title: Injectable, high-density collagen gels for annulus fibrosus repair: An in vitro rat tail model.
abstract: A herniated intervertebral disc often causes back pain when disc tissue is displaced through a damaged annulus fibrosus. Currently, the only methods available for annulus fibrosus repair involve mechanical closure of defect, which does little to address biological healing in the damaged tissue. Collagen hydrogels are injectable and have been used to repair annulus defects in vivo. In this study, high-density collagen hydrogels at 5, 10, and 15 mg/mL were used to repair defects made to intact rat caudal intervertebral discs in vitro. A group of gels at 15 mg/mL were also cross-linked with riboflavin at 0.03 mM, 0.07 mM, or 0.10 mM. These cross-linked, high-density collagen gels maintained their presence in the defect under loading and contributed positively to the mechanical response of damaged discs. Discs exhibited increases to 95% of undamaged effective equilibrium and instantaneous moduli as well as up to fourfold decreases in effective hydraulic permeability from the damaged discs. These data suggest that high-density collagen gels may be effective at restoring mechanical function of injured discs as well as potential vehicles for the delivery of biological agents such as cells or growth factors that may aid in the repair of the annulus fibrosus.
authors.affiliation: Department of Biomedical Engineering, Cornell University, Ithaca, New York.
authors.forename: Brandon
authors.initials: B
authors.lastname: Borde
authors.affiliation: Department of Neurological Surgery, Weill Cornell Medical College, New York, New York.
authors.forename: Peter
authors.initials: P
authors.lastname: Grunert
authors.affiliation: Department of Neurological Surgery, Weill Cornell Medical College, New York, New York.
authors.forename: Roger
authors.initials: R
authors.lastname: Härtl
authors.affiliation: Department of Biomedical Engineering, Cornell University, Ithaca, New York.|Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York.
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Bonassar
mesh_terms: D000818:Animals; D003094:Collagen / Q000008:administration & dosage*; D005782:Gels; D007405:Intervertebral Disc Displacement / Q000628:therapy*; D008954:Models, Biological; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D005782:Gels; D003094:Collagen
keywords: biomaterial; crosslinking; intervertebral disc; riboflavin; tissue engineering