Regenerating soleus and extensor digitorum longus muscles of the rat show elevated levels of TNF‐α and its receptors, TNFR‐60 and TNFR‐80

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Abstract
We measured the mRNA and protein levels of tumor necrosis factor-α (TNF-α) and the transcript levels of its receptors (TNFR-60 and TNFR-80) in the rat soleus (slow twitch) and extensor digitorum longus (EDL; fast twitch) muscles regenerating from notexin-induced necrosis. On the first day after administration of the toxin, when most fibers were necrotic and invaded by inflammatory cells/macrophages, dramatic increases of transcript and protein levels of TNF-α and of the mRNA levels of its receptors were observed. The transcript levels of TNF-α and TNFR-60, but not of TNFR-80, showed a second but smaller increase at the time when newly formed muscle fibers became reinnervated. In situ hybridization showed that on day 1, during the phase of extensive necrosis, the transcript of TNF-α was abundantly present and on day 4 of regeneration it was most often seen in areas devoid of desmin. The mRNA level of TNF-α was not detectable in BC3H1- and C2C12-cultured myoblasts and it was low in freeze-injured muscle, corresponding to the relatively mild degree of inflammation elicited by freezing. Therefore, our results are most consistent with the view that inflammatory cells/macrophages are the main source of TNF-α. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 1058–1067, 2001
Funding Information
  • OMFB (B-10/96, B-3/99)
  • Ministry of Flemish Community (BIL96/15, BIL99/19)

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