The actin-binding protein caldesmon is in spleen and lymph nodes predominately expressed by smooth-muscle cells, reticular cells, and follicular dendritic cells

Transmembrane protein 119 is neither a specific nor a reliable marker for microglia

Microglia are the resident innate immune cells of the central nervous system (CNS) parenchyma. To determine the impact of microglia on disease development and progression in neurodegenerative and neuroinflammatory diseases, it is essential to distinguish microglia from peripheral macrophages/monocytes, which are eventually equally recruited. It has been suggested that transmembrane protein 119 (TMEM119) serves as a reliable microglia marker that discriminates resident microglia from blood-derived macrophages in the human and murine brain. Here, we investigated the validity of TMEM119 as a microglia marker in four in vivo models (cuprizone intoxication, experimental autoimmune encephalomyelitis (EAE), permanent filament middle cerebral artery occlusion (fMCAo), and intracerebral 6-hydroxydopamine (6-OHDA) injections) as well as post mortem multiple sclerosis (MS) brain tissues. In all applied animal models and post mortem MS tissues, we found increased densities of ionized calcium-binding adapter molecule 1⁺ (IBA1⁺ ) cells, paralleled by a significant decrease in TMEM119 expression. In addition, other cell types in peripheral tissues (i.e., follicular dendritic cells and brown adipose tissue) were also found to express TMEM119. In summary, this study demonstrates that TMEM119 is not exclusively expressed by microglia nor does it label all microglia, especially under cellular stress conditions. Since novel transgenic lines have been developed to label microglia using the TMEM119 promotor, downregulation of TMEM119 expression might interfere with the results and should, thus, be considered when working with these transgenic mouse models.

Caldesmon: Biochemical and Clinical Implications in Cancer

Caldesmon, an actin-binding protein, can inhibit myosin binding to actin and regulate smooth muscle contraction and relaxation. However, caldesmon has recently attracted attention due to its importance in cancer. The upregulation of caldesmon in several solid cancer tissues has been reported. Caldesmon, as well as its two isoforms, is considered as a biomarker for cancer and a potent suppressor of cancer cell invasion by regulating podosome/invadopodium formation. Therefore, caldesmon may be a promising therapeutic target for diseases such as cancer. Here, we review new studies on the gene transcription, isoform structure, expression, and phosphorylation regulation of caldesmon and discuss its clinical implications in cancer.

Interferon-γ induces biphasic changes in caldesmon localization as well as adherens junction organization and expression in HUVECs

Endothelial barrier dysfunction leads to increased endothelial permeability and is an early step in the development of vascular inflammatory diseases such as atherosclerosis. Interferon-γ (IFN-γ), a proinflammatory cytokine, is known to cause increased endothelial permeability. However, the mechanisms by which IFN-γ disrupts the endothelial barrier have not been clarified. This study aimed to investigate how IFN-γ impairs the endothelial barrier integrity by specifically examining the roles of caldesmon, adherens junctions (AJs) and p38 mitogen-activated protein (MAP) kinase in IFN-γ-induced endothelial barrier dysfunction. IFN-γ exhibited a biphasic effect on caldesmon localization and both the structural organization and protein expression of AJs. In the early phase (4-8 h), IFN-γ induced the formation of peripheral caldesmon bands and discontinuous AJs, while AJ protein expression was unchanged. Interestingly, IFN-γ also stimulated caldesmon phosphorylation, resulting in actin dissociation from caldesmon at 8 h. Conversely, changes seen in the late phase (16-24 h) included cytoplasmic caldesmon dispersal, AJ linearization and junctional area reduction, which were associated with reduced membrane, cytoskeletal and total AJ protein expression. In addition, IFN-γ enhanced myosin binding to caldesmon at 12 h and persisted up to 24 h. Furthermore, inhibition of p38 MAP kinase by SB203580 did not reverse either the early or late phase changes observed. These data suggest that IFN-γ may activate signaling molecules other than p38 MAP kinase. In conclusion, our findings enhance the current understanding of how IFN-γ disrupts endothelial barrier function and reveal potential therapeutic targets, such as caldesmon and AJs, for the treatment of IFN-γ-associated vascular inflammatory diseases.

