Högskolan i Skövde

Stem cell niches serve as vital reservoirs, maintaining stem cells in a dormant state through specific niche components. Various biomarkers associated with stem cell niches have been identified in different tissues, including cardiac tissue, particularly at the atrioventricular junction. This study collected mouse, donor, and explanted cardiac tissue from the right side of the heart, focusing on the atrioventricular junction. Additionally, left ventricle samples from donor hearts were harvested. All samples were examined via immunohistochemistry to detect niche-related biomarkers. The study aimed to validate the atrioventricular junction as a potential niche area and to explore Cathepsin K asa possible cardiac stem cell marker, noting its slight nuclear expression. Clear expression of the stemcell marker SSEA4, the hypoxia marker Hif-1α, and the extracellular matrix marker ACAN, along with weak expression of the extracellular matrix marker CILP2, was observed, alongside Cathepsin K. Notably, explanted cardiac samples exhibited lower marker expression, except for Hif-1α, suggesting reduced oxygen levels in failing hearts. Mouse samples displayed the highest expression for each marker, mirroring the distribution seen in human hearts. Although the study does not conclusively validate the existence of a cardiac stem cell niche or the role of Cathepsin K, its findings significantly advance niche research. Further investigation is warranted to elucidate the role of the atrioventricular junction and associated biomarkers in cardiac stem cell biology.