Differentiated cell types and the regulation of collagen synthesis

Ogerin mediated inhibition of TGF-β(1) induced myofibroblast differentiation is potentiated by acidic pH

Transforming growth factor beta (TGF-β) induced myofibroblast differentiation is central to the pathological scarring observed in Idiopathic Pulmonary Fibrosis (IPF) and other fibrotic diseases. Our lab has recently identified expression of GPR68 (Ovarian Cancer Gene Receptor 1, OGR1), a pH sensing G-protein coupled receptor, as a negative regulator of TGF-β induced profibrotic effects in primary human lung fibroblasts (PHLFs). We therefore hypothesized that small molecule activators of GPR68 would inhibit myofibroblast differentiation. Ogerin is a positive allosteric modulator (PAM) of GPR68, inducing a leftward shift of the dose response curve to proton induced signaling. Using PHLFs derived from patients with both non-fibrotic and IPF diagnoses, we show that Ogerin inhibits, and partially reverses TGF-β induced myofibroblast differentiation in a dose dependent manner. This occurs at the transcriptional level without inhibition of canonical TGF-β induced SMAD signaling. Ogerin induces PKA dependent CREB phosphorylation, a marker of Gαs pathway activation. The ability of Ogerin to inhibit both basal and TGF-β induced collagen gene transcription, and induction of Gαs signaling is enhanced at an acidic pH (pH 6.8). Similar findings were also found using fibroblasts derived from dermal, intestinal, and orbital tissue. The biological role of GPR68 in different tissues, cell types, and disease states is an evolving and emerging field. This work adds to the understanding of Gαs coupled GPCRs in fibrotic lung disease, the ability to harness the pH sensing properties of GPR68, and conserved mechanisms of fibrosis across different organ systems.

Circular Dichroism Spectroscopy of Collagen Fibrillogenesis: A New Use for an Old Technique

Type-I collagen assembles in a stepwise, hierarchic fashion from the folding of the triple helix to the assembly of fibrils into fibers. The mature assembled fibers are crucial for tissue structure and mechanics, cell interactions, and other functions in vivo. Although triple helix folding can be followed with the use of optical methods such as circular dichroism (CD) spectroscopy, fibrillogenesis is typically measured by alternative methods such as turbidity, rheology, and microscopy. Together, these approaches allow for investigation of the mechanical properties and architectures of collagen-based scaffolds and excised tissues. Herein, we demonstrate that CD spectroscopy, a technique that is used primarily to evaluate the secondary structure of proteins, can also be employed to monitor collagen fibrillogenesis. Type-I collagen suspensions demonstrated a strong, negative ellipticity band between 204 and 210 nm under conditions consistent with fibrillogenesis. Deconvolution of CD spectra before, during, and after fibrillogenesis identified a unique fibril spectrum distinct from triple helix and random coil conformations. The ability to monitor multiple states of collagen simultaneously in one experiment using one modality provides a powerful platform for studying this complex assembly process and the effects of other factors, such as collagenases, on fibrillogenesis and degradation.

New Phenotypical and Ultrastructural Findings in Spindle Cell (Desmoplastic/Neurotropic) Melanoma

Spindle cell melanoma is a rare and distinctive variant of malignant melanoma that is composed of spindled neoplastic cells and includes desmoplastic and neurotropic melanoma. The lack of expression of several melanoma markers may result in a delayed or wrong diagnosis. In this study, we have analyzed in detail the phenotype of the tumor cells in 9 spindle cell melanomas on both paraffin-embedded and frozen material, using melanocytic, neural, and mesenchymal markers. The neoplastic cells expressed the melanocytic markers S-100, Mel-CAM, and NKIC3, but lacked gp100 and Melan-A; tyrosinase and c-Kit were expressed in 2 of 7 cases. Most cases expressed the neural markers p75-nerve growth factor receptor, neural cell adhesion molecule, and NSE. All cases expressed vimentin but lacked the mesenchymal markers CD34 and alpha-smooth muscle actin. Remarkably, all spindle cell melanomas strongly and diffusely expressed the fibroblastic markers Thy1 (CD90) and aminopeptidase N (CD13) and variably expressed the enzyme prolyl-4-hydroxylase, involved in procollagen formation. The coexpression of melanocytic, neural, and fibroblastic markers suggests bidirectional differentiation of neoplastic melanocytes toward (myo)fibroblasts and Schwann cells, a feature that was confirmed by electron microscopy. Furthermore, the lack of CD90 and CD13 staining in a wide range of melanocytic lesions suggests specificity of these markers for spindle cell melanoma.

