Neuronal survival and neurite growth in cultured cerebral explants: assessment of the effect of cytosine arabinoside using improved stereology

Color subtractive-computer-assisted image analysis for quantification of cutaneous nerves in a diabetic mouse model

Immunohistochemistry (IHC) is a valuable tool for labeling structures in tissue samples. Quantification of immunolabeled structures using traditional approaches has proved to be difficult. Manual counts of IHC-stained structures are inherently biased, require multiple observers, and generate qualitative data. Stereological methods provide accurate quantification but are complex and labor-intensive when staining must be compared among large numbers of samples. In an effort to quickly, objectively, and reproducibly quantify cutaneous innervation in a large number of counterstained tissue sections, we developed a color subtractive-computer-assisted image analysis (CS-CAIA) system. To develop and test the CS-CAIA method, tissue sections of diabetic (db/db) mouse skin and their wild-type (db/-) littermates were stained by IHC for the neural marker PGP 9.5. The brown-red PGP 9.5 peroxidase stain was colorimetrically isolated through a scripted process of color background removal. The remaining stain was thresholded and binarized for computer determination of nerve profile counts (number of stained regions), area fraction (total area of nerve profiles per unit area of tissue), and area density (total number of nerve profiles per unit area of tissue). Using CS-CAIA, epidermal nerve profile counts, area fraction, and area density were significantly lower in db/db compared to db/- mice.

A simple procedure for quantification of neurite outgrowth based on stereological principles

The molecular mechanisms controlling formation and remodelling of neuronal extensions are of considerable interest for the understanding of neuronal development and plasticity. Determination of neurite outgrowth in cell culture is a widely used approach to investigate these phenomena. This is generally done by a time consuming tracing of individual neurites and their branches. We have used stereological principles to determine the length of neurites. The total neuritic length per cell was estimated by counting the number of intersections between neurites and test lines of an unbiased counting frame superimposed on images of cell cultures obtained by conventional computer-assisted microscopy. The absolute length, L, of neurites per cell was subsequently estimated from the number of neurite intersections, I, per cell by means of the equation L=(pid/2)I describing the relationship between the number of neurite intersections and the vertical distance, d, between the test lines used. When measuring neurite outgrowth from PC12 cells and primary hippocampal neurons, data obtained by counting neuritic intersections correlated statistically significantly with data obtained using a conventional tracing technique. However, information was acquired more efficiently using the stereological approach. Thus, using the described set-up, the stereological procedure was approximately five times less time consuming than the conventional method based on neurite tracing. The study shows that stereological estimation of neuritic length provides a precise and efficient method for the study of neurite outgrowth in cultures of primary neurons and cell lines.

Determination of neuronal number and process surface area in organotypic cultures: a stereological approach

Preparation of nervous tissue as an organotypic culture permits examination of nervous system development and interactions between neurons and with their environment. In order to evaluate the statistical significance of morphological changes, it is necessary to quantify tissue populations and parameters. Recent advances in stereology facilitate the gathering of morphometric data, while eliminating sources of error associated with traditional methods. Unfortunately, the new stereology has been perceived as complex and, therefore, has been slow to gain acceptance within neuroscience investigations in general and in vitro applications in particular. Here, we present a detailed application of the new, unbiased stereology to organotypic hippocampal cultures. These methods allow assessment of neuronal survival and morphological plasticity to culture conditions with increasing culture age. Neuronal number was assessed from point-sampled intercepts of cells sampled without bias by the selector procedure in vertical sections through hippocampal cultures. Surface area was estimated from profile intersects of neuronal processes with a cycloid array. The reference volume was determined by the Cavalieri method; this permitted expression of results as absolute values rather than as component densities. The importance of absolute values to valid interpretation of quantitative data is demonstrated by the results for neuronal number. The methods applied here provide a powerful approach to quantitation of organotypic cultures, and represent an important extension of qualitative studies of cultured nervous tissue.