As one of the authors, may I respond. The method is described in
Korsgaard N, Mulvany MJ: Cellular hypertrophy in mesenteric resistance vessels from renal hypertensive rats. Hypertension 1988,12:162-167. The principle is as follows.
First, estimate nucleus length as section thickness times ratio between number of nuclei in section and number of nucleus ends in section (determined by the disector technique).
Second, estimate cell length as nucleus length time ratio between total number of cell profiles on section and number of nuclear profiles.