Lipocyte Proliferation Research Articles

Weber-Christian disease (idiopathic panniculitis): Clinical aspects

Weber-Christian disease (WCD), or idiopathic panniculitis, refers to rare diseases from a group of systemic connective tissue diseases. To verify the diagnosis of WCD is a difficult task, for there are no precise diagnostic tests for this disease. Objective: to study the clinical features and additional investigation data of WCD as one of the variants of lobular panniculitis (LP). Subjects and methods. Nineteen patients (2 men and 17 women) aged 32 to 71 years with WCD were examined. The average disease duration was 65.1±11.3 months. Results. The medical history data of 12 patients could identify three suspected factors of disease development: surgical intervention (n = 6); supercooling (n=4), and acute respiratory viral infection (n=2). In 10 (53%) patients aged 47–71 years, the Quetelet index was as high as 31.8±7.2 cm/kg, which allowed grade 2 obesity to be diagnosed. According to its clinical manifestations, there were 3 WCD forms: nodular (n=10), plaque (n=6), and infiltrative (n=3). The saucer symptom was present in 74%, including in all cases of the chronic course (p=0.02). The number of affected areas significantly differed in the nodular and plaque forms (p=0.01). ROC analysis showed that the optimal values of sensitivity (80%) and specificity (83%) on visual analog scale (VAS) in patients with these forms corresponded to a separation point of 60 mm, with the prognostic value of a positive result being 0.89 (CI 0.71–1.1; p=0.011). The infiltrative form showed a typical clinical picture (VAS, 83.1±12.5 mm) in 3 patients, one of them was found to have mesenteric panniculitis. The level of C-reactive protein was shown to be correlated with the form of the disease; the former being maximal in infiltrative WCD. The pathomorphological examination of skin and subcutaneous fat biopsy specimens from the nodule of all the patients detected diffuse leukolymphocytic infiltration, single multinucleated cells, necrotic foci, and lipocyte proliferation. Conclusion. WCD is a clinical variant of LP, which requires an extended diagnostic search.

Sonographic findings of a large vulvar lipoma

Lipomas of the vulva are rare benign tumors that consist of mature fat cells often interspersed with strands of fibrous connective tissue. They arise from the vulvar fatty pads and present as soft, multilobulated subcutaneous neoplasms. Histological examination reveals a thin capsule surrounding a lobular proliferation of lipocytes. Liposarcomas of the vulva have been described rarely. We present the sonographic findings of a large lipoma of the vulva, and demonstrate the contribution of topical application of a high-frequency transvaginal transducer in depicting lobular structural features, characteristic of this soft tissue tumor.

Rat liver ferritin selectively inhibits expression of alpha-smooth muscle actin in cultured rat lipocytes.

The role of ferritin in lipocyte activation is unknown. This study examined the effect of rat liver ferritin (RLF), human recombinant H-ferritin (HrHF), human recombinant L-ferritin (HrLF), apo-ferritin (apo-RLF), and hemin on lipocyte activation. Lipocytes were cultured on uncoated plastic and were incubated with these agents for 7 days, at concentrations ranging from 10(-14) to 10(-7) M (0.5 to 50 microM for hemin). Collagen/noncollagen protein production and lipocyte proliferation were determined by [3H]proline and [3H]thymidine incorporation, respectively, and the expression of alpha-smooth muscle actin (alpha-SMA) and desmin was determined by Western blot. RLF, at concentrations ranging from 10(-10) to 10(-7) M, decreased alpha-SMA expression by 65-88%. Apo-RLF, HrHF, and HrLF decreased alpha-SMA by 17-45% at 10(-7) and 10(-8) M. Hemin (10 or 50 microM) inhibited alpha-SMA by 37 and 54%, respectively. Desmin expression was not altered by ferritin or hemin. Collagen and noncollagen protein production were not altered by either RLF or apo-RLF. Lipocyte proliferation was decreased by 54, 32, and 40%, by 10(-7) M RLF, HrHF, and HrLF, respectively, whereas apo-RLF had no effect. Thus RLF inhibited lipocyte alpha-SMA expression, which may be due to an effect of sequestered iron, since neither apo-RLF, HrHF, nor HrLF had a potent effect on alpha-SMA expression and all are essentially iron-free. The inhibitory effect of iron-loaded RLF on alpha-SMA expression suggests that tissue ferritin does not initiate lipocyte activation in iron overload, but rather may have a suppressive action on this process.

