All too often, explanations for why we get wrinkles are quite disappointing.
For example, we get wrinkles “because of UV damage”. That’s not a good explanation. Parts of our body that are never exposed to UV light also become wrinkly, saggy and thinner.
Or we are told that wrinkles are caused due to “genetics”. Of course, everything that happens in the body can ultimately be explained by genetics, because without genes there would not even be a body!
Or we get vague descriptions of what happens. Like, that the “amount of collagen in the skin is reduced”, or “the elastin network gets more disorganized”.
These are not very satisfactory explanations. Why does the skin contain less collagen and elastin? Why does the skin become more thin and saggy?
To explain this, we have to explore the more deeply-rooted causes of skin aging.
There are two kinds of damage to our skin: extrinsic damage and intrinsic damage.
Extrinsic damage is caused by things coming from outside of us or is caused by our behavior, like sun exposure, smoking, unhealthy food, taking specific medications, drinking too much alcohol, stress, specific repetitive facial expressions, sleep deprivation, and so on.
Intrinsic damage is the real and most important cause of wrinkles. It’s what happens in the body as a natural part of the aging process. This intrinsic aging process leads eventually to wrinkles on every body.
It doesn’t matter how much you protect yourself against extrinsic factors, like sun rays or eating very healthily, you will get wrinkles eventually, given they are the consequence of the natural, intrinsic aging process.
So what causes skin aging?
In essence, specific intrinsic aging mechanisms damage the stem cells and other cells in our skin, making them dysfunctional. That way, they cannot create new skin cells or maintain the skin properly by secreting collagen, elastin, and so on.
This aging damage is caused by aging mechanisms like epigenetic dysregulation, mitochondrial damage, oxidative damage, genomic instability, protein accumulation, cross-linking, and altered intracellular communication. To learn more about these aging mechanisms, click here.
These aging mechanisms first damage all of the stem cells in the skin. That’s not good, given stem cells need to generate new skin cells, such as fibroblasts, keratinocytes and melanocytes, which build up and maintain the skin.
For example, when the stem cells that create new melanocytes get damaged, we get grey hair. This is because melanocytes are cells that surround the hair root and pump melanin (a pigment with a brown or blackish color) into the hair root, giving hair its color. When skin stem cells cannot produce melanocytes anymore, we get grey hair (learn why we get grey hair).
When the skin stem cells cannot generate new skin cells anymore, the skin becomes depleted of cells like fibroblasts that produce collagen, elastin, and hyaluronic acid, all molecules that surround skin cells, glue them together and give elasticity, firmness and plumpness to our skin.
These aging mechanisms also cause damage to the non-stem cells in our skin, like fibroblasts. And some of these aging mechanisms can also convert these normal, innocuous cells into dangerous cells: senescent cells.
Senescent cells and skin aging
This brings us to another reason for skin aging besides skin stem cell depletion and dysfunction: the rise of senescent cells in our skin. Senescent cells are normal cells that became too damaged. But instead of killing themselves, they keep lingering around in the skin, secreting all kinds of substances that damage the healthy neighboring skin cells.
Senescent fibroblasts, for example, damage healthy surrounding fibroblasts and other skin cells and contribute to wrinkles, loose sagging skin, age spots and other forms of pigmentation we see increasing during aging.
Skin cells become senescent because of the sorts of damage we described before, such as damage to the genome, including the telomeres, mitochondrial dysfunction, epigenetic dysregulation and so on.
The aged, systemic milieu of our cells
The skin also gets hit by processes that happen far away from it, nowhere near the skin tissue. One such process is called “altered intracellular communication”.
When we get older, cells everywhere in the body start to secrete more and more substances that are unhealthy and damage our cells (often these cells are also senescent cells, like senescent liver, gut or bone cells). Examples are substances that increase inflammation. Or substances coming from a permeable gut layer (leaky gut). These deleterious substances also reach the skin, and when they do, damage the skin cells.