Over expression of Plk1 does not induce cell division in rat cardiac myocytes in vitro

BACKGROUND: Mammalian cardiac myocytes withdraw from the cell cycle during post-natal development, resulting in a non-proliferating, fully differentiated adult phenotype that is unable to repair damage to the myocardium, such as occurs following a myocardial infarction. We and others previously have shown that forced expression of certain cell cycle molecules in adult cardiac myocytes can promote cell cycle progression and division in these cells. The mitotic serine/threonine kinase, Polo-like kinase-1 (Plk1), is known to phosphorylate and activate a number of mitotic targets, including Cdc2/Cyclin B1, and to promote cell division. PRINCIPAL FINDINGS: The mammalian Plk family are all differentially regulated during the development of rat cardiac myocytes, with Plk1 showing the most dramatic decrease in both mRNA, protein and activity in the adult. We determined the potential of Plk1 to induce cell cycle progression and division in cultured rat cardiac myocytes. A persistent and progressive loss of Plk1 expression was observed during myocyte development that correlated with the withdrawal of adult rat cardiac myocytes from the cell cycle. Interestingly, when Plk1 was over-expressed in cardiac myocytes by adenovirus infection, it was not able to promote cell cycle progression, as determined by cell number and percent binucleation. CONCLUSIONS: We conclude that, in contrast to Cdc2/Cyclin B1 over-expression, the forced expression of Plk1 in adult cardiac myocytes is not sufficient to induce cell division and myocardial repair

Protecting Workers in the Home Care Industry: Workers\u27 Experienced Job Demands, Resource Gaps, and Benefits Following a Socially Supportive Intervention

The Community of Practice and Safety Support (COMPASS) program is a peer-led group intervention for home care workers. In a randomized controlled trial, COMPASS significantly improved workers\u27 professional support networks and safety and health behaviors. However, quantitative findings failed to capture workers\u27 complex emotional, physical, and social experiences with job demands, resource limitations, and the intervention itself. Therefore, we conducted qualitative follow-up interviews with a sample of participants (n=28) in the program. Results provided examples of unique physical and psychological demands, revealed stressful resource limitations (e.g., safety equipment access), and elucidated COMPASS\u27s role as a valuable resource