Rat hepatic lipocytes synthesize and secrete transin (Stromelysin) in early primary culture

Background & Aims : Hepatic lipocyte proliferation and activation are pivotal in liver fibrosis. Disruption of normal lipocyte-matrix interactions may contribute to this process. The synthesis of transin, which degrades normal liver matrix, by culture-activated hepatic lipocytes was investigated. Methods : Lipocytes were isolated by pronase/collagenase perfusion, density gradient centrifugation, and centrifugal elutriation. Transin messenger RNA in lipocytes was analyzed by Northern blotting. Transin activity was analyzed by zymography, Western blotting, immunocytochemistry, and quantitative [ 14C]β-casein degradation assay. Results : Transin messenger RNA was detected in early primary culture (3–5 days) but not in freshly isolated lipocytes or late primary culture. Zymography of lipocyte medium showed caseinolytic activity (relative molecular weight, 57 kilodaltons and 60 kilodaltons) inhibited by ethylenediaminetetraacetic acid but not thiol or serine protease inhibitors. Immunoblotting and immunocytochemistry confirmed the presence of transin in media and cells. Quantitative transin activity decreased progressively with increasing duration of primary lipocyte culture and myofibroblastic transformation. Conclusions : Rat hepatic lipocytes express the transin gene and secrete its product during the early phase of lipocyte activation in primary culture. Because this enzyme degrades a wide spectrum of normal basement membrane proteins and activates progelatinase B and interstitial collagenase, it may have an important role in liver injury and fibrosis.

Stromelysin expression and activity is necessary for lipocyte proliferation in vitro: [formula omitted] and M.J.P. Arthur. University Medicine, University of Southampton, United Kingdom

Stromelysin expression and activity is necessary for lipocyte proliferation in vitro: [formula omitted] and M.J.P. Arthur. University Medicine, University of Southampton, United Kingdom

The response of rat liver perisinusoidal lipocytes to polypeptide growth regulator changes with their transdifferentiation into myofibroblast-like cells in culture

During culture on uncoated plastic wells rat liver perisinusoidal lipocytes change their differentiated phenotype (transdifferentiate) within 1-2 weeks and obtain a myofibroblast-like phenotype (myofibroblast-like cells). This transdifferentiation was documented by morphologic (loss of fat droplets, flat cell shape, cytoplasmic extensions, expression of iso-alpha smooth muscle actin) and biochemical criteria (loss of retinyl-palmitate, enhanced matrix synthesis). Whereas transforming growth factor alpha (TGF alpha) stimulated and transforming growth factor beta (TGF beta 1) inhibited the proliferation of perisinusoidal lipocytes (early culture) these cytokines did not effect the growth of the myofibroblast-like cells. Opposite effects were obtained with platelet-derived growth factor (PDGF) which stimulated the growth of myofibroblast-like cells only. Insulin-like growth factor (IGF1) was mitogenic in both perisinusoidal lipocytes and myofibroblast-like cells, respectively. Furthermore, whereas the expression of the mRNAs of decorin and biglycan was stimulated by TGF beta 1 in perisinusoidal lipocytes, the synthesis of these mRNAs was stimulated in myofibroblast-like cells predominantly by TGF alpha. Similar effects of TGF alpha and TGF beta 1 have been observed on the glycosaminoglycan-([35S]sulfate incorporation) and proteoglycan level ([3H]leucin incorporation into decorin and biglycan). Neither IGF1 and PDGF stimulated glycosaminoglycan synthesis in perisinusoidal lipocytes or in myofibroblast-like cells. The results demonstrate that the effects of the polypeptide growth regulators TGF alpha, TGF beta 1 and PDGF depend on the cell phenotype (stage of cell activation/transdifferentiation) and may be completely different in perisinusoidal lipocytes and its transformed counterpart the myofibroblast-like cells.

Inhibition of rat hepatic lipocyte activation in culture by interferon-gamma.

