Submesothelial Cells Research Articles

Solitary Fibrous Tumors of the Pleura: Report of Eight Cases and Literature Review

Primary pleural tumors have been classified as diffuse or localized types. The diffuse type or malignant mesothelioma (MM) is the most frequently encountered lesion. Localized variety is less frequent and defined. Although its hystogenesis is not well established, new histological and immunohistochemical techniques are giving us a better understanding of it. Now, the common consensus is that this tumor origins from a primitive submesothelial mesenchymal cell (16,17,18,19). Concerning the advances done during the last decade in the understanding, imaging, diagnostic and therapeutic approaches to this rare tumor, we decided to conduct a retrospective study of the cases seen at our institution and a review of the available English literature.

Ungewöhnlicher Kombinationsbefund eines zystischen Ovarialtumors mit einer Leiomyomatosis peritonealis disseminata

Leiomyomatosis peritonealis disseminata (LPD) is a rare disease, which is most often found in women in reproductive age - seldom pre- and postmenaupausal. LPD has been described in women taking oral contraceptives or during pregnancy. LPD is mostly asymptomatic and discovered during operations like section caesarea, etc. Because of the macroscopic aspect (multiple small nodules <2 cm) a metastasing tumour is suspected during operation. These nodules consist of smooth muscle fibres and show benign histologic features. An increased level of cases with similar endometriosis (10%), myoms of uterus or functional ovarian tumours have been reported. Few cases of malignant transformation have also been described. In the pathogenesis of LPD a metaplastic change of submesothelial multipotential mesenchymal cells as an abnormal response on hormonal stimulation is debated. A regression of LPD after delivery or after stopping oral contraceptives is possible. Another therapeutic option is the application of GnRH-agonists. We present a case of a 35-year old female patient with sudden abdominal pain and suspicious findings in abominal ultrasound and CT-abdomen. The intraoperative aspect shows diffuse intraabdominal nodules consisting of smooth muscle fibres and a cystic left ovary. LPD, endometriosis and a borderline lesion of the left ovary were diagnosed by intraoperative histological examination. A bilateral salpingo-oophorectomy and omentectomy were performed.

Myofibroblastic Differentiation in Simple Peritoneal Sclerosis

To analyze the presence of myofibroblasts in a series of peritoneal dialysis (PD) patients with simple sclerosis and non-PD, uremic patients. Since there is a close correlation between active fibrosis and myofibroblastic differentiation we wanted to test if myofibroblasts are present in uremic, non-PD peritoneal samples. To determine if there are correlations between myofibroblastic presence and other functional and morphologic peritoneal parameters. Biopsies were collected from three patient groups: 1) Normal control samples (n = 15) of parietal and visceral peritoneum 2) non-PD uremic patients (n = 16); and 3) uremic patients on PD (n = 32). Peritoneal morphologic and functional parameters and immunohistochemical expression of alfa-smooth muscle actin was analyzed in each case. Vascular endothelial growth factor (VEGF), bcl-2 anti-apoptotic protein, and progesterone receptor was evaluated in a subset of cases. Myofibroblasts were present in 56.3% of the patients with PD-related simple sclerosis. In most cases they were distributed in the upper submesothelial area. None of the biopsies from normal controls and uremic, non-PD patients showed myofibroblasts. Within the group of PD patients, myofibroblasts showed no correlation with time on dialysis, urea/creatinine MTAC, episodes of peritonitis, submesothelial thickening, hyalinizing vasculopathy or mesothelial status. In a subset of PD patients VEGF expression was observed in submesothelial fibroblastic cells. No expression of progesterone receptor or bcl-2 was observed. Myofibroblasts are a reliable and simple indicator of fibrosis since they appear in early stages of PD treatment and in patients with minor morphologic anomalies. They are not exclusive of patients with sclerosing peritonitis, ultrafiltration loss or long standing treatment. Their absence in non-PD, uremic patients suggest that uremia-related fibrosis takes place without a significant participation of myofibroblasts.

Is gliomatosis peritonei derived from the associated ovarian teratoma?

Gliomatosis peritonei, a rare condition that occurs almost exclusively in the setting of ovarian immature teratoma, is characterized by the occurrence of nodules of mature glial tissues in the peritoneum. It is controversial whether glial tissues are derived from maturation of the associated teratomatous tissue that has implanted in the peritoneum, or glial differentiation of subperitoneal stem cells. In this study, we employed the unique genetic characteristics of ovarian teratomas (often with a duplicated set of maternal chromosomes and thus homozygous at many polymorphic microsatellite loci) versus normal tissues (heterozygous pattern due to presence of maternal and paternal genetic materials) to investigate the origin of gliomatosis peritonei. DNA samples were extracted from microdissected paraffin-embedded tissues, including the glial implants, the associated ovarian teratomas, and normal tissues, to determine their patterns of microsatellite loci in a multiplex polymerase chain reaction system. Two cases were not informative because the ovarian teratoma showed a heterozygous microsatellite pattern. In the 5 informative cases, the normal tissues showed a heterozygous pattern in the microsatellite loci, the associated teratomas showed a homozygous pattern, and the glial tissues showed a heterozygous pattern. Thus, gliomatosis peritonei is genetically unrelated to the associated teratoma but is probably derived from nonteratomatous cells, such as through metaplasia of submesothelial cells.

Mesothelial differentiation as reflected by differential gene expression.

Human mesothelial cells obtained from benign effusions retain their proliferative capacity and grow uniformly either with a fibroblastic or epithelioid morphology in vitro. These cultures therefore provide a model for the process of mesothelial differentiation in vivo. To study this differentiation, we isolated differentially expressed genes obtained by suppression subtractive hybridization. Of the nine genes found to be overexpressed in fibroblastic mesothelial cells, three are matrix-associated (integrin alpha5, collagen binding protein 2, human cartilage glycoprotein 39), whereas the others are associated with a proliferative cell type (14-3-3 epsilon, plexin B2, N33, and three genes encoding ribosomal elements). Seven of the eight genes upregulated in the epithelioid phenotype are related rather to specialized functions, such as metabolism (aldose reductase, lecithin:cholesterol acyltransferase, ATPase 6), cytoskeletal composition (cytokeratins 7 and 8), and regulation of differentiation (granulin, annexin II). Immunohistochemistry with available antibodies to six of the differentially expressed gene products confirmed the differences also in pleural tissues, where submesothelial cells displayed the fibroblastic markers, whereas surface cells displayed the epithelioid markers. In summary, this approach revealed a pattern of genes coordinately regulated during mesothelial differentiation and suggests that mesothelium may regenerate also by recruiting cells from the submesothelial layer. Some of the gene products may also be useful markers for differentiation and activation in serosal tissues.

Intraperitoneal levonorgestrel-releasing intrauterine device following uterine perforation: the role of progestins in adhesion formation.

Intrauterine contraception is a widely used, highly effective means of birth control. Uterine perforation is a serious, albeit rare, complication of intrauterine device (IUD) use. Although uterine perforation by levonorgestrel-releasing (20 micro g/day) intrauterine system (LNG-IUS) has already been reported, the peritoneal adhesion potential of this IUD is unknown. The medical files of all patients diagnosed with an intra-peritoneal IUD between the years 1990-2002 at Hadassah Medical Center were reviewed. Histopathological study of peritoneal adhesion tissue adjacent to levonorgestrel medicated IUD was conducted in one case. Eight cases of dislocated IUDs were found. Four cases used LNG-IUS and four other cases used copper-IUD. Laparoscopy for IUD removal disclosed mild local peritoneal adhesions between omentum and pelvic organs in all cases. No difference was noted in the appearance of the peritoneum in the presence of either a copper-IUD or LNG-IUS. Histological examination of peritoneal tissue encasing the levonorgestrel-intrauterine system revealed loose connective tissue with aggregates of submesothelial cells with a pseudo-decidual change. Immunohistochemical staining for progesterone receptor was negative. The peritoneal adhesions potential of LNG-IUS is low, similar to that of the copper-bearing IUD.

Sarcoma-like mural nodules in mucinous cystic tumors of the ovary revisited: a clinicopathologic analysis of 10 additional cases.

