Immortalization of cell cultures for regenerative biomedicine: approaches, opportunities and limitations

Primary cell cultures are one of the main research objects and at the same time a promising tool for regenerative biomedicine. However, their use is largely limited by their short lifespan and rapid aging. Existing approaches to prolonging the "youth" of cell cultures inevitably change their properties, which raises questions about the possibility of their use in regenerative biomedicine. In this literature review, we consider the main mechanisms of cell culture aging, existing ways to overcome it and the safety issues of the obtained cultures, analyze existing data on immortalization as a process and its relationship with tumor transformation. Among the methods considered for prolonging the proliferative activity of cells are spontaneous immortalization and immortalization induced by overexpression of the catalytic subunit of telomerase (TERT), viral oncogenes (SV40 polyomavirus T-antigens, HPV16 E6/E7 proteins, E1A and E1B adenovirus proteins) and cellular transcription factors-proto-oncogenes (c-MYC, BMI1). The accumulated data suggest that TERT gene overexpression is one of the relatively safe approaches to prolonging the proliferative activity of a cell line, because it in itself does not rouse tumor transformation of the cell line. Based on the analyzed data, an attempt was made to identify the "boundary" between acceptable prolongation of cell culture life and its malignant transformation.