Hepatic lipocytes (perisinusoidal, Ito cells) are the primary matrix-producing cells in liver fibrosis. During liver injury they undergo activation, a process characterized by cell proliferation and increased fibrogenesis. We and others have established a culture model in which in vivo features of lipocyte activation can be mimicked by cells grown on plastic. Additionally, we recently showed that activation is associated with new expression of smooth muscle-specific alpha-actin both in vivo and in culture. Although interferon-gamma is known to inhibit collagen production in some systems, its action as a general modulator of lipocyte activation has not been examined; this issue forms the basis for our study. In culture-activated lipocytes, interferon-gamma (1,000 U/ml) significantly inhibited lipocyte proliferation as assessed by [3H]thymidine incorporation assay and nuclear autoradiography. In time-course studies of activation, it also markedly reduced expression of smooth muscle-specific alpha-actin and its messenger RNA. In dose-response experiments, maximal inhibitory effects on smooth muscle-specific alpha-actin mRNA gene expression were achieved with as little as 10 U interferon-gamma/ml. Inhibition of cellular activation was reversible; after interferon-gamma withdrawal, messenger RNA levels of smooth muscle-specific alpha-actin returned to untreated control levels. The effect of interferon-gamma extended to extracellular matrix gene expression, with reduction of type I collagen, type IV collagen and total fibronectin messenger RNAs to 3%, 24% and 15% of untreated control levels, respectively. In contrast to the marked effects on smooth muscle-specific alpha-actin and extracellular matrix gene expression, interferon-gamma reduced total protein synthesis by only 17.7%.(ABSTRACT TRUNCATED AT 250 WORDS)

Uridine diphosphoglucose restores lipocyte proliferation in the regenerating liver of ethanol-treated rats

The effect of continuous intraperitoneal infusion of undine diphosphoglucose on ethanlol-induced suppression of lipocyte proliferation was studied in regenerating rat livers from 1–4 days after hepatectomy. Proliferating lipocytes were positively identified using a two-sequence immunohistochemical staining for cytoplasmic desmin and bromodeoxyuridine-labelled nuclei. Hepatectomy rapidly stimulated lipocyte proliferation which peaked 2 days after hepatectomy (labelling index, 17.9 ± 0.81%). uridine diphosphoglucose or glucose infusion did not modify the time course of lipocyte proliferation. Ethanol feeding to hepatectomized rats receiving saline or glucose infusion resulted in a 71% ( p < 0.005) and 61% ( p < 0.005) inhibition of lipocyte proliferation, respectively, 2 days after hepatectomy, thereby abolishing the characteristic proliferative peak observed in rats not treated with ethanol. In contrast, uridine diphosphoglucose infusion doubled the labelling index (13.1 ± 2.34%) in ethanol-fed rats compared to that in corresponding rats treated with saline (5.28 ± 1.29%; p < 0.005) or glucose (6.51 ± 0.64%; p < 0.005). This resulted in the appearance of a proliferative peak, albeit smaller than normal, 2 days after hepatectomy. In sham-operated rats, lipocyte proliferation was low with a labelling index of 1.88 ± 0.13% at the time of operation and of 1.69 ± 0.23% 2 days thereafter. Uridine diphosphoglucose infusion to sham-operated rats for 2 days did not significantly affect lipocyte proliferation (labelling index 1.79 ± 0.06%). The present study demonstrated that uridine diphosphoglucose does not affect lipocyte proliferation in the regenerating or sham-operated livers, but that it partially reverses the ethanol-induced suppression of lipocyte proliferation after hepatectomy.

Effects of ethanol and hepatic vitamin A on the proliferation of lipocytes in regenerating rat liver

The effects of ethanol and hepatic vitamin A on lipocyte proliferation were studied in regenerating rat livers. Positive identification of proliferating lipocytes was achieved by a double immunostaining sequence for cytoplasmic desmin and bromodeoxyuridine-labelled nuclei. Ethanol administration caused a 76 and 36% reduction in labelling indices of lipocytes 2 and 3 days after hepatectomy, respectively, thereby delaying the onset of the proliferative peak of lipocytes by 1 day compared to the control. Hepatic vitamin A did not decrease until 4 days after hepatectomy. The relationship between hepatic vitamin A and lipocyte proliferation was further evaluated in rats fed diets containing four different amounts of vitamin A. Despite the striking differences in liver vitamin A levels, the proliferative activity of lipocytes was unaffected, as measured at the peak of lipocyte proliferation 2 days after hepatectomy. These data indicate that ethanol ingestion suppresses the proliferative response of lipocytes to partial hepatectomy but that this ethanol effect is independent of changes of vitamin A levels in the liver.

