Wound healing and repair in the intestinal tract is a particularly complex process because of the presence of the intestinal microbiota which, depending on their composition and function, can either enhance the healing process or severely impair it. The intestinal tract routinely undergoes a variety of injuries both as a resultof disease processes as well as from direct surgical manipulation. The process by which successful repair and return of function occurs following these insults is highly dependent on the composition and function of the intestinal microbiota. In addition, iatrogenic injury to the intestinal tract, can disrupt the normal microbiota and leave a large wound to heal in the presence of highly pathogenic bacteria. We and others have discovered that certain bacteria capable of producing high levels of the tissue-destroying enzyme collagenase can cause healing impairment, leading to life-threatening problems such as obstruction and anastomotic leak. Yet, more antibiotics are not the answer as they eliminate the normal microbiota which have been shown to enhance intestinal healing. To this end, our groups have focused on phosphate-based compounds to achieve this endpoint given that phosphate has had a major regulatory effect on all of life on earth, including bacteria. Our previous findings show that high phosphate media can render highly problematic pathogens to become apathogenic as they do not express virulence during phosphate (Pi) abundant conditions. When Pi is covalently bonded onto high molecular weight PEG tri-block copolymers (i.e. Pi-PEG) it remains mucoadhesive and durable in the gut, as its parent non-phosphorylated compound, while also selectively suppressing bacterial virulence. We have recently found that Pi-PEG can also suppress collagenase activity in gram- positive collagenolytic strains of E. faecalis, yet fails to do so in gram negative pathogens (i.e. P. aeruginosa and S. marcescens). Yet, polyphosphate (i.e. sodium hexametaphosphate, PPi) is highly effective in suppressing collagenase in these pathogens. Thus, we have developed a method for the production of PEG hydrogel nanoparticles (NPs) loaded with polyphosphate (NP-PPi) allowing for prolonged and sustained phosphate release. The NPs favorably interact with the PEG copolymer allowing for efficient NP incorporation, sustained release of bioavailable phosphate, and durable adherence to the treatment site. We hypothesize that sustained release of PPi will have a beneficial effect on intestinal healing and inflammation when locally delivered to sites of surgical injury. This hypothesis will be addressed by the following aims:
Aim 1 : Optimize the effectiveness of NP-PPi polymer formulations to suppress bacterial collagenase production in pathogens known to complicate intestinal healing.
Aim 2 : Determine the functional durability and mucoadhesiveness of NP-PPi polymer formulations on cultured intestinal epithelial cells, cultured whole tissue intestinal explants, and mice subjected to an intestinal injury model.
Aim 3 : Test the pre-clinical efficacy of NP-PPi polymer formulations to accelerate healing in a murine model of intestinal injury and healing.
Intestinal injury due to disease processes or to direct surgical manipulation can disrupt the normal microbiota and leave a large wound to heal in the presence of highly pathogenic bacteria. We have discovered that certain bacteria capable of producing high levels of the tissue-destroying enzyme collagenase can cause healing impairment, leading to life-threatening problems such as obstruction and anastomotic leak. As an alternative to the use of antibiotics that eliminate normal microbiota which have been shown to enhance intestinal healing, this proposal seeks to explore whether sustained release of polyphosphate will suppress collagenase production of problematic pathogens potentially leading to beneficial effects on intestinal healing and inflammation when locally delivered to sites of surgical injury.
