Auckland Bioengineering Institute

Tissue structure

Our work originated from the detailed measurement of cardiac structure in which we characterised myocyte arrangement throughout the ventricular wall in dog and pig hearts. These data have been incorporated into detailed finite element models of cardiac anatomy that have been used by ourselves and others to study the electrical and mechanical function of the heart.


Automated imaging system

In order to visualize myocyte and connective tissue organization at appropriate resolution we have developed an automated imaging system that enables extended-volume images to be acquired rapidly. A high precision three-axis translation stage and digital camera are coupled with a confocal microscope and histological ultramill under the control of a central computer.

With this system it is feasible to rapidly capture extended 3D images of tissue and acquire morphological data in systematic serial studies of structure and function for any soft biological tissue. Use of the system is expanding to cover a wide range of tissues including: myocardium from hypertensive rats, infarct border zone, coronary vasculature, pig atrium, rat kidney, gastro-oesophageal junction, lymph nodes, cochlea, and neural tissue.

The structural information collected will typically be used in computer modeling studies investigating the relationship between organ structure and function.


Extended-volume images of left ventricular myocardium

Rat hearts are perfused with Bouin's fixative and picrosirius red which labels connective tissue. Transmural samples are embedded in resin and extended-volume confocal microscopy is performed to assemble large 3D images that provide detailed structural information, for example on the organisation of myocardial laminae, blood vessels and connective tissue. The adjacent figure was obtained from a tissue block of dimension 4.25 x 0.9 x 1.1 mm. The upper image highlights the laminar structure of ventricular myocardium, while the lower image has been thresholded to extract collagen organisation.


Surface imaging microscopy

Surface imaging microscopy is also used when specimens are very large or where non-fluorescent histological stains are most appropriate. Specimens are embedded in wax or resin. The upper surface is etched so that a thin layer can be exposed to a rapidacting histological stain, such as toluidine blue. The surface is imaged using a digital camera, then planed in the ultramill and the complete process is repeated.

The figure at the right is a montage of four contiguous images of the endocardial surface of a segment of pig right atrial appendage. The terminal crest can be seen on the lower left boundary and the complex network of pectinate muscles is also evident. (A photo micro lens (1:1) was used and the largest dimension is 52 mm.) The figure at the left is a single image of a rat right ventricular trabeculum.

This cross-sectional view shows the organisation of myocytes, capillaries and elastic tissue. (Acquired through a microscope using a 20 x 0.7NA objective; largest dimension 80 um).


Extended-volume image of the rat kidney

The kidney is perfusion-fixed and the vascular endothelium is stained with TRITC conjugated to wheat germ agglutinin. Segments of kidney are embedded in resin and extended-volume confocal microscopy is performed to assemble 3D images over the whole cross-section of the organ. The adjacent figure shows a longitudinal section of the kidney (composed of 228 montaged confocal microscope images), which highlights glomerular distribution (bright spots) in the renal cortex.

Funding partners

The Tissue Structure Group gratefully acknowledges the support of its funding partners: