Structure-function relations in the human placenta

The human haemochorial placenta is a complex and dynamic interface between embryonic and maternal tissues. A myriad array of compounds has been identi fied at this interface, some of which exert local effects which might be im portant in maintaining the integrity of the organ. These compounds are dive rse in nature and function; they include enzymes, hormones and bioactive pe ptides. Successful nidation requires the synchronization of endometrial mat uration and embryonic development. The complex nature of this interface req uires the application of sound sampling strategies. The new stereological m ethods have thrown fresh light on the growth and development of the human p lacenta. These methods permit the objective, quantitative description of mo rphology by efficient design-based methods. This approach has permitted a b etter definition of the functional morphology of the placenta. Applications of these methodologies are providing a spatial and temporal framework on w hich to lay the new physiological and molecular information. Here we review the essential features of the stereological approach, identify useful stru ctural quantities and provide some examples of their application. The probl ems associated with the quantification of immunocytochemistry are illustrat ed with the use of immunoreactivity to insulin-like growth factor I recepto r in normal placentae and in pre-eclampsia. Although stereology can provide useful quantitative information about the structure of this dynamic tissue , other anatomical methods that could be applied to better define the relat ionships between structure and function will be discussed. These include co nfocal microscopy, to examine the dynamic physiological interactions of the different tissue compartments, and low-temperature electron microscopy tec hniques such as cryosubstitution, to allow better access to the biochemical information resident in the tissue. The complex and dynamic nature of the tissue requires a multidisciplinary approach; central to these investigatio ns is a comprehensive understanding of its fine structure.