- Human keratinocyte motility is a critical early event in the process of wound healing. The biological elements that directly influence human keratinocyte migration are poorly understood. Moreover, the fact that keratinocyte migration must occur within the microenvironment of the healing wound dictates that experiments be designed that directly examine elements of the wound environment and evaluate how they influence the biological behavior of cells. Their assays are designed to dissect the functions of keratinocyte motility from other biological functions such as cell proliferation. Their recent work demonstrates clearly that the type of connective tissue component or components juxtaposed to the basal keratinocyte is a major influence upon inducing migration and stopping migration. In addition to extracellular matrix effects, keratinocyte migration can be influenced by selected growth factors (such as EGF, TGFA, and IL-1) but not by a number of other soluble factors (e.g., NGF, IL-8, TGFb, etc.). Hypoxia is also a major element in influencing keratinocyte migration. In human skin wounds treated with semi-permeable occlusive dressings that have been demonstrated to promote re-epithelialization and wound healing, the healing skin wound micro-environment is characterized by very low oxygen tension and low pH. In accordance with this in vivo observation, their recent preliminary observations demonstrate that keratinocytes exhibit enhanced migration under hypoxic conditions. In this proposal, they wish to explore the cellular mechanisms of human keratinocyte migration over connective tissue components. Moreover, they wish to examine these cellular mechanisms under normoxic and hypoxic conditions in order to validate their biological importance in the setting of a micro- environment akin to true wound healing.
The specific aims are (i) to examine the role of laminin and laminin isoforms (laminin 5 = epiligrin, kalinin, nicein) in keratinocyte motility and determine if hypoxia alters the keratinocyte synthesis and deposition of matrix-adherence molecules, (ii) to determine the role of lamellipodia-associated proteins (ezrin, moesin, radixin) in keratinocyte migration and determine the influence of hypoxia upon the expression of these lamellipodia-associated components, (iii) to examine integrin receptors in motile and non-motile keratinocytes under normoxic and hypoxic conditions, and (iv) to examine the role of metalloproteinases and their respective inhibitors in the process of keratinocyte migration and determine if hypoxic and normoxic conditions alter their expression.
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