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The goal of this study was to establish a reliable three-dimensional culture system for the mammalian retina that allows the analysis of retinal function and dysfunction. To produce three-dimensional retinal tissues in vitro, dissociated retinal cells of neonatal rats were maintained in culture dishes on a self-made orbital shaker. On the basis of well-defined rotation conditions, dissociated free-floating cells reaggregate in the center of the culture dish to form a multicellular cluster. Subsequently, cells begin to proliferate, whereby they form spherelike retinal tissues that grow to a size of 180-210 microm. Immunohistochemical characterization of mature retinal spheres revealed the presence of ganglion cells, amacrine cells, Müller cells, and rod photoreceptors, which are arranged in different retina-like layers. Although a small number of cells undergo programmed cell death, retinal spheres remain viable for at least 35 days in culture as revealed by fluorescein diacetate and TUNEL staining. Because most biological processes involved in tissue organization such as proliferation, differentiation, apoptosis, and survival are also observable in retinal spheres, the presented novel mammalian three-dimensional culture system is not only an outstanding model for basic research but may also be of great benefit for stem cell tissue engineering and the pharmaceutical industry.

Background: We developed a highly sensitive cardiomyocyte based screening system for the non-destructive electronic detection of chronotropic drugs and tissue-secreted factors involved in AT₁ receptor-mediated cardiovascular diseases. Methods: For this purpose we cultured spontaneously beating neonatal rat cardiomyocytes on microelectrode arrays (MEAs), and tested the optimised, stable culture parameters for a reproducible real-time recording of alterations in contraction frequency. After the evaluation of culture parameters, computer-based electronic measurement systems were used for counting of contractions by recording of the field potential of cardiomyocytes. Results: Using the biosensor, angiotensin II, the predominant ligand of the AT₁ receptor, was detected at very low concentrations of 10^-11 M via altered contractions of cardiomyocytes. Moreover, we demonstrated that cardiomyocyte coupled microarrays allow the detection of blood-derived low concentrated anti-AT₁ receptor autoimmune antibodies of pregnant women suffering from preeclampsia. Conclusion: This study demonstrates the first well-suited electrophysiological recording of cardiomyocytes on multielectrode arrays as a benefit for functional biomonitoring for the detection of AT₁ receptor/ligand interactions and other marker proteins in sera directed to cardiovascular diseases.

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