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.Comparative StudyJournal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Quantification of eumelanin and pheomelanin: stereologic image analysis method.

OBJECTIVE: To develop an ultrastructural stereologic image analysis method allowing quantification of intracellular melanization. STUDY DESIGN: First, in the field of image analysis, a newly elaborated segmentation method, SEM2, was compared with a previously described method based on gray level histograms. Only SEM2 allows the segmentation of melanin in micrographs of poorly melanized melanocytes. Second, in the field of stereology, estimation of cell volume remains problematic in the case of mixed cell populations. This problem is approached by the comparison of stereologic alternatives and cytochemistry (L-3, 4-dihydroxyphenylalanine reaction) in epidermal melanocytes and melanoma cells from several in vitro experiments. The cytochemical approach was found to be the best choice. RESULTS: Concerning the quantification of eumelanin and pheomelanin, the alkali elution method, permitting the specific dissolution of pheomelanin on ultrathin sections, was validated in normal human follicular melanocytes. CONCLUSION: These results allow us to envisage the stereologic quantification of eumelanin and pheomelanin at the ultrastructural level. At present our method is undergoing evaluation by comparison with the present method of reference based on high-performance liquid chromatography.Comparative StudyJournal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

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.Comparative StudyJournal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe