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The cardiac regeneration and development fields lack low-barrier-to-entry techniques that distinguish cardiomyocyte division from alternative outcomes in vivo. Here, we present a protocol in rodents to determine if cardiomyocyte cell division has occurred. We describe thymidine analog administration, Langendorff procedure, immunofluorescent labeling, microscopy, and analysis of fluorescent images to assess ploidy, thereby allowing an investigator to retrospectively claim cell division. Finally, we provide instructions for additional metrics including quantification of total cardiomyocytes, total cycling cardiomyocytes, and cellular dimensions.

Cardiomyocyte proliferation is a challenging metric to assess. Current methodologies have limitations in detecting the generation of new cardiomyocytes and technical challenges that reduce widespread applicability. Here, we describe an improved cell suspension and imaging-based methodology that can be broadly employed to assess cardiomyocyte cell division in standard laboratories across a multitude of model organisms and experimental conditions. We highlight additional metrics that can be gathered from the same cell preparations to enable additional relevant analyses to be performed. We incorporate additional antibody stains to address potential technical concerns of miscounting. Finally, we employ this methodology with a dual-thymidine analog-labeling approach to a post-infarction murine model, which allowed us to robustly identify unique cycling events, such as cardiomyocytes undergoing multiple rounds of cell division.

Background/Purpose Racism and hidden bias experienced by underrepresented nursing students contribute to a loss of confidence and anxiety. The A-CHARM nursing project developed virtual simulation experiences for nursing students to practice how to address racism. ‘Nik's Story’ virtual simulation was created as part of the A-CHARM project. The purpose of this study was to examine the effectiveness of an education intervention, that included Nik's story, on cultural humility and cultural diversity awareness.Method This quasi-experimental study included a convenience sample of final year nursing students. After informed consent, participants completed a pre-intervention questionnaire that included the Cultural Humility Scale “context for difference in perspective” subscale, and the Cultural Diversity Awareness questionnaire to assess baseline knowledge. Students participated in an education intervention that included a lecture, Nik's story virtual simulation experience, a debrief and then completed a post-education/simulation questionnaire that included usability/learner engagement questions and the Cultural Humility Scale “context for difference in perspective” subscale, and the Cultural Diversity Awareness questionnaire.Results Forty-seven students consented and completed the pre/post intervention questionnaire. Participants rated the effectiveness, engagement and usability of the simulation experience highly. There was a significant positive change in cultural humility “context for difference in perspective” subscale (pre-scores = 6.9, SD = 3.3; post-scores = 31.0, SD = 3.8, p< 0.001), and cultural diversity awareness (pre-scores = 95.4, SD = 8.9; post-scores = 103.4, SD = 9.8, p< 0.001).Discussion This intervention was effective in improving cultural humility and cultural diversity awareness in nursing students.Conclusion Simulation experiences regarding racism in the clinical setting provide a strategy for students to learn how to professionally navigate unwanted experiences.

Adult mammalian cardiomyocyte regeneration after injury is thought to be minimal. Mononuclear diploid cardiomyocytes (MNDCMs), a relatively small subpopulation in the adult heart, may account for the observed degree of regeneration, but this has not been tested. We surveyed 120 inbred mouse strains and found that the frequency of adult mononuclear cardiomyocytes was surprisingly variable (>7-fold). Cardiomyocyte proliferation and heart functional recovery after coronary artery ligation both correlated with pre-injury MNDCM content. Using genome-wide association, we identified Tnni3k as one gene that influences variation in this composition and demonstrated that Tnni3k knockout resulted in elevated MNDCM content and increased cardiomyocyte proliferation after injury. Reciprocally, overexpression of Tnni3k in zebrafish promoted cardiomyocyte polyploidization and compromised heart regeneration. Our results corroborate the relevance of MNDCMs in heart regeneration. Moreover, they imply that intrinsic heart regeneration is not limited nor uniform in all individuals, but rather is a variable trait influenced by multiple genes.