Generation of somatic cell hybrids for the production of biologically active factors that stimulate proliferation of other cells

OBJECTIVE

Some normal somatic cells in culture divide a limited number of times before entering a non-dividing state called replicative senescence and fusion of normal cells with immortal cells claimed to produce hybrid cells of limited proliferation. We reinvestigated the proliferative capacity of hybrid cells between normal cell and immortal cell.

MATERIALS AND METHODS

Normal pig fibroblast cells and cells of immortal mouse fibroblast cell line F7, a derivative of GM05267, were fused by polyethylene glycol treatment and subsequently the fused cells were cultured in a selective medium containing hypoxanthine-aminopterin-thymidine in order to enrich the hybrid cells. The hybrid cells were then monitored for chromosome content and proliferation.

RESULTS

Cytogenetic analysis revealed that the hybrid cells contained polyploidy chromosomes derived from normal pig fibroblasts. These hybrid cells exhibit no sign of replicative senescence after more than 190 population doublings in vitro. Instead, these hybrid cells have an accelerated growth and proliferate even in the complete absence of glutamine. In addition, these hybrids produce biologically active factors in the conditioned media, which not only can accelerate their own proliferation but also can reinitiate mitotic activity in the senescent-like normal fibroblast cells.

CONCLUSIONS

Our results question the validity of cellular senescence as a dominant trait. Additionally, the generation of hybrid cells using the specific mouse cell line can be applied to the generation of hybrids with other normal cell types and can be used to produce tissue-specific growth-factor(s) to extend the lifespan and/or improve the proliferation of various normal cells, including adult stem cells.

Polyethylene Glycol-Mediated Fusion between Primary Mouse Mesenchymal Stem Cells and Mouse Fibroblasts Generates Hybrid Cells with Increased Proliferation and Altered Differentiation

Bone marrow-derived mesenchymal stem cells (MSCs) can differentiate into different cell lineages with the appropriate stimulation in vitro. Transplantation of MSCs in human and other animal models was found to repair tissues through the fusion of transplanted MSCs with indigenous cells. We have generated mouseâmouse hybrid cell lines in vitro by polyethylene glycol-mediated fusion of primary mouse MSCs with mouse fibroblasts to investigate the characteristics of hybrid cells, including their potentials for proliferation and differentiation. Similar to the parental MSCs, hybrid cells are positive for the cell-surface markers CD29, CD44, CD49e, and Sca-1, and negative for Gr-1, CD11b, CD13, CD18, CD31, CD43, CD45, CD49d, CD90.2, CD445R/B220, and CD117 markers. The hybrid cells also produce a high level of tissue nonspecific alkaline phosphatase compared to the parental cells. Conditioned medium of hybrid cells contain biologically active factors that are capable of stimulating proliferation of other cells. Although the parental MSCs can differentiate into adipogenic and osteogenic lineages, hybrid cells held disparate differentiation capacity. Hybrid cell lines in general have increased proliferative capacity than the primary MSCs. Our study demonstrates that proliferative hybrid cell lines can be generated in vitro by induced fusion of both immortal and primary somatic cells with primary MSCs.

Functional characterization of cell hybrids generated by induced fusion of primary porcine mesenchymal stem cells with an immortal murine cell line