Ten mucinous cystic ovarian tumors that contained sarcoma-like mural nodules are described. The nodules were studied by conventional and immunohistochemical methods. The sarcoma-like mural nodules occurred predominantly in middle-aged women, were multiple and sharply demarcated from the adjacent mucinous tumor, had small size, and exhibited a heterogeneous cell population. Distinction of these lesions from true sarcomatous nodules and foci of anaplastic carcinoma is important because of the worse prognosis of the two latter tumors compared with the favorable behavior of the sarcoma-like mural nodules. Six of the eight patients with follow-up information were alive and clinically free of recurrence at a mean follow-up interval of 12 years. Two patients died of other causes (thyroid and breast carcinomas). The nature of the nodules is not clear. Sarcoma-like mural nodules probably represent a reactive and self-limited phenomenon within a neoplasia. Their coexpression of vimentin and cytokeratins is consistent with an origin from submesothelial mesenchymal cells, which undergo partial transformation into epithelial cells.

Steroid hormone receptor in pleural solitary fibrous tumours and CD34+ progenitor stromal cells.

Solitary fibrous tumours (SFT), originally described in the pleura, were subsequently recognized in numerous extrapleural sites. This suggests that a common stem cell, present in various organs and tissues, may be at the origin of SFT and that specific factors may be involved in the proliferation of such cells. Recently it has been described that steroid hormone receptors, progesterone receptors in particular, are expressed by extrapleural SFT. In addition, progesterone may participate as growth factor in many CD34(+) stromal neoplasms, which express low levels of the hormone receptors. The present study analysed the expression of androgen (AR), oestrogen (ER) and progesterone (PR) receptors in a series of 32 pleural SFT, 10 mesotheliomas and in reactive tissue of chronic pleuritis. ER and AR were never expressed by SFT or by chronic pleuritis, whereas PR were demonstrated in 2/16 "large" (>8 cm) and in 6/16 "small" (< or =8 cm) pleural SFT (all expressing CD34, bcl-2 and CD99). PR(+) SFT had a significantly higher proliferative activity (p = 0.04) (Ki-67 mean value 6.5%) and lower p27(kip1) (mean value 51.5%) expression than the PR(-) cases (Ki-67 mean value 3.81% and p27(kip1) mean value 57.86%). One of the cases expressing a high level of PR (80%) recurred 1 year after first surgery and the recurrence was PR(+) as well, but with a lower percentage of nuclear receptor expression (12%). In addition, in chronically inflamed subserosal tissue, a subpopulation of CD34(+) endothelial and interstitial dendritic cells was identified, which also expressed PR. These findings suggest that the CD34(+) submesothelial interstitial dendritic cells, activated during reactive processes, may be the stem cells that give rise to SFT, and that progesterone might participate in the growth of SFT through modulation of its specific receptors.

Origin of endothelial cells from mesothelial-derived mesenchymal cells in the liver of avian embryos

We have tested the hypothesis of an origin of mesenchyme from the coelomic mesothelium of the developing avian liver and the differentiation of sinusoidal endothelial cells from mesothelial-derived mesenchymal cells. Our results have shown that 1) Mesothelial cells of the developing liver and the submesothelial mesenchymal cells are simultaneously cytokeratin (CK) and vimentin (VIM) immunoreactive between HH18 and HH28.2) A number of early sinusoidal cells are also CK immunoreactive. In the quail, CK colocalizes with the vascular marker QH1 in these cells. 3) In late embryos (>HH30), only the mesothelium remains CK+. 4) Mesothelial and submesothelial mesenchymal cells express the transcription factors Slug and WT1, both related to the epithelial-mesenchymal transition. 5) When the surface mesothelium was stained in vivo with CCFSE, a carboxyfluorescein derivative, isolated sinusoidal cells were labelled after 24-48 h, These observations suggest that mesenchymal cells originate from the coelomic mesothelium of the developing liver and differentate into endothelial cells of the hepatic sinusoids.