Use of Smooth Muscle Myosin Heavy Chain as an Effective Marker of Follicular Dendritic Cells

Smooth muscle myosin heavy chain (SMMHC) is a major structural component of the contractile apparatus in smooth muscle cells. Even though it is considered a relatively specific marker for terminal smooth muscle cell differentiation, expression in other cell types such as follicular dendritic cells (FDCs) has rarely been reported. To determine whether SMMHC represents an effective FDC marker in lymphoid tissues, we compared the immunohistochemical results for SMMHC with those of the traditional FDC markers podoplanin (D2-40) and CD21. Paraffin sections of 44 lymphoid tissues were analyzed, including 31 cases of follicular hyperplasia, 6 cases of follicular lymphoma, 2 cases of peripheral T-cell lymphoma, 3 cases of diffuse large B-cell lymphoma arising in follicular lymphoma, 1 case of nodular sclerosis classical Hodgkin lymphoma, and 1 case of small lymphocytic lymphoma. There was no statistically significant difference between the number of SMMHC-positive and D2-40-positive or CD21 lymph nodes (P>0.05). The extent and intensity of SMMHC-positive FDCs were similar to those of D2-40-positive FDCs (P=0.127 and 0.733, respectively), but significantly lower compared with those of CD21 cells (P=0.009 and 0.00002, respectively). However, in contrast to CD21 which was also positive in some germinal center B cells, SMMHC expression was restricted to FDCs. Our results indicate that SMMHC is an excellent marker for FDCs and can be particularly helpful in demonstrating the underlying architecture in lymphoid processes.

Myofibroblastic reaction is a common event in metastatic disease of breast carcinoma: a descriptive study

BACKGROUND

The modification of stromal components with the disappearance of CD34 positive fibrocytes and by contrast the acquisition of smooth-muscle actin positive myofibroblasts is a frequent event in breast carcinomas but has been little studied in its metastatic sites. Therefore, the aim of the present study is to examine the stromal expression of CD34 and SMA in lymph node and liver metastases which are two of the most frequent metastatic breast cancer sites.

METHODS

The distribution of CD34 fibrocytes and SMA myofibroblasts has been studied by immunohistochemistry in 41 lymph node and 36 liver metastases from patients with invasive carcinoma of no special type.

RESULTS

No CD 34 fibrocytes were noted in the stroma of metastasis. By contrast, smooth-muscle actin stromal expression was observed in 95.1% of lymph node and 97.2% of liver metastases, independently of histological features of tumours.

CONCLUSIONS

Myofibroblasts represent a major and constant component in the metastatic tumoral stroma of breast carcinoma highlighting that these cells could play an active role in tumour cells proliferation and spread.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_196.

Histochemical localization of caldesmon in the CNS and ganglia of the mouse

The author has recently reported the distribution of the cytoskeleton-associated protein caldesmon in spleen and lymph nodes detected with different antibodies against caldesmon (J Histochem Cytochem 58:183-193, 2010). Here the author reports the distribution of caldesmon in the CNS and ganglia of the mouse using the same antibodies. Western blot analysis of mouse brain and spinal cord showed the preponderance of l-caldesmon and suggested at least two l-caldesmon isoforms in the brain. Immunostaining revealed the predominant reactivity of smooth muscle cells and cells resembling pericytes of many large and small blood vessels, ependymocytes, and secretory cells of the pineal gland and pituitary gland. Neuronal perikarya and neuropil in general displayed no or weak immunoreactivity, but there was stronger labeling of neuronal perikarya in dorsal root and trigeminal ganglia. In the brain, staining of the neuropil was stronger in the molecular layers of the dentate gyrus and cerebellum. Results show that caldesmon is expressed in many different cell types in the CNS and ganglia, consistent with the notion that l-caldesmon is ubiquitously expressed, but it appears most concentrated in smooth muscle cells, pericytes, epithelial cells, secretory cells, and neuronal perikarya in dorsal root and trigeminal ganglia.

Analysis of differential proteomes of induced pluripotent stem cells by protein-based reprogramming of fibroblasts

The recent generation of induced pluripotent stem (iPS) cells represents a novel opportunity to complement embryonic stem (ES) cell-based approaches. iPS cells can be generated by viral transduction of specific transcription factors, but there is a potential risk of tumorigenicity by random retroviral integration. We have generated novel iPS (sFB-protein-iPS) cells from murine dermal fibroblasts (FVB-sFB) that have ES cell characteristics, using ES cell-derived cell extracts instead of performing viral transduction. Notably, only cell extracts from an ES cell line (C57-mES) on the C57/BL6 background generated iPS cells in our protocol-not an ES cell line (E14-mES) on the 129 background. Hypothesizing that determining the differences in these 2 mES cell lines will provide vital insight into the reprogramming machinery, we performed proteomic and global gene expression analysis by iTRAQ and mRNA microarray, respectively. We observed that pluripotent ES cells and ES cell extract-derived iPS cells had differential proteomes and global gene expression patterns. Notably, reprogramming-competent C57-mES cells highly expressed proteins that regulate protein synthesis and metabolism, compared with reprogramming-incompetent 129-mES cells, suggesting that there is a threshold that protein synthetic machinery must exceed to initiate reprogramming.