, Volume 42, Issue 1, pp 193-214

Regeneration of hamster tracheal epithelium after mechanical injury

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Summary

All stages of epithelial regeneration following a focal denuding mechanical injury have been quantified in hamster trachea. The epithelium was divided into wound and non-wound sites and every cell around the entire tracheal circumference was counted and catergorized according to cell type. The control hamster tracheal epithelium was composed of about 33% ciliated cells, 57% secretory cells and 10% basal cells. Proliferative activity, measured as mitotic rate (MR) following a 6 h colchicine metaphase blockade, was low and confined to the secretory and basal cells. The total cell population had a MR of 0.12% (0.08% secretory cells; 0.04% basal cells).

Following a focal denuding wound in the ventral portion of the epithelium, 18% of all the epithelial cells were lost by 6 h. This loss increased to 31% by 12 h. Secretory cells and basal cells from the adjacent non-wounded epithelium flattened into a squamous morphology and during the first 12 h migrated into the wound at about 0.5 μ per min to cover the defect. Cell division at the wound was low at 12 h (MR = 0.4%), but by 24 h an exponential increase in cell proliferation had occured in the wound site (MR = 31.1%). Secretory cells (MR = 19.9%), basal cells (MR = 1.4%) and squamous cells-a mixture of flattened secretory and basal cells (MR = 9.8%)-contributed to this proliferative activity. Mitotic activity in the non-wounded epithelium remained low (MR= 0.6%).

Cell proliferation at the wound site produced a multilayered epidermoid metaplastic epithelium by 36 and 48 h. Mitotic activity remained high at these times (36 h MR = 21%, 48 h MR = 12%). Thereafter (60 h–120 h) mitotic activity fell to near control levels, and the wound epithelium was gradually replaced by recognizable basal, secretory and preciliated cells. The latter, first seen in the wound at 48 h, and recognized as very large pale non-ciliated cells, developed cilia through 60, 72, and 96 h so that a nearly normal epithelium was restored by 120 h.

The opinions and assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of Defense. The experiments reported herein were conducted according to the principles set forth in the “ Guide for the Care and Use of Laboratory Animals”, Institute of Laboratory Animal Resources, National Research Council, DHEW Publ. No. 78-23. This is contribution No. 1265 from the Cellular Pathobiology Laboratory, Department of Pathology, University of Maryland School of Medicine
This work was supported in part by USPHS NIH Grant HL≠ 24722
Submitted by K.P.K. in partial fulfillment of a Doctor of Philosophy degree from the Department of Pathology, University of Maryland School of Medicine