Lymph node homeostasis and adaptation to immune challenge resolved by fibroblast network mechanics

Emergent physical properties of tissues are not readily understood by reductionist studies of their constituent cells. Here, we show molecular signals controlling cellular, physical, and structural properties and collectively determine tissue mechanics of lymph nodes, an immunologically relevant adult tissue. Lymph nodes paradoxically maintain robust tissue architecture in homeostasis yet are continually poised for extensive expansion upon immune challenge. We find that in murine models of immune challenge, cytoskeletal mechanics of a cellular meshwork of fibroblasts determine tissue tension independently of extracellular matrix scaffolds. We determine that C-type lectin-like receptor 2 (CLEC-2)-podoplanin signaling regulates the cell surface mechanics of fibroblasts, providing a mechanically sensitive pathway to regulate lymph node remodeling. Perturbation of fibroblast mechanics through genetic deletion of podoplanin attenuates T cell activation. We find that increased tissue tension through the fibroblastic stromal meshwork is required to trigger the initiation of fibroblast proliferation and restore homeostatic cellular ratios and tissue structure through lymph node expansion.

Podoplanin drives dedifferentiation and amoeboid invasion of melanoma

Melanoma is an aggressive skin cancer developing from melanocytes, frequently resulting in metastatic disease. Melanoma cells utilize amoeboid migration as mode of local invasion. Amoeboid invasion is characterized by rounded cell morphology and high actomyosin contractility driven by Rho GTPase signalling. Migrastatic drugs targeting actin polymerization and contractility are therefore a promising treatment option for metastatic melanoma. To predict amoeboid invasion and metastatic potential, biomarkers functionally linked to contractility pathways are needed. The glycoprotein podoplanin drives actomyosin contractility in lymphoid fibroblasts and is overexpressed in many cancers. We show that podoplanin enhances amoeboid invasion in melanoma. Podoplanin expression in murine melanoma drives rounded cell morphology, increasing motility, and invasion in vivo. Podoplanin expression is increased in a subset of dedifferentiated human melanoma, and in vitro is sufficient to upregulate melanoma-associated marker Pou3f2/Brn2. Together, our data define podoplanin as a functional biomarker for dedifferentiated invasive melanoma and a promising migrastatic therapeutic target.

Fibroblastic reticular cell response to dendritic cells requires coordinated activity of podoplanin, CD44 and CD9

In adaptive immunity, CLEC-2+ dendritic cells (DCs) contact fibroblastic reticular cells (FRCs) inhibiting podoplanin-dependent actomyosin contractility, permitting FRC spreading and lymph node expansion. The molecular mechanisms controlling lymph node remodelling are incompletely understood. We asked how podoplanin is regulated on FRCs in the early phase of lymph node expansion, and which other proteins are required for the FRC response to DCs. We find that podoplanin and its partner proteins CD44 and CD9 are differentially expressed by specific lymph node stromal populations in vivo, and their expression in FRCs is coregulated by CLEC-2 (encoded by CLEC1B). Both CD44 and CD9 suppress podoplanin-dependent contractility. We find that beyond contractility, podoplanin is required for FRC polarity and alignment. Independently of podoplanin, CD44 and CD9 affect FRC-FRC interactions. Furthermore, our data show that remodelling of the FRC cytoskeleton in response to DCs is a two-step process requiring podoplanin partner proteins CD44 and CD9. Firstly, CLEC-2 and podoplanin binding inhibits FRC contractility, and, secondly, FRCs form protrusions and spread, which requires both CD44 and CD9. Together, we show a multi-faceted FRC response to DCs, which requires CD44 and CD9 in addition to podoplanin.

The fate of cells undergoing spontaneous DNA damage during development

Embryonic development involves extensive and often rapid cell proliferation. An unavoidable side effect of cell proliferation is DNA damage. The consequences of spontaneous DNA damage during development are not clear. Here, we define an approach to determine the effects of DNA damage on cell fate choice. Using single cell transcriptomics, we identified a subpopulation of Dictyostelium cells experiencing spontaneous DNA damage. Damaged cells displayed high expression of rad51, with the gene induced by multiple types of genotoxic stress. Using live imaging, we tracked high Rad51 cells from differentiation onset until cell fate assignment. High Rad51 cells were shed from multicellular structures, excluding damaged cells from the spore population. Cell shedding resulted from impaired cell motility and defective cell-cell adhesion, with damaged cells additionally defective in activation of spore gene expression. These data indicate DNA damage is not insulated from other aspects of cell physiology during development and multiple features of damaged cells prevent propagation of genetic error. Our approach is generally applicable for monitoring rare subpopulations during development, and permits analysis of developmental perturbations occurring within a physiological dynamic range.

