinculin were the same as aortic smooth muscle. Mesangial cells contained five tropomyosin isoforms: TM-1, -2, -3, -4, and -5. TM-1 was present as a major isoform in mesangial cells, and it had an immunological cross reactivity with beta-tropomyosin of aortic smooth muscle. On the other hand, the molecular mass of caldesmon was similar to dermal fibroblasts, and differed from aortic smooth muscle. Immunofluorescent studies showed that the staining patterns of tropomyosin and caldesmon between cultured mesangial cells and cultured vascular smooth muscle cells were somewhat different. From these results, we conclude that mesangial cells abound in contractile proteins, and that the compositions of these proteins are similar to those of aortic smooth muscle with minor differences. Thus, this study appears to biochemically support a hypothesis that mesangial cells are derived from vascular smooth muscle cells, but with a minor modification in their evolution.

Extracellular matrix contraction by cultured mesangial cells: an assay system for mesangial cell-matrix interaction

To investigate the interaction between glomerular mesangial cells (MCs) and extracellular matrix (ECM), we have developed a quantitative assay using a floating culture of MC-populated collagen gel matrix (MCGM). Since MCs can contract such a matrix consisting of type I collagen, MCGM exhibited marked contraction. The apparent cause was tensional interaction between MCs and collagen fibers, because: (1) MCs in the gel attached tightly to surrounding collagen fibers; (2) collagen fibrils surrounding MCs were ordered in a radial array; (3) collagen fibers aggregated around MCs in the contracted gel, but not in an uncontracted gel; (4) cytochalasin B, an actin polymerization blocker, inhibited gel contraction in a dose-dependent manner. We found that this interaction was modulated by some factors. Serum in the medium stimulated the contraction of MCGM. The degree of MCGM contraction was proportional to the number of MCs embedded above 2.3 x 10(4) cells/ml of gel. In MCGM containing a basement membrane-type gel matrix (BGM), gel contraction was increasingly inhibited as the content of BGM rose. Our method is useful for elucidating physiological and pathological interactions between MCs and ECM.

Expression of smooth muscle cell phenotype by rat mesangial cells in immune complex nephritis. Alpha-smooth muscle actin is a marker of mesangial cell proliferation

Mesangial cell proliferation is common in glomerulonephritis but it is unclear if proliferation is associated with any in vivo alteration in phenotype. We investigated whether mesangial of mesangial proliferative nephritis induced with antibody to the Thy-1 antigen present on mesangial cells. At day 3 glomeruli displayed de novo immunostaining for alpha-smooth muscle actin in a mesangial pattern, correlating with the onset of proliferation, and persisting until day 14. An increase in desmin and vimentin in mesangial regions was also noted. Immunoelectron microscopy confirmed that the actin-positive cells were mesangial cells, and double immunolabeling demonstrated that the smooth muscle actin-positive cells were actively proliferating. Northern analysis of isolated glomerular RNA confirmed an increase in alpha and beta/gamma actin mRNA at days 3 and 5. Complement depletion or platelet depletion prevented or reduced proliferation, respectively; these maneuvers also prevented smooth muscle actin and actin gene expression. Studies of five other experimental models of nephritis confirmed that smooth muscle actin expression is a marker for mesangial cell injury. Thus, mesangial cell proliferation in glomerulonephritis in the rat is associated with a distinct phenotypic change in which mesangial cell assume smooth muscle cell characteristics.

Cytokeratins and cytokeratin filaments in subpopulations of cultured human and rodent cells of nonepithelial origin: modes and patterns of formation

