mesohi....harvest the top 2/3 of the plant or so. Leave as many of the lower leaves as you can. Put it back ubder 24/0 with a dose of "Vegging" ferts, and hope for the best. Some strains regenerate pretty easily, others won't.
Though I have done this in the past in order to preserve a specific strain or phenotype, regenerating to reflower, is a total waste of time and effort..IMHO.