Depression and the perpetuation of an incapacitated identity as an inhibitor of return to work

The aim of the current study was to conduct a qualitative investigation of attitudes to work among people diagnosed with clinical depression. It was of particular interest to understand the role played by illness in attitudes to recovery. The economic and social burden of adult depression on society is becoming increasingly apparent. It has been argued that recovery from mental illness of this kind is most appropriately understood in 'functional terms' (i.e. 'getting on with life beyond illness'). One important goal in this process is return to work. Accordingly, in-depth semi-structured interviews were conducted with 19 people formally diagnosed with clinical depression. These interviews were the analyzed using Interpretative Phenomenological Analysis: a method of investigation and analysis concerned with making sense of participant experiences and accounts of their ill-health. This process identified three master themes, only one of which is the focus of this paper. This theme pertains to the unwitting role that can be played by the health care system in reinforcing the 'sick role' and in so doing providing a continued justification for an 'off-work' identity. Consequently, this study provides an unusually penetrating insight into the way depression can, through institutional practices, become inextricably part of someone's identity, with important implications for functional recovery.

The team survey: a tool for health care team development

AIMS

The aim of this study was to validate a psychometric tool, the team survey, in a health care setting with a range of teams from a Large National Health Service (NHS) Trust.

BACKGROUND

The team survey was developed by Millward and Ramsay (1998) to measure the team dimensions identified in the cognitive-motivational model of team effectiveness (Millward & Purvis 1998). The team dimensions are team potency, team identification, Shared Mental Models and team meta-cognitions.

DESIGN AND METHODS

The psychometric properties of the tool as a reliable and valid predictor of team effectiveness was assessed by way of a survey of 10 teams (comprising 124 members in all) located on different premises, within a large NHS Trust. Team size ranged between 5 and 19 members, with average team size being 10 members. Two independent ratings of 'effectiveness' were made for each team. Factor and multiple regression analyses were employed to identify the most powerful predictors of health care team effectiveness from a cognitive and motivational perspective.

RESULTS

The results suggest that the team survey is psychometrically robust within a health care setting.

CONCLUSIONS

It is concluded that the tool has a potentially key role in informing and evaluating team development initiatives in support of the work of practice development nurses and nursing team leaders.

Running shared mental models as a distributed cognitive process

Shared mental models theory normally takes the individual as its unit of analysis. This paper proposes a theoretical framework for studying shared mental models in which the model is considered to be distributed amongst the team. From this framework a cognitive process is predicted which describes how shared mental models are run. A team reasoning task requiring planning was used to illustrate this framework and test predictions derived from it. Two aspects of sharing mental models were studied; the degree of overlap between team members' mental models and the organization of the division of the model between team members. Experimental results showed that the cognitive processes used were distributed amongst the team and support was found for most, but not all, aspects of the proposed process of running a shared mental model. The organization of sharing was found to influence this process.

Sexual self-concept and sexual risk-taking

Data are presented from a postal survey of 474 randomly selected 16-19-year-olds from one U.K. suburban area. A 14-item Sexual Self-Concept Checklist was used to explore the structure of the differences between male and female sexual identities. Two main dimensions in male sexual self-concept emerged: the socio-emotional (romance, sensitivity, eroticism) and the relational (exploitative, seductive, experimental). Female sexual self-concept revolved around concerns with assertiveness (unwillingness to have sex before marriage, controlling when sex occurs, pretending to enjoy sex). Internally reliable scales were constructed for these aspects of the sexual self-concept and were found to relate to both sexual and other forms of risk-taking likely to endanger health. Males with a high relational emphasis in their sexual self-concept were less likely to have had sex and less likely to use alcohol or tobacco. Females with a greater assertiveness score were less likely to be virgins, had had more sexual partners and consumed more alcohol and tobacco. They were not, however, less likely to use condoms. It is concluded that models seeking to explain health behaviours in adolescence should incorporate estimates of the significance of the behaviour for stable aspects of the self-concept. It is further argued that the structure of the sexual self-concept is significantly influenced by dominant social representations of gender differences and relationships. Both identity and social representational processes need to be considered if a comprehensive model of health behaviour is to be evolved.