Van Vuuren, who is 28 years old, initially made the switch to Franklin’s Gardens from Bath in the summer of 2019.
The South African-born hooker has made nine appearances in black, green and gold this season, but he will soon be plying his trade in the Championship having signed for Ealing Trailfinders.
Meanwhile, 22-year-old loosehead Trinder came through Saints' Academy system and represented England Under-20s in 2018.
He was only able to make two first-team appearances for Saints.
“Michael and Toby have been important members of our squad in their time at Franklin’s Gardens,” said Saints boss Chris Boyd.
“Both have had a positive influence on the group, on and off the pitch.
“I know they will be missed here, but they are two ambitious guys looking for more time on the pitch, and leave with our very best wishes.”
Scottish prop Gordon Reid will also depart Saints on June 30 having been unable to make a single appearance for the club due to the Covid-19 pandemic.
Reid signed as injury cover earlier on March 11, five days after what is still Saints' most recent match, at Worcester Warriors.
Earlier this week, it was confirmed that two other Saints players would be leaving the club, with prop Will Davis and scrum-half James Mitchell heading to Ealing and Doncaster respectively.