Agarose mold embedding of cultured cells for tissue microarrays

There are several indications for the placement of samples of cultured cells in tissue microarrays (TMAs). To optimize this technique, three embedding procedures were compared: embedding of fixed cells pelleted by centrifugation, embedding of cells dispersed in an agarose matrix, and embedding of pelleted cells packed into the center of hollow agarose molds. TMAs were made from these preparations. The number of cells per tissue spot and the number of histologic sections that could be obtained from the preparations were determined. The agarose matrix and agarose mold techniques resulted in the longest core samples, while the cell pellet and agarose mold methods resulted in the greatest cell density. Thus, the use of cylindrical agarose molds optimizes both the number of cells present on a histologic section of a TMA, and the number of histologic sections that can be obtained from a TMA. This technique results in a paraffin-embedded cell preparation that yields a cell density of approximately 1000 cells per 0.6-mm diameter circular histologic section, and that produces uniform core samples the full thickness of the donor block. Histologic sections of TMAs prepared in this manner were validated in immunohistochemical and in situ hybridization assays.