The pilot was landing the helicopter on a nose-up slope when he "noticed the helicopter started to tilt aft." As the pilot "immediately" increased collective pitch and applied forward cyclic to abort the landing, 3 of 4 main rotor blades struck the wire strike protection system on the cabin roof, which resulted in substantial damage to the blades. Representatives from the helicopter manufacturer inspected the helicopter, replaced the 3 damaged rotor blades, and the helicopter was returned to service. According to the pilot, there were no mechanical deficiencies with the helicopter that prevented normal operation.