The Arcanobacterium pyogenes collagen-binding protein, CbpA, promotes adhesion to host cells

Arcanobacterium pyogenes is an opportunistic pathogen associated with suppurative diseases in economically important food animals such as cattle, pigs, and turkeys. A. pyogenes adheres to host epithelial cells, and adhesion is promoted by the action of neuraminidase, which is expressed by this organism. However, a neuraminidase-deficient mutant of A. pyogenes only had a reduced ability to adhere to host epithelial cells, indicating that other factors are involved in adhesion. Far Western blotting revealed the presence of an approximately 120-kDa A. pyogenes cell wall protein that binds collagen type I. The 3.5-kb gene that encodes the 124.7-kDa CbpA protein was cloned, and sequence analysis indicated that CbpA contains a typical MSCRAMM protein domain structure. Recombinant, six-His-tagged CbpA (HIS-CbpA) was capable of binding collagen types I, II, and IV but not fibronectin. In addition, CbpA was involved in the ability of A. pyogenes to adhere to HeLa and 3T6 cells, as a cbpA knockout strain had 38.2 and 57.0% of wild-type adhesion, respectively. This defect could be complemented by providing cbpA on a multicopy plasmid. Furthermore, HIS-CbpA blocked A. pyogenes adhesion to HeLa or 3T6 cells in a dose-dependent manner. cbpA was only present in 48% of the A. pyogenes strains tested (n = 75), and introduction of plasmid-encoded cbpA into a naturally cbpA-deficient strain increased the ability of this strain to bind to HeLa and 3T6 cells 2.9- and 5.7-fold, respectively. These data indicate that CbpA, a collagen-binding protein of A. pyogenes, plays a role in the adhesion of this organism to host cells.

Natural biology of polyomavirus middle T antigen

"It has been commented by someone that 'polyoma' is an adjective composed of a prefix and suffix, with no root between--a meatless linguistic sandwich" (C. J. Dawe). The very name "polyomavirus" is a vague mantel: a name given before our understanding of these viral agents was clear but implying a clear tumor life-style, as noted by the late C. J. Dawe. However, polyomavirus are not by nature tumor-inducing agents. Since it is the purpose of this review to consider the natural function of middle T antigen (MT), encoded by one of the seemingly crucial transforming genes of polyomavirus, we will reconsider and redefine the virus and its MT gene in the context of its natural biology and function. This review was motivated by our recent in vivo analysis of MT function. Using intranasal inoculation of adult SCID mice, we have shown that polyomavirus can replicate with an MT lacking all functions associated with transformation to similar levels to wild-type virus. These observations, along with an almost indistinguishable replication of all MT mutants with respect to wild-type viruses in adult competent mice, illustrate that MT can have a play subtle role in acute replication and persistence. The most notable effect of MT mutants was in infections of newborns, indicating that polyomavirus may be highly adapted to replication in newborn lungs. It is from this context that our current understanding of this well-studied virus and gene is presented.

