Development of age spots as a result of accumulation of aged cells in aged skin

Age spots are the brown spots that develop in the skin but change in color and shape with time. To understand the mechanism of development of age spots, characteristics of age spots are analyzed with Misrepair mechanism, a mechanism introduced in Misrepair-accumulation aging theory. An age spot is pathologically a group of aggregated basal cells, which contain lipofuscin bodies. Accumulation of lipofuscin bodies is a sign of aging of a cell. Characteristics of age spots include: in-homogeneity in distribution, growing flatly before becoming protruding, irregularity on shape, in-homogeneity on the color and the protruding degree of a spot, and softness of the protruding spots. Based on these characteristics, we make a hypothesis on the development of age spots. A. Aging of a tissue is the basis for the development of age spots. Deposition of a lipofuscin-containing cell is a consequence of aging of the skin, and it is a manifestation of Misrepair. B. A flat spot results from the accumulation of lipofuscin-containing cells. When an aged cell remains, this cell can accelerate the aging of its neighbor cells by increasing the damage-sensitivity and reducing the repair-efficiency of local tissue. By a viscous circle, more and more neighbor cells become aged and they form a flat spot with irregular shape. C. A protruding spot develops when some of the cells in a flat spot die and release lipofuscin bodies. For the survival of the organism, un-degradable lipofuscin bodies have to be isolated by a capsule composed of fibrotic membrane for maintaining the structural integrity of the local epidermis. Successive deaths of lipofuscin-containing cells make the capsule “grow” in three-dimension with multiple layers of fibrotic membrane, resulting in the protruding of a spot. In conclusion, development of an age spot is a result of accumulation of aged cells in aged skin.