Characterization of human myocardial fibroblasts immortalized by HPV16 E6--E7 genes

Development and characterization of a novel immortalized human vaginal fibroblast cell line for advanced applications in reproductive health

BACKGROUND

Reproductive health issues related to the vagina, face significant challenges due to the lack of standardized research models. Vaginal fibroblasts, which constitute approximately 55% of the vaginal wall's cellular composition, are crucial for tissue repair, remodelling, and reproductive health. These fibroblasts have broad applications in regenerative medicine and gynaecological treatments. Despite their importance, current research relies primarily on epithelial cells or primary vaginal fibroblasts, but primary fibroblasts are limited by their short lifespan, donor-to-donor variability, and susceptibility to senescence. Immortalized fibroblast lines offer a solution by extending the lifespan and enabling reproducible studies. However, a well-characterized immortalized human vaginal fibroblast line has not been established, highlighting the need for novel models to better understand and address vaginal-associated conditions.

METHODS

Primary human vaginal fibroblasts were immortalized via the lentiviral transfection of human telomerase reverse transcriptase. The resulting cell line was characterized through histological, immunofluorescent, RT-qPCR and flow cytometry analyses. Proliferation, senescence, gene expression, hormone responsiveness and genomic stability were assessed via quantitative polymerase chain reaction, transcriptome sequencing, gene set enrichment analysis, short tandem repeat profiling, and karyotype analysis.

RESULTS

The immortalized human vaginal fibroblasts (ihVFs) retained typical spindle-shaped fibroblast morphology and fibroblast-specific marker expression. Compared with primary vaginal fibroblasts, ihVF exhibited significantly reduced senescence, maintained sustained growth through extended culture passages, and preserved genetic stability. Transcriptome sequencing revealed high gene expression similarity between immortalized and primary fibroblasts, with no significant alterations in oncogenic pathways. PCR and immunofluorescent analyses revealed that ihVFs are responsive to estrogen and progesterone stimulation. Short tandem repeat analysis confirmed the novelty of the immortalized cell line, with no overlap with existing cell databases.

CONCLUSIONS

The novel ihVF cell line retains key phenotypic, functional, and genetic characteristics of primary vaginal fibroblasts, providing a stable, reproducible, and physiologically relevant model for reproductive health research. This cell line addresses the limitations of primary fibroblasts and has broad applications in tissue engineering, gynaecological disorder research, and drug screening, advancing our understanding of vaginal fibroblast biology and therapeutic interventions.

Virus-host coevolution in a persistently coxsackievirus B3-infected cardiomyocyte cell line

Coevolution of virus and host is a process that emerges in persistent virus infections. Here we studied the coevolutionary development of coxsackievirus B3 (CVB3) and cardiac myocytes representing the major target cells of CVB3 in the heart in a newly established persistently CVB3-infected murine cardiac myocyte cell line, HL-1(CVB3). CVB3 persistence in HL-1(CVB3) cells represented a typical carrier-state infection with high levels (10(6) to 10(8) PFU/ml) of infectious virus produced from only a small proportion (approximately 10%) of infected cells. CVB3 persistence was characterized by the evolution of a CVB3 variant (CVB3-HL1) that displayed strongly increased cytotoxicity in the naive HL-1 cell line and showed increased replication rates in cultured primary cardiac myocytes of mouse, rat, and naive HL-1 cells in vitro, whereas it was unable to establish murine cardiac infection in vivo. Resistance of HL-1(CVB3) cells to CVB3-HL1 was associated with reduction of coxsackievirus and adenovirus receptor (CAR) expression. Decreasing host cell CAR expression was partially overcome by the CVB3-HL1 variant through CAR-independent entry into resistant cells. Moreover, CVB3-HL1 conserved the ability to infect cells via CAR. The employment of a soluble CAR variant resulted in the complete cure of HL-1(CVB3) cells with respect to the adapted virus. In conclusion, this is the first report of a CVB3 carrier-state infection in a cardiomyocyte cell line, revealing natural coevolution of CAR downregulation with CAR-independent viral entry in resistant host cells as an important mechanism of induction of CVB3 persistence.

