Transdifferentiation of Endothelial and Renal Tubular Epithelial Cells into Myofibroblast-Like Cells under in vitro Conditions: A Morphological Analysis

Sewing up the wounds : The epithelial morphogenesis as a central mechanism of calcaronean sponge regeneration

Sponges (Porifera) demonstrate prominent regeneration abilities and possess a wide variety of mechanisms, used during this process. In the current study, we combined in vivo observations with histological, immunohistochemical, and ultrastructural technics to elucidate the fine cellular mechanisms of the regeneration in the calcareous sponge Leucosolenia cf. variabilis. The regeneration of Leucosolenia cf. variabilis ends within 4-6 days. The crucial step of the process is the formation of the transient regenerative membrane, formed by the epithelial morphogenesis-spreading of the intact exopinacoderm and choanoderm. The spreading of the choanoderm is accompanied by the transdifferentiation of the choanocytes. The regenerative membrane develops without any contribution of the mesohyl cells. Subsequently, the membrane gradually transforms into the body wall. The cell proliferation is neither affected nor contributes to the regeneration at any stage. Thus, Leucosolenia cf. variabilis regeneration relies on the remodeling of the intact tissues through the epithelial morphogenesis, accompanied by the transdifferentiation of some differentiated cell types, which makes it similar to the regeneration in homoscleromorphs and eumetazoans.

Effector mechanisms of rejection

Organ transplantation appears today to be the best alternative to replace the loss of vital organs induced by various diseases. Transplants can, however, also be rejected by the recipient. In this review, we provide an overview of the mechanisms and the cells/molecules involved in acute and chronic rejections. T cells and B cells mainly control the antigen-specific rejection and act either as effector, regulatory, or memory cells. On the other hand, nonspecific cells such as endothelial cells, NK cells, macrophages, or polymorphonuclear cells are also crucial actors of transplant rejection. Last, beyond cells, the high contribution of antibodies, chemokines, and complement molecules in graft rejection is discussed in this article. The understanding of the different components involved in graft rejection is essential as some of them are used in the clinic as biomarkers to detect and quantify the level of rejection.

SU6668 suppresses proliferation of triple negative breast cancer cells through down-regulating MTDH expression

Background

The multiple tyrosine kinase inhibitors SU6668 have a promising therapeutic effect on the progression of hematological malignancies and some solid tumors. Here, we determined its effect on triple negative breast cancer (TNBC) cells and explored the potential molecular mechanism.

Methods

In this study, MDA-MB-231 cells were treated with SU6668 (15 μM, 30 μM) for 72 h and the change of proliferation was examined by MTT and tablet cloning. DNA ploidy was detected by flow cytometric analysis with PI staining. Double-label immunofluorescence method was used to detect the expression and distribution of MTDH proteins. VEGFR2, HIF-1α, MTDH, E-cadhrein, and SMA expressions were detected by Western bolt assay.

Results

This study showed that SU6668 inhibited the proliferation and induced polyploidization of MDA-MB-231 cells in a dose dependent form. SU6668 exposure increased the distribution of MTDH in cytoplasm and decreased its distribution in nuclei. After the treatment of SU6668, VEGFR2, HIF-1α, MTDH and SMA proteins were down-regulated, while E-cadhrein was up-regulated in MDA-MB-231 cells.

Conclusions

In conclusion, SU6668 exposure maybe induces polyploidization, inhibit EMT and influence the expression of MTDH, which suppresses the proliferation in TNBC cells. MTDH is a key signal protein in downstream of VEGF/HIF-1αpathway in MDA-MB-231 cells, which may be used as the potential target in the treatment of TNBC.

Recapitulation of fibromatosis nodule by multipotential stem cells in immunodeficient mice

Musculoskeletal fibromatosis remains a disease of unknown etiology. Surgical excision is the standard of care, but the recurrence rate remains high. Superficial fibromatosis typically presents as subcutaneous nodules caused by rapid myofibroblast proliferation followed by slow involution to dense acellular fibrosis. In this study, we demonstrate that fibromatosis stem cells (FSCs) can be isolated from palmar nodules but not from cord or normal palm tissues. We found that FSCs express surface markers such as CD29, CD44, CD73, CD90, CD105, and CD166 but do not express CD34, CD45, or CD133. We also found that FSCs are capable of expanding up to 20 passages, that these cells include myofibroblasts, osteoblasts, adipocytes, chondrocytes, hepatocytes, and neural cells, and that these cells possess multipotentiality to develop into the three germ layer cells. When implanted beneath the dorsal skin of nude mice, FSCs recapitulated human fibromatosis nodules. Two weeks after implantation, the cells expressed immunodiagnostic markers for myofibroblasts such as α-smooth muscle actin and type III collagen. Two months after implantation, there were fewer myofibroblasts and type I collagen became evident. Treatment with the antifibrogenic compound Trichostatin A (TSA) inhibited the proliferation and differentiation of FSCs in vitro. Treatment with TSA before or after implantation blocked formation of fibromatosis nodules. These results suggest that FSCs are the cellular origin of fibromatosis and that these cells may provide a promising model for developing new therapeutic interventions.

