Stem Cells and Daughter Cells in Regeneration of Epithelial Surfaces

Following the development of technologies that allowed the in vitro expansion of keratinocytes, groups in multiple countries initiated the application of cultured epithelial grafts and suspensions for treatment of partial and full-thickness cutaneous and ocular surface injuries.  The observation that cultured epithelia also re-express body site specific markers after transplantation further demonstrated cultured cells can serve as stem cells and that microenvironment can dictate expression of lineage specificity. Although partial thickness wounds can be treated with viable grafts and cell suspensions to re-populate the wound and speed re-epithelialization and/or dermal remodeling, factors derived from epithelial and mesenchymal cells, can also enhance wound healing. In vitro studies have shown that these factors promote epithelial cell migration even when tested in a background of media replete with epidermal growth factor, cholera toxin, insulin, and hydrocortisone. In addition, when  lyophilized under specific conditions, cell derived factors maintain their growth promoting and chemotactic activities towards keratinocytes and fibroblasts for up to 9-months at -80^oC to 4^oC, 6-months at 37^oC and up to 3-months at 50^oC. When rehydrated growth promoting and chemotactic activities are stable at 37^oC for up to 2-days. In vivo efficacy is evaluated using a porcine model of sulfur mustard injury with treatment on days 2-9 and evaluations using a normalcy model. On days 0, 2, 9 and 16, non-invasive assessments are carried out (e.g., clinical assessment, torsional ballistometry, reflectance colorimetry, digital image analysis of wound contracture, high frequency ultrasonography), and on day 16 biopsies are taken for histopathology and immunohistochemistry. Preliminary data demonstrates efficacy of the rehydrated formulation compared to the non-treatment control group. In light of the stability profile, this material may offer therapeutic benefit to individuals with partial thickness chemical or thermal burns, who may be housed either in environmentally controlled conditions or are subject to extreme temperatures that may be experienced in the field.