New research conducted at Queen Mary University of London (QMUL) has discovered that the regulation of the length of primary cilia, which are small hair-like projections on the surfaces of most cells, can prevent the production of fat cells taken from adult human bone marrow. Such a discovery might be used to develop a way of preventing obesity.
What are primary cilia? For many years, almost all attention was focused on cilia that moved because their function was readily observable. However, Alexander Kowalevsky first reported in 1867 the presence of single (nonmotile) cilia in a variety of vertebrate cells. These solitary and nonmotile cilia are far more widespread than the motile type. In humans, only a few cell types have motile cilia, namely epithelial cells in the bronchi and oviducts, and ependymal cells that line brain vesicles. However, virtually all other cells have a primary cilium.
What makes primary cilia different from the motile form? First, they lack the central pair of microtubules, which would explain the lack of motility. Primary cilia also seem to lack dynein, one of the molecular motors needed for motility. In addition, some primary cilia do not project beyond the cell surface, and most, but not all, are very short. What do these organelles do if they are not sticking out of the cell, or motile?
Further work has shown that primary cilia are important in intracellular transport and also in sensory function for cells. Now it seems that primary cilia are also important in the process of adipogenesis.
Adipogenesis refers to the differentiation of stem cells into fat cells. The QMUL research team showed that during adipogenesis, the length of primary cilia increases, which increases the movement of specific proteins associated with the cilia. When the QMUL team genetically restricted primary cilia elongation by genetic means, they were able to stop the formation of new fat cells.
One of the lead authors or this study, Melis Dalbay, said that it was the first time that subtle changes in primary cilia structure can influence the differentiation of stem cells into fat.
Since the length of primary cilia can be influenced by various factors including pharmaceuticals, inflammation and even mechanical forces, this study provides new insight into the regulation of fat cell formation and obesity.
This research points toward a new type of treatment known as “cilia-therapy” where manipulation of primary cilia may be used in the future to treat a growing range of conditions including obesity, cancer, inflammation and arthritis.