Actin-rich desmoplastic malignant melanoma: report of three cases

We report three cases of desmoplastic malignant melanoma (DMM) rich in smooth muscle actin. They occurred in two men (Cases 1 and 3) and in one woman (Case 2). Cases 1 and 2 were recurrent lesions from common melanomas excised, respectively, 3 and 1 years previously. In Case 3, DMM was associated with lentigo maligna at the time of presentation. Morphologically, DMMs were composed of spindle neoplastic cells organized in haphazardly orientated long fascicles separated by collagen bundles. Perineural invasion was present and mitotic activity was prominent in all cases. The neoplastic spindle cells were intensely positive with S100 protein and smooth muscle actin antisera and negative with HMB45 and Melan-A (Mart-1) antibodies. Double staining for smooth muscle actin and S100 protein revealed no definite coexpression of the two antigens. Follow-up was available for patients 1 and 2 who had local recurrences and are still alive. It is possible that actin rich elements differentiate toward mesenchymal elements, paralleling the phenotypic changes seen in sarcomatoid carcinomas. Therefore, multidirectional differentiation may explain the mesenchymal (sarcomatoid) differentiation of neoplastic melanocytes and may be responsible for the different biologic behavior of DMMs, which is closer to mesenchymal tumors than to conventional melanomas.

Desmoplastic neurotropic melanoma

Desmoplastic neurotropic melanoma (DNM) is a rare variant of a spindle cell melanoma. The majority of these tumors occur on the head and neck of elderly patients. The rather variable clinical appearance (e.g. frequent lack of pigmentation) makes initial diagnosis often difficult. Histologically, DNM may show a lentiginous melanocytic proliferation with atypia and pleomorphic spindle cells in the dermis. Immunostaining for S-100 is usually positive although staining for HMB-45 is frequently absent. As with other melanomas, surgery is the first line treatment for DNM. Unlike other melanomas, however, survival for DNM may be better compared with other forms of melanoma.

Desmoplastic neurotropic melanoma. A clinicopathologic analysis of 28 cases

BACKGROUND

Desmoplastic neurotropic melanoma (DNM) is a rare variant of malignant melanoma, the natural history and histogenesis of which still are being defined.

METHODS

The clinical and histologic features of 28 cases of DNM were studied. All published cases of DNM to date were reviewed. Paraffin sections from 26 cases were investigated with a panel of 10 tissue markers. The ultrastructural features of seven cases were evaluated.

RESULTS

A comparison of this study's findings with that of other published cases revealed many similarities regarding clinical and pathologic findings and outcome. The patients were white (15 men:13 women; mean and median age, 59 years; range, 22-83 years). Most tumors were located on the head and neck (75%) and were nonpigmented (57%). An associated intraepidermal melanocytic proliferation was identified in 85% of the patients (lentigo maligna in 56%). Histologically, the dermal tumors were composed of tapered, nonpigmented spindle cells in peripheral nerve sheath patterns resembling neuromas, schwannomas, neurofibromas, and perineurial proliferations accompanied by variable neurotropism and desmoplasia; desmoplasia was the most notable feature in most tumors. The mean depth of tumor invasion was 4.1 mm (range, 0.32-9.0 mm). Tumors with continuity between the epidermal and dermal components had a significantly thinner depth of invasion and a more extensive intraepidermal melanocytic proliferation than those tumors with a grenz zone between the two components (2.3 mm vs. 4.6 mm, P = 0.015). Mitotic activity ranged from 0/HPF in 10 cases, 1-6/high power field (HPF) in 12 cases, and to greater than 6/HPF in 4 cases. An ulcer was present in 5/27 tumors, regression in 4/27, a microsatellite in 1, and brisk and had nonbrisk tumor infiltrating lymphocytic responses in 2 and 14, respectively. Vimentin was uniformly positive and keratins AE1.3 and Cam 5.2 and Leu-7 were uniformly negative. S100 protein, also uniformly positive, had patchy reactivity in most tumors that expressed EMA (43%). Smooth muscle actin (52%), neuron-specific enolase (42%), and FXIIIa (30%) had patchy positivity. HMB-45 was reactive only in the epidermal and superficial papillary dermal component in 21% of cases. Ultrastructurally, the common features were long, often intertwining cellular processes, intercellular junctions, and discontinuous basal lamina. Melanosomes were not identified. Follow-up data available on 26/28 patients (mean, 36 months; median, 24 months; range, 5-132 months) showed 20 (70%) alive without disease, 2 alive with disease and 3 dead from disease. Seven patients had recurrent local tumor (multiple in four); four had lymph node metastases, and three had visceral metastases. Patients with recurrent disease of any type had significantly thicker tumors (5.4 mm vs. 3.4 mm, P = 0.046) and were more likely to have an ulcerated tumor (P = 0.03). Actuarial 5-year survival for tumors with greater than a 4-mm thickness was 72%, which was greater than that for other types of melanoma with greater than a 4-mm thickness.

