Stereological image analysis of cultured human melanocytes observed by transmission electron microscopy

Application of stereology to dermatological research

Stereology is a set of mathematical and statistical tools to estimate three-dimensional (3-D) characteristics of objects from regular two-dimensional (2-D) sections. In medicine and biology, it can be used to estimate features such as cell volume, cell membrane surface area, total length of blood vessels per volume tissue and total number of cells. The unbiased quantification of these 3-D features allows for a better understanding of morphology in vivo compared with 2-D methods. This review provides an introduction to the field of stereology with specific emphasis on the application of stereology to dermatological research by supplying a short insight into the theoretical basis behind the technique and presenting previous dermatological studies in which stereology was an integral part. Both the theory supporting stereology and a practical approach in a dermatological setting are reviewed with the aim to provide the reader with the capability to better assess papers employing stereological estimators and to design stereological studies independently.

Treatment of atrophoderma of Pasini and Pierini-associated hyperpigmentation with the Q-switched alexandrite laser: a clinical, histologic, and ultrastructural appraisal

BACKGROUND AND OBJECTIVE

Atrophoderma of Pasini and Pierini (APP) is an uncommon cutaneous disorder, with no known effective treatment, manifested by hyperpigmented patches that appear to be depressed compared with surrounding skin. This study investigated the effectiveness of the Q-switched alexandrite laser on a patient with extensive APP, and evaluated histopathologic and ultrastructural changes.

STUDY DESIGN/MATERIALS AND METHODS

A man with stable APP underwent Q-switched alexandrite laser treatment to a patch on the trunk. Biopsies were obtained from treated and untreated sites of involvement. Light and transmission electron microscopic evaluation was performed to investigate melanosome number, size, and volume, as well as melanin granule number and size.

RESULTS

After three treatment sessions, the treated area showed marked clinical improvement. Electron microscopy showed a 19% reduction in melanin granule number and size and a 65% reduction in melanosome number, size, and volume in larger melanosomes in treated compared with untreated sites.

CONCLUSION

Treatment of APP with the Q-switched alexandrite laser results in clinical improvement. Electron microscopic evaluation suggests that the mechanism may be a reduction in the number, size, and volume of larger melanosomes as well as a decrement in melanin granule number and size.

Alternatives for morphometric and stereologic analysis in toxicopathology

Total cell numbers within a confined tissue volume, or fractions of cell numbers may be relevant in toxicopathology. They can be estimated with the disector, or the formula of Ebbeson and Tang. For the latter the thicknesses of the sections should be estimated, e.g. with confocal microscopy, or with a vertically embedded section. The use of these methods, in combination with Cavalieri's principle, will avoid the inconsistencies possibly associated with differences in the level of sectioning. Biochemical tests on intracellular specific molecules may be applied on homogenized tissue. If the tissue is composed of different cell types reacting differently to the tested substance, it may be necessary to estimate the fractions of different types of cells in the tissue concerned. Because of cell size differences, single sections do not give truthful results. The problem is solved by applying the formula of Ebbeson and Tang.

Comparison of HPLC and stereologic image analysis for the quantitation of eu- and pheomelanins in nevus cells and stimulated melanoma cells

The aim of the study was to compare two methods of quantitating eumelanins and pheomelanins, pigments synthesized by melanocytes. One is based on the high performance liquid chromatography quantitation of specific degradation products of each melanin type. The other requires image analysis, transmission electron microscopy, and stereology. In a previous study, we showed good correlations between both methods for total melanin but not for eumelanins or pheomelanins. We describe here the same comparison in more pigmented cells (nevus cells and stimulated HBL melanoma cells). Transmission electron microscopy micrographs were image analyzed to generate several primary parameters. Stereology was used for estimating melanosomal maturation, intracellular melanin content, and the number of melanized melanosomes per cell, for total melanin, eumelanins, or pheomelanins. Our results showed a good correlation between both methods for total melanin, eumelanins, and pheomelanins with an r equal to 0.99, 0.91, and 0.93, respectively, when all the points were used in the linear regression analyses. In the melanoma cell group (HBL cells cultured in media of different compositions), the chemical and morphometric estimations were not parallel in the case of eumelanins and pheomelanins. In addition, the stereologic and high performance liquid chromatography pheomelanins to eumelanins ratios were still not correlated. These results demonstrate the relevancy of the stereologic method, but the low level of melanization, the possible lack of specificity of melanogenesis in melanoma cells, and a problem of sensitivity of the stereologic method in this context seem to be obstacles in obtaining better results. The utilization of normal human melanocytes could give some answers to our hypotheses.

Comparison of high performance liquid chromatography and stereological image analysis for the quantitation of eumelanins and pheomelanins in melanoma cells

The aim of the study was to compare two methods quantifying eumelanins and pheomelanins, pigments synthesized by melanocytes. One is based on the high performance liquid chromatography (HPLC) quantitation of specific degradation products of each melanin type. The other requires image analysis, transmission electron microscopy (TEM), and stereology. This study was carried out in cultured human melanoma cells and for each line, melanins were measured by HPLC and cells were fixed and embedded as pellets for TEM. Ultrathin sections were treated or not by the alkali elution method allowing the elimination of pheomelanins. The obtained micrographs were analyzed with our image analysis program permitting the estimation of several primary parameters. Stereology was used for estimating melanosomal maturation, intracellular melanins content, and number of melanized melanosomes per cell, for total melanin, eumelanins, or pheomelanins. Our results show a good correlation between both methods for total melanin, particularly when using the cytoplasmic volume density of melanin (r=0.93). Moreover, we report that the number of melanized melanosomes per cell and not the melanosomal maturation is responsible for the differences in total melanin content observed between the different cell lines. However, none of the stereological melanization parameters was correlated in the case of eumelanins or pheomelanins. In order to demonstrate the utter relevancy of this stereological approach, utilization of more pigmented melanoma cells, comparative study of HPLC and stereology, in normal epidermal melanocytes and a new evaluation of the alkali elution method in appropriate animal models would help us to explain the present results.