How wounds heal and why it takes longer as you get older

Why does a child's scraped knee generally heal faster than an adult's? Does the saying “time (usually) heals all wounds” still ring true?

Future Industries Institute (FII), Foundation Fellow, Dr Zlatko Kopecki, was recently interviewed on this topic by ABC Science reporter, Belinda Smith, His recent work seeks to understand the mechanism behind wound healing and developing therapies that promote regeneration of the skin.

The job of the skin is to close a wound as quickly as it can to prevent infection, but that comes with the expense of getting a scar. Something like a graze on a knee would be an acute wound and go through the four stages of wound healing.

The first stage called “Hemostasis” involves a blood clot forming in order to prevent further bleeding. This results in a scab formation which also functions to prevent wound infection but delays the wound healing process.

The second stage is “Inflammation” where inflammatory cells called neutrophils and macrophages help fight infection by eating pathogens, dead cells and other debris. In an acute wound the inflammation subsides in three (3) days and if this doesn’t occur the wound may become chronic.

The third stage is “Proliferation”, where resident skin cells, keratinocytes and fibroblasts, proliferate to reinstate a skin barrier and produce collagen matrix giving skin its elasticity and structure. As the new epidermis is established and as the scab begins to lift from the edges, it begins to itch. And while it's tempting to have a bit of a scratch or pick at the scab at this point “DON’T”. If the wound starts bleeding again, you're back to square one.

Finally, we get to last phase of wound healing called “Remodeling”, the longest of the phases, which can take months. During “Remodelling”, the collagen fibres end up lying parallel to each other and the scar flattens. This parallel arrangement is the reason scar tissue is only around 80 per cent the tensile strength of healthy skin, Dr Kopecki said.

Collagen in unbroken skin is laid down in a much stronger basket weave pattern. Some people end up with bulging scar tissue, called keloid scars. "They're completely benign. All it means is in the remodelling phase, a wound doesn't get the signal to stop secreting collagen, so you end up with a big scar," Dr Kopecki said. There's evidence that gels containing silicone can help here, he added.  Massaging scars can help minimize them too.

Children heal faster than adults and while we don’t fully understand why, the child’s skin needs to keep up with their development.  While older adults do heal however, the process is much slower and often leads to development of chronic non-healing ulcers and further complications. In much older people, wound healing can be a real problem. As we age, our skin becomes thinner, almost papery, and tears more easily.

On top of that, there's just not enough tissue to get the healing ball rolling quickly. Throw in poor circulation, and acute wounds can become chronic, sometimes lasting decades. At the other end of the age spectrum, foetuses up to the third trimester are able to heal not by repair, but by tissue regeneration. So instead of ending up with scar tissue, a wound will heal to include sweat glands and hair follicles, Dr Kopecki said. "We're trying to understand how we can develop therapies which will move the healing process from wound repair to tissue regeneration," he said. Novel approaches being developed at Future Industries Institute, UniSA aimed at improving the healing process, decreasing scarring and wound infection, as well as preventing chronic wounds and promoting tissue regeneration hold promise to significantly impact the lives of thousands of Australians suffering from chronic wounds in the community.