John Yeuk-Hon Chan

Cardiac telocytes were decreased during myocardial infarction and their therapeutic effects for ischaemic heart in rat.

Recently, cardiac telocytes were found in the myocardium. However, the functional role of cardiac telocytes and possible changes in the cardiac telocyte population during myocardial infarction in the myocardium are not known. In this study, the role of the recently identified cardiac telocytes in myocardial infarction (MI) was investigated. Cardiac telocytes were distributed longitudinally and within the cross network of the myocardium, which was impaired during MI. Cardiac telocytes in the infarction zone were undetectable from approximately 4 days to 4 weeks after an experimental coronary occlusion was used to induce MI. Although cardiac telocytes in the non‐ischaemic area of the ischaemic heart experienced cell death, the cell density increased approximately 2 weeks after experimental coronary occlusion. The cell density was then maintained at a level similar to that observed 1–4 days after left anterior descending coronary artery (LAD)‐ligation, but was still lower than normal after 2 weeks. We also found that simultaneous transplantation of cardiac telocytes in the infarcted and border zones of the heart decreased the infarction size and improved myocardial function. These data indicate that cardiac telocytes, their secreted factors and microvesicles, and the microenvironment may be structurally and functionally important for maintenance of the physiological integrity of the myocardium. Rebuilding the cardiac telocyte network in the infarcted zone following MI may be beneficial for functional regeneration of the infarcted myocardium.

Alterations in expression and structure of the DNA repair gene XRCC1.

The repair-associated gene XRCC1 was previously cloned by complementing the hamster mutant EM9, which has a high rate of spontaneous SCE and hypersensitivity to DNA damaging agents. In analyzing XRCC1 gene expression, similar levels of steady-state mRNA were found in normal cells, Blooms syndrome cells with altered SCE, and in squamous carcinoma cells with differential X-ray sensitivity. An EcoRI restriction fragment-length polymorphism previously identified in XRCC1 did not correlate with the repair phenotypes of these cells. The mRNA of XRCC1 decreased to 20-40% after treatment of cells with a DNA damaging agent. XRCC1 also showed tissue specific expression in rats. The mRNA levels were high in testis (7-8 fold), ovary (3-4 fold) and brain (4-5 fold), when compared with those in intestine, liver and spleen (1-2 fold). These data and the high levels of XRCC1 protein detected in testis indicate that XRCC1 may play an important role in DNA processing during meiogenesis and recombination in germ cells.

TRGV and TRDV repertoire distribution and clonality of T cells from umbilical cord blood

Umbilical cord blood (CB) has been used as a valuable source of hematopoietic stem cells for allogeneic transplantation, specific CTL response and immunotherapy for decades. We previously analyzed the distribution and clonality of T-cell receptor alpha and beta variable region (TRAV) and (TRBV) of the subfamily T cell receptors in T cells from umbilical cord blood. Recent data indicated that gammadelta(+) T cells may play an important role in mediating the graft versus leukemia effect after stem cells transplantation and in anti-cancer response. In order to further characterize the repertoire of CB T-cells, the frequency of alphabeta(+) and gammadelta(+) T cells were examined in CB by FACS. The CDR3 size of 4 TRGV and 8 TRDV subfamily genes were analyzed in mononuclear cells (MCs) from 16 CB samples, using RT-PCR and genescan technique. To determine the expression level of TRGV subfamily genes, we performed quantitative analysis of TRGVI-III subfamilies by real-time PCR. Low percentage of CD3(+)TCRgammadelta(+) cells was observed in CB. The frequency of expression in TRGVI, TRGVII and TRGVIII in CBMCs was 93.75%, 81.25% and 56.25%, respectively. The mean value of the number of expressed TRDV subfamilies in CBMCs is higher than that from adult peripheral blood (PB) group. The frequently expressed members in CB were TRDV1 (100%), TRDV2 (93.75%), TRDV8 (93.75%) and TRDV3 (81.25%), respectively. The frequencies of TRDV5 and TRDV8 in CBMCs were significantly higher than those from PBMCs. Most of the PCR products of TRGV and TRDV subfamilies from 10 CB samples displayed polyclonal rearrangement pattern, whereas one or two PCR products from 6 CB samples showed oligoclonality or biclonality. In contrast, PCR products from 9 of 10 adult healthy controls contained at least an oligoclonal peak in different TRGV or TRDV subfamilies respectively. The pattern of TRGV subfamily expression level in CBMCs was TRGVI>TRGVIII>TRGVII, and in contrast, TRGVII>TRGVI>TRGVIII was found in PBMCs. In conclusion, our results indicate polyclonal and more diverse TRDV segment usage in CB gammadelta(+) T-cells. The pattern of TRGV expression levels in CB T cells was found to be quite different from the one in PB T cells. These findings are apparently the first report regarding the repression pattern of TRGV repertoire in CB. It also provides a detailed profile of the global TRGV and TRDV repertoire and TRGVI-III expression levels in cord blood T cells in Chinese subjects. The biological significance of the differences observed between CB and PB is at present obscure. However, this study will definitively contribute to understand the cellular immune features better and to exploit more efficiently the therapeutic potentials of CB.

