Handstands are the ultimate test of balance—even the slightest weight shift can topple the pose. Similarly, healthy skin involves a delicate balance of cell renewal and cell death. As skin cells gradually move from the inner to outer layers of our skin, they divide, differentiate into hardy forms, and eventually die to form our body’s protective barrier against the elements.
However, in skin disease such as psoriasis, a hyperproliferative disorder, skin cells can multiply up to 10 times faster than usual, often resulting in itchy, scaly and inflamed patches. Researchers studying the skin’s mysteries have uncovered new details about the root of this uncontrolled proliferation: a balancing act between a triad of metabolites known as polyamines.
"Polyamines are a family of metabolites that are essential for normal cellular function in all cells,” explained Leah Vardy, Covering Executive Director at the A*STAR Skin Research Labs (A*SRL). Polyamine levels have previously been observed to be lowered in ageing skin and elevated in hyperproliferative skin showing the importance of tight control of their levels.
To better understand the factors affecting this triad of polyamines in our skin, Vardy and colleagues focused on a polyamine regulator protein called adenosylmethionine decarboxylase 1, or AMD1. In particular, the research group was interested in how AMD1 influenced gene expression patterns in skin cells, and how these changes impacted the skin’s overall ability to act as a protective barrier.
First, the researchers took a closer look at patterns of AMD1 expression within the various layers of healthy human skin. They found that the AMD1 protein was least expressed in the deepest or basal layers of the epidermis, where skin cells normally focus on dividing themselves. Moving outwards, however, AMD1 expression gradually increased, peaking in the outermost skin layers where cells were most differentiated. They also found that AMD1 promoted high levels of Spm, a polyamine essential for the cell differentiation process.
Taking these two findings together, the researchers suggested AMD1 helps skin cells shift their behavioral gears—stopping division and starting differentiation—by gradually altering the balance of the three polyamines in different skin layers.
In follow-on cell culture experiments, the team blocked AMD1 activity in differentiating skin cells and found that this threw off the balance between Put, Spm and Spd, resulting in skin cells that behaved much like they would in patients with psoriasis. However, adding Spd and Spm into the culture ‘rescued’ skin cell differentiation, restoring a robust epidermal barrier.
Moving forward, Vardy said the team plans to explore the possibility of using AMD1 as a treatment target to tackle hyperproliferative skin disorders and ageing-related skin conditions.
“Our findings have demonstrated the importance of fine-tuning the levels and ratios of the three polyamines,” Vardy commented, adding that they identified AMD1 as being central to maintaining this equilibrium. “We need a better understanding of how these polyamine ratios change in hyperproliferative conditions, as any therapeutic methods would need to control them to be effective.”
The A*STAR-affiliated researchers contributing to this research are from the A*STAR Skin Research Labs (A*SRL).