Pathological changes in the COPD lung mesenchyme--novel lessons learned from in vitro and in vivo studies.

Chronic obstructive pulmonary disease (COPD) is currently the fourth leading cause of death worldwide and, in contrast to the trend for cardiovascular diseases, mortality rates still continue to climb. This increase is in part due to an aging population, being expanded by the "Baby boomer" generation who grew up when smoking rates were at their peak and by people in developing countries living longer. Sadly, there has been a disheartening lack of new therapeutic approaches to counteract the progressive decline in lung function associated with the disease that leads to disability and death. COPD is characterized by irreversible chronic airflow limitation that is caused by emphysematous destruction of lung elastic tissue and/or obstruction in the small airways due to occlusion of their lumen by inflammatory mucus exudates, narrowing and obliteration. These lesions are mainly produced by the response of the tissue to the repetitive inhalational injury inflicted by noxious gases, including cigarette smoke, which involves interaction between infiltrating inflammatory immune cells, resident cells (e.g. epithelial cells and fibroblasts) and the extra cellular matrix. This interaction leads to tissue destruction and airway remodeling with changes in elastin and collagen, such that the epithelial-mesenchymal trophic unit is dysregulated in both the disease pathologies. This review focuses on: 1--novel inflammatory and remodeling factors that are altered in COPD; 2--in vitro and in vivo models to understand the mechanism whereby the extra cellular matrix environment in altered in COPD; and 3--COPD in the context of wound-repair tissue responses, with a focus on the regulation of mesenchymal cell fate and phenotype.

Therapeutic Silencing of p120 in Fascia Fibroblasts Ameliorates Tissue Repair.

Deep skin wounds rapidly heal by mobilizing extracellular matrix and cells from the fascia, deep beneath the dermal layer of the skin, to form scars. Despite wounds being an extensively studied area and an unmet clinical need, the biochemistry driving this patch-like repair remains obscure. Lacking also are efficacious therapeutic means to modulate scar formation in vivo. In this study, we identify a central role for p120 in mediating fascia mobilization and wound repair. Injury triggers p120 expression, largely within engrailed-1 lineage-positive fibroblasts of the fascia that exhibit a supracellular organization. Using adeno-associated virus‒mediated gene silencing, we show that p120 establishes the supracellular organization of fascia engrailed-1 lineage-positive fibroblasts, without which fascia mobilization is impaired. Gene silencing of p120 in fascia fibroblasts disentangles their supracellular organization, reducing the transfer of fascial cells and extracellular matrix into wounds and augmenting wound healing. Our findings place p120 as essential for fascia mobilization, opening, to our knowledge, a previously unreported therapeutic avenue for targeted intervention in the treatment of a variety of skin scar conditions.

Characterization of the ROK-family transcriptional regulator RokA of Streptococcus pneumoniae D39.

The Gram-positive human pathogen Streptococcus pneumoniae possesses an unusually high number of gene clusters specific for carbohydrate utilization. This provides it with the ability to use a wide array of sugars, which may aid during infection and survival in different environmental conditions present in the host. In this study, the regulatory mechanism of transcription of a gene cluster, SPD0424-8, putatively encoding a cellobiose/lactose-specific phosphotransferase system is investigated. We demonstrate that this gene cluster is transcribed as one transcriptional unit directed by the promoter of the SPD0424 gene. Upstream of SPD0424, a gene was identified encoding a ROK-family transcriptional regulator (RokA: SPD0423). DNA microarray and transcriptional reporter analyses with a rokA mutant revealed that RokA acts as a transcriptional repressor of the SPD0424-8 operon. Furthermore, we identified a 25 bp AT-rich DNA operator site (5'-TATATTTAATTTATAAAAAATAAAA-3') in the promoter region of SPD0424, which was validated by promoter truncation studies, DNase I footprinting and electrophoretic mobility-shift assays. We tested a large range of different sugars for their effect on the expression of the SPD0424-8 operon, but only moderate variation in expression was observed in the conditions applied. Therefore, a co-factor for RokA-mediated transcriptional control could not be identified.

Injury triggers fascia fibroblast collective cell migration to drive scar formation through N-cadherin.

Scars are more severe when the subcutaneous fascia beneath the dermis is injured upon surgical or traumatic wounding. Here, we present a detailed analysis of fascia cell mobilisation by using deep tissue intravital live imaging of acute surgical wounds, fibroblast lineage-specific transgenic mice, and skin-fascia explants (scar-like tissue in a dish - SCAD). We observe that injury triggers a swarming-like collective cell migration of fascia fibroblasts that progressively contracts the skin and form scars. Swarming is exclusive to fascia fibroblasts, and requires the upregulation of N-cadherin. Both swarming and N-cadherin expression are absent from fibroblasts in the upper skin layers and the oral mucosa, tissues that repair wounds with minimal scar. Impeding N-cadherin binding inhibits swarming and skin contraction, and leads to reduced scarring in SCADs and in animals. Fibroblast swarming and N-cadherin thus provide therapeutic avenues to curtail fascia mobilisation and pathological fibrotic responses across a range of medical settings.

Two succeeding fibroblastic lineages drive dermal development and the transition from regeneration to scarring.

During fetal development, mammalian back-skin undergoes a natural transition in response to injury, from scarless regeneration to skin scarring. Here, we characterize dermal morphogenesis and follow two distinct embryonic fibroblast lineages, based on their history of expression of the engrailed 1 gene. We use single-cell fate-mapping, live three dimensional confocal imaging and in silico analysis coupled with immunolabelling to reveal unanticipated structural and regional complexity and dynamics within the dermis. We show that dermal development and regeneration are driven by engrailed 1-history-naive fibroblasts, whose numbers subsequently decline. Conversely, engrailed 1-history-positive fibroblasts possess scarring abilities at this early stage and their expansion later on drives scar emergence. The transition can be reversed, locally, by transplanting engrailed 1-naive cells. Thus, fibroblastic lineage replacement couples the decline of regeneration with the emergence of scarring and creates potential clinical avenues to reduce scarring.