BDNF-mediated migration of cardiac microvascular endothelial cells is impaired during ageing.

This study indicates that brain‐derived neurotrophic factor (BDNF) can promote young cardiac microvascular endothelial cells (CMECs) to migrate via the activation of the BDNF‐TrkB‐FL‐PI3K/Akt pathway, which may benefit angiogenesis after myocardial infarction (MI). However, the ageing of CMECs led to changes in the expression of receptor Trk isoforms in that among the three isoforms (TrkB‐FL, TrkB‐T1 and TrkB‐T2), only one of its truncated isoforms, TrkB‐T1, continued to be expressed, which leads to the dysfunction of its ligand, a decrease in the migration of CMECs and increased injury in ageing hearts. This shift in receptor isoforms in aged CMECs, together with changes in the ageing microenvironment, might predispose ageing hearts to decreased angiogenic potential and increased cardiac pathology.

Promyelocytic Leukemia (PML) Protein Plays Important Roles in Regulating Cell Adhesion, Morphology, Proliferation and Migration

PML protein plays important roles in regulating cellular homeostasis. It forms PML nuclear bodies (PML-NBs) that act like nuclear relay stations and participate in many cellular functions. In this study, we have examined the proteome of mouse embryonic fibroblasts (MEFs) derived from normal (PML+/+) and PML knockout (PML−/−) mice. The aim was to identify proteins that were differentially expressed when MEFs were incapable of producing PML. Using comparative proteomics, total protein were extracted from PML−/− and PML+/+ MEFs, resolved by two dimensional electrophoresis (2-DE) gels and the differentially expressed proteins identified by LC-ESI-MS/MS. Nine proteins (PML, NDRG1, CACYBP, CFL1, RSU1, TRIO, CTRO, ANXA4 and UBE2M) were determined to be down-regulated in PML−/− MEFs. In contrast, ten proteins (CIAPIN1, FAM50A, SUMO2 HSPB1 NSFL1C, PCBP2, YWHAG, STMN1, TPD52L2 and PDAP1) were found up-regulated. Many of these differentially expressed proteins play crucial roles in cell adhesion, migration, morphology and cytokinesis. The protein profiles explain why PML−/− and PML+/+ MEFs were morphologically different. In addition, we demonstrated PML−/− MEFs were less adhesive, proliferated more extensively and migrated significantly slower than PML+/+ MEFs. NDRG1, a protein that was down-regulated in PML−/− MEFs, was selected for further investigation. We determined that silencing NDRG1expression in PML+/+ MEFs increased cell proliferation and inhibited PML expression. Since NDRG expression was suppressed in PML−/− MEFs, this may explain why these cells proliferate more extensively than PML+/+ MEFs. Furthermore, silencing NDRG1expression also impaired TGF-β1 signaling by inhibiting SMAD3 phosphorylation.

Silencing BRE expression in human umbilical cord perivascular (HUCPV) progenitor cells accelerates osteogenic and chondrogenic differentiation.

