In Situ 3d Printing Of Adhesive Hydrogel Scaffolds For The Treatment Of Skeletal Muscle Injuries
Yori Endo, MD1, Carina S. Russell2, Azadeh Mostafavi2, Jacob P. Quint2, Adriana C. Panayi1, Kodi Udeh1, Tyrell J. Williams2, Jocelyn G. Daubendiek2, Victor Hugo Sánchez2, Zack Bonick2, Mairon Trujillo-Miranda3, Su Ryon Shin1, Olivier Pourquie1, Sahar Salehi3, Indranil Sinha1, Ali Tamayol2.
1Harvard Medical School/Brigham and Women's Hospital, Boston, MA, USA, 2University of Nebraska, Lincoln, NE, USA, 3University of Bayreuth, Bayreuth, Germany.
Purpose: Reconstructive surgery remains inadequate for the treatment of volumetric muscle loss (VML). Implementation of various scaffolds has been explored to improve treatment outcome, but the variability in the geometry of skeletal muscle defects in VML presents a major challenge for scaffold-based interventions. Three-dimensional (3D) printing has emerged as a promising strategy for producing scaffolds that match the geometry of the defect site. The time and facilities needed for generation of suitable 3D-printed scaffold, however, prevent immediate reconstructive interventions post-traumatic injuries. In addition, proper implantation of hydrogel-based scaffolds is difficult to achieve in vivo. To overcome these problems, a new paradigm is proposed, in which gelatin-based hydrogels are printed directly into the defect area and crosslinked in situ.
Methods: The adhesiveness of the bioink hydrogel to the skeletal muscles was assessed ex vivo. The scaffolds are directly printed into the defect site of mice with VML injury in vivo and assessed histologically for their integration into the surrounding tissue and muscle regeneration.
Results: The resultant bioink hydrogel composed of 7% (w/v) GelMA demonstrated the maximum sheer adhesion stress of 74 kPa to skeletal muscle and compressive modulus of 34 ± 5 kPa, comparable to that of typical mechanical loads reported in rodent animal models. The histological analysis of the scaffolds directly printed into the defect site of VML injury in mice revealed good adhesion with some degree of integration into the surrounding tissue, as well as a superior hypertrophic regenerative response in the remnant skeletal muscle as indicated by 25% larger average cross-sectional area of regenerating fibers 4 weeks after injury (4231 ± 69 μm2 in GelMa group vs 3394 ± 46 μm2 in VML only group).
Conclusions: The developed handheld printer capable of in situ 3D printing of adhesive scaffolds is a paradigm shift that allows rapid yet precise filling of complex skeletal muscle tissue defects.
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