Solitary Fibrous Tumors Arising in Abdominal Wall Hernia Sacs

Solitary fibrous tumor (SFT) of the peritoneum is an unusual spindle-cell neoplasm. SFT was originally described in the pleura; however it is now diagnosed in multiple extrathoracic sites. Most believe that the tumor is of mesenchymal origin and should be classified as a variant of fibroma. SFT of the pleura and peritoneum have also been called fibrous mesothelioma, and the cell of origin is felt to be a pluripotential submesothelial mesenchymal cell. Primary tumors arising in hernia sacs are rare, and we report on two patients with hernia SFT. The first is a 67-year-old man who had a diffusely thickened distal left inguinal hernia sac. Within the sac was copious myxoid material mimicking pseudomyxoma peritonei. Herniorrhaphy and orchiectomy were performed. The second is a 44-year-old woman with a midepigastric mass attached to a ventral hernia. Wide local excision was performed. Both tumors demonstrated plump spindle cells, one with myxoid background and the other with keloidal collagen. Calretinin immunostaining was positive in both tumors, whereas CD34 was negative. This suggests tumor origin from a submesothial pluripotential cell that maintains potential for mesothelial differentiation. Surgical excision is the treatment of choice with the degree of resectability being a powerful predictor of outcome.

Paraneoplastische Hypoglykämie beim lokalisierten fibrösen Tumor der Pleura

Localized fibrous tumor of the pleura is a rare, slowly growing, benign tumor which originates from the submesothelial stem cells of the pleura visceralis. Most of these tumors clinically behave asymptomatically, although tumor-associated hypoglycemia occurs in a few cases and can lead to hypoglycemic coma. Laboratory investigations show significant elevation of paraneoplastic IGF-II with a 2-3 times higher effect on the blood glucose level than insulin. Further, one finds reduced synthesis of IGFBP-3, which inhibits the action of IGF-II by inducing a complex with the paraneoplastic protein. As treatment, surgical resection of the tumor is recommended. We report on the case of a 72-year-old man with diabetes mellitus type II, who complained of recurrent hypoglycemic episodes. Diagnostic evaluation showed a fibrous tumor attached to the right diaphragm. After surgical treatment the hypoglycemic episodes disappeared.

Mesothelial regeneration is not dependent on subserosal cells

It has been proposed that after mesothelial injury, resident cells within the subserosal connective tissue proliferate, differentiate, and migrate to the serosal surface. The aim of this study was to examine the temporal and spatial changes of proliferating cells in a murine model of testicular mesothelial healing and assess the potential of submesothelial cells to reconstitute the damaged mesothelium. Histology and autoradiography were employed to determine the number of cells within the submesothelial connective tissue, as well as the proportion of cells undergoing DNA synthesis on and beneath the injured serosa. Mesothelial cells surrounding the wound demonstrated maximal DNA synthesis 48 h after injury (27.82±5.64% SEM, compared with 0.17±0.16% 3H-TdR labelled cells for resting mesothelium), whereas a significant increase in proliferating submesothelial cells was not seen until day 4 post-injury (7.79±3.31% compared with 0.85±0.64% 3H-TdR labelled cells at day 2). Furthermore, this small number of dividing submesothelial cells must include cells other than the proposed mesothelial precursors, indicating a very low proportion of precursor cells in the submesothelial cell population. As large numbers of mesothelial cells were seen at the wound centre by 3–4 days after injury, it is unlikely that submesothelial cells contributed significantly to the repopulation of the injured mesothelium. It is hypothesized that regenerating mesothelium is more likely to originate from the surrounding uninjured mesothelial cell population. Copyright © 2000 John Wiley & Sons, Ltd.

Mesothelial regeneration is not dependent on subserosal cells.

