Equine Endothelial Colony Forming Cells: In Vitro and In Vivo Analysis

Abstract

Endothelial colony forming cells (ECFCs) are a subset of the endothelial progenitor cell (EPC). EPCs are found in bone marrow and in peripheral blood samples, and their subset the ECFC can be isolated from these samples for use. ECFCs have a high proliferative capacity, the ability to heal damaged blood vessels, and can form de novo blood vessels. The ease of isolating ECFCs and the potential clinical applications of their use makes these cells an attractive therapeutic option for regenerative medicine. When used for in vivo studies, stem or progenitor cells may aid wound healing either directly or indirectly by paracrine mechanisms. In order to determine if equine ECFCs aid in wound healing by direct blood vessel incorporation, the ability to track cell movement and their final destination is paramount. Equine ECFCs were labeled with semiconductor quantum nanodots, and cell growth and function characteristics were then assessed. These results were used to aid study design for in vivo ECFC use in an equine distal limb wound model. The distal limb wound is a disease of clinical importance in equine medicine that is characterized by local ischemia, hypoxia, and poor wound healing which can lead to exuberant granulation tissue. To assess the effects of equine ECFCs on wound healing, a distal limb wound model was created in the horse. Wound healing was assessed with non-invasive analyses as well as histologic evaluation. In addition to wound healing parameters, ECFCs were labeled with fluorescent nanodots prior to injection and then tracked with serial biopsies in order to identify their final location within the wound. Results from this and other studies show that distal limb wounds in the horse are characterized by prolonged inflammation. The effects of tumor necrosis factor alpha, a pro-inflammatory cytokine known to be present in equine distal limb wounds, were evaluated in equine ECFCs under in vitro conditions to understand how ECFC function is affected by this pro-inflammatory stimulus.