Fine analysis of the short arm of chromosome 1 in sporadic and familial pheochromocytoma

OBJECTIVE

Despite the very recent discovery that about 25% of apparently sporadic forms of pheochromocytoma are actually due to germline mutations of RET, VHL, SDHB or SDHD genes, the genetic bases of the tumourigenesis of this type of cancer are still incompletely understood. Recent studies provided evidence that a new tumour suppressor gene, mapping on the short arm of chromosome 1, could be involved in early tumourigenesis of pheochromocytoma.

DESIGN

We have performed a fine analysis of loss of heterozygosity (LOH) of this region. In particular, we have analysed 31 highly polymorphic microsatellites distributed at 3.8 Mege base (Mb) mean intervals along the short arm of the chromosome 1 in paired samples of DNA extracted from peripheral blood lymphocytes and tumour tissues.

PATIENTS

The study was carried out on 38 patients with pheochromocytoma that had been grouped, by careful clinical and molecular investigation, in the following classes: 21 sporadic, five multiple endocrine neoplasia type 2 (MEN2), two type 1 neurofibromatosis (NF1), five von Hippel-Lindau (VHL), one somatic VHL mutated and four nonsyndromic familial cases.

RESULTS

In 12/21 sporadic cases (57.1%), in 4/5 MEN2 (80%), 2/4 non-syndromic familial cases (50%), and in 2/2 NF1 (100%), the entire short arm was deleted, while in 6/21 sporadic (28.6%) and 1/5 MEN2 (20%) cases a partial deletion was detected. On the other hand, none of the five cases due to VHL mutation (either germline or somatic) had LOH at chromosome 1. In total, complete or partial deletion of 1p was detected in 27/38 (71%) of the cases. The most frequently deleted marker was D1S2890, which maps at 1p32.1. This region, which spans from 50 to 62 Mb from telomere, was therefore further investigated with markers located at a mean interval of 1.3 Mb in the subset of cases that showed a partial deletion of 1p. This analysis showed that a small region between 55.1 and 59.0 Mb was most frequently missing, which could therefore contain a novel pheochromocytoma locus.

CONCLUSIONS

The results presented here confirm that the short arm of chromosome 1 harbours one or more genes responsible for the development of pheochromocytoma and suggest that one of them could map in a 3.9-Mb fragment between 1p32.3 and 1p32.1.

Macrophage-secreted myogenic factors: a promising tool for greatly enhancing the proliferative capacity of myoblasts in vitro and in vivo

In this work we set out to determine if the murine macrophage J774 cell line can be used to produce myogenic growth factors. Activated J774 macrophages were grown in serum-free conditions. The macrophage-conditioned medium (MCM) was then used to treat cultures of primary myoblasts and regenerating muscle tissue, in vitro and in vivo respectively. MCM activity in vitro was tested by analyzing the expression of muscle-specific transcription factors, in parallel with the proliferation and differentiation rates of the cells. The macrophage-secreted factors greatly enhanced the proliferative potential of both rat and human primary myoblasts and were found to be highly muscle-specific. In vivo, MCM administration markedly enhanced the regenerative processes in damaged muscles. The ability to produce large amounts of macrophage-secreted myogenic factor(s) in the absence of serum holds great promise for its biochemical characterization and successive application in therapeutic protocols, both for ex vivo gene therapy and for muscle repair.

Gene transfer in skeletal muscle by systemic injection of DODAC lipopolyplexes

Lipid-based vectors are a promising tool for gene therapy applications. Several studies have reported their use in vivo to transfect different organs. Few data, however, are available about lipid-mediated gene transfer in skeletal muscle. Here we report the initial results obtained after systemic administration of lipopolyplexes based on the DODAC cationic lipid in an animal model of muscle regeneration. In particular, we compared three routes of administration: intravenous (i.v.), intracardiac (IC) and intra-arterial (IA). Analysis of reporter gene expression (luciferase) showed that regenerating muscle is more efficiently transfected in all cases and that IA injection is by far the best approach.

Transforming growth factor beta1 involvement in the conversion of fibroblasts to smooth muscle cells in the rabbit bladder serosa

In an attempt to identify the growth factors or cytokines involved in the serosal thickening that occurs in rabbit bladder subjected to partial outflow obstruction, the following growth factors--transforming growth factor beta1, platelet-derived growth factor, epidermal growth factor, granulocyte colony-stimulating factor and granulocyte-monocyte colony-stimulating factor--were delivered separately onto the serosal surface of the intact bladder via osmotic minipumps. The proliferative/differentiative cellular response of the rabbit bladder wall was evaluated by bromodeoxyuridine incorporation and immunofluorescence staining with a panel of monoclonal antibodies to cytoskeletal proteins (desmin, vimentin, keratins 8 and 18 and non-muscle myosin) and to smooth muscle (alpha-actin, myosin and SM22) proteins. Administration of the transforming growth factor, but not of the other growth factors/cytokines, was effective in inducing serosal thickening. Accumulating cells in this tissue were identified as myofibroblasts, i.e. cells showing a mixed fibroblast-smooth muscle cell differentiation profile. The phenotypic pattern of myofibroblasts changed in a time-dependent manner: 21 days after the growth factor delivery, small bundles of smooth muscle cells were found admixed with myofibroblasts, as occurs in the obstructed bladder. These 'ectopic' muscle structures displayed a variable proliferating activity and expressed an immature smooth muscle cell phenotype. The complete cellular conversion to smooth muscle cells was not achieved if transforming growth factor beta1 was delivered to fibroblasts of subcutaneous tissue. These findings suggest a tissue-specific role for this growth factor in the cellular conversion from myofibroblast to smooth muscle cells.

