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KMID : 0363219620020020001
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Korean Journal of Dermatology
1962 Volume.2 No. 2 p.1 ~ p.22
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Histologic Studies in Korean Fetal Skin, Especially on Pigment Cells and Pigment Granules
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Abstract
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For many decades, problem concerning the origin and function of pigment cells in skin has attracted great interest of many investigators, and the debate is still going on.
Since it is known that the skin color in vertebrate and human depends on melanocytes and melanin granules, many works on melanocytes in different human races have been accumulated. The effort has been conoentrated on the study of the origin and function of melanocytes.
In 1901 Bloch suggested intraepidermal origin from transformation of basal cells by a certain stimulus, and pigment cells in corium is derived by so-called "Abtropfung". His theory has been supported by many followers even today. However, Masson (19 26), Becker (1927), Peck (1930), Rawles (1948), Billingham (1948, 1949), Zimmermann (1948), Becker et al. (1952), Lerner and Fitzpatrick (1950, 1953), Zimmermann and Becker (1959) claimed neuro-ectodermal origin of melanocytes in human and mammalians, instead of intraepidermal origin. According to them melanocytes derived from neural crest and migrate to epidermis through corium during early developmental life. At the present the consensus of opinion in neuro-ectodermal origin and an only minor group of investigators still insists epidermal origin.
In 1948, by transplantation experiment in mouse embryo Rawles proved that pigment formation was impossible by mouse transplantation of epidermis or hair follicles without ganglion. However, such schematic experiment in human was not applicable. Therefore, the studies on the origin of melanocytes in human epidermis focused naturally to demonstrate immature melanocytes and their mode in the corium Such study has been rather extensively carried out in adult, but similar study in fetal life is rat-her sparse. In 1955 Becker and Zimmermann observed many melanin containing spider cells on horizontal shaving of fetal Negro skin of the 3rd to the 4¼ th month old.
In the later period of fetal life, from the 6th month, pigment cells in the corium we-re found only at limited areas; head, sacral region, fingers and toes, whereas pigment cells in epidermis were found throughout the body surface from the 3rd month of fetal life and there on, although individual variation was rather marked.
In 1958 Tanaka stated that epidermal color and appearance of melanocytes in epidermis differ by races, and in Japanese the first appearance was noted in the 3rd and the 4th month of fetus. And the most of the pigments were confined in melanocytes in fetal epidermis rather than Malpighiaa cells in contrast to adult. In view of racial difference of melanocytes in skin, present investigation is undertaken to investigate pattern of melanocytes in Korean fetal skin, as well as in attempt to clarify the basic problem of the origin of epidermal melanocytes.
Materials and Methods
55 fetuses obtained from healthy mother, ranging from the 2½th month to full term fetal ages were used. The sex, weight, length (Crown-Rump and Crown-Heel), and cranial circumference were measured accurately. The fetal age was calculated by formula of Scammon and Calkins with consideration of clinical history.
The distribution of fetuses was as follows.
Month 2½ 3 3½ 4 4½ 5 5½ 6 6½ 7 7½ 8 9 10 Total
Number 2 5 1 7 4 7 1 7 2 7 2 5 2 3 55
An 1 cm of skin was taken from scalp, upper arm, buttock, abdomen, thigh, palm and sole in each fetus. Tissue was fixed in 10% formalin and sectioned after paraffin embedding. Hematoxylin-eosin and Masson Fontana stain were applied in all sections and all sections were examined microscopically.
Melanocytes were divided into immature and mature form. Round and spindle sha: ped melanocytes are considered as immature and melanocytes with processes as mature form.
Results
A. Distribution of pigment cells in corium
1. The earlist appearance of pigment cells in corium were noted at upper arm of the 21½th month old fetus, in round shape with fine granular pigments in cytoplasm (fetus No. 1).
2. At the 3rd fetal month pigment cells became spindle shaped with concentration of pigments at poles. These -cells scattered irregularly at upper corium. In buttock, some pigment cells were still round shaped, and mostly scattered around blood vessels.
3. At the 3½th month, small numbers of mature melanocytes appeared in all areas except abdomen and buttock, and only a negligible numbers of immature melanocytes are found in scalp, palm and sole.
4. At the 4th and 4½th month, marked increase of immature melanocytes are noted at scalp, and small number in thigh, upper arm, palm and sole, but yet no mature form was found in abdomen and buttock.
