Tonight I will have to eat crow. I am meeting a friend for dinner in a few hours and it has been a few months since we last got together. On that occasion, I was utterly disdainful about her twice-yearly trips to top up her hyaluronic dermal filler. Doesn't last, waste of money, I rasped. Not for the first time, I may have been wrong.

Although, to be fair, I was in good company. It has been widely assumed that Restylane and other impermanent, injectable fillers simply worked by providing volume and puffing out the face (especially around the nasolabial folds) to give the impression of bonny youthfulness. A 2007 study by the University of Michigan strongly suggests that injectable fillers actually lead to the creation of new collagen.

That's a pretty big deal. And before you ask, this is an independent study; Restylane did not pay for it, although it did provide the syringes that were used on 11 volunteers aged 64 to 84. Biopsies were taken to analyze the skin. Eleven people doesn't sound like a convincing mass of evidence to me. But then again, this was a properly conducted, independent trial and the researchers seem pretty clear about having produced meaningful results.

Fibroblasts are in the dermis, the layer of the skin below the epidermis (outer layer). In young people, fibroblasts are stretched, and this produces enough collagen to make the skin appear relatively smooth. As people age, the fibroblasts become relaxed and do not stretch as easily, and therefore do not release as much collagen, causing creases and wrinkles to appear. According to the Michigan team, Restylane relaxed the fibroblasts, which were then re-stretched, and formed collagen.