BRE is a multifunctional adapter protein involved in DNA repair, cell survival and stress response. To date, most studies of this protein have been focused in the tumor model. The role of BRE in stem cell biology has never been investigated. Therefore, we have used HUCPV progenitor cells to elucidate the function of BRE. HUCPV cells are multipotent fetal progenitor cells which possess the ability to differentiate into a multitude of mesenchymal cell lineages when chemically induced and can be more easily amplified in culture. In this study, we have established that BRE expression was normally expressed in HUCPV cells but become down-regulated when the cells were induced to differentiate. In addition, silencing BRE expression, using BRE-siRNAs, in HUCPV cells could accelerate induced chondrogenic and osteogenic differentiation. Hence, we postulated that BRE played an important role in maintaining the stemness of HUCPV cells. We used microarray analysis to examine the transcriptome of BRE-silenced cells. BRE-silencing negatively regulated OCT4, FGF5 and FOXO1A. BRE-silencing also altered the expression of epigenetic genes and components of the TGF-β/BMP and FGF signaling pathways which are crucially involved in maintaining stem cell self-renewal. Comparative proteomic profiling also revealed that BRE-silencing resulted in decreased expressions of actin-binding proteins. In sum, we propose that BRE acts like an adaptor protein that promotes stemness and at the same time inhibits the differentiation of HUCPV cells.

Gene expression profiling of CD3γ, δ, ϵ, and ζ chains in CD4+ and CD8+ T cells from human umbilical cord blood

Abstract In order to elucidate the feature of T-cell immune status in umbilical cord blood (CB) from humans, the expression levels of CD3γ, δ, ϵ, and ζ chain genes in CD4+ and CD8+ T cells of CB were analysed by real-time PCR. CD4+ and CD8+ T cells sorted from 12 cases of CB and 10 peripheral blood (PB) samples from healthy adults were used in the study. The β2-microglobulin gene was used as an endogenous reference, and the evaluations of mRNA expression level of each CD3 gene were used by the 2−ΔCt × 100% method. In CD4+ T cells, the expression levels of CD3γ, δ, and ζ genes (16·54±6·49, 3·53±1·15, and 5·48±1·10%) from CB were significantly higher than those from PB (P=0·001, P=0·017, and P=0·000, respectively). Higher expression levels of CD3δ and ζ genes (3·43±1·19 and 5·24±1·42%) in CD8+ T cells from CB were found than those from PB (P=0·000 and P=0·004). Moreover, the expression level of CD3ϵ gene in CD4+ T cells from CB (13·29±5·72%) was significantly different from that in CD8+ T cells (7·81±4·72%, P=0·018). Thus, the expression pattern of four CD3 genes were γ>ϵ>ζ>δ in both CD4+ and CD8+ T cells from CB, while similar expression pattern was found in CD8+ T cells from PB samples. In contrast, the expression pattern was presented as ϵ>γ>ζ>δ in CD4+ T cells from PB. In conclusion, the present study characterized the expression pattern of CD3γ, δ, ϵ, and ζ chain genes in CD4+ and CD8+ T cells from CB, which might be very useful for further understanding the feature of T-cell immune status in umbilical cord blood. Higher expression of CD3 genes in CD4+ T cells might relate to the strong ability of activation of TCR-mediated signals, and suggests that this is one of the features responsible for the low allo-reactivity of CB T cells.

Anti-apoptotic protein BRE/BRCC45 attenuates apoptosis through maintaining the expression of caspase inhibitor XIAP in mouse Lewis lung carcinoma D122 cells.