5. At the 5th month, "marked increase of mature melanocytes is noted in buttock and upper arm, and considerable numbers in thigh and scalp. A few immature
form was noted at sole and upper arm.
6. At the 5½th month, similar pattern as the 5th month was noted. Many mature cells were found in scalp, upper arm, and buttock. A few immature form was noted in palm and sole.
7. At the 6th month, the pattern was similar to preceding, except limitation, of immature form only in palm in very few numbers.
8. At the 61½th month, no pigment cells were observed in sole, and only immature form was found at buttock. Otherwise same as preceding.
9. At the 7th month, pigment cells decreased markedly in palm and sole, slightly in thigh, and a few immature form was noted in scalp.
10. At the 7½th month, pigment cells decreased in numbers throughout the most part of skin, except buttock and thigh, and immature form was difficult to find.
11. At the 8th month, considerable number of mature melanocytes were observed in buttock, and upper arm, but in the remaining areas only scanty numbers were noted.
12. At the 9th month, immature form could no longer be found, but numerous mature form were noted, in buttock, small numbers in scalp and upper arm, scanty numbers in thigh.
13. At the 10th month, pigment cells were found with great difficulty in corium of the most areas, except scalp and buttock.
B. Distribution of pigment cells in epidermis
1. No pigment cells were found in epidermis of the. 2 ½th month fetus.
2. At the 3rd month, considerable numbers of mature melanocytes were observed in epidermis of scalp and thigh and mixed with occasional immature form.
3. At the 3½th month, abrupt increase of mature melanocytes with processes is noted, mixed with scattered immature form. Mature melanocytes also begin to
appear in palm and sole.
4. At the 4th and 4+th month, the pattern was similar to preceding, but immature form decreased in number.
5. At the 5th month, many mature melanocytes were found in thigh, scalp and buttock, but immature form decreased markedly in numbers.
6. At the 5½th month, distribution was similar to preceding month, but immature form decreased further or almost disappeared.
7. At the 6th and 6+th month, many mature melanocytes were found in buttock, upper arm and scalp and immature form was almost absent.
8. At the 7th month, marked decrease of melanocytes is noted in sole and palm but considerably large numbers of mature melanocytes were found in abdomen and upper arm.
9. At the 7½th month, number of melanocytes further decreased in palm and sole, particularly in palm, and the thigh showed most numerous number of melanocytes.
10. At the 8th month, immature form could no longer be observed.
11. At the 9th and 10th month, many spider shaped melanocytes were found in buttock, abdomen and upper arm but melanocytes were completely absent in palm and sole.
12. Pigment granules confined mainly inside of cytoplasm of melanocytes at early fetal life. But as the age increases processes developed from melanocytes and extended into adjacent intercellular spaces which anastomosed with neighboring melanocytes, and pigment granules started to deposit in adjacent epithelial cells at the 5th month.: After the 6th month, pigment diffusely deposited in basal layer, except in palm and sole. From the 7th month melanocytes decreased markedly in palm and sole, especially more in palm.
Conclusion
1. Appearance, distribution, and alteration of melanocytes and melanin pigment of skin at 7 different locations in 55 Korean fetuses were studied according to the age of fetuses.
2. The earlist appearance of immature melanocytes were observed at corium of upper arm in the 2½th month old fetus. They were round shaped containing fine pigment granules.
3. The number of melanocytes in corium was rather scanty. They were round or oval shaped immature forms at the early fetal life, but became spider shaped and processed as the fetal age increases, and were mostly mature forms at full term.
4. In full term fetuses, melanocytes were observed in corium of buttock, thigh, scalp, and upper arm only, and absent or very scanty in other locations.
5. In early fetal life melanocytes "were observed in -all part of corium, particularly around hair follicles, blood vessels and upper corium. In palm and sole, melanocytes decreased rapidly in numbers after the 7th month.
6. In epidermis, melanocytes were observed as spider shaped mature form already in the 3rd month.
7. Melanocytes in epidermis were spindle shaped with long axis parallel to the surface of skin in early fetal life, but became gradually swollen with development of processes which spread into adjacent intercellular spaces and anastomosed with neighboring melanocytes, and situated vertical to the surface of skin as the fetal age increased.
8. Pigment granules were confined inside of melanocytes at early period of fetal life, and become dispersed and deposited in adjacent basal and epithelial cells in later period of fetal life.
9. Based on the result obtained by present investigation, author support the theory of Masson´s neuro-ectodermal origin of melanocytes and migration to epidermis through corium during fetal life.
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