Abstract-During the "response-to-injury" process after a mechanical insult to the porcine coronary arteries, the adventitial cells acquire the structural characteristics of myofibroblasts before being incorporated into smooth muscle (SM) layer.We assessed whether the SM-specific SM22 protein can be used as a tracer of adventitial cell-myofibroblast differentiation in the mild balloon injury of rabbit carotid artery. To achieve this goal, we used 2 monoclonal anti-SM22 antibodies (E-11 and 1-B8) and a molecular probe for the SM22␣ mRNA isoform in immunocytochemical and in situ hybridization experiments. The differentiation profile and the migratory and proliferative ability of activated adventitial cells were evaluated by a panel of antibodies to some SM and nonmuscle antigens and pulse-and end-labeling with bromo-deoxyuridine, respectively. In adventitial cells, SM22 antigenicity and SM22␣ mRNA were detectable at days 2 and 4 and, to a lesser extent, at days 7 and 21 after injury, particularly near the adventitia-media interface and mostly colocalizing with bromo-deoxyuridine-positive cells. The pulse-labeling experiments showed that the large majority of these cells penetrated the outermost layer of the tunica media without migrating to the subendothelial region. The phenotypic features of activated migrating and nonmigrating adventitial cells resembled those of vimentin-actin myofibroblast subtype and fetal-type SM cells. These findings indicate that a direct exposure of adventitia to the lumen is not required for phenotypic changes and proliferation/migration of these cells. After comparison of the SM22 expression in arterial vessels during early stages of development, we hypothesize that in the injured carotid artery the mural incorporation of adventitial cells and the spatiotemporal activation of SM22 expression are reminiscent of the vascular morphogenetic process and suggest the existence of a stem cell-like reservoir in adventitia. The early adventitial upregulation of SM22 expression in the injured vessel might be related to a multistep transition process in which nonmuscle cells are converted to myofibroblasts and, possibly, to SM cells. (Arterioscler Thromb Vasc Biol.

The implementation of Clinical Governance will require a redefinition of duties and accountability as a prerequisite to develop and achieve an overall improvement in clinical care through a culture of assessment and monitoring of quality. External Quality Assessment Schemes (EQAS) are the main tool enabling laboratories to measure the quality of their results; they must carefully assess and monitor all elements contributing to the formulation of laboratory information (results, reference ranges/decisional levels, interpretative comments and diagnostic algorithms). There are different ways to design and manage a Scheme and EQAS coordinators are mainly responsible for its effectiveness. The present paper reports, as an example, some experiences of the Centre of Biomedical Research (CRB), which manages EQAS according to high quality specifications and laboratories' needs, that can reflect the Clinical Governance philosophy. Our findings show that EQAS are able to control all the above aspects and, if organisers are committed to fulfilling the responsibility and accountability principles, they will be of great value in quality assessment and in developing an External Quality Assurance Program (EQAP). This is an inter-laboratory comparison designed and conducted to assure the following: evaluation of participants' performance (by evaluating not only analytical performance, but also test interpretation, and advice for clinicians on laboratory requests and diagnosis); evaluation of method performance; and continuous education, training and help. The main aim of the activities of an EQAP in Laboratory Medicine is to sustain improvements in the quality of services provided by participating laboratories for the benefit of patients.

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The ro le of the Exter nal Qua li ty Asses sme ntLau ra Scia co vel li, San dra Sec chie ro, Lo re na Zar do, Ma rio Ple ba ni*