Using immunofluorescence microscopy, we observed that in several established cell culture lines derived from different nonepithelial tissues and species, cells spontaneously emerge, usually at low frequencies, which contain cytoplasmic structures decorated by antibodies specific for cytokeratins 8 and 18. This phenomenon was further examined at both the protein (gel electrophoreses of cytoskeletal proteins, followed by immunoblotting) and the RNA (Northern blots, "nuclear run-on" analysis, in situ hybridization) level. Positive cell lines included simian virus (SV40)-transformed human fibroblasts (HF-SV80, WI-38 VA13), human astrocytic glioma cells (U333 CG/343MG), rat (RVF-SMC) and hamster (BHK-21/13) cells derived from vascular smooth muscle and murine sarcoma MS-180 cells. In two cell lines (HF-SV80 and BHK-21/13), the frequency of the cytokeratin-containing cells and of the cytokeratin fibril arrays per cell was drastically increased upon treatment with 5-azacytidine. The structural appearance of the cytokeratins was variable in the different cell lines but could also differ among cells of the same culture: While small granular or comma-shaped structures or bizarrely shaped filament arrays prevailed in WI-38, RVF and normally grown BHK-21 cells, most of the other lines revealed extended normal-looking, fibrillar arrays. In one line (MS-180), the appearance of cytokeratins was associated with a morphological change, as it was only found in a subpopulation of cells that had lost their typical elongated and spindle-shaped phenotype and assumed a rounded ("coccoid") shape. Our results show that the expression of the genes encoding cytokeratins 8 and 18 is not necessarily restricted to programs of epithelial differentiation and that factors stochastically effective appear in cultured cell lines that allow the synthesis of these cytoskeletal components. Mechanisms possibly involved in this spontaneous and selective advent of cytokeratins 8 and 18 and implications for tumor diagnosis are discussed.

Desmin distinguishes cultured fat-storing cells from myofibroblasts, smooth muscle cells and fibroblasts in the rat

To differentiate cultured rat liver myofibroblasts, fat-storing cells, aortic smooth muscle cells and skin fibroblasts from each other, desmin and vimentin stainings were undertaken by indirect immunofluorescence using monoclonal antibodies. In myofibroblasts, the reaction with antibodies to vimentin was positive but that with antibodies to desmin was virtually negative. In primary cultures as well as subsequent passage of fat-storing cells, reactions with antibodies to both desmin and vimentin were positive. In primary culture of smooth muscle cells, both reactions were positive, but in the first passage, smooth muscle cells lost the reactivity with antibodies to desmin. Fibroblasts showed a positive reaction with antibodies to vimentin and a negative one with antibodies to desmin. Thus, immunohistochemistry of intermediate filaments allows for the differentiation between fat-storing cells, which are desmin- and vimentin-positive, and myofibroblasts or fibroblasts, which are desmin-negative but vimentin-positive. Smooth muscle cells are also vimentin-positive and become desmin-negative after the first passage.

Glomerular disease in hypercholesterolemic guinea pigs: a pathogenetic study

Recent evidence suggests a role for lipid deposition in the pathogenesis of some forms of glomerular disease. To gain further insight into this phenomenon guinea pigs (GP) were fed a 2% cholesterol (HC) diet and compared to GP on a normal diet (C). Serial observations were made 5, 10, 30 and 70 days after the initiation of the experiment. HC gained less weight than C (P less than 0.001) and developed hemolytic anemia after 30 days. At all time periods serum total cholesterol (TC) was significantly elevated in HC (P less than 0.001). High density lipoprotein-cholesterol and total phospholipids (PL) were significantly higher in HC at days 30 and 70. Lipoprotein-X was detected in HC serum. The relative proportion (%) of cholesteryl ester (CE) at day 70 was significantly higher in HC than in C when renal cortical lipids were analyzed (P less than 0.017). Renal function was normal in both groups throughout the 70 days. The HC group developed proteinuria and hematuria (proteinuria, HC = 22.1 +/- 7.2 mg/24 hr; C, 6.4 +/- 2.3 mg/24 hr), which was detected at day 70 but not at day 30. HC developed significant progressive mesangial expansion which was first evident at day 30. In HC only oil red 0 material was first detected in glomeruli at day 5 and was very conspicuous at day 70. Increased intraglomerular monocyte numbers were detected at day 70 (P less than 0.017) but not at day 30 in HC. No glomerulosclerosis was observed in GP's with drug-induced hemolysis on a normal diet. To see the effect of high protein intake on HC GP's, a group of GP's was put on a HC diet for 30 days followed by a 2% cholesterol-high protein (HCHP) diet for 40 days. Compared to HC GP's, the HCHP group showed significantly higher serum TC and PL (P less than 0.017), mesangial expansion (P less than 0.01) and proteinuria (P less than 0.01). The results indicate that hypercholesterolemia plays an important role in the pathogenesis of glomerulosclerosis in this model and that the process appears to be mediated, at least in part in the later stages, by monocytes. The addition of protein to the HC diet augments these effects.