Combined enzyme histochemical and ultrastructural study on cryostat sections of pig heart to detect early reperfusion damage after ischaemia

Evaluating Novel Targets of Ischemia Reperfusion Injury in Pig Models

Coronary heart diseases are of high relevance for health care systems in developed countries regarding patient numbers and costs. Disappointingly, the enormous effort put into the development of innovative therapies and the high numbers of clinical studies conducted are counteracted by the low numbers of therapies that become clinically effective. Evidently, pre-clinical research in its present form does not appear informative of the performance of treatments in the clinic and, even more relevant, it appears that there is hardly any consent about how to improve the predictive capacity of pre-clinical experiments. According to the steadily increasing relevance that pig models have gained in biomedical research in the recent past, we anticipate that research in pigs can be highly predictive for ischemia-reperfusion injury (IRI) therapies as well. Thus, we here describe the significance of pig models in IRI, give an overview about recent developments in evaluating such models by clinically relevant methods and present the latest insight into therapies applied to pigs under IRI.

Organotypic glioma spheroids for screening of experimental therapies: how many spheroids and sections are required?

Cancer spheroids are a valuable model for screening anticancer strategies. However, studies are published using various numbers of spheroids and sections per spheroid. Here, we establish the sample size requirements for valid screening strategies to treat glioma: how many spheroids per experimental group and how many sections per spheroid are required to detect one-third reduction in an endpoint measurement after treatment? From two glioblastoma patients, 32 untreated organotypic spheroids were cultured and sectioned entirely (14-100 sections per spheroid). The viable fraction was determined as endpoint by automated image analysis in sections and used to establish the minimally-detectable difference between a treatment and reference group. Variance was considerable with a coefficient of variance of 21%. The biological variation in viability in sections of spheroids produced 97% of variance when sample size was large. Variance increased when numbers of spheroids but not numbers of sections per spheroid were reduced. A minimum of 12 spheroids per group and one section per spheroid was required for a valid comparison of a treatment group and a control group. When 10 treatment groups and one control group were compared, 16 spheroids per group were required. Thus, the statistical power depended almost entirely on the number of organotypic glioma spheroids and hardly on the number of sections per spheroid. The organotypic glioma spheroid model does not appear to be suitable for high-throughput screening of anticancer strategies, because of the relatively large number of spheroids required. It is the model of choice for low-throughput screening, because this model is far more representative for the parental tumor than any other more efficient glioma model.

Quantification of viability in organotypic multicellular spheroids of human malignant glioma using lactate dehydrogenase activity: a rapid and reliable automated assay

Organotypic spheroids from malignant glioma resemble the biological complexity of the original tumor and are therefore appealing to study anticancer drug responses. Accurate and reproducible quantification of response effect has been lacking to determine drug responses in this three-dimensional tumor model. Lactate dehydrogenase (LDH) activity was demonstrated in cryostat sections of spheroids using the tetrazolium salt method. Calibrated digital image acquisition of the stained cryostat sections enables quantification of LDH activity. Fully automated image cytometry reliably demarcates LDH-active and LDH-inactive tissue areas by thresholding at specific absorbance values. The viability index (VI) was calculated as ratio of LDH-active areas and total spheroid tissue areas. Duplicate staining and processing on the same tissue showed good correlation and therefore reproducibility. Sodium azide incubation of spheroids induced reduction in VI to almost zero. We conclude that quantification of viability in cryostat sections of organotypic multicellular spheroids from malignant glioma can be performed reliably and reproducibly with this approach.

Electron microscopical enzyme histochemistry on unfixed tissues and cells. Bridging the gap between LM and EM enzyme histochemistry

In principle, enzyme histochemistry should be performed on unfixed tissues and cells to avoid inhibition of enzyme activity by chemical fixation. For EM enzyme histochemistry, unfixed tissue specimens include fresh tissue blocks, non-frozen tissue chopper sections, cryostat sections and cell preparations. Studies on localization of enzyme activity at the ultrastructural level in unfixed specimens, be it fresh or frozen, are reviewed here. Preservation of ultrastructural morphology is discussed with special attention to the effects of freezing. It is concluded that unfixed cryostat sections are the best alternative for EM histochemistry of tissues, when interposing a semipermeable membrane in between cryostat section and gelled incubation medium. It is an adequate method to preserve structural integrity of unfixed tissue on the one hand and to avoid inactivation of the enzyme by chemical fixation on the other. For EM cytochemistry on individual cells, a better preservation of ultrastructure may be obtained because freezing can be avoided, but mild pretreatment with a fixative or detergent may be necessary to permeabilize cellular membranes for demonstration of intracellular enzyme activity.