Fibromatosis stem cells rather than bone-marrow mesenchymal stem cells recapitulate a murine model of fibromatosis

Palmar fibromatosis is a benign fibroproliferative tumor of unknown etiology, with a high rate of recurrence after excision. The offending cells of palmar fibromatosis are myofibroblasts and the cellular origin of other myofibroblasts has previously been reported to be the bone marrow. However, further clarification of the relationship between bone marrow precursors and palmar fibromatosis is required. Stem cells (SCs) are known to exist in various tissues, but whether SCs can be isolated from fibromatosis tissue is still unclear. The purpose of this study was to isolate and identify stem cells from human palmar fibromatosis, and to evaluate the differences in the differentiation and fibrogenic capacities of bone marrow stem cells (BMSCs) and fibromatosis-derived stem cells (FSCs). We found that FSCs had better fibrogenic differentiation potential than BMSCs, whereas BMSCs had better adipogenic and chondrogenic differentiation capacities. Treatment with transforming growth factor-β1 increased the expression of α-smooth muscle actin, and types III and I collagen significantly more in FSCs than in BMSCs. An in vivo study further confirmed the results of fibrogenesis and suggested that FSCs can recapitulate the fibromatosis nodule. In summary, their myofibroblastic differentiation both in vivo and in vitro makes FSCs a potential cell source for future applications in murine models of fibromatosis or fibrogenesis.

Fibronexus junctions associated with in vivo human endothelium

The fibronexus is recognized as a characteristic marker of the myofibroblast. However, it is not completely specific for this cell, having been seen in aortic smooth muscle (in attenuated form) and endothelium in experimental animals. This paper documents fibronexus junctions in human in vivo endothelium. Ultrastructural observations were made on the vasculature of a desmoplastic and focally neurotropic malignant melanoma. Cross-sectioned fibronectin fibrils were seen outside the stromal surface of the endothelial plasmalemma. Often, they were positioned directly opposite the actin-filament bundles in the peripheral cytoplasm. Neoplastic and in vitro cultured cells apart, endothelium is the only nonmyofibroblastic cell type to show well-developed fibronexus junctions. Mostly, they have been documented in aortic endothelium in experimental animals, where they possibly constitute an adaptation to hemodynamic stress, and where they might more securely anchor endothelium on to subjacent connective tissue. They might also function as mechanotransducers of extracellular stress in the extracellular milieu. The present observations constitute a further, rare example of endothelium-associated fibronexuses in reactive human vessels.

Caveolin-1-/- null mammary stromal fibroblasts share characteristics with human breast cancer-associated fibroblasts

Recently, we reported that human breast cancer-associated fibroblasts show functional inactivation of the retinoblastoma (RB) tumor suppressor and down-regulation of caveolin-1 (Cav-1) protein expression. However, it remains unknown whether loss of Cav-1 is sufficient to confer functional RB inactivation in mammary fibroblasts. To establish a direct cause-and-effect relationship, mammary stromal fibroblasts (MSFs) were prepared from Cav-1(-/-) null mice and subjected to phenotypic analysis. Here, we provide evidence that Cav-1(-/-) MSFs share many characteristics with human cancer-associated fibroblasts. The Cav-1(-/-) MSF transcriptome significantly overlaps with human cancer-associated fibroblasts; both show a nearly identical profile of RB/E2F-regulated genes that are up-regulated, which is consistent with RB inactivation. This Cav-1(-/-) MSF gene signature is predictive of poor clinical outcome in breast cancer patients treated with tamoxifen. Consistent with these findings, Cav-1(-/-) MSFs show RB hyperphosphorylation and the up-regulation of estrogen receptor co-activator genes. We also evaluated the paracrine effects of "conditioned media" prepared from Cav-1(-/-) MSFs on wild-type mammary epithelia. Our results indicate that Cav-1(-/-) MSF "conditioned media" is sufficient to induce an epithelial-mesenchymal transition, indicative of an invasive phenotype. Proteomic analysis of this "conditioned media" reveals increased levels of proliferative/angiogenic growth factors. Consistent with these findings, Cav-1(-/-) MSFs are able to undergo endothelial-like transdifferentiation. Thus, these results have important implications for understanding the role of cancer-associated fibroblasts and RB inactivation in promoting tumor angiogenesis.