Bone marrow mesenchymal stem cells (MSC) integrate into various organs and contribute to the regeneration of diverse tissues. However, the mechanistic basis of the plasticity of MSC is not fully understood. The change of cell fate has been suggested to occur through cell fusion. We have generated hybrid cell lines by polyethylene-glycol-mediated cell fusion of primary porcine MSC with the immortal murine fibroblast cell line F7, a derivative of the GM05267 cell line. The hybrid cell lines display fibroblastic morphology and proliferate like immortal cells. They contain tetraploid to hexaploid porcine chromosomes accompanied by hypo-diploid murine chromosomes. Interestingly, many hybrid cell lines also express high levels of tissue-nonspecific alkaline phosphatase, which is considered to be a marker of undifferentiated embryonic stem cells. All tested hybrid cell lines retain osteogenic differentiation, a few of them also retain adipogenic potential, but none retain chondrogenic differentiation. Conditioned media from hybrid cells enhance the proliferation of both early-passage and late-passage porcine MSC, indicating that the hybrid cells secrete diffusible growth stimulatory factors. Murine F7 cells thus have the unique property of generating immortal cell hybrids containing unusually high numbers of chromosomes derived from normal cells. These hybrid cells can be employed in various studies to improve our understanding of regenerative biology. This is the first report, to our knowledge, describing the generation of experimentally induced cell hybrids by using normal primary MSC.

A case report of drinking glass in rectum

A fifty years old man was admitted in the Dept. of Surgery of Community Based Medical College, Bangladesh, Hospital with the history of pain and distension of lower abdomen for 4 days with obstipation for the same duration. He gave history of being assaulted and forceful introduction of some foreign body per-rectally 5 days back. History, clinical examination and abdominal X-rays diagnosed the case as impacted foreign body in rectum. He was undergone laparotomy and a big drinking glass was extracted from sigmoid colon. Patient developed subcutaneous stitch infection postoperatively and discharged from the hospital after controlling the infection.

In vitro activity of a novel diaminopyrimidine compound, iclaprim, against Chlamydia trachomatis and C. pneumoniae

The in vitro activities of iclaprim, a novel dihydrofolate reductase inhibitor, azithromycin, and levofloxacin were tested against 10 strains of Chlamydia trachomatis and 10 isolates of Chlamydia pneumoniae. For C. trachomatis and C. pneumoniae, the iclaprim MIC and minimal bactericidal concentration at which 90% of isolates were inhibited (MIC(90) and MBC(90)) were 0.5 micro g/ml, compared to an azithromycin MIC(90) and MBC(90) of 0.125 micro g/ml and levofloxacin MIC(90)s and MBC(90)s of 1 micro g/ml for C. trachomatis and 0.5 micro g/ml for C. pneumoniae.

Regional mapping of suppressor loci for anchorage independence and tumorigenicity on human chromosome 9

By microcell-mediated chromosome transfer to the malignant Syrian hamster cell line BHK-191-5C, we previously identified two suppressor functions on human chromosome 9 (HSA9), one for anchorage independence and another for tumorigenicity. However, the precise chromosomal locations of these suppressor functions were not determined. The present study was undertaken to define the regional location of these suppressor loci using a panel of microcell hybrids containing structurally altered HSA9 with different deleted regions in the BHK-191-5C background. DNA derived from the cell hybrids was analyzed by PCR for verification of the presence of HSA9 genetic material by amplifying 62 microsatellite markers and 13 genes, covering the entire length of HSA9. Our deletion mapping data on anchorage independent and tumorigenic hybrids suggest that the suppressor function for anchorage independence is located in the region between 9q32 to 9qter. The suppressor for tumorigenicity may be located in one of three deleted regions on HSA9, the first one between the markers D9S162 and D9S1870, the second one between the markers D9S1868 and TIGRA002I21, and the third one between the markers D9S59 and D9S155.

Differential binding regulation of microtubule-associated proteins MAP1A, MAP1B, and MAP2 by tubulin polyglutamylation

