The reversion to diploid cells from established triploid V79 cells

DNA-unstable decaploid mouse H1 (ES) cells established from DNA-stable pentaploid H1 (ES) cells polyploidized using demecolcine

OBJECTIVES

DNA content of diploid H1 (ES) cells (2H1 cells) has been shown to be stable in long-term culture; however, tetraploid and octaploid H1 (ES) cells (4H1 and 8H1 cells, respectively) were DNA-unstable. Pentaploid H1 (ES) cells (5H1 cells) established recently have been found to be DNA-stable; how, then is cell DNA stability determined? To discuss ploidy stability, decaploid H1 (ES) cells (10H1 cells) were established from 5H1 cells and examined for DNA stability.

MATERIALS AND METHODS

5H1 cells were polyploidized using demecolcine (DC) and 10H1 cells were obtained by one-cell cloning.

RESULTS

Number of chromosomes of 10H1 cells was 180 and durations of their G(1), S, and G(2)/M phases were 3, 7 and 6 h respectively. Volume of 10H1 cells was double that of 5H1 cells and morphology of 10H1 cells was flagstone-like in shape. 10H1 cells exhibited alkaline phosphatase activity and their DNA content decayed in 91 days of culture. 10H1 cells injected into mouse abdomen formed solid tumours that contained several kinds of differentiated cells with lower DNA content, suggesting that 10H1 cells were pluripotent and DNA-unstable. Loss of DNA stability was explained using a hypothesis concerning DNA structure of polyploid cells as DNA reconstructed through ploidy doubling was arranged in mirror symmetry in a new configuration.

CONCLUSION

In the pentaploid-decaploid transition of H1 cells, cell cycle parameters and pluripotency were retained, but morphology and DNA stability were altered.

Hexaploid H1 (ES) cells established from octaploid H1 cells are as DNA stable as pentaploid H1 cells

Hexaploid H1 (ES) cells (6H1 cells) were established from octaploid H1 cells (8H1 cells), as were pentaploid H1 cells (5H1 cells). 6H1 cells were compared with 5H1 cells. The number of chromosomes of 6H1 cells was 115, 20 more than the 95 of 5H1 cells. The durations of G(1), S, and G(2)/M phases of 6H1 cells were 3, 7, and 6 h, respectively, almost the same as those of 5H1 cells. The cell volume of 6H1 cells was equivalent that of 5H1 cells. The morphology of 6H1 cells was flattened circular cluster, different from the spherical cluster of 5H1 cells. 6H1 cells exhibited alkaline phosphatase activity as well as 5H1 cells. The DNA content of 6H1 cells was stable and maintained for 300 days of culturing, the same as that of 5H1 cells. The DNA stability of 6H1 cells was explained using a hypothesis concerning the DNA structure of polyploid cells because the asymmetric configuration of homologous chromosomes in 6H1 cells inhibited chromosome loss.

DNA stable pentaploid H1 (ES) cells obtained from an octaploid cell induced from tetraploid cells polyploidized using demecolcine

Pentaploid H1 (ES) cells (5H1 cells) were accidentally obtained through one-cell cloning of octaploid H1 (ES) cells (8H1 cells) that were established from tetraploid H1 (ES) cells (4H1 cells) polyploidized using demecolcine. The number of chromosomes of 5H1 cells was 100, unlike the 40 of diploid H1 (ES) cells (2H1 cells), 80 of 4H1, and 160 of 8H1 cells. The durations of G(1), S, and G(2)/M phases of 5H1 cells were 3, 7, and 6 h, respectively, almost the same as those of 2H1, 4H1, and 8H1 cells. The cell volume of 5H1 cells was half of that of 8H1 cells, suggesting that 5H1 cells were created through abnormal cell divisions of 8H1 cells. The morphology of growing 5H1 cells was a spherical cluster similar to that of 2H1 cells and differing from the flagstone-like shape of 4H1 and 8H1 cells. Pentaploid solid tumors were formed from 5H1 cells after interperitoneal injection into the mouse abdomen, and they contained endodermal, mesodermal, and ectodermal cells as well as undifferentiated cells, suggesting both that the DNA content of 5H1 cells was retained during tumor formation and that the 5H1 cells were pluripotent. The DNA content of 5H1 cells was stable in long-term culturing as 2H1 cells, meaning that 5H1 and 2H1 cells shared similarities in DNA structure. The excellent stability of the DNA content of 5H1 cells was explained using a hypothesis for the DNA structure of polyploid cells because the pairing of homologous chromosomes in 5H1 cells is spatially forbidden.