Brain and Reproductive Organ Expressed (BRE), or BRCC45, is a death receptor-associated antiapoptotic protein, which is also involved in DNA-damage repair, and K63-specific deubiquitination. BRE overexpression attenuates both death receptor- and stress-induced apoptosis, promotes experimental tumor growth, and is associated with human hepatocellular and esophageal carcinoma. How BRE mediates its antiapoptotic function is unknown. Here we report based on the use of a mouse Lewis lung carcinoma cell line D122 that BRE has an essential role in maintaining the cellular protein level of XIAP, which is the most potent endogenous inhibitor of the caspases functioning in both extrinsic and intrinsic apoptosis. shRNA-mediated exhaustive depletion of BRE sensitized D122 cells to apoptosis induced not only by etopoxide, but also by TNF-α even in the absence of cycloheximide, which blocks the synthesis of antiapoptotic proteins by TNF-α-activated NF-κB pathway. In BRE-depleted cells, protein level of XIAP was downregulated, but not the levels of other antiapoptotic proteins, cIAP-1, 2, and cFLIP, regulated by the same NF-κB pathway. Reconstitution of BRE restored XIAP levels and increased resistance to apoptosis. XIAP mRNA level was also reduced in the BRE-depleted cells, but the level of reduction was less profound than that of the protein level. However, BRE could not delay protein turnover of XIAP. Depletion of BRE also increased tumor cell apoptosis, and decreased both local and metastatic tumor growth. Taken together, these findings indicate that BRE and its XIAP-sustaining mechanism could represent novel targets for anti-cancer therapy.

Livers overexpressing BRE transgene are under heightened state of stress-response, as revealed by comparative proteomics

BRE (TNFRSF1A modulator/BRCC45) is a stress‐responsive gene that is normally expressed at low levels in human and mouse livers. It binds to TNF‐R1 and Fas, and modulates the actions of these cytokines [Chan, B.C.L., Ching, A.K.K., To, K.F., Leung, J.C.K. et al., Oncogene 2008, 27, 1208–1217]. We demonstrated that BRE expression was rapidly induced when the liver was insulted with carbon tetrachloride. In addition, it is highly expressed in human hepatocellular carcinoma. Transgenic mice were produced that specifically overexpressed BRE in the liver to determine the effects of high levels of BRE on the liver. We found these transgenic livers were histologically normal when compared with their wild‐type counterpart. Hence, comparative proteomics were used to elucidate the molecular alterations in these tissues. It was established that several stress‐responsive proteins were upregulated in BRE‐transgenic hepatocytes. These include heat shock‐related 70 kDa protein 2, putative heat shock 70 kDa protein 7 and mitogen‐activated protein kinase 12. Furthermore, we demonstrated that silencing BRE expression in non‐tumoral Chang cells could directly inhibit the expression of these stress‐responsive genes. In conclusion, we propose that the liver in our BRE transgenic mice is under constant heightened stress‐response and this may be a major contributing factor to the hepatocellular carcinoma phenotype.

Tissue specific expression and sequence analysis of a stress responsive gene Bre in adult golden hamster (Mesocricetus auratus)

Bre (brain and reproductive organ-expressed) is a new and putative stress-modulating gene of yet unknown function. BRE has previously been shown to interact with type 1 tumor necrosis factor receptor (TNFR1) and modulate the action of TNF. Apart from the brain and reproductive organs, Bre and BRE are highly expressed in steroid producing tissues such as the adrenal gland. Here we report for the first time the cloning of the Bre gene from golden hamster, a model organism extremely valuable for reproduction and steroid research, and examination of its tissue specific expression. Sequence analysis demonstrated that the peptide sequence of BRE in hamster shares ~99% homology with those of human, monkey and mouse. The hamster Bre gene transcribed a ~1.8-kb mRNA which translated a 44-kDa protein. Bre was strongly expressed in neurons and luminal epithelia of urogenital, digestive and respiratory organs. Bre was also detected in lymphoid tissues and endocrine glands. Immunohistochemistry demonstrated a similar protein expression pattern. Exceptions to this included the adrenal gland, where a high level of Bre was accompanied by weak immunoreactivity; as well as the oocytes and islets of Langerhans, where BRE protein but not the mRNA was localized. These data indicated that Bre gene products were expressed in a wide variety of tissues other than the brain and reproductive organs, as was originally described. Based on our findings, we propose that Bre is a housekeeping gene in tissues that are constantly subjected to environmental hazards such as luminal epithelia. Our results further support the proposed role for BRE in endocrine and immune functions.