The major neuronal post-translational modification of tubulin, polyglutamylation, can act as a molecular potentiometer to modulate microtubule-associated proteins (MAPs) binding as a function of the polyglutamyl chain length. The relative affinity of Tau, MAP2, and kinesin has been shown to be optimal for tubulin modified by approximately 3 glutamyl units. Using blot overlay assays, we have tested the ability of polyglutamylation to modulate the interaction of two other structural MAPs, MAP1A and MAP1B, with tubulin. MAP1A and MAP2 display distinct behavior in terms of tubulin binding; they do not compete with each other, even when the polyglutamyl chains of tubulin are removed, indicating that they have distinct binding sites on tubulin. Binding of MAP1A and MAP1B to tubulin is also controlled by polyglutamylation and, although the modulation of MAP1B binding resembles that of MAP2, we found that polyglutamylation can exert a different mode of regulation toward MAP1A. Interestingly, although the affinity of the other MAPs tested so far decreases sharply for tubulins carrying long polyglutamyl chains, the affinity of MAP1A for these tubulins is maintained at a significant level. This differential regulation exerted by polyglutamylation toward different MAPs might facilitate their selective recruitment into distinct microtubule populations, hence modulating their functional properties.

Thoracic lymphangioma

Thoracic lymphangioma is a benign congenital condition that may involve any organ within the chest. Here, a case of intra thoracic isolated extramediastinal lymphangioma is reported. The child had respiratory distress from neonatal period. Surgery completely cured the patient. However, it is only the 3rd reported case in English literature.

Microtubule-associated protein 1B is a component of cortical Lewy bodies and binds alpha-synuclein filaments

Lewy bodies, neuropathological hallmarks of Parkinson's disease and dementia with Lewy bodies, comprise alpha-synuclein filaments and other less defined proteins. Characterization of Lewy body proteins that interact with alpha-synuclein may provide insight into the mechanism of Lewy body formation. Double immunofluorescence labeling and confocal microscopy revealed approximately 80% of cortical Lewy bodies contained microtubule-associated protein 1B (MAP-1B) that overlapped with alpha-synuclein. Lewy bodies were isolated using an immunomagnetic technique from brain tissue of patients dying with dementia with Lewy bodies. Lewy body proteins were resolved by polyacrylamide gel electrophoresis. Immunoblotting confirmed the presence of MAP-1B and alpha-synuclein in purified Lewy bodies. Direct binding studies revealed a high affinity interaction (IC(50) approximately 20 nm) between MAP-1B and alpha-synuclein. The MAP-1B-binding sites were mapped to the last 45 amino acids of the alpha-synuclein C terminus. MAP-1B also bound in vitro assembled alpha-synuclein fibrils. Thus, MAP-1B may be involved in the pathogenesis of Lewy bodies via its interaction with monomeric and fibrillar alpha-synuclein.

Evidence for suppression of cellular growth in vitro and selection against the indigenous mouse X chromosome in A9 cell hybrids after microcell-mediated transfer of an X from other mammalian species

Introduction of a human or Syrian hamster X chromosome (derived from BHK-191-5C cell hybrids) into tumorigenic mouse A9 cells via microcell fusion induced changes in cellular morphology and a retardation of cellular growth. The suppression of growth of the hybrids could be abolished, however, by daily changes of medium containing 20% serum. G-banding analysis showed the absence of a single, cytogenetically identifiable, indigenous X chromosome (marker Z) in two of four hybrid clones after an X chromosome was transferred from either hamster or human cells. All hybrids were tumorigenic when tested in nude mice. Together, these data suggest that the loss of the mouse X chromosome took place probably because of growth inhibitory effects imposed on hybrid cells due to the increase in X chromosome dosage. In addition, our results show a lack of association between the phenotype of cellular growth suppression in vitro and the phenotype of suppression of tumorigenicity in vivo.

Suppressor genes for malignant and anchorage-independent phenotypes located on human chromosome 9 have no dosage effects

