Melanocyte Migration Research Articles

Incontinentia Pigmenti Achromians

The occurrence of multiple cases of incontinentia pigmenti achromians within a single family is reported for the first time. The disease is a genetic defect exhibiting autosomal dominant inheritance, and is thus a distinct entity, not a less severe variant of the Bloch-Sulzberger type of incontinentia pigmenti. The phenotype is manifest as two distinct clones of melanocytes with different structural and possibly functional properties. The appearance of the phenotypes, before the migration of melanocytes from the neural crest has occurred, may explain the bizarre pigmentary pattern.

STUDIES ON THE MIGRATORY BEHAVIOR OF MELANOCYTES IN GUINEA PIG SKIN

Pigment spread is the natural or experimentally procured (through grafting) progressive encroachment of pigmentation from black or red skin areas into juxtaposed white skin areas, or from black skin areas into red skin areas in spotted guinea pigs and other mammals. So far as spread from black into white skin is concerned, it had previously been shown that migration of epidermal melanocytes into skin lacking homologues of these cells was responsible. However, since red skin already has its own complement of phenotypically "red" melanocytes, the intriguing possibility remained that when black pigment encroaches upon red, rather than melanocyte migration being responsible, phaeomelanin (red)-producing melanocytes are transformed into eumelanin (black)-producing cells by some kind of serially transmissible factor derived from contiguous eumelanotic melanocytes. By utilizing two isogenic strains (Nos. 2 and 13) of spotted guinea pigs and their F(1) hybrids, the mechanism underlying the spread of pigment from black into red skin has been analyzed, employing cellular transplantation antigens as melanocyte "markers." The findings demonstrate unequivocally that a physical migration of pigment cells is responsible. By comparing the extents of pigment spread from black ear skin grafts, or from epidermal cell suspensions prepared therefrom, from parental strain or from F(1) hybrid donors in white host skin areas of F(1) hybrid guinea pigs, it has been possible to evaluate the influence of the intimate contact of melanocytes with alien transplantation antigens on their survival and migratory behavior. No evidence was forthcoming that pigment spread takes place less readily when the cells responsible are confronted by epidermal cells bearing foreign antigens than when they are confronted by cells of their own antigenic constitution. These findings are contrary to expectation if the phenomena of allogeneic inhibition or contact-induced cytotoxicity apply to normal cells in in vivo situations.

Treatment of Vitiligo With Topical Methoxsalen and Blacklite

Fourteen of 15 vitiligo patients responded to the topical use of methoxsalen and subsequent exposure to long-wave ultraviolet light. Three of the subjects showed complete repigmentation. Adverse reactions were prevented by using a controlled energy source with a light emission pattern corresponding to the biologic action spectrum of the photosensitizer. As a delayed 48 to 72 hour erythema was produced, only weekly treatments were necessary. Repigmentation began after two to ten treatments and migrated out from the hair follicles or advanced in from the borders of the vitiliginous areas. This repigmentation was associated with the migration of Dopa-positive melanocytes into the treated areas.

Migration of limbal melanocytes.

RECENTLY, we suggested1,2 that pigmented melanocytes from the limbus of the eye of the guinea-pig could be stimulated to enter the basal layer of corneal epithelium. Within the cornea, normally transparent and colourless, the pigmented dendritic cells could be studied in vivo and in vitro with little technical difficulty. Our method involved topical application of a solution of colchicine (0.1–0.01 per cent in saline) to the cornea once or twice daily for a week or more. In another experiment a solution of alloxan was injected into the anterior chamber of the eye. In both cases melanocyte migration occurred after the superficial cornea became vascularized; the greater the extent of superficial corneal vascularization, the more extensive the melanocyte invasion of the basal layer of the corneal epithelium. As corneal pigmentation increased, the limbal band became less pigmented. The observations seemed to support the concept that mature melanocytes (at least the melanocytes from the corneal limbus of a mature animal) are capable of migration, and that there is a relationship between this movement and the underlying neovascularization. It should be made clear that the melanocytes in the experimental model were not in direct contact with the new vessels, but were separated from them by Bowman's membrane and a variable amount of corneal stroma.

Migration of limbal melanocytes into the corneal epithelium of guinea-pigs

The corneal epithelium of the guinea-pig normally contains few if any pigmented melanocytes. Following the injection of alloxan into the anterior chamber, or topically applied colchicine drops, the guinea-pig develops corneal vascularization, and this is accompanied by melanocyte migration from the pigmented limbus into the basal layers of the corneal epithelium. Though the melanocytes can be demonstrated in routine histological preparations, flat preparations of the epithelium, with or without underlying stroma, are more instructive. Corneal epithelial melanocyte migration is distinet from the process of limbal ȁslidingȁ. In the former, melanocytes actively migrate into the basal layers of the epithelium, whereas in the latter, pigment-containing Malpighian cells from the limbus cover previously denuded corneal epithelium.

Origin of Pigment Cells from the Neural Crest in the Mouse Embryo

testing the pigment-forming potency of various portions of mouse embryos of a potentially pigmented (black) strain, evidence was obtained which suggested that the migratory pigment-forming cells, the melanophores, take their origin from the neural crest, as in other vertebrates, e.g., amphibians and birds.The results of grafting a variety of embryonic mouse tissues, such as skin ectoderm plus the underlying mesoderm, somites with and without the adjacent neural tube, limb buds and prospective limb buds, from various body levels, showed