M. F. Bowers1,2, T. C. Huang1, M. D. Sabbagh1, S. L. Moran1 1Mayo Clinic,Rochester, MN, USA 2Meharry Medical College,Nashville, TN, USA
Introduction: Exsomes are extracellular vesicles that are secreted by cells and execute intracellularcommunication1. Exosomes convey cell communication through the export of their contents. Exosomes are known to contain tissue-specific mRNA, miRNA and proteins. Their ability to transfer these contents has been implicated in physiological processes including stem cell renewal, tumor formation, and inflammation reduction2. One of the standard therapies for advanced and tunneled wounds is application of Integra flowable wound matrix [Integra LifeSciences Corporation, NJ, USA] and a subsequent wound vacuum. Previous literature has shown that PEPs can accelerate cutaneous wound healing by upregulating blood vessel and collagen synthesis. However, the effect of PEPs in ischemic or tunneled cutaneous wounds has yet to be examinated in depth. The aim of this study is determine the effectivenss of purified exosome product (PEP) in healing full-thickness and ischemic wounds.
Methods: 10 New Zealand White rabbits were used for this study and randomly distributed into thee groups: Control (Saline + Integra, n=3), 5% PEP +Integra (n=4), and 20% PEP + Integra (n=3). Each underwent a surgical creation of an ischemic wound in the right ear while under general anesthesia. Two of the three ear neurovascular bundles were dissected and ligated within the ear. A circumferential skin tunnel was created and a 2cm full thicknesss wound was created by punch biopsy. Integra with either saline or PEP was applied on the wound for complete coverage and sealed with a Tegaderm film (3M). The incisions were closed with sutures and the ear was wrapped in a light dressing. Wound tissue samples were collected after three weeks and wound healing was analyzed via analyzed histologically and through 3D scanning. Gene Expression profiles for each wound were quantified via reverse transcriptase real-time PCR.
Results: Control wounds were indurated while all of treated wounds (n=7) showed less induration and inflammation on observation compared to the control group. Analysis from RT-qPCR data showed that the 5% PEP group had up-regulation of TGF-B, TNF-A, CTGF, and PDGF and down-regulation of COL-1 and FGF-1 compared to the control group. The 20% PEP group had down-regulation of BMP-2, COL-1, TNF-A, CD3, CD31, and TGF-B among others. There was no up-regulation of any genes studied in the 20% compared to control. None of the Control wounds showed evidence of epidermal regeneration of histological analysis while half of the 5% wounds, and all of the 20% wounds showed epidermal regeneration.
Conclusion: PEP use in conjunction with Integra matrix correlated with morphological improvement in ischemic wound healing vs Integra alone. Along with that, wounds treated with PEP showed gene expression profiles indicative of more mature wound healing. Also, data shows that PEP may enhance epidermal regeneration of ischemic wounds and increase the capillary density of these wounds through an unknown mechanism.