Practice question

Primary cell culture defines culture establishment directly from living tissue obtained via biopsy, surgical resection, embryonic dissection or enzymatic disaggregation without prior in vitro passage or immortalization step, preserving in vivo characteristics. Tissue fragments minced to one cubic millimeter pieces, digested with collagenase type I, trypsin-EDTA, dispase or liberase cocktails to release single cells, filtered to remove debris and seeded into tissue culture flasks containing medium supplemented with serum providing growth factors, antibiotics preventing contamination and attachment factors like fibronectin. Such cultures retain diploid karyotype, tissue-specific markers such as albumin secretion by hepatocytes, surfactant production by alveolar type II cells or contractility by cardiomyocytes, limited proliferative capacity subject to Hayflick limit of 50 to 60 divisions, contact inhibition mediated by Hippo YAP signaling and senescence markers SA-beta-galactosidase. Heterogeneity reflects original organ containing fibroblasts, epithelial and endothelial populations requiring purification by differential adhesion or magnetic sorting. Unlike continuous lines transformed by SV40 large T antigen, telomerase hTERT activation or spontaneous mutation leading to aneuploidy and infinite growth, primary cells closely mimic physiology for drug toxicity testing, virology and regenerative medicine, demanding careful handling and short-term use.