Regenta is a title used in two separate incarnations of TMNT, for two different (but not dissimilar) species, with completely different connotations.
Mirage[]
Regenta is a title for Protoceraton royalty that is roughly equivalent to the idea of a "princess" on Earth - a female or feminine child of a seated royal ruler. The Regenta seen in this series is Seri, Regenta of N'Yood Minor.
IDW[]
In the culture of Triceratons, a Regenta is an acting leader in lieu of one chosen politically or legally, the traits which the Triceraton had never really had, instead defaulting to military leadership. Once again, the Regenta in this incarnation is Seri.