It has been proposed that after mesothelial injury, resident cells within the subserosal connective tissue proliferate, differentiate, and migrate to the serosal surface. The aim of this study was to examine the temporal and spatial changes of proliferating cells in a murine model of testicular mesothelial healing and assess the potential of submesothelial cells to reconstitute the damaged mesothelium. Histology and autoradiography were employed to determine the number of cells within the submesothelial connective tissue, as well as the proportion of cells undergoing DNA synthesis on and beneath the injured serosa. Mesothelial cells surrounding the wound demonstrated maximal DNA synthesis 48 h after injury (27. 82+/-5.64% SEM, compared with 0.17+/-0.16% (3)H-TdR labelled cells for resting mesothelium), whereas a significant increase in proliferating submesothelial cells was not seen until day 4 post-injury (7.79+/-3.31% compared with 0.85+/-0.64% (3)H-TdR labelled cells at day 2). Furthermore, this small number of dividing submesothelial cells must include cells other than the proposed mesothelial precursors, indicating a very low proportion of precursor cells in the submesothelial cell population. As large numbers of mesothelial cells were seen at the wound centre by 3-4 days after injury, it is unlikely that submesothelial cells contributed significantly to the repopulation of the injured mesothelium. It is hypothesized that regenerating mesothelium is more likely to originate from the surrounding uninjured mesothelial cell population.

Adenomatoid Tumor of the Genital Tract: Evidence of Mesenchymal Cell Origin

The objective of this study was to re-examine the histogenesis of adenomatoid tumors. This benign neoplasm is characterized by gland-like structures with a pseudodinfiltrative pattern, usually involving fibromuscular tissue at a certain distance from an overlying surface mesothelium. Twenty cases of adenomatoid tumors and four cases of reactive submesothelial lesions, characterized by marked proliferation of subserosal mesenchymal cells, were reviewed. Nineteen of twenty adenomatoid tumors, including lesions with ill-defined borders, showed no connection with surface mesothelium. At the periphery of small tumors, isolated glands, clusters of epithelioid cells and single epithelioid, and spindled cells showing no connection to adjacent glands or cell clusters were identified. The tumor cells shared features with reactive subserosal stromal cells including an infiltrative pattern and histochemical and immunohistochemical properties. The differences between adenomatoid tumors and reactive submesothelial tissue are quantitative in nature: predominant amount of spindled cells in reactive submesothelial lesions, and predominant amount of gland-like structures in adenomatoid tumors. It is proposed that adenomatoid tumors arise from pluripotent mesenchymal cells that differentiate toward submesothelial cells and eventually mesothelial cells. This differentiation is probably induced by the adjacent submesothelial cells.

Serosal thickening, smooth muscle cell growth, and phenotypic changes in the rabbit bladder wall during outflow obstruction and regeneration.

In the last five years we have been studying the phenotypic changes that the rabbit bladder wall undergoes at the level of serosal compartment in experimental models known to induce an increase of organ mass. Gene expression of submesothelial mesenchymal cells (SMMC) were monitored by a panel of monoclonal antibodies specific for smooth muscle (SM) and non-muscle (NM) differentiation markers. Both the phenotypic profile and growth pattern of these cells were compared in developing, obstructed and regenerating bladder. In the obstruction model, the whole organ hypertrophy is accompanied by a hypertrophy/hyperploidy of SM cells and a marked serosal thickening due to the proliferation of SMMC. Concomitant with changes in the growth pattern of detrusor muscle, there is a SM cell phenotype switching to that of fetal type. The hyperplastic response of serosal compartment was paralleled by a spatiotemporal modification of the differentiation status of these cells, that was related to the shift of the submesothelial elastic membrane towards the underlying detrusor muscle. As a result, the thickened serosa was divided into two tissues: the ‘extrinsic’ and the ‘intrinsic’ region with respect to this membrane. The inherent differentiation plasticity of SMMC was evidenced by the two-step cellular innervation-independent conversion process from resident fibroblast to myofibroblast (or keratin-containing myofibroblast) to fetal-type SM cell which took place in the obstructed bladder. In the regenerating bladder wall this process was faster and small bundles of SM cells could be observed at both sides of the elastic membrane in the thickened serosa. Similarly, fibroblast-like interstitial cells participated in the detrusor muscle regeneration by a recruitment and subsequent differentiation within the regenerating SM cell fasicles. In chemically denervated bladder, however, interstitial cells could complete their SM-type differentiation before being incorporated in newly formed SM cell bundles, suggesting a repressive role of innervation on differentiation of these cells. Infusion experiments delivering both growth factors and cytokine to the bladder surface indicated that TGFβ1 was able to reproduce serosal thickening, transition from SMMC to myofibroblast and formation of small bundles of SM cells near the elastic membrane.

