Psoriasis is a chronic autoimmune disorder that affects 2% of the world population.  It is characterised by inflammation and scaling of the skin, accompanied by a greater risk of contracting some type of metabolic syndrome, predisposing patients to pathologies, such as obesity, diabetes or cardiovascular diseases. However, it is still not well understood how different inflammatory stimuli can lead to these other diseases.

Now, a study from researchers at the Spanish National Cancer Research Centre (CNIO) shows that psoriasis patients experience a widespread bone loss as a result of the disease and describes the molecular communication that is established between the inflamed skin and loss of bone mass. The team state that their data highlights the possibility of treating psoriasis with drugs that are already on the market, or in advanced clinical trial stages, that would have additional benefits for bone strength and quality.  The study is published in the journal Science Translational Medicine.

Earlier studies from the lab generated a mouse model, from which they had removed the JunB gene in keratinocytes, cells that form the epidermis, mimicking what happens during cutaneous inflammatory disorders in humans. The current study shows how this mouse model suffers from bone loss.

The current study shows that the immune cells in the skin of this animal model generate large amounts of the cytokine IL-17, a protein of the immune system that activates cellular inflammation in response to damage. Results show that IL-17 travels through the bloodstream to the bones and acts on the osteoblasts to inhibit Wnt activity.  The group explain that the Wnt pathway is a cellular signalling pathway which is involved in the formation of the skeleton and in certain disorders, such as osteoporosis and myeloma. Data findings show that treating these mice with IL-17 blockers allows the Wnt pathway to regain its normal activity and leads to bone formation.

The researchers also analyzed human samples using high resolution peripheral computed tomography, an imaging method known as virtual bone biopsy.  They observed that psoriasis patients had bone loss when compared to healthy people, and this correlated with increased levels of cytokine IL-17A in blood.

The team surmise that they have detected that psoriasis causes the widespread and progressive loss of bone tissue.  They go on to add that their observations suggest that patients with psoriasis should be monitored for this loss of bone mass, or the presence of high levels of these factors in the blood.  For the future, the researchers state that treating psoriasis patients with IL-17 blockers could have a beneficial effect on the loss of bone tissue, unlike other compounds that might only affect skin inflammation.

Source: Spanish National Cancer Research Centre (CNIO)