CONCLUSIONS

Desmoplastic neurotropic melanomas are neuroectodermal tumors that usually arise from an intraepidermal melanocytic proliferation but rarely develop de novo in the dermis. Schwannian and perineurial differentiation may account for the desmoplasia and neurotropism encountered in these neoplasms. Desmoplastic neurotropic melanomas present at a more advanced stage locally and may be associated with a better survival than associated with conventional melanomas of similar depth of invasion.

Desmoplastic melanoma

Desmoplastic melanoma is a rare tumour of which a limited number of cases have been described. The clinical and histopathological features of desmoplastic melanoma and its variants may give rise to perplexing diagnostic and therapeutic dilemmas. In the past decades, some insight has been gained into the histogenesis of these lesions and discriminating clinical and morphological features are now recognized. Review of the literature reveals an extensive list of differential diagnoses. Adequate surgical excision and close follow-up of these radioresistant, frequently-recurring tumours is strongly advocated.

Fibronectin and collagen gene expression during in vitro ageing of pig skin fibroblasts

The fibronectin, collagen type I, and collagen type III genes code for three major proteins of the cell matrix. The age-related alterations in their expression were measured during the in vitro lifespan of pig skin fibroblasts. We observed changes in the transcription rate of these specific genes during ageing. The levels of fibronectin and type III collagen mRNA rose markedly during the senescence phase. The level of collagen type I mRNA decreased during cell ageing, while that of beta-actin did not change. As regards proteins, we observed a sharp increase in the secreted noncollagenous proteins and in the total proteins of the cell layer during senescence. On the contrary, the secretion of the collagenous proteins decreased during senescence. Moreover, most of the newly synthesized molecules of collagen were immediately degraded in the cells, before their extracellular secretion. The terminal phenotype of pig senescent cells was therefore characterized by overexpression of fibronectin and type III collagen genes and reduced expression of the type I collagen gene. Surprisingly, for fibronectin and type III collagen, that terminal phenotype resembled the one normally found in the fibroblasts during the processes of tissue repair, cicatrization, and development.

Malignant melanoma with desmoplasia and neurotropism

Desmoplastic (DMM) and neurotropic (NMM) malignant melanoma are two variants of the vertical growth phase of malignant melanoma. Both lesions commonly present clinically as firm nodules that are often mistaken for fibromas. Histologically, they are associated with a pleomorphic spindle cell population of cells that widely infiltrate the dermis. An accompanying fibrosis is present. DMM usually lies beneath a lentiginous proliferation of a typical melanocytes, whereas NMM may arise without obvious epidermal involvement. Because the lesions infiltrate widely, adequate therapy results only when complete extirpation is performed. Otherwise, there may be recurrence. Recurrent lesions act more aggressively.

Nucleotides in the polyomavirus enhancer that control viral transcription and DNA replication

The polyomavirus enhancer is required in cis for high-level expression of the viral early region and for replication of the viral genome. We introduced multiple mutations in the enhancer which reduced transcription and DNA replication. Polyomaviruses with these mutant enhancers formed very small plaques in whole mouse embryo cells. Revertants of the viral mutants were isolated and characterized. Reversion occurred by any of the following events: restoration of guanosines at nucleotide (nt) 5134 and nt 5140 within the adenovirus 5 E1A enhancer core AGGAAGTGACT; acquisition of an A----G mutation at nt 5258, which is the same mutation that enables polyomavirus to grow in embryonal carcinoma F9 cells; duplication of mutated sequences between nt 5146 and 5292 (including sequences homologous with immunoglobulin G, simian virus 40, and bovine papillomavirus enhancer elements). Reversion restored both the replicative and transcriptional functions of the viruses. Revertants that acquired the F9 mutation at nt 5258 grew at least 20-fold better than the original mutant in whole mouse embryo cells, but replicated only marginally better than the original mutant in 3T6 cells. Viruses with a reversion of the mutation at nt 5140 replicated equally well in both types of cells. Since individual nucleotides in the polyomavirus enhancer simultaneously altered DNA replication and transcription in specific cell types, it is likely that these processes rely upon a common element, such as an enhancer-binding protein.