Sensitization of Hepatic Lipocytes by High–Fat Diet to Stimulatory Effects of Kupffer Cell–Derived Factors: Implication in Alcoholic Liver Fibrogenesis

A high-fat diet has previously been shown to be a key factor for induction of alcoholic liver fibrosis in a rat model of intragastric ethanol infusion. To explore a possible mechanism by which the high-fat diet facilitated such an effect, the present study examined how the high-fat diet with or without ethanol affected proliferation and collagen formation of hepatic lipocytes, perisinusoidal cells that have been suggested to be involved in liver fibrogenesis. We also evaluated effects of the high-fat diet on the sensitivity of lipocytes to stimulatory effects of Kupffer cell-derived factors. Intragastric infusion of ethanol and the high-fat diet for 9 to 10 wk resulted in induction of a varying degree of perivenular fibrosis in 75% of animals. Lipocytes isolated from these animals (A) had significantly higher basal rates of proliferation (three to four times) and collagen formation (1.5 times) than those isolated from control animals, which were isocalorically infused with the high-fat diet (H) or the low-fat diet (L), or those that were fed chow ad libitum (C). Lipocytes from the H group exhibited significantly higher relative production of collagen than those from the L group, but their net collagen production was not enhanced. The dialyzed Kupffer cell-conditioned medium from the A group markedly stimulated proliferation and collagen formation of lipocytes from the groups given the high-fat diet (A and H) but had minimal effects on those from the L and C groups, establishing the order of decreasing lipocyte sensitivity from the A, H, L to C group. Similarly, lipocytes from the H and A groups exhibited a more profound responsiveness to the stimulatory effect of transforming growth factor beta 1 on collagen formation. These results demonstrate (a) that lipocytes isolated from the rats given the high-fat diet and ethanol are markedly proliferative and produce more collagen; and (b) that the Kupffer cells derived from these animals release factors that stimulate proliferation and collagen formation of lipocytes and (c) that the high-fat diet sensitizes lipocytes for stimulatory effects of the Kupffer cell-derived factors and transforming growth factor beta 1.

Mouse hepatic endothelial cells in culture secrete a growth inhibitor for hepatic lipocytes and Balb/c 3T3 fibroblasts

Hepatic lipocytes are sinusoidal cells in close contact to endothelial cells. They proliferate, switch to a fibroblastic phenotype and synthetize collagen during hepatic fibrosis. Since it is known that vascular endothelial cells can influence the proliferation of neighboring cells such as smooth muscle cells, we investigated the role of hepatic endothelial cells on the growth of lipocytes and Balb/c 3T3 fibroblasts. Concentrated conditioned medium from endothelial cells inhibited both [ 3H]thymidine incorporation and actual growth of lipocytes and Balb/c 3T3 fibroblasts. The inhibition was lost when conditioned medium was treated with heat or trypsin, or when medium was conditioned in the presence of cycloheximide. We conclude that hepatic endothelial cells secrete a proteic growth inhibitor for lipocytes and hepatic Balb/c 3T3 fibroblasts. This inhibitor could be of importance in limiting lipocyte proliferation in the liver and possibly in preventing hepatic fibrosis.

Body fat accumulation in the guinea pig.

Seventy-two guinea pig carcasses divided into three series: a) adult, b) growth (4 days to 8 months) and c) exercise (adults on an exercise regimen) were separated into eleven gross body components by dissection. Each component was freeze dried and extracted with ethyl and petroleum ether. Distribution of fat and the fat content of the gross components were studied statistically. Accretion of fat in all three series is accomplished primarily by saturating existing adipose tissue, and secondarily by an increase in either number or size of lipocytes. Females have an appreciably larger fat storage capacity than males without resorting to either lipocyte proliferation or hypertrophy. Except in immature individuals the fraction of total body fat in subcutaneous and in internal depots is constant at all levels of body fatness. Males have 6–7% less of their total fat in the subcutaneous depot and proportionately more in the internal depots than do females. Fat depots account for about 95% of total body fat, most of the remainder being distributed among gut, bone, liver, kidneys and heart. In all three series with increasing body fatness these organs acquire additional fat, but in each case the rate of fat accretion is less than that of the body as a whole. Fat distribution to the organs appears similar in the two sexes. Body fatness in the adult series was shown to be related to specific gravity of the eviscerated carcass by the following equation: (See PDF)