Abstract: Provided is a method for producing naive induced pluripotent stem cells from human somatic cells, comprising the following steps (1) to (3): (1) introducing one or more vectors containing a reprogramming factor into human somatic cells, (2) culturing said somatic cells in the presence of a naive medium, and (3) after step (2), culturing the resulting cells in the presence of the naive medium under the condition in which the amount of the vectors per the somatic cell is reduced to 30% or less of that at the start of step 3.

Abstract: There is provided a quality improving agent for iPS cells, including a polynucleotide, in which the polynucleotide contains an H1foo gene and a regulatory sequence that is capable of regulating at least one of the amount and the period of existence of an H1foo protein expressed from the H1foo gene in cells when the H1foo gene is transduced into the cells.

Abstract: An object of the present invention is to provide an agent for improving quality of an iPS cell, a method for producing an iPS cell, an iPS cell produced by such a method for production, and a composition for producing an iPS cell. The method for producing an iPS cell according to the present invention comprises the step of introducing (a) a nuclear reprogramming substance and (b) an H1foo gene or a gene product thereof into a somatic cell. High-quality iPS cells can be produced in greater quantity by introducing not only a nuclear reprogramming substance but also an H1foo gene or a gene product thereof into a somatic cell.