Nucleotides in the polyomavirus enhancer that control viral transcription and DNA replication

The polyomavirus enhancer is required in cis for high-level expression of the viral early region and for replication of the viral genome. We introduced multiple mutations in the enhancer which reduced transcription and DNA replication. Polyomaviruses with these mutant enhancers formed very small plaques in whole mouse embryo cells. Revertants of the viral mutants were isolated and characterized. Reversion occurred by any of the following events: restoration of guanosines at nucleotide (nt) 5134 and nt 5140 within the adenovirus 5 E1A enhancer core AGGAAGTGACT; acquisition of an A----G mutation at nt 5258, which is the same mutation that enables polyomavirus to grow in embryonal carcinoma F9 cells; duplication of mutated sequences between nt 5146 and 5292 (including sequences homologous with immunoglobulin G, simian virus 40, and bovine papillomavirus enhancer elements). Reversion restored both the replicative and transcriptional functions of the viruses. Revertants that acquired the F9 mutation at nt 5258 grew at least 20-fold better than the original mutant in whole mouse embryo cells, but replicated only marginally better than the original mutant in 3T6 cells. Viruses with a reversion of the mutation at nt 5140 replicated equally well in both types of cells. Since individual nucleotides in the polyomavirus enhancer simultaneously altered DNA replication and transcription in specific cell types, it is likely that these processes rely upon a common element, such as an enhancer-binding protein.

Gene expression in flow sorted mouse teratocarcinoma X human fibroblast heterokaryons

Mouse teratocarcinoma cells and primary human fibroblasts were fluorescently labelled with fluorescein isothiocyanate (FITC)- and trimethylrhodamine isothiocyanate (TRITC)-stearylamine respectively. After fusion populations highly enriched for red-green heterokaryons (around 80%) were isolated from the fusion mixture using a FACS II cell sorter. To study gene expression in the early hybrids [35S] methionine-labelled proteins synthesized by the sorted cells at two and three days after fusion were analysed by two-dimensional gel electrophoresis. Three spots were denser in gels of the fused cells than in those of 1:1 mixtures of parental cells. For one of these proteins it could be demonstrated that this reflects the enhanced synthesis of a mouse-specific protein present only in small amounts in teratocarcinoma cells. All three proteins were synthesized in relatively large amounts by differentiated mouse cells. Collagen (type I) synthesis by the sorted hybrid cells was studied by analysing the [3H] proline-labelled material secreted into the medium. Analysis by sodium dodecyl sulphate (SDS)-gel electrophoresis and two-dimensional nonequilibrium pH gradient electrophoresis showed that the material secreted by the fused cells five days after fusion was the same as that secreted by the human fibroblasts. No evidence was obtained for synthesis of mouse alpha 2(I) collagen. The amount of collagen produced by the sorted cells five days after fusion was about half the amount produced by the human fibroblasts. Immunofluorescence studies also showed that collagen synthesis was not suppressed after fusion both in heterokaryons and synkaryons. In conclusion, we did not find evidence for activation of a previously completely silent mouse gene in the fused cells. The results show, however, that the fused cells do resemble the differentiated fibroblasts rather than the undifferentiated teratocarcinoma cells.

