Continued in vitro growth of fibroblast-like cells (RBCF-1) derived from the caudal fin of the fish, Carassius auratus

Abstract Fibroblast-like cells derived from primary culture of the caudal fin of a 2-year old goldfish were used to find out whether or not fish cells have a limited in vitro lifespan during the observation period of 22 months. The cells cultivated at 37°C (RBCF-1 line) attained exponential growth from the beginning of culture and reached to 200 population doubling number ( PDN ) at the 310th day. The growth rate of the cells cultured at 30°C (RBCF-2 line) was almost the same as that of RBCF-1 cells except for a temporal decline between the 80 and 160th day of culture. The plating efficiency of RBCF-1 cells, as determined by colony formation, increased with passage and reached around 20% after 183 PDN . Subcutaneous injection of RBCF-1 cells into nude mice failed to develop any tumour so far as examined up to 5 months after injection. Feulgen-DNA cytofluorometry simultaneously combined with tritiated thymidine autoradiography revealed that, in both RBCF-1 and RBCF-2 lines, unlabelled cells which escaped from 48 hours' labelling gradually diminished from each population as PDNs increased and also that labelling indices for each line were 83 and 90% at 113 and 91 PDNs , respectively. The distribution of DNA content per cell was almost the same irrespective of the line and PDN . The modal number of RBCF-1 chromosomes was 100 at both 62 and more than 200 PDNs , and no significant change in the distribution of chromosome number could be found. The saturation cell density of RBCF-1 cells was almost identical at 20, 30 and 37°C, while extremely high saturation density was observed at 27°C. These results were discussed from a viewpoint of ageing characteristics of fish cells in culture.