Rosiglitazone increases PPARgamma in renal tubular epithelial cells and protects against damage by hydrogen peroxide

BACKGROUND/AIMS

Thiazolidinediones (TZD) are ligands known to bind to and activate the nuclear peroxisome proliferator-activated receptor gamma (PPARgamma), and are currently used as insulin sensitizers in type 2 diabetes. Recently, several studies have shown that TZD may have a role in renal protection in various experimental models. However, the precise mechanisms by which TZD may possibly affect tubular cell survival after injury remain unclear. We studied the influence of the TZD rosiglitazone on PPARgamma expression and cell function with cellular damage induced by increasing hydrogen peroxide (H2O2) concentrations in bovine renal tubular epithelial cells (bEPC) to determine whether rosiglitazone is cytoprotective under these conditions.

METHODS

bEPC were cultured in the presence of H2O2 after pretreatment with or without 25 microM rosiglitazone. The expression of PPARgamma mRNA and protein were determined using RT-PCR or Western blots, respectively, after 6 and 24 h. Some cells also received actinomycin D or cycloheximide and PPARgamma protein expression was tested. Proliferation rates of cultures were compared after 15 h and after a recovery phase of 6 days. Apoptosis was assessed by DNA fragmentation. Nuclear PPARgamma activity was evaluated by electrophoretic mobility shift assay (EMSA), and the cellular location was detected using immunofluorescence.

RESULTS

Incubation of bEPC with H2O2 concentrations up to 0.75 mM did not induce apoptosis as tested by DNA fragmentation assay, but significantly and dose-dependently reduced proliferation 15 h after injury as measured by [3H]thymidine incorporation. 25 microM rosiglitazone alone also reduced proliferation and failed to attenuate the H2O2-mediated inhibition of proliferation. However, rosiglitazone facilitates recovery of tubular cells 6 days after H2O2-induced injury. Rosiglitazone (25 microM) increased PPARgamma mRNA and protein expression in bEPC in the absence of H2O2. Rosiglitazone failed to increase PPARgamma mRNA in cells with oxidative stress, but Western blots revealed an increase in cellular PPARgamma protein content in the presence of rosiglitazone and increasing concentrations of H2O2. This increase in PPARgamma protein content was almost totally abolished in the presence of 1 microg/ml cycloheximide, but was only marginally reduced by 0.1 microg/ml actinomycin D. EMSA showed a robust increase in nuclear PPARgamma protein binding in vitro to its consensus site after rosiglitazone whereas H2O2 treatment reduced PPARgamma activation. Rosiglitazone treatment of cells with oxidative stress preserved nuclear transactivation of PPARgamma.

CONCLUSIONS

Rosiglitazone increases the PPARgamma content in bEPC after H2O2-induced injury by a posttranscriptional mechanism. Activation of PPARgamma facilitates the long-term recovery of tubular cells 6 days after oxidative injury, but had no effect on the attenuated proliferation shortly after injury. TZD cannot prevent oxidative injury to tubular cells, but may be important mediators to enhance cellular recovery after oxidative stress.

Inflammatory cytokines induce the transformation of human dermal microvascular endothelial cells into myofibroblasts: a potential role in skin fibrogenesis

BACKGROUND

The myofibroblast plays a central role in wound contraction and in the pathology of fibrosis. The origin(s) of this important cell type in skin has not been firmly established.

METHODS

Human epithelioid dermal microvascular endothelial cells (HDMEC) were isolated from foreskin tissue and maintained in cell culture. The transformation of epithelioid HDMEC into myofibroblasts (EMT) was induced by the inflammatory cytokines interleukin-1beta (IL-1beta) or tumour necrosis factor-alpha (TNF-alpha), and the transformed cells were characterized by electron microscopy, immunohistochemistry and quantitative RT-PCR.

RESULTS

After short-term exposure to IL-1beta or TNF-alpha (<3 days), EMT was reversible; after long-term exposure (>10 days), EMT was permanent. The transformed cells were identified as myofibroblasts by cytoplasmic microfilaments with dense bodies and attachment plaques, by the expression of alpha-smooth muscle actin, type I collagen and calponin, and by quantitative RT-PCR gene expression of type I collagen and alpha-smooth muscle actin.

CONCLUSIONS

Long-term exposure to TNF-alpha or IL-1beta induced the permanent transformation of HDMEC into myofibroblasts in cell culture. A similar transformation following chronic inflammatory stimulation in vivo may explain one source of myofibroblasts in skin fibrogenesis.

Renal cell carcinoma associated with prominent angioleiomyoma-like proliferation: Report of 5 cases and review of the literature

Five cases of renal cell carcinoma of clear cell type are presented, Fuhrmann's grade 2, associated with a peculiar stromal proliferation having angioleiomyoma-like features. This proliferation was particularly prominent at the interphase between the tumor edge and the surrounding normal tissues, in which it acquired the configuration of a tumor capsule. Four similar cases were taken from the literature. We postulate that this angioleiomyoma-like change is a tumor epiphenomenon and that it represents yet another manifestation of the well-documented capacity of renal cell carcinoma to induce vascular proliferation, probably through the secretion of angiogenic and other growth factors by the tumor cells.