Chronic tympanic membrane (TM) perforation is a tubotympanic disease caused by traumatic or inflammatory factors. To date, various types of tissue engineered techniques have been applied for the regeneration of chronic TM perforations. However, the application of nanofibers with radially aligned nanostructures and release of growth factors simultaneously has never been applied in the regeneration of chronic TM perforations. In this study, Growth factor-releasing radially aligned nanofibrous patches were developed and applied for the regeneration of chronic perforated TMs.
In the first purpose, the insulin-like growth factor-binding protein 2 (IGFBP2) were incorporated to radially aligned nanofibrous patches. At first, radially aligned nanofibrous polycaprolactone (PCL) patches were developed using electrospinning. Random nanofibers (NFs) were deposited onto a planar plate, and aligned nanofibers (AFs) were deposited onto custom-made round shape collector. For the experimental groups, patches were classified by alignments and the presence of IGFBP2: random fibers without IGFBP2 (RF-w/oIGFBP2), aligned fibers without IGFBP2 (AF-w/oIGFBP2), random fibers with IGFBP2 (RF-wIGFBP2), and aligned fibers with IGFBP2 (AF-wIGFBP2). To confirm the efficiency of each patch, in vitro and in vivo studies were performed. In the second purpose, epidermal growth factor (EGF) was incorporated to radially aligned nanofibrous patches. These patches were fabricated by the same methods which used for the IGFBP2-incoporated patches. And also these patches were classified as follows; random fibers without EGF (RF-w/oEGF), aligned fibers without EGF (AF-w/oEGF), random fibers with EGF (RF-wEGF), and aligned fibers with EGF (AF-wEGF). The effectiveness of EGF-releasing nanofibrous patches were confirmed by cell viability, cell morphology, wound healing assay, and animal studies. In addition, the mechanism of TM regeneration also was studied by mRNA and protein level studies.
In the first experiment, the presence of IGFBP2 was analyzed by fourier-transform infrared spectroscopy (FTIR). In addition, the releasing of IGFBP2 was sustained until 20 days. In the cell viability test, there was no significant difference among all patches on day 1, 3, and 5. By the animal studies, 96 ears were applied, and both IGFBP-2 incorporated patches showed the efficiency for regeneration of chronic TM perforations. However, there were no significant difference between RF-wIGFBP2 and AF-wIGFBP2. From the second experiment, radial alignments and the presence of EGF in the patches were analyzed. EGF was confirmed to be released from the patches until 8 weeks. In an in vitro study, cell viability, immunocytochemistry, and wound healing assay were rationally enhanced by the combination of radial alignments and EGF release ability. An in vivo animal study showed that the EGF-releasing nanofibrous patches effectively stimulated the healing of the chronic TM perforations. The TMs healed by AF-wEGF showed histological properties similar to those of normal TMs. The markers of proliferation and migration were confirmed by quantitative real-time polymerase chain reaction, which enhanced by the combination of radial alignments and EGF. Hence, the EGF-releasing radially aligned nanofibrous patches will be an efficient platform for the regeneration of chronic TM perforations, opening the gate for nonsurgical treatments of chronic otitis media.