Wnt/frizzled signalling modulates the migration and differentiation of immortalized cardiac fibroblasts

AIMS

The Wnt/frizzled (Fzd) signal transduction cascade has been implicated in the proliferation, differentiation, and migration of many cell types, but the role of this pathway in cardiac fibroblast differentiation is not known. Our lab previously showed an up-regulation of Fzd-1 and -2 expression in myofibroblasts after myocardial infarction (MI), indicating a potential role for the Fzd receptor in fibroblast-myofibroblast differentiation. The present study was performed to further define the role of specific Wnt and Fzd proteins in the proliferation, migration, and differentiation of cardiac fibroblasts.

METHODS AND RESULTS

Because primary fibroblasts become senescent after a few passages and are difficult to transfect, we immortalized rat cardiac fibroblasts with telomerase [cardiac fibroblasts immortalized with telomerase (CFIT)]. Proliferation of CFIT was not significantly influenced by Wnt/Fzd signalling. The migration, however, was attenuated by all Wnt/Fzd combinations tested. Also, specific Wnt/Fzd combinations modulated the expression of the following myofibroblast markers: collagen Ialpha1, collagen III, fibronectin and its splice variants, and alpha-smooth muscle actin.

CONCLUSION

The results indicate that myofibroblast migration and differentiation, but not proliferation, can be modulated by interventions in Wnt/Fzd signalling. Therefore, Wnt/Fzd signalling may serve as a novel therapeutic target to ameliorate wound healing after MI.

Cardiac interstitial cells express GATA4 and control dedifferentiation and cell cycle re-entry of adult cardiomyocytes

Interstitial cells of the adult rat heart were characterized with respect to i) expression of cardiac markers of commitment and differentiation, ii) myogenic potential in vitro and iii) ability to modulate cardiomyocyte differentiation state. We demonstrate for the first time that fibroblasts and a proportion of pericytes in the adult rat heart express the transcription factor GATA4. This appears to be a peculiar property of the heart. Fibroblasts that are also derived from the splanchnopleuric mesoderm, such as those of the gut, or fibroblasts of different embryological origin, such as those of skin and skeletal muscle, lack this property. Of note, a nestin+/GATA4+ putative stem cell population is also detected in the adult heart. GATA4+ cardiac interstitial cells do not display myogenic potential in vitro. However, cardiac fibroblasts, but not skin fibroblasts, stimulate dedifferentiation of adult cardiomyocytes and their re-entry into the cell cycle in vitro, as demonstrated by the high number of cardiomyocytes expressing Ki67, phosphorylated histone H3 (H3P) and incorporating 5-bromodeoxiuridine (BrdU) in the co-cultures. In conclusion, cardiac fibroblasts have peculiar expression of myogenic transcription factors, a property that may have an impact for reprogramming these cells to the myogenic differentiation. In addition, they are able to modulate the behavior of adult cardiomyocytes, a property that may be used to promote dedifferentiation and proliferation of cardiac cells in the damaged myocardium.

Serum-derived hepatitis C virus infectivity in interferon regulatory factor-7-suppressed human primary hepatocytes

BACKGROUND/AIMS

The development of an efficient in vitro infection system for HCV is important in order to develop new anti-HCV strategy. Only Huh7 hepatocyte cell lines were shown to be infected with JFH-1 fulminant HCV-2a strain and its chimeras. Here we aimed to establish a primary hepatocyte cell line that could be infected by HCV particles from patients' sera.

METHODS

We transduced primary human hepatocytes with human telomerase reverse transcriptase together with human papilloma virus 18/E6E7 (HPV18/E6E7) genes or simian virus large T gene (SV40 T) to immortalize cells. We also established the HPV18/E6E7-immortalized hepatocytes in which interferon regulatory factor-7 was inactivated. Finally we analyzed HCV infectivity in these cells.

RESULTS

Even after prolonged culture HPV18/E6E7-immortalized hepatocytes exhibited hepatocyte functions and marker expression and were more prone to HCV infection than SV40 T-immortalized hepatocytes. The susceptibility of HPV18/E6E7-immortalized hepatocytes to HCV infection was further improved, in particular, by impairing signaling through interferon regulatory factor-7.

