Insights into the mechanisms of wound repair and the role of TP508 in tissue regeneration
From the moment we are born we become susceptible to injury and infection and must, therefore, have mechanisms in place to rapidly and effectively repair damaged tissues. The goal of this dissertation work was two-fold. First, this work sought to gain insights into the mediators of inflammatory-induced tissue injury using the protein tyrosine phosphatase PTP-PEST as a potential regulator of endothelial adherens junctions and the tissue repair peptide TP508 as a potential modulator of inflammatory-induced endothelial activation. Second, these experiments aimed to determine how TP508 promoted dermal wound healing using two models of impaired dermal healing.
To gain insights into the mediators of inflammatory-induced tissue injury and the role of PTP-PEST in regulating endothelial AJ, human pulmonary artery endothelial cells (HPAEC) were treated with the barrier-disruptive agents lipopolysaccharide (LPS) and tumor necrosis factor-α (TNF-α). Using electric impedance measurements, it was shown that knockdown of PTP-PEST in HPAEC conferred resistance to barrier disruption, suggesting LPS and TNF-α may activate PTP-PEST. However, subsequent experiments showed that PTP-PEST protein and activity levels had no direct effect on barrier disruption and that neither TNF-α nor LPS were able to regulate PTP-PEST. In addition, TP508 was also used to investigate endothelial activation following inflammatory activation of HPAEC by LPS and TNF-α. In this model, it was discovered that TP508 was able to inhibit barrier disruption in higher plasticity, transdifferentiated cells but not HPAEC, suggesting a possible role for TP508 in stimulation of progenitor-like cells.
Finally, as TP508 has been shown to accelerate healing in human diabetic foot ulcers, these studies used two models of impaired wound healing to investigate the role of TP508 in dermal wound healing. These studies found that TP508 promoted wound healing in mouse models of radiation combined with injury (RCI) and type 2 diabetes. Furthermore, it was shown that injected TP508 had equal or greater efficacy than topical administration in accelerating wound healing. This led to the discovery that TP508 was eliciting effects on survival and acceleration of wound healing through effects on activation and proliferation of the leucine-rich repeat containing G protein-coupled receptor 5 positive (LGR5+) bone marrow stem cells.