Correlations between hyaluronan and epidermal proliferation as studied by [H]glucosamine and [H]thymidine incorporations and staining of hyaluronan on mitotic keratinocytes

The rates of keratinocyte proliferation and synthesis of Hyaluronan (HA) were studied in human whole-skin organ culture by labeling with [6-³H]glucosamine and [³H]thymidine, respectively, to reveal possible correlations between the two functions of the cell. HA distribution in epidermis was examined by staining with a specific probe prepared front cartilage proteoglycan. The keratinocyte proliferation rate was low on the first 2 culture days, but showed a tenfold increase on the third and fourth days while the synthesis of HA proceeded at a relatively stable level throughout the same period. The most intensive staining of HA occurred in the uppermost spinous cell layer, whereas mitotic cells resided in the basal and suprabasal layers. The keratinocytes under various stages of mitosis were surrounded by a HA staining not more intense than that around nondividing basal cells, but a thick pad of HA appeared rapidly between the daughter cells. These findings suggest that newly synthesized HA is associated with the separation of keratinocytes following mitosis but the majority of the synthesis and content of HA in epidermis is involved in other keratinocyte activities such as maintenance of the extracellular space and cell-cell interactions during migration and differentiation.