To obtain 10 hearts, you need 8 PA-1's (8 + 2 base hearts)
The locations of the PA-1's in the game are here:
1. Lighthouse bathroom
2. Entrance to Black Isle Mines
3. Inside the Black Isle Mines
4. Buy from Nouri in the City
5. Ming Tsu's shop
6. Nutripills factory, the generator area in the electrical room (Knock a
mech into the electrical field to get to it)
7. Nutripills factory, in a cabinet guarded by two alpha-sections.
Nutripills factory, after defeating robot boss.
8. Slaughterhouse, in the North Wing, protected by 2 Alpha Section
soldiers and mines!
9. Slaughterhouse, North Wing, up a mined ramp with an Alpha Section
guarding the door.
10. Slaughterhouse, East Wing, after travelling under the crate
11. Lunar Transmitter, in the Vending Machine.
(Credit: Necroscope - Team Xbox Forums )
Note: You need Jade to have 8 of these at once herself.