No abstract

Abstract. Interleukin (IL)-8 is a pro-inflammatory cytokine that has a direct effect on immune cells, including polymorphonuclear cells. Keratinocytes are a rich source of IL-8. However, there is little knowledge on the role of IL-8 in clinical wound healing and the direct biological effect of IL-8 on keratinocytes. In this study, the effect of recombinant human IL-8 (rhIL-8) on migration and adhesion was tested using HaCaT keratinocytes as a cell model. The cell functions were evaluated using impedance cell sensing. The expression of IL-8 receptor (IL-8R) transcripts in human skin and wounds (acute and chronic) was assessed using real-time transcript analysis. rhIL-8 significantly increased the migration of keratinocytes (3.5±0.3 for cells treated with IL-8 vs. 2.7±0.6 for controls; p= 0.029). It is interesting to note that treatment of keratinocytes with IL-8 resulted in a marked shift in the responsive frequencies. IL-8 only resulted in a marginal increase in cell adhesion, which was particularly noticeable at high frequencies. The PLC-γ inhibitor completely eradicated the action of IL-8 on the migration of HaCaT cells. Using real time PCR, it was found that chronic wounds had significantly lower levels of the B form of the IL-8R (IL-8RB) (p=0.045) and marginally lower levels of the A form, IL-8RA, in comparison with acute wounds. Therefore, IL-8 has a direct and profound stimulatory effect on the migration of human keratinocytes, which is likely to occur via the PLC-γ pathway. Together with a reduced level of IL-8Rs in difficult-healing wounds, IL-8 has a clear prognostic and therapeutic value in wound healing.

These data indicate that human wound-associated lymphocyte populations are modulated during healing; the increase in numbers of CD8+ T-suppressor lymphocytes is in accordance with previous animal data, indicating a role for these cells in downregulating healing as the wound closes. This study also documents an associated increase in B lymphocytes and healing of human wounds, with an as yet undefined role.

Oligodendrocytes were studied in the anterior medullary velum (AMV) of the rat using the monoclonal antibody Rip, an oligodendrocyte marker of unknown function. Confocal microscopic imaging of double immunofluorescent labelling with antibodies to Rip and carbonic anhydrase II (CAII) revealed two biochemically and morphologically distinct populations of oligodendrocyte which were either Rip+CAII+ or Rip+CAII-. Double immunofluorescent labelling with Rip and myelin basic protein (MBP) or glial fibrillary acidic protein (GFAP) provided direct evidence that Rip-labelled cells were phenotypically oligodendrocytes and confirmed that Rip did not recognise astrocytes. Oligodendrocytes which were Rip+CAII+ supported numerous myelin sheaths for small diameter axons, whilst Rip+CAII- oligodendrocytes supported fewer myelin sheaths for large diameter axons. Morphologically, Rip+CAII+ oligodendrocytes corresponded to types I or II of classical nomenclature, whilst Rip+CAII- oligodendrocytes corresponded to types III and IV. The results demonstrated a biochemical difference between oligodendrocytes which myelinated small and large diameter fibres.

The objective of this study was to characterize the leucocyte infiltrate which accumulates at the margin of chronic wounds. These leucocytes are a rich source of cytokines and growth factors, and an inappropriate function of these cells may contribute to the maintenance of wound chronicity. The leucocyte populations were stained immunohistochemically with monoclonal antibodies specific for surface receptors which give an indication of cellular function. Wound margin biopsies taken from chronic leg ulcers exhibited a localized infiltrate of CD45+ leucocytes associated with vascularized tissue in the dermis adjacent to the wound margin. Lymphocytes were identified in highest numbers in this area and CD45RO+ T lymphocytes predominated over B lymphocytes, which were either absent or present in very low numbers. In the majority of chronic wounds examined, CD4+ T lymphocytes were present in greater numbers than CD8+ T lymphocytes with a mean (+/-SD) ratio of CD4+:CD8+ of 1.5 +/- 0.6. CD68+ macrophages were identified in all layers of the dermis at the chronic wound margin. In 60% of wounds examined, macrophages were negative for the activation associated markers CD16 (Fc gamma III receptor) and CD35 (C3b receptor). In those biopsies where CD16 and CD35 positive macrophages were observed these were preferentially located in the perivascular regions. These data indicate that as monocytes extravasate into chronic wound tissue they may be subjected to microenvironmental influences which either suppress or do not induce macrophage activation. Suppression of macrophage activation may lead to an inappropriate cytokine/growth factor secretion and contribute to the maintenance of wound chronicity.