Phenotypic changes in the regenerating rabbit bladder muscle. Role of interstitial cells and innervation on smooth muscle cell differentiation

We have studied the phenotypic changes in regenerating smooth muscle (SM) tissue of detrusor muscle after local application of a necrotizing, freeze-thaw injury to the serosal surface of rabbit bladder. Bromo-deoxyuridine (BrdU) incorporation and immunofluorescence studies were performed on bladder cryosections from day 2 up to day 15 after surgery with monoclonal antibodies specific for some cytoskeletal markers [desmin, vimentin, non-muscle (NM) myosin] and for SM-specific proteins (alpha-actin, myosin, and SM22). Four days after lesion, some clls incorporated in regenerating SM bundles are BrdU positive, but all display a phenotypic pattern identical to that of the interstitial, highly proliferating cells, i.e., expression of vimentin. By days 7-15 the differentiation profile of regenerating SM returns to that of uninjured SM tissue (appearance of desmin, SM-type alpha-actin, and SM myosin). A chemical denervation achieved by 6-hydroxydopamine treatment for 2 weeks induces the formation of vimentin/SM alpha-actin/NM myosin/SM22-containing myofibroblasts in the interstitial, fibroblast-like cells of uninjured bladder. In the bladder wall, alteration of reinnervation during the regenerating SM process produces: (1) in the outer region, the activation of vimentin/SM alpha-actin/desmin myofibroblasts in the de novo SM cell bundles; and (2) in the inner region of bladder, including the muscularis mucosae, the formation of proliferating, fully differentiated SM cells peripherally to newly formed SM cell bundles. These findings suggest that: (1) the de novo SM tissue formation in the bladder can occur via incorporation of interstitial cells into growing SM bundles; and (2) the alteration of reinnervation during the regenerating process induces a spatial-specific differentiation of interstitial myofibroblasts in SM cells before SM cell bundling.

Time-dependent remodeling of the bladder wall in growing rabbits after partial outlet obstruction

PURPOSE

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.

MATERIALS AND METHODS

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.

RESULTS

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.

CONCLUSION

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.

Cytoskeletal and cytocontractile protein composition of stromal tissue in normal, hyperplastic, and neoplastic human prostate. An immunocytochemical study with monoclonal antibodies

Monoclonal antibodies specific for protein markers of smooth muscle and nonmuscle cell differentiation were applied to cryosections of normal, hyperplastic, and neoplastic human prostate specimens in order to determine whether differences in the distribution of target antigens could be detected among the various tissues. Immunofluorescence assays showed that vimentin, desmin, smooth-muscle-type alpha-actin, and both smooth muscle and nonmuscle myosin heavy chains do not change their patterns of labeling in the stromas of normal, BPH, and carcinomatous prostates. By contrast, cytokeratin 18, a differentiation marker of simple epithelia, and to a lesser extent cytokeratin 8, was consistently found in stromal tissue of the "transition zone", but only scarcely in the stroma of the "peripheral zone" from normal prostate, and was completely unexpressed in benign hyperplasia. Prostatic carcinoma from the "peripheral zone" expressed this cytoskeletal component only in trace amounts. Moreover, in prostate showing coexistence of hyperplasia and neoplasia (in the "peripheral zone"), the stroma of BPH closely resembled the stroma surrounding the carcinoma; that is, it was completely unreactive with the anti-cytokeratin 18 antibody. Expression of cytokeratins in extraepithelial tissues has been previously correlated with the achievement of a proliferative state, notably in embryogenesis, in tissue regeneration, and in various pathological forms of proliferation and growth, including some tumors of mesenchymal origin. Our results indicate the following: (1) cells in the stromal tissue of normal prostate are of smooth muscle type and are heterogeneous as concerns cytokeratin distribution; (2) we show, for the first time, the existence of a marker that is differentially distributed in the "transition" versus "peripheral" zone; (3) the expression of cytokeratins in the stroma is lost with the development of hyperplasia and only partially recovers with neoplasia; (4) the pattern of stromal tissue, concerning cytokeratin 18 expression, does not change with different BPH locations ("transition" versus "peripheral" zone); and (5) contrary to expectations, cytokeratin 18 expression disappears in conditions presumably involving stromal cell proliferation.

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. Buoro et 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/differentiation in vivo and in 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.