Biocompatibility of a Peritoneal Dialysis Solution with Amino Acids: Histological Evaluation in the Rabbit

To determine the biocompatibility of a peritoneal dialysis (PD) solution containing amino acids compared to PD solutions containing glucose. The biocompatibility of three dialysis solutions containing 1.1% amino acids, 1.36% glucose, and 3.86% glucose, respectively, was evaluated in vivo in rabbits. After 60 days of PD, peritoneal histological changes in rabbits were investigated by light and transmission electron microscopy. The parameters investigated were: (1) mesothelial damage; (2) submesothelial edema; (3) submesothelial cell infiltration; (4) submesothelial fibrosis; and (5) vascular alterations. Semiquantitative evaluations were performed for all the above alterations; quantitative morphometric evaluation was performed for mesothelial damage (cubic transformation of the mesothelium, areas devoid of mesothelium, submesothelial edema) and thickness of peritoneal arteriole walls. (1) Mesothelial damage was practically nonexistent in rabbits dialyzed with the solution containing amino acids, and intermediate and severe with low-glucose and high-glucose solutions, respectively. Both controls and rabbits dialyzed with amino acid solution showed flat continuous mesothelium; rabbits dialyzed with low-glucose solution showed cubic continuous mesothelium; and rabbits dialyzed with high-glucose solution showed cubic discontinuous mesothelium. Cytopathic mesothelial effects were slight with the solution containing amino acids and severe with both the low- and high-glucose solutions. Duplication and thickening of mesothelial basement membrane were never observed. (2) Submesothelial edema showed a worsening trend from controls to rabbits dialyzed with solution containing amino acids, low glucose, and high glucose. (3) No difference in submesothelial infiltration was found between groups. (4) Submesothelial fibrosis was never observed. (5) Vascular alterations were never observed. These results are evidence that PD solution with amino acids is more biocompatible than high- and also low-glucose solutions.

Time-Dependent Remodeling of the Bladder Wall in Growing Rabbits After Partial Outlet Obstruction

We asked whether a urethral constriction gradually developed during growth would give rise to a structural remodeling of the bladder wall distinct from that of the mature rabbits in terms of cellular response. We examined the serosa and detrusor muscle in immature rabbits whose urethra was obstructed at 30 days postnatal and studied 7 to 30 days after partial outlet obstruction. Morphometry, bromo-deoxyuridine (BrdU) incorporation, Western blotting and immunocytochemical staining with a panel of monoclonal antibodies specific to selected cytoskeletal, cytocontractile and membrane-related proteins unique to non-muscle and smooth muscle cells (SMC) were used to analyze the effects of obstruction on the differentiation pattern. In comparison with results in adult obstructed bladders, we have found that in growing rabbits: (1) the cell conversion from fibroblasts to SMC, occurring within the 'extrinsic' region of serosal thickening, takes place earlier; (2) newly formed SMC are localized exclusively to the thickened serosa, and can group in bundles depending on the density of the regional innervation; (3) the peak level of BrdU incorporation is more elevated than in the adult bladder wall; and (4) change in the phenotypic profile of SMC of detrusor muscle is delayed. These data indicate that the basic features of structural remodeling in the two models are similar, though partial outlet obstruction produced in growing animals accelerates the fibroblast conversion to SMC and their spatial, differentiation-specific arrangement in the serosa. The late phenotypic changes in obstructed detrusor muscle correlate with the decline of the DNA synthesis level after an initial burst and strongly suggest that newly formed SMC in the serosa do not derive from pre-existing SMC.

Proliferation of Submesothelial Mesenchymal Cells during Early Phase of Serosal Thickening in the Rabbit Bladder Is Accompanied by Transient Keratin 18 Expression

Partial outlet obstruction of the rabbit bladder induces serosal thickening and smooth muscle (SM) hypertrophy. Within thickened serosa, submesothelial (mesenchymal) cells differentiate into SM cells after 30 days of obstruction [S. Buoroet al. Lab. Invest.69, 589–602, 1993]. Here, we show that submesothelial cells transiently express keratin (K) 18 but not K8 soon after obstruction. We investigated a possible relationship between keratin expression and cell proliferation/differentiationin vivoandin vitro.The results of this study indicate that expression of K18 is spatiotemporally related to the pattern of cell proliferation with respect to the localization of an elastic membrane which divides the thickened serosa into an “extrinsic” and an “intrinsic” region. Moreover, K18 is not present in bladder mesenchyma during early development, indicating that its expression in the adult is not attributable to a dedifferentiation process. However, simultaneous K18, K8, and desmoplakin (DP) expression can be induced in normal and thickened serosa upon treatment with bromo-deoxyuridine. Our results indicate that K18 is a marker of proliferating mesenchymal cells in rabbit serosa, whereas the combined expression of K18, K8, and DP might be related to the hypothesized alterations in the stability of gene expression. A model is proposed in which keratin-containing submesothelial cells can act as a “transit” cell phenotype involved in both regenerating mesothelial cells and formation of SM cells.

Ovarian mesothelial and extramesothelial cells in interactive culture.

The ovarian mesothelium (OM) represents the tissue of origin of ovarian epithelial cancer. To gain insight into the regulation of this tissue, OM organoids and submesothelial ovarian stromal cells (SC) were isolated from New Zealand White rabbits by a stepwise tissue dispersal technique, while granulosa cells (GC) were aspirated from mature follicles (14 +/- 4 groups/animal). OM and SC dispersal were sequentially accomplished by: a) 1-h incubation in collagenase type I (300 U/ml), gentle scraping of the ovarian surface, and 1 g sedimentation of OM organoids (equivalent to 0.93 +/- 0.40 x 10(6) cells/animal) on 5% bovine serum albumin (BSA); b) 2-h incubation in pronase-collagenase (0.5%-300 U/ml) under periodical resuspension and gentle scraping of SC (1.40 +/- 0.25 x 10(6)/animal) from OM-denuded ovaries. After a week-long in vitro expansion, OM cells (OMC) were cultured alone and with SC or GC within monocameral vessels or bicameral transfilter vessels in serumless, fibronectinrich (4 micrograms/ml) HL-1 medium. After 7 d of contact cell-cell interaction, cytokeratin-positive OMC became surrounded by fibroblastoid, vimentin-positive SC or by cytokeratin and vimentin-weakly positive GC. Filter-bound OMC humorally interacting with underlying SC or GC displayed a biphasic, epithelioid and spindle, morphology with universal cytokeratin expression. Bromo-2'-deoxyuridine (BrdU) immunoperoxidase revealed mean cell proliferation indices of 14.88% for OMC cultured alone, 11.21% and 19.39% for OMC cultured with GC or SC in monocameral dishes, and 15.25% or 22.47% for OMC cultured in bicameral vessels over GC or SC, respectively. This model provides an experimental tool for investigating the unexplored role of stromal-mesothelial interaction in OM pathobiology.

Cigarette smoke causes rapid cell proliferation in small airways and associated pulmonary arteries

To determine whether smoke could directly affect the cells of the small airways and the small vessels, we exposed Sprague-Dawley rats to the whole smoke of 7 cigarettes/day for 1, 2, or 7 days. Three hours before the rats were killed, 5-bromo-2'-deoxyuridine (BrdU) was administered. Labeled nuclei were counted in histological sections stained with antibodies to BrdU. In smokers, pulmonary artery walls at the level of the membranous bronchioles (MB), respiratory bronchioles (RB), and alveolar ducts (AD) showed significant increases in labeled nuclei at all three times; increases in endothelial labeling were only present in vessels associated with AD. Significantly increased labeling was also seen in the epithelium and walls of MB and RB themselves at all time periods. However, there was no correlation between labeling indexes in matched pairs of airways and vessels. Smoke had no effect on the labeling of mesothelial and submesothelial cells. We conclude that cigarette smoke rapidly causes proliferation of intrinsic cells in the airways and small vessels; this effect may lead eventually to airway wall muscular hyperplasia and fibrosis (small airways disease) and to vascular changes associated with pulmonary hypertension. However, the lack of correlation between labeling indexes in the vessels and airways suggests that different mediators are involved at these two sites. At least over the time course of this experiment, smoke does not cause proliferation of mesothelial or submesothelial cells.