DNase I sensitivity of the alpha 2(I) collagen gene: correlation with its expression but not with its methylation pattern

The chromatin structure of the chick alpha 2(I) collagen gene was probed with DNase I. Because our previous work strongly suggested that the 5' end of this gene is not methylated whereas the rest of the gene is methylated whether or not the gene is expressed, we compared the relative DNase I sensitivity of the methylated and unmethylated segments. Both regions demonstrate similar relative DNase I sensitivities within a given tissue. In chromatin of chick embryo fibroblasts, we find a DNase I hypersensitive site which maps between 100 and 300 bp preceding the start of transcription. This site is not found in brain chromatin but is present in chick embryo fibroblasts transformed by Rous Sarcoma virus although the rate of transcription of the alpha 2(I) collagen gene is greatly reduced in these cells. Hence, the mechanism responsible for the large decrease in alpha 2(I) collagen gene expression in RSV transformed cells is different from the mechanism that is responsible for the presence of a DNase I hypersensitive site in the promoter. Furthermore, changes in the DNase I sensitivity of the chromatin of the alpha 2(I) collagen promoter occur without changes in the methylation pattern of the gene.

Ultrastructural morphometry of collagen from lamina propria during experimental oral carcinogenesis and chronic inflammation

Stereological point-counting methods were used to determine the volumetric alterations in collagen from the lamina propria immediately beneath the epithelial-connective tissue junction in hamster check-pouch mucosa treated with the chemical carcinogen DMBA. In addition, a non-neoplastic inflammatory control was evaluated in which a delayed hypersensitivity reaction was induced by the contact-sensitising agent DNCB. DMBA-treated tissues were assigned to histopathologically defined hyperplasia, dysplasia and carcinoma stages. The volume densities of collagen present in unit volume of extracellular lamina propria were found to decrease progressively and significantly in DMBA-treated tissues when compared with values obtained from normal untreated mucosa. Values from the inflammatory control were comparable with those from the dysplasia stage of carcinogenesis. The mechanisms responsible for these decreases in collagen volume density are unknown, but contributory factors might include collagen destruction by enzymes originating in either the epithelium or the cells of the inflammatory infiltrate, dilution of collagen produced by inflammatory oedema or alterations in the synthetic capabilities of fibroblasts.

Loss of type I procollagen gene expression in SV40-transformed human fibroblasts is accompanied by hypermethylation of these genes

Transformation of human lung fibroblasts (WI-38) by Simian Virus 40 (SV40) resulted in a decline of 25-30% in the amount of secreted collagen. The collagen produced by the transformed fibroblasts contained no type I collagen (i.e. alpha 1(I) and alpha 2 chains), which was the major collagen component produced by untransformed fibroblasts. Measurement of the procollagen mRNA levels by dot hybridization with nick-translated procollagen-cDNA clones showed that the absence of type I collagen was due to the absence of alpha 1(I) and alpha 2 procollagen mRNAs. This result was confirmed by hybridization of cDNA to total RNA with southern blots of the procollagen clones. To clarify the mechanism by which type I procollagen gene transcription is abolished in transformed cells, the methylation patterns of the alpha 1(I) and alpha 2 procollagen genes in normal and SV40-transformed fibroblasts were compared, using the chicken alpha 1(I) and alpha 2 procollagen-cDNA clones as probes. Methylated sites were detected by means of the restriction endonuclease isoschizomers HpaII and MspI. Methylation of the procollagen alpha 1(I) and alpha 2 genes was increased in the SV40-transformed fibroblasts, concurrently with the loss of type I collagen synthesis. DNA methylation may thus contribute to altered regulation of gene expression upon cell transformation.

Unusual methylation pattern of the alpha 2 (l) collagen gene

We studied the methylation pattern of the alpha 2 (type 1) collagen gene in DNA from five cell types with varying rates of type I collagen synthesis: chick embryo fibroblast (CEF), CEF transformed by Rous sarcoma virus, erythrocyte, brain and sperm. The methylation-sensitive restriction enzymes, Msp I, Hpa II, Ava I and Sma I were used to detect methylation in three regions of the alpha 2 (type I) collagen gene: a 5.7 kb region, which includes the start site of transcription and the first two exons of the collagen gene; a 5.2 kb region containing exons in the middle of the gene; and a 3.5 kb region containing exons in the 3' portion of the gene. The DNA around the start site of transcription is not methylated whether or not the cells synthesize collagen. In contrast, the DNA from the central and 3' region of the gene is methylated to about the same extent whether or not the cells make collagen. Our data indicate that a gene that is methylated can be actively transcribed and that the level of expression of the alpha 2 (type I) collagen gene seems to be independent of methylation.

