CRYOMICROSCOPY OF AN IN-SITU CELL MODEL OF SKIN

The assessment of the post freeze/thaw viability or morphology of tiss ues provides limited evidence of the dynamic processes of interstitial ice growth and ice-cell interactions that occur. An in situ cell mode l of skin has therefore been developed for the study of freezing event s in skin using a convection cryomicroscope. The model consists of a 2 0 to 30 mu m- thick cross-sectional slice of skin and contains a colla genous dermis, an intact basement membrane zone, a viable epidermis, a nd a stratum corneum. Ice nucleation within the tissue resulted from a dvancement of external ice over or under the tissue. Primary ice nucle ation sites were in the papillary dermis below the basement membrane z one and just below the stratum corneum, and these initiated numerous s econdary nucleation events which propagated into basal and non basal l ayers of the epidermis. Repeated freezing after thawing of samples res ulted in ice nucleation and growth in the same preferred regions of sk in, and the progression of nucleation events occurred more quickly fol lowing an initial freeze/thaw cycle. Cells in situ were more susceptib le to the nucleation of ice than were isolated basal cells. Cryomicros copy of this experimental in situ cell model of skin has provided earl y qualitative insight into the osmotic and freezing events in tissues, including the ice-cell interactions that occur.