We have previously shown that microcell-mediated transfer of a der(9)t(X;9) human chromosome (HSA), derived from human fibroblast strain GM0705, into the Syrian hamster cell line BHK-191-5C produced only near-tetraploid hybrids, although the recipient cell line contained a 1:1 ratio of near-diploid and near-tetraploid cells. However, the tumorigenicity and the anchorage independence could be suppressed in the near-tetraploid hybrids with one copy of the der(9)t(X;9) chromosome. The introduction of an HSA X chromosome did not suppress either of these phenotypes. We concluded that in addition to two suppressor genes, one for tumorigenicity and another for anchorage independence, HSA 9 might carry a third gene capable of inhibiting cellular growth in vitro, which had dosage effects. In the present study, keeping one copy of the der(9)t(X;9) chromosome, we have increased the hamster background chromosome number beyond hexaploid level by fusing two microcell-generated hybrid cell lines, where both malignant and anchorage-independent phenotypes were suppressed, with the parental malignant BHK-191-5C cell line. Tests with nude mice showed that hybrids containing one copy of the der(9)t(X;9) chromosome against the increased background of chromosomes of malignant parental origin were still suppressed for both phenotypes. These results suggest that the suppressor genes for malignancy and for anchorage independence have no dosage effects, in contrast to the suppressor gene(s) for cellular growth.

Lack of tumor suppression but induced loss of copies of indigenous chromosome 10 in vitro following microcell-mediated transfer of a deleted human der(9)t(X;9) chromosome to Syrian hamster BHK-191-5C cells

We have previously shown that microcell-mediated transfer of a der(9)t(X;9) chromosome, containing an almost complete human chromosome (HSA) 9 derived from the human fibroblast strain GM0705, into the Syrian hamster (Mesocricetus auratus) cell line BHK-191-5C suppressed the anchorage independence and tumorigenicity of the hybrids. Transfer of a normal HSA X did not have any effect on these phenotypes. Although the recipient cell line contained a 1:1 ratio of near-diploid and near-tetraploid cells, all hybrids retaining the der(9) chromosome were near-tetraploid, in contrast to hybrids retaining a normal X chromosome. In the present study, we have generated microcell hybrids by transferring another der(9)t(X;9) chromosome derived from the human fibroblast strain GM01429. This derivative chromosome contained a deletion on the short arm of HSA 9 and was also missing the distal part of the long arm of HSA 9 due to the involvement in a reciprocal (constitutive) translocation of this chromosome with HSA X. Cytogenetic analysis showed that all hybrid clones were near-tetraploid, confirming our previous finding. We also observed that the introduction of the deleted der(9) chromosome forced the hybrids to lose Syrian hamster chromosome 10. A soft agar test and nude mice assay indicated that none of the hybrids was suppressed for either anchorage independent growth or tumor formation. These data suggest that there is an antagonistic relationship between growth-promoting genes and antiproliferative genes. The observed dosage effects of both growth-promoting and growth-suppressing genes indicate that cellular growth may be a quantitative trait.

A new functional classification of tumor-suppressing genes and its therapeutic implications

Cell fusion studies have demonstrated that malignancy can be suppressed by a single dose of malignancy suppressor genes (MSGs), indicating that malignancy is a recessive phenotype. Correspondingly, it is widely believed that mutational inactivation of both alleles of tumor suppressor genes (TSGs), in familial and sporadic tumors, is the formal proof of the recessive nature of malignancy. Evidence presented here, however, shows that unlike MSGs, identified solely through cell fusion studies with no gene of this class yet cloned, many well-known TSGs have gene dosage effects and inhibit cellular growth in vitro. Moreover, homozygous inactivation of a growth-inhibitory TSG (GITSG) is not directly correlated with malignancy. An alternative interpretation is provided for the loss of wild-type alleles of these genes in the tumors. It is concluded that the MSGs and the GITSGs do not belong to the same class of genes. The functional classification of tumor-suppressing genes has important implications for developing effective cancer therapies.

Mobilisation of triacylglycerol stores

Triacylglycerol (TAG) is an energy dense substance which is stored by several body tissues, principally adipose tissue and the liver. Utilisation of stored TAG as an energy source requires its mobilisation from these depots and transfer into the blood plasma. The means by which TAG is mobilised differs in adipose tissue and liver although the regulation of lipid metabolism in each of these organs is interdependent and synchronised in an integrated manner. This review deals principally with the mechanism of hepatic TAG mobilisation since this is a rapidly expanding area of research and may have important implications for the regulation of plasma very-low-density lipoprotein metabolism. TAG mobilisation plays an important role in fuel selection in non-hepatic tissues such as cardiac muscle and pancreatic islets and these aspects are also reviewed briefly. Finally, studies of certain rare inherited disorders of neutral lipid storage and mobilisation may provide useful information about the normal enzymology of TAG mobilisation in healthy tissues.