Regulation or procollagen messenger ribonucleic acid levels in Rous sarcoma virus transformed chick embryo fibroblasts

Using cloned cDNAs for pro-alpha 1 and pro-alpha 2 collagen messenger ribonucleic acid (mRNA), we have investigated the regulation of collagen mRNA levels in Rous sarcoma virus (RSV) transformed chick embryo fibroblasts (CEF). We find that both pro-alpha 1 and pro-alpha 2 mRNA levels are decreased approximately 10-fold in CEF transformed by either the Bryan high-titer strain or the Schmidt-Ruppin strain of RSV. Using temperature-sensitive mutants in the transforming gene src, we also investigated the rate of change in the levels of the two mRNA species. We employed mutants of both the Bryan high-titre strain (BHTa) and the Schmidt-Ruppin strain (ts68). With both mutants the results were similar. Upon shift from the permissive temperature (35 degrees C) to the non-permissive temperature (41 degrees C), collagen mRNA synthesis, did not increase until more than 5 h had passed, suggesting that action of src on collagen gene expression is indirect. Upon shift from 41 to 35 degrees C, collagen mRNA levels fell with a half-life of 10 h. Whether this fall reflects the half-life of procollagen mRNA or an effect of src on procollagen RNA stability is unclear. Both pro-alpha 1 and pro-alpha 2 mRNA levels were coordinately controlled.

Some aspects of the modulation and regulation of collagen synthesis in vitro

We reviewed here a number of publications containing data on the quantitative aspects of collagen synthesis in vitro. In one section we discussed the factors which modulate the amount of collagen synthesized in various culture systems and in another section we presented experimental evidence for regulatory mechanisms operating in collagen synthesis on the transcriptional and/or translational levels. We believe that growing knowledge of the mechanisms controlling collagen synthesis will help us to understand and deal with fibrotic processes better.

[Behaviour of the prolyl hydroxylase to collagen synthesis in KB cells]

KB cells, which synthetized collagen at a low rate, shown a prolyl hydroxylase activity at the same rate that fibroblast. The relationship between collagen synthesis and prolyl hydroxylase activity in these cells was discussed.

Sulfated glycosaminoglycans of cells grown in culture: dermatan sulfate disappearance in successive fibroblast subcultures

Sulfated glycosaminoglycan content of primary cultures of guinea pig embryo fibroblast in reported. It is shown that changes of sulfated glycosaminoglycans occur in successive subcultures: 1) disappearance of dermatan sulfate and 2) a slight increase in the proportion of heparitin sulfate. The sulfated glycosaminoglycan composition of the mammalian cell established lines: VERO, SIRK, Hep-2, MK-2, BGM, IB-RS-11 (S6) and 3T6 is also reported. It is shown that chondroitin sulfate AC and/or heparitin sulfate are the main glycosaminoglycans of the established cell lines (except 3T6). A possible role of these glycosaminoglycans in cell biology is discussed.

Ascorbate-independent proline hydroxylation resulting from viral transformation of Balb 3T3 cells and unaffected by dibutyryl cAMP treatment

Collagen synthesis, hydroxylation of proline in collagen, and collagen secretion were studied in the contact-inhibited mouse fibroblast line, Balb 3T3; the Kirsten virus transformed line, Ki-3T3; and dibutyryl cAMP (dbcAMP)-treated Ki-3T3 cells, during the various phases of the growth cycle. Transformed cells in both logarithmic and stationary phase produced lower levels of collagen than the parent line but 85-90% of the theoretically possible hydroxyproline residues of the collagen were formed even when ascorbic acid was not added to the culture medium. Moreover, the transformed cells showed only about a 20% increase of collagen secretion upon addition of ascorbate. This was in contrast to the ascorbate requirement for maximal proline hydroxylation and the 2-3 fold stimulation of collagen secretion by ascorbate in the parent Balb 3T3 cells. Although dbcAMP treatment caused Ki-3T3 cells to assume a more normal morphology and increased the relative rate of collagen synthesis to levels similar to that of 3T3, such treatment did not restore an ascorbate requirement for proline hydroxylation or collagen secretion. The specific activity of the enzyme prolyl hydroxylase also was not affected by dbcAMP treatment although collagen synthesis was increased by such treatment. In addition, it was found that ascorbic acid was not effective in activating prolyl hydroxylase derived from Ki-3T3 or dbcAMP-treated Ki-3T3 cell cultures either in logarithmic phase or stationary phase. Ki-3T3 cultures did not accumulate ascorbic acid in cells or medium nor was ascorbic acid synthesized from the precursor 14C-glucuronate in cell homogenates. The results suggest that virally transformed Balb 3T3 cells acquire the capacity to synthesize a reducing cofactor for prolyl hydroxylase and that this function may be related to the increased glycolytic metabolism of these cells since neither cellular metabolism nor ascrobate-independent hydroxylation was altered by treatment with dbcAMP.

