Cutaneous Wounds in Mice Lacking Tumor Necrosis Factor-stimulated Gene-6 Exhibit Delayed Closure and an Abnormal Inflammatory Response
We investigated how loss of tumor necrosis factor-stimulated gene-6 (TSG-6) affects wound closure and skin inflammation. TSG-6 has several known biological functions including enzymatic transfer of heavy chain proteins (HC) from inter--trypsin inhibitor to hyaluronan (HA) to form HC-HA complexes. TSG-6 and HC-HA are constitutively expressed in normal skin and increase post-wounding, but are completely absent in TSG-6 null mice. Wound closure rates are significantly delayed in TSG-6 null mice relative to wildtype mice. Neutrophil recruitment is delayed in early wounds (12 h and Day 1), whereas late wounds (Day 7) show elevated neutrophil accumulation. In addition, the granulation phase is delayed, with persistent blood vessels and reduced dermal collagen at 10 days. The pro-inflammatory cytokine TNF is elevated >3 fold in unwounded TSG-6 null skin, and increases further after wounding (from 12 h to 7 days) before returning to baseline by day 10. Other cytokines examined such as IL-6, IL-10, and MCP-1 showed no consistent differences. Importantly, reintroduction of TSG-6 into TSG-6 null wounds rescues both the delay in wound closure and the aberrant neutrophil phenotype. In summary, our study indicates that TSG-6 plays an important role in regulating wound closure and inflammation during cutaneous wound repair.