CONCLUSIONS

HPV18/E6E7-immortalized hepatocytes are useful for the analysis of HCV infection, anti-HCV innate immune response, and screening of antiviral agents with a variety of HCV strains.

Caspase-3-dependent apoptosis in cardiac myxoma: not associated with human papillomavirus or Epstein-Barr virus

Cardiac myxoma is the most common tumor of the heart, has a variable clinical presentation and immunohistochemical profile. Viral infections, such as herpes simplex virus, human papillomavirus (HPV), and Epstein-Barr virus (EBV), may play an important role in the causes of cardiac myxoma. This investigation will demonstrate caspase-3-dependent apoptosis in cardiac myxoma without HPV or EBV infection. This study included 15 patients with cardiac myxoma, who were treated with surgical excision of the lesion. Data were collected on detailed clinical parameters. Terminal deoxynucleotidyl transferase nick-end labeling assay, electrophoresis, and caspase-3 immunohistochemical studies were performed to characterize apoptosis. Genechip containing 39 subtypes was used to elucidate HPV; and polymerase chain reaction to detect LMP-1 gene of EBV. The patient population comprised of eight (53%) women and seven (47%) men. The mean age of patient participants was 45 years, with an age range of 30-70 years. All patient cases were sporadic myxomas rather than familial myxomas. The patient presentations included dyspnea (53%), asymptomatic (27%), stroke (7%), chest pain (7%), and fever (7%). All lesions were located in the left atrium. The individual patient cases of myxoma did not differ in location or clinical event in terms of pathological scores, such as vascular proliferation, inflammation, cellularity, hyaline, calcification, or thrombosis. Cardiac myxoma is characterized by apoptosis through caspase-dependent pathway. HPV or EBV was not detected in any of the study patient samples. In conclusion, no viral genomes of HPV or EBV were detected in these 15 patients. This study demonstrates that caspase-3-dependent apoptosis in cardiac myxoma is not dependent on concurrence of previous HPV and/or EBV infection.

Quantitative multiplex real-time PCR for the sensitive detection of interferon beta gene induction and viral suppression of interferon beta expression

Interferon-beta (IFN-beta) protein and activity can be detected by enzyme immunoassays and biological assays. However, precise quantification of low IFN-beta mRNA concentrations, which is advantageous for investigating IFN-beta gene expression in small tissue samples or during the early stage of a virus infection, remains a challenge. Therefore, we established a quantitative real-time PCR (qPCR) for IFN-beta and the housekeeping gene porphobilinogen deanimase (PBGD) in separated assays as well as in a multiplex procedure. Sensitivity for both the templates was less than 20 copies with an intra- and interassay variability of less than 5%. IFN-beta qPCR was utilized to optimize IFN-beta induction with dsRNA polyinosic-polycytidylic acid (poly I:C), delivered by a liposomal transfection agent for reproducible but low, non-cell-toxic IFN-beta concentrations. For studying coxsackievirus B3 (CVB3) interference with IFN-beta expression, CVB3 infected fibroblasts were induced with poly I:C. A significant reduction of IFN-beta mRNA but not PBGD mRNA was demonstrated 5 h after CVB3 infection, indicating a specific inhibition of IFN-beta expression by CVB3 on the mRNA level, in addition to previously reported effects on the translation/post-translation level. In conclusion, sensitive IFN-beta/PBGD multiplex qPCR proved to be a useful tool to study viral interaction with IFN-beta expression.

Immortalization without neoplastic transformation of human mesenchymal stem cells by transduction with HPV16 E6/E7 genes

hMSCs derived from bone marrow are useful as a species-specific cell culture system for studying cell lineage differentiation and tissue remodeling. However, hMSCs usually have a short in vitro life span due to replicative senescence. We therefore used a high dose of retroviral vector LXSN-16E6E7 to transduce hMSCs of an aging donor and obtained an actively proliferating cell line, designated KP-hMSCs, which expressed HPV16 E6/E7 mRNA. Whereas parental hMSCs ceased to grow after 30 PDs, KP-hMSCs could be propagated beyond 100 PDs. With culture procedures to avoid selection pressure and crowded cell growth, KP-hMSCs showed no signs of neoplastic transformation as examined by soft-agar anchorage-independent growth and NOD-SCID mouse tumorigenicity assays. KP-hMSCs gave similar cytofluorimetric profiles of 31 CD markers to those of the parental primary hMSCs, except with some morphologic changes and expansion of an originally very minor CD34(dim)CD38(+)CD50+ cell population. Upon exposure to specific stimulating conditions in vitro, KP-hMSCs could respond and differentiate along the mesenchymal (bone, fat and cartilage) and nonmesenchymal (neuron) cell lineages. Our results indicated that hMSCs could be immortalized by transduction with HPV16 E6/E7, maintained without neoplastic transformation by careful culture procedures and thus useful for stem cell research and clinical application.

