Mateusz S. Wietecha

We have employed the receptor-ligand binding technique in an attempt to determine if specific binding sites (receptors) for serotonin and opiates are present on rat intestinal epithelial cell membranes. A wide variety of ligands for serotonin and opiate receptors bound to specific receptor sites in rat brain. However, the same ligands failed to bind in a specific (receptor-related) manner to isolated membranes of rat ileal and colonic cells. Additional washing of the tissue pellet (to remove soluble peptidases), pretreatment with p-chlorophenylalanine (to deplete endogenous serotonin), alteration of sodium concentration (to antagonize the effects of putative endogenous inhibitors of opiate ligand binding), changes in incubation time, temperature, tissue protein and tritiated ligand concentration failed to yield meaningful results with the enterocyte membranes. We conclude that, as assessed under the present conditions, serotonergic and opiate receptors are not present or are not accessible on rat intestinal epithelial cell membranes.

Matrix deposition is essential for wound repair, but when excessive, leads to hypertrophic scars and fibrosis. The factors that control matrix deposition in skin wounds have only partially been identified and the consequences of matrix alterations for the mechanical properties of wounds are largely unknown. Here, we report how a single diffusible factor, activin A, affects the healing process across scales. Bioinformatics analysis of wound fibroblast transcriptome data combined with biochemical and histopathological analyses of wounds and functional in vitro studies identify that activin promotes pro-fibrotic gene expression signatures and processes, including glycoprotein and proteoglycan biosynthesis, collagen deposition, and altered collagen cross-linking. As a consequence, activin strongly reduces the wound and scar deformability, as identified by a non-invasive in vivo method for biomechanical analysis. These results provide mechanistic insight into the roles of activin in wound repair and fibrosis and identify the functional consequences of alterations in the wound matrisome at the biomechanical level.

Significance: Re-establishment of a functional vascular network is a critical component of successful wound repair. One of the most potent pro-angiogenic agents is vascular endothelial growth factor (VEGF), which, from a basic science and pre-clinical perspective, seems ideal for the therapeutic stimulation of blood vessel growth in non-healing wounds. Critical Issues: Current strategies to improve the dysfunctional angiogenesis that occurs in non-healing wounds are inadequate with regard to the nature and magnitude of the clinical problem. However, VEGF therapy has so far been unsuccessful in promoting healing in the clinic. More effective means of delivery to the wound, which take into account the biochemical and spatio-temporal aspects of angiogenesis, may be necessary to realize VEGF's therapeutic potential. Reviewed approaches for the regulation of wound angiogenesis include: targeting regulators of intracellular VEGF signaling, making use of collagen-binding VEGF fusion proteins for increased retention in the wound, and implantation of heterogeneous scaffold systems for spatial control of angiogenesis with simultaneous use of VEGF and its inhibitor. Future Directions: To maximize efficacy of therapeutic VEGF, it may be necessary to also target its intracellular inhibitory mechanisms. Immobilizing VEGF to the wound matrix may increase its bioavailability and therapeutic efficacy. Gaining spatial control of angiogenesis opens up possibilities for advanced directed therapy. The reviewed studies present innovative approaches to in vivo directed modulation of angiogenesis utilizing VEGF biology which can, if taken further and validated in human subjects, have significant impact on clinical wound care in the future.