Critical cells involved in scleroderma identified
Scleroderma, a term that is often used interchangeably with systemic sclerosis, refers to an autoimmune disease that mainly affects the skin and the connective tissue. Regardless of age and gender, all people may be affected by scleroderma. But the illness is most common in people aged 20 to 50, and occurs much more frequently in women than in men.
Although the exact cause of scleroderma still remains a mystery, several risk factors have been identified. First, genetic factors influence people's susceptibility to scleroderma. Statistics show that native American and African-American are more likely to develop scleroderma. Second, exposure to environmental factors like silica dust and organic solvents contributes to the development of scleroderma. Third, women, particularly in their childbearing years, are at a higher risk of scleroderma.
Scleroderma leads to changes in the skin, including hardening of the skin, loss of hair, change in skin color, ulcers or sores, and swelling. The illness is not confined to the skin; it also affects many other tissues and organs including the digestive system, heart, lungs, and kidneys. In scleroderma, there is an overproduction of collagen, which causes hardening and other damage. The blood vessels in the affected tissues may become narrow, leading to poor blood flow. The patient's fingers, toes, tips of ears, nose, and tongue become very sensitive to cold. The illness triggers not only physical pain but also emotional distress.
Unfortunately, at this time there are no effective ways to treat or prevent the debilitating illness, largely because its cause and pathogenesis have not been fully understood. Current treatment is mainly focused on reducing specific symptoms or protecting organ systems. As mentioned above, scleroderma is an autoimmune disease. Autoimmune diseases occur when the immune system that normally helps defend the body mistakenly attacks the body's own tissues. In scleroderma, the immune system triggers the excessive deposition of collagen and other connective tissue molecules in the skin and other organs. A class of drugs known as immunosuppressants, which are designed to weaken the immune system, have been used in the treatment of scleroderma.
Recently, scientists studying scleroderma have gained new insights into the illness. Their study has implicated a type of cells, known as plasmacytoid dendritic cells (pDCs), in the pathogenesis of scleroderma. The discovery suggests that pDCs could be targeted to develop novel treatments for scleroderma.
The full paper (Plasmacytoid dendritic cells promote systemic sclerosis with a key role for TLR8) appears in the journal Science Translational Medicine.
Activation of pDCs has been seen in lupus and other autoimmune diseases, according to corresponding author, Dr. Franck Barrat at HSS Research Institute, Hospital for Special Surgery. The research interests of Dr. Barrat include understanding the biology of human pDCs, which represent a link between innate and adaptive immunity. The unique role of pDCs in immunity could have potential clinical applications for treatment of many diseases such as cancer, allergies, and viral infections.
pDCs are potent producers of type I interferon. Upon stimulation and activation, these cells produce large amounts of type I interferon, which in turn mediates a wide range of anti-viral effects. In the current study, Dr. Barrat and colleagues discovered that pDCs infiltrate the skin of patients with scleroderma and are chronically activated. Working with mice, Dr. Barrat's team found that depletion of pDCs could prevent or revert scleroderma. Additionally, they found that pDCs contribute to scleroderma largely through activation of TLR8 and secretion of CXCL4.
In summary, the study implicated pDCs in the pathogenesis of scleroderma. Thus, removing these cells using antibodies or inhibiting their function may be a way to treat this debilitating disease.