Oronasal fistulas (ONF) following cleft palate repair remain a challenging problem that is frequently encountered clinically. Preclinical evidence from our lab and multiple literature reports show that immune response, including monocyte recruitment, is dysregulated in ONF, leading to a non-healing environment with scarring and a large fistula. This is a major problem in the pediatric population which causes trouble talking and eating and requires repeat surgeries in these children who are then still left with permanent defects. Prior research shows that non-classical monocytes are biased progenitors of pro-angiogenic, anti-fibrotic macrophages within excisional skin and oral cavity wounds, and that they function within the injury niche to enhance microvascular network expansion. This proposal seeks to develop new degradable poly(ethylene glycol)-maleimide (PEG) hydrogels that are functionalized with photoactivatable caged RGD peptide. Preliminary data shows that regulating the timing of immune cell adhesion in cutaneous tissues enhances regeneration. These findings suggest that light triggering of stimulus-responsive hydrogel biomaterials is a potent new technology for initiating pro-regenerative immune signaling. Because of the widespread potential application of light-initiated biomaterial responses in the oral cavity (e.g. light-cured resin), this proposal will investigate whether local, time-regulated presentation of RGD in an oral cavity repair model can prevent complications during oral cavity wound healing, similar to those observed following cleft palate repair. The overarching hypothesis of these studies is that temporal control of light-triggered RGD presentation during oral cavity wound healing will increase the adhesion of non-classical monocytes and enhance their pro-regenerative contributions associated with vascularization, tissue remodeling and regeneration. This hypothesis will be addressed in the following specific aims:
Aim 1 : To investigate the effects of spatial patterning and gradient presentation of light-triggered RGD peptides in vivo on the recruitment of pro-regenerative monocyte / macrophage subsets.
This aim will employ a dorsal skinfold window chamber model for repetitive, non-invasive intravital microscopy analysis of monocyte recruitment kinetics in situ after light-triggering.
Aim 2 : To investigate how time-regulated presentation of RGD from PEG hydrogels influences pro-regenerative monocyte / macrophage subset recruitment and vascularization in a murine cleft palate repair model.
This aim will investigate immune infiltration and repair mechanisms in palatal wounds and will determine how the time-regulated presentation of adhesive ligands from PEG hydrogels influences wound repair.
This aim will also include novel enhancement-of-function experiments using FTY720 delivery to increase pro-regenerative Ly6clo monocyte accumulation. These experiments will determine whether light-triggering the exposure of RGD combined with increased tissue accumulation of reparative immune cells will improve healing in post-surgical palatal defects. These innovative studies will establish how stimulus response hydrogel materials can be used alone or in combination with immune modulatory treatments in the oral cavity to enhance wound healing. Success of this proposal will also demonstrate how clinically available drugs such as FTY720 can be re-purposed to locally target endogenous repair cells in the host as a novel form of regenerative immunotherapy.
Occurrence of cleft palate is the most common craniofacial congenital anomaly (1:1000 live births) and cleft palate repair is associated with wound healing complications in up to 60% of these patients resulting in an oro- nasal fistula (ONF). Healing of the oral cavity is poorly understood, compared to cutaneous wound healing, and ONF occurrence is associated with poor feeding and speech and further surgery is necessary, often requiring multiple future surgeries to repair. In this proposal we will use an immunomodulatory delivery strategy of FTY720 containing nanofibers in an ONF model to improve oral cavity wound healing by attracting pro- regenerative monocytes and macrophages and thereby reducing the incidence of ONF formation in a mouse model..