Unguided percutaneous transthoracic fine needle aspiration cytology in the diagnosis of the peripheral lung lesions

Percutaneous transthoracic fine needle aspiration cytology (PTFNAC) of lung was done in 614 cases at the department of Pathology of Institute of Diseases of Chest and Hospital (IDCH), Dhaka, during the period from July 1994 to July 1996. A definite diagnosis was possible in 417 cases (78.83%). More than half (57.65%) of the cases were proved to have malignant diseases. PTFNAC detected malignant lesion in these patients for the first time as because no other investigation was able to establish the diagnosis. Diagnostic accuracy was 74%. Only 12 (1.95%) patients developed pneumothorax and mild haemoptysis occurred in 23 (3.74%) patients. So unguided PTFNAC is a simple, time saving, safe and inexpensive method of diagnosis of peripheral lung lesions.

Effect of antifungal agents on the binding of Candida albicans to immobilized amino acids and bovine serum albumin

In this study the effects of different antifungal agents on the binding of Candida albicans yeast cells to different supports were examined. Pre-treatment with amphotericin B or dithiothreitol (DTT) severely reduced the ability of C. albicans yeasts to bind to plastic, while the effects of pre-treatment with fluconazole, ketoconazole or flucytosine were less marked. Both DTT and amphotericin B reduced the binding of yeasts to bovine serum albumin (BSA) and amino acids at low concentrations, while the other antifungal agents were effective at concentrations several-fold higher than their MICs. These data suggest that DTT and amphotericin B affect the yeast cell wall components, and alter both hydrophobic interactions with plastic, and the more specific interactions with BSA and amino acids. By contrast, the effect of the azoles and flucytosine appears to be largely restricted to hydrophobic interactions.

Aspirochlorine: a highly selective and potent inhibitor of fungal protein synthesis

Aspirochlorine, a compound belonging to the gliotoxin family of compounds, exhibits antifungal and antibacterial activity but its mechanism of action remains unknown. In this study we show that aspirochlorine inhibits the pathogenic fungus Candida albicans by acting on fungal protein synthesis. The compound selectively inhibits cell-free protein synthesis when using a C. albicans system, but does not inhibit this synthesis in vitro when tested with bacterial and mammalian systems. Moreover, in intact C. albicans cells, aspirochlorine inhibits protein synthesis but does not inhibit chitin, DNA or glucan synthesis though at high concentrations some inhibition of RNA synthesis is observed. By contrast, in intact Bacillus subtilis cells, aspirochlorine did not inhibit protein, DNA, or cell wall synthesis though it significantly inhibited RNA synthesis. Furthermore, using heterologous systems (mammalian ribosomes and C. albicans cytosolic factors) the data suggest that the inhibitory action of aspirochlorine is not exerted through a direct interaction with C. albicans EF-1 or EF-2.

Comparisons of the effects of fungicidal and fungistatic antifungal agents on the morphogenetic transformation of Candida albicans

Eleven different antifungal agents were compared, and their ability to inhibit the morphogenetic transformation of Candida albicans was examined together with their ability to inhibit growth, as measured by MIC methodology. The fungicidal potential of each agent was also determined. Of the antifungal agents tested, only amphotericin B, mulundocandin and aculeacin inhibited the transformation at sub-MIC values; all three agents showed fungicidal activity at concentrations close to the MIC. All other agents were fungicidal only at concentrations much higher than the MIC and inhibited the morphogenetic transformation only at concentrations above the MIC. These data suggest that fungicidal antifungal agents are more likely to act by inhibiting the morphogenetic transformation of C. albicans while fungistatic agents are unable to do so and are more likely to block growth by budding.

