Abstract
To investigate auricular reconstruction by tissue engineering means, this study compared cartilage regenerated from human chondrocytes obtained from either microtia or normal (conchal) tissues discarded from otoplasties. Isolated cells were expanded in vitro, seeded onto nanopolyglycolic acid (nanoPGA) sheets with or without addition of bone morphogenetic protein-7 (BMP7), and implanted in nude mice for 10 weeks. On specimen harvest, cartilage development was assessed by gross morphology, histology, and RT-qPCR and microarray analyses. Neocartilages from normal and microtia surgical tissues were found equivalent in their dimensions, qualitative degree of proteoglycan and elastic fiber staining, and quantitative gene expression levels of types II and III collagen, elastin, and SOX5. Microarray analysis, applied for the first time for normal and microtia neocartilage comparison, yielded no genes that were statistically significantly different in expression between these two sample groups. These results support use of microtia tissue as a cell source for normal auricular reconstruction. Comparison of normal and microtia cells, each seeded on nanoPGA and supplemented with BMP7 in a slow-release hydrogel, showed statistically significant differences in certain genes identified by microarray analysis. Such differences were also noted in several analyses comparing counterpart seeded cells without BMP7. Summary data suggest a possible application for BMP7 in microtia cartilage regeneration and encourage further studies to elucidate whether such genotypic differences translate to phenotypic characteristics of the human microtic ear. The present work advances understanding relevant to the potential clinical use of microtia surgical remnants as a suitable cell source for tissue engineering of the pinna.
Highlights
For more than twenty years, the field of auricular tissue engineering has investigated a wide variety of cell sources, polymer scaffolds and growth factors in vitro and in vivo with the hope of making present surgical procedures for auricular repair obsolete [1,2,3,4,5]
The thickness of these same growth factor-enhanced neocartilages appeared greater than the thickness of their respective non-treated samples, and microtia with bone morphogenetic protein-7 (BMP7) when compared to microtia without BMP7 was statistically significantly increased (Fig 2)
Previous work utilized chondrocytes from the two tissue types that were seeded onto nPGA sheets identical to those in this report and the cell/scaffold constructs were implanted without BMP7 into nude mice for up to 40 weeks [34]
Summary
For more than twenty years, the field of auricular tissue engineering has investigated a wide variety of cell sources, polymer scaffolds and growth factors in vitro and in vivo with the hope of making present surgical procedures for auricular repair obsolete [1,2,3,4,5]. Current ear reconstruction implements the use of autologous costal cartilage, Medpor or other prostheses for the auricular framework [6,7]. Further advancement of auricle reconstruction through tissue engineering approaches requires optimization in the utilization of autologous cartilage biopsies or auricular surgical remnants [16,17,18,19]. The use of auricular chondrocytes isolated from microtia tissue, expanded in culture and grown in the abdominal wall of patients for human autologous ear reconstruction without a scaffold has been reported [26]. Autologous chondrocytes from microtia patients were seeded onto biodegradable scaffolds after expansion in vitro for three months and utilized in auricular reconstructions with patient monitoring for thirty months post-surgery [27]
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