Doctors have long known that Restylane patients need fewer maintenance injections- and many can even stop treatment. Now University of Michigan researchers have figured out why: Restylane restretches fibroblast cells into a more youthful shape, triggering them to boost collagen production. Although the study was conducted on sun-damaged volunteers ages 64 to 84, the new collagen is a healthy “teen” type, lasting up to 15 years, David E. Bank, MD, a dermatologist in Mt. Kisco, NY.