MSI-78 Magainin Pharmaceuticals

Magainin is developing MSI-78, a 22-amino acid peptide, based on compounds discovered in frog skin, as a topical anti-infective. It has broad-spectrum activity, covering Gram-positive and -negative bacteria, anaerobic bacteria and Candida albicans. The compound also has potential for the treatment of impetigo and healing wounds with various infections. In July 1998, Magainin filed an NDA with the US FDA for the treatment of infections in diabetic foot ulcers [292671]. It expects to launch the drug during the second quarter of 1999 [275844]. A completed pivotal, 584 patient, phase III trial demonstrated statistical equivalence between MSI-78 and orally-administered ofloxacin, for the treatment of infection in diabetic foot ulcers. MSI-78 was comparable to ofloxacin with respect to the primary endpoint of clinical response of infection at day ten of treatment, and at subsequent time points through to day 28, and at follow-up [220339]. These data were confirmed by the company's second phase III trial for the same indication, for which successful results were announced in March 1997 [239274]. Additional data from this second trial, presented at the 37th Annual Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC), demonstrated that both drugs were comparable in terms of eradication rate of individual organisms and wound healing [264410]. Between 10% and 15% of wounds in patients treated with a combination of both drugs reached closure within four weeks. After six weeks, the closure rate increased to between 18% and 30%. This suggested that additional studies should be performed to evaluate the wound-healing effects further [275279]. The side-effects of both treatments were well-tolerated, although treatment with ofloxacin was associated with a significant excess of insomnia compared to MSI-78 [275844]. Further phase III trials are planned for treatment of surgical wounds, decubitus ulcers, venous stasis ulcers and infections associated with burns [173293]. The primary clinical endpoint is the cure of the infection and the secondary endpoint is the eradication of the organism. The first study has enrolled approximately 400 patients [195065]. The drug was also being developed for impetigo, but proved no better than placebo in phase III trials for the treatmentprimarily because 75% of controls showed clinical improvement as a result of better hygiene [293751]. Magainin is attempting to develop a recombinant process for commercial synthesis of MSI-78 to allow it to compete on price with conventional antibiotics [174944], [176153]. Magainin has a contract with Abbott for the manufacture of the drug [174944]. In February 1997, Magainin entered into a development, supply and distribution agreement in North America with SmithKline Beecham (SB) for Cytolex [234035]. Magainin has retained all rights to the drug outside of North America [275844], although it has also signed an agreement with Ambalal Sarabhai Enterprises (ASE) to commercialize MSI-78 (as Cytolex) in India [274544], [275556]. Analysts estimate the potential revenues of this compound, including off-label usage is between $200 and $250 million in the US and up to half as much again outside the US [191231].

Binding of Candida albicans to immobilized amino acids and bovine serum albumin

In this study, we examined the binding of Candida albicans synchronized yeast-phase cells to plastic, immobilized amino acids and bovine serum albumin (BSA) and quantified the binding by using an XTT tetrazolium salt assay and absorbance determination. Our results show that C. albicans binds efficiently and specifically to several nonpolar aliphatic amino acids and positively charged amino acids and to BSA immobilized on tissue culture plastic but not to polar uncharged, negatively charged, or aromatic amino acids. Adhesion of yeasts to immobilized amino acids was not affected by preincubation of cells with BSA, whereas binding to immobilized BSA was affected by preincubation of yeasts with alanine, proline, and leucine but not by arginine or lysine. The ability to distinguish the chirality of these amino acids was also examined by using both the D and L amino acid configurations, and the results show that C. albicans yeasts recognize only the L configuration of these amino acids. The observations that C. albicans specifically binds to certain amino acids indicate that these amino acids may prove useful tools for studying the binding interactions of C. albicans yeasts with host proteins such as components of the extracellular matrix.