On the nature of desmoplastic melanoma

Pathologic study demonstrated lentigo maligna melanoma in three of four cases of desmoplastic melanoma and demonstrated spindle cell masses with features of atypical fibroxanthoma in all four of the cases. Pigment enzymes of melanosomes were not found in the mesenchymal portion of the tumor. The cellular atypia and the histochemical and ultrastructural findings favor the fibroblastic nature of this melanoma-related dermal mass.

Transformation by simian virus 40 of spleen cells from a hyperimmune rabbit: evidence for synthesis of immunoglobulin by the transformed cells

Spleen cells derived from a rabbit hyperimmunized with a Type III pneumococcal vaccine were exposed to simian virus 40 in vitro. After 114 days, transformed cells growing on the surface of one culture dish were observed and a cell line was established. The transformed cells had a morphology characteristic of cells transformed by simian virus 40, contained the simian virus 40-specific T antigen, and yielded infectious simian virus 40 upon cultivation with indicator cells in the presence of Sendai fusion factor. Transformed cells incorporated labeled amino acid into protein with the antigenic properties of rabbit immunoglobulin G.

Identification of a novel cell type in peripheral lymphoid organs of mice. II. Functional properties in vitro

Dendritic cells are morphologically distinct cells isolated in vitro from peripheral lymphoid organs of mice. They have a buoyant density of less than 1.082 and can be enriched 7-20-fold by isopycnic centrifugation in albumin columns. Surface adherence of enriched populations may yield cultures containing 50% dendritic cells-preparations which can then be studied in more detail. By functional tests, dendritic cells do not represent morphological variants of either lymphocytes or macrophages. They lack lymphocyte surface differentiation markers and do not exhibit the endocytic capacities of macrophages. In tissue culture, they do not differentiate into macrophages. Dendritic cells have a low labeling index in vitro (1.5-2.5%) following administration of [(3)H]thymidine, and this property distinguishes them from large lymphocytes and promonocytes. Dendritic cells also do not possess the functional properties of other types of reticular cells proposed to exist in lymphoid organs, i.e., they do not synthesize collagen-like macromolecules, they are not stem cells for erythroid and myeloid colony formation, and they do not retain antigens or immune complexes on their cell surface. Dendritic cells thus represent a novel cell type on both functional and morphological grounds.

Expression of differentiated functions in hepatoma cell hybrids: induction of mouse albumin production in rat hepatoma-mouse fibroblast hybrids

The synthesis of serum albumin has been studied in hybrids between well-differentiated rat hepatoma cells, which synthesize serum albumin, and mouse fibroblasts (3T3) that do not synthesize albumin. By immunodiffusion techniques with noncrossreacting antisera, the production of both rat and mouse albumin by the hybrids has been examined. Karyologically identified hybrids were produced between 3T3 cells and cells of a 1s hepatoma (Fu5) clone, and of a 2s hepatoma (2s Fu5-5cl.lE) clone. Each of the 3T3 x Fu5 hybrids produces only rat albumin. Among five 3T3 x 2s Fu5-5cl.lE hybrid clones isolated, one produces both rat and mouse albumin, two produce only mouse albumin, and two do not produce rat or mouse albumin.