Distinct patterns of gene expression induced by viral oncogenes in human embryonic brain cells

1. The limited lifespan of human embryonic brain (HEB) cells hampers their therapeutic use for the treatment of neurodegenerative diseases. 2. Stable expression of SV40 large T antigen (LTA) or E6E7 genes of human papillomavirus type 16 significantly increased the lifespan of HEB cells, but did not induce transformation. 3. The extended lifespan was triggered by changes in the expression of antiproliferative genes. We found that changes in the expression of p16 (INK4a), p21 (WAFI), p14ARF, and p53 tumor suppressor gene, but not p27 (Kip1), differed between the LTA- and E6E7-HEB cells. 4. Despite the induction of p53 RNA, p53 protein was undetectable in HEB-E6E7 cells. In contrast, p53 protein was increased in HEB-LTA cells as compared with the parental cells. Expression of p21 was, however, reduced in both cell lines. 5. While p16 was decreased in HEB-E6E7 cells, its expression was increased in HEB-LTA cells. 6. Despite these changes, HEB cell lines showed neuron-like morphological differentiation when the intracellular level of cAMP was elevated. 7. This suggests that the mechanisms for inducing neuronal differentiation are still intact in HEB-E6E7 and HEB-LTA cells. More importantly, differentiation signals can override the effects of viral oncogenes in HEB cells.

Human articular chondrocytes immortalized by HPV-16 E6 and E7 genes: Maintenance of differentiated phenotype under defined culture conditions

OBJECTIVE

To establish an immortalized normal human articular chondrocyte line which could be useful for a better understanding of cell molecular mechanisms relevant for the development of new therapeutic approaches in rheumatic diseases.

DESIGN

Chondrocytes from human adult articular healthy cartilage were transfected in primary culture with a plasmid containing two human papilloma virus type 16 (HPV-16) early function genes: E6 and E7, using the highly efficient cationic liposome-mediated (lipofection) procedure. The transfection was verified by reverse transcriptase-polymerase chain reaction analysis of E7 mRNA and by immunofluorence localization of the E7 protein in the cell cytoplasm. The established chondrocyte cell line was examined in monolayer and in two culture conditions that were described to re-induce differentiated characteristics: culturing in a serum-free defined medium supplemented with an insulin-containing serum substitute and seeding on a hyaluronan-based non-woven structured biomaterial. The expression of markers characteristic of cartilage was shown in the mRNA by reverse transcriptase-polymerase chain reaction. Immunohistological staining and Western blotting analysis were performed to evaluate type II collagen synthesis. Proteoglycans deposition was detected by Alcian Blue staining. A Field Emission In Lens Scanning Microscopy was used to look at the morphology of the immortalized cells at very high magnification.

RESULTS

Normal human articular chondrocytes were efficiently transfected leading to the establishment of an immortalized cell line as confirmed by HPV-16 E7 mRNA and protein detection. These cells were able to re-express type II collagen both at mRNA and protein levels under the two defined cultured conditions we used, still maintaining type I collagen expression. Collagen IX mRNA was present only in early primary culture while collagen type X and aggrecan transcripts were always detected. Alcian Blue staining showed a proteoglycan-rich matrix production. The ultrastructural analysis of the immortalized cells revealed that their morphology strictly resembled that of normal chondrocytes.

CONCLUSIONS

The cell line that we obtained may be a useful tool for increasing our knowledge of the genetic and biochemical events involved in the processes of cartilage growth and differentiation. Moreover, it appears to be a suitable model for pharmacological and toxicological studies related to rheumatic diseases relevant to humans.