Bioartificial Sponges for Auricular Cartilage Engineering

Auricle reconstruction due to congenital, post-infective or post-traumatic defects represents a challenging procedure in the field of aesthetic and reconstructive surgery due to the highly complex three-dimensional anatomy of the outer ear. Tissue engineering aims to provide alternatives to overcome the shortcomings of standard surgical reconstructive procedure. In the present study, poly(vinyl alcohol)/gelatin (PVA/G) sponges at different weight ratios were produced via emulsion and freeze-drying, and crosslinked by exposure to glutaraldehyde vapors. PVA/G sponges gave rise to highly porous, water stable and hydrophilic scaffolds. Characterization of PVA/G sponges showed round-shaped interconnected pores, high swelling capacity (>200%) and viscoelastic mechanical behavior. The PVA/G 70/30 (w/w) scaffold was selected for in vitro biological studies. Bone marrow derived human mesenchymal stromal cells (hMSCs) were used and differentiated towards chondrogenic lineage under different culture conditions: 1) commercial versus handmade differentiation medium; 2) undifferentiated versus pre-differentiated hMSC seeding; and 3) static versus dynamic culture [i.e. ultrasound (US) or bioreactor stimulation]. Histological results highlighted intense glycosaminoglycan, glycoprotein and collagen syntheses after three weeks, mostly using the commercial medium, whereas round morphology was observed in pre-differentiated cells. In static culture, immunohistochemistry for chondrogenic markers revealed an early differentiation stage, characterized by the expression of Sox-9 and collagen type I fibers. The application of US on cell/scaffold constructs increased extracellular matrix deposition and resulted in 30% higher collagen type II expression at the gene level. Bioreactor culture induced collagen type II, aggrecan and elastin formation. This study demonstrated that 70/30 PVA/G sponge is a suitable candidate for auricle reconstruction.