EXPRESSION OF TYPE-XII COLLAGEN BY WOUND EPITHELIAL, MESENCHYMAL, ANDEPENDYMAL CELLS DURING BLASTEMA FORMATION IN REGENERATING NEWT (NOTOPHTHALMUS-VIRIDESCENS) TAILS

Previously we showed that type XII collagen (col XII) is highly upregu lated in the regenerating newt (Notophthalmus viridescens) forelimb. H ere, using immunohistochemistry and in situ hybridization, we studied the pattern of expression of col XII during early stages of adult newt tail regeneration. The results show that immunoreactivity of col XII is first seen as a thin layer beneath the wound epithelium (WE) at 3 d ays after amputation. Reactivity associated with the mesenchyme become s obvious at day 4 and increases considerably between days 6 and 7 aft er amputation. In situ hybridization indicates that the early WE-assoc iated reactivity and later mesenchymal reactivity are due to increased col XII gene expression by the WE and mesenchyme, respectively. At 7 days after tail amputation both wound epithelial and mesenchymal cells exhibit a strong riboprobe signal. Interestingly, a distinct riboprob e signal is also seen in the cells of the outgrowing ependymal tube at day 7 but little if any col XII immunoreactivity is present. The spat ial pattern of col XII gene expression changes by day 14 after amputat ion in that transcription in mesenchyme is maintained at a high level, in the WE it is reduced, and in ependyma it ceases to be detectable. Local deprivation of the spinal cord significantly lowers the level of col XII message in the mesenchyme. Much of this decrease in transcrip tion is due to minimal mesenchymal cell accumulation secondary to spin al cord ablation. The temporal and spatial patterns of expression of t he col XII gene in the WE, mesenchyme, and ependyma during tail regene ration strongly suggest a role for col XII in regulating both spinal c ord outgrowth and spinal cord-dependent tail regeneration. (C) 1996 Wi ley-Liss, Inc.