The wound-healing process has been used in the rejuvenative model. This process consists of overlapping phases of inflammation, proliferation, and remodeling. During inflammation, neutrophils, leukocytes, monocytes, and/or macrophages migrate to the site of the wound; monocytes differentiate into phagocytic cells to phagocytose debris and secrete growth factors. Complement system proteins are activated, stimulating mast cell degranulation and attracting more neutrophils. Macrophages release platelet-derived growth factor, which stimulates the chemotaxis and proliferation of fibroblasts. Leukocytes and macrophages also secrete fibroblast growth factor, which promotes the recruitment and growth of more fibroblasts, establishing the proliferative phase of the wound-healing process.[6,7] Leukocyte numbers decrease, and macrophages begin to diminish slowly as fibroblast levels peak days later. The remodeling phase begins with a fall in the number of fibroblasts; active fibroblasts either differentiate into myofibroblasts or dedifferentiate into dormant fibrocytes. The fibroblast plays a key role in the dermis during the second and third phases: it not only synthesizes collagen and elastin but also regulates the homeostasis of the ground substance in addition to maintaining the collagen fibers. Myofibroblasts position themselves along collagen fibers and exert a longitudinal force that tightens and aligns the latter. Remodeling may take 3-6 months or longer. The end result is the deposition of new collagen fibers in a better organized cellular matrix accompanied by elastogenesis and angiogenesis. A layer of new, tightly-organized collagen runs below and is attached to the basement membrane of the dermoepidermal junction.
Red light (633 nm) may aid in effectively healing long-term torpid ulcers and may enhance angiogenesis in the rabbit ear chamber model. Six hundred thirty-three nm light significantly stimulates a faster and better linearly-oriented monolayer formation of fibroblasts in vitro as compared with controls. It accelerates mast cell degranulation and increases the synthesis of fibroblast growth factor from photoactivated macrophage-like cells.[9,10] Irradiation with low-level narrowband 660 nm red light induced the release of growth factors from macrophages in vitro and significantly improved postoperative wounds in vivo.[11,12]
Red light, in the absence of a wound, may be beneficial as an antiaging therapy. Mast cells are always present in the dermis; 633 nm red light may have the same effect on them regardless of their involvement in the inflammatory process. The surrounding tissue recognizes this degranulation as inflammation, and so the wound healing process is jump-started. Visible yellow light (588 nm) may also be beneficial as antiaging therapy through mechanisms similar to the action of red light (see Gentlewaves, Light BioScience, LLC, Virgina Beach, VA; please see Table 1 for sources of red light).
© 2005 Le Jacq Communications, Inc.
Cite this: Light Emitting Diode-Based Therapy - Medscape - Jan 01, 2005.