This led, among other things, to a generalization of the fundamental decomposition theorems of Alexander Beilinson, Joseph Bernstein, Deligne, and Ofer Gabber about perverse sheaves in positive characteristic to characteristic 0.
[1] The theory of Hodge D-modules forms the starting point for the theory of the twistor D-modules developed by Claude Sabbah and Takurō Mochizuki, which lead to led to another generalization of the Beilinson–Bernstein–Deligne–Gabber theorem by Mochizuki.
In 2006 Saito, with Nero Budur and Mircea Mustață, generalized the notion of a Bernstein–Sato polynomial (aka b-function or b-polynomial) to an arbitrary variety.
[2] Saito's research deals with "applications of the theory of mixed Hodge modules to algebraic geometry, including the theories of singularities, algebraic cycles, characteristic classes, and so on.
"[3] In 1990 he was an Invited Speaker with talk Mixed Hodge Modules and Applications at the International Congress of Mathematicians in Kyoto.