title: Long-term effects of porcine small intestine submucosa on the healing of medial collateral ligament: a functional tissue engineering study.
abstract: Porcine small intestinal submucosa (SIS) was previously shown to enhance the mechanical properties of healing medial collateral ligaments (MCL), and the histomorphological appearance and collagen type V/I ratio were found to be close to those of normal MCL. We hypothesized that at a longer term, 26 weeks, SIS could guide a better organized neo-ligament formation, increasing mechanical properties and increasing collagen fibril diameters mediated by a reduction in collagen type V. A 6 mm gap injury in the right MCL was surgically created in 38 rabbits, while the contralateral intact MCL served as a sham-operated control. In half the animals, a strip of SIS was sutured onto the severed ends. In the other half, no SIS was applied. The cross-sectional area (CSA) was determined with a laser micrometer system. The femur-MCL-tibia complex was mechanically tested in uniaxial tension. Histomorphology was determined through H&E and immunofluorescent staining and transmission electron microscopy (TEM). Sodium-dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was used to determine collagen type V/I ratio. SIS-treated MCLs displayed a 28% reduction in CSA, a 33% increase in tangent modulus, and a 50% increase in tensile strength compared with the nontreated group (p < 0.05). TEM showed groups of collagen fibrils with larger diameters in the SIS-treated ligaments in comparison with uniformly small fibrils for the nontreated group. H&E staining showed more densely stained collagen fibers in the SIS-treated group aligned along the longitudinal axis with more interspersed spindle-shaped cells. Immunofluorescent staining showed less collagen type V signals, confirmed by a 5% lower ratio of collagen type V/I compared with the nontreated controls (p < 0.05). The findings extend the shorter term 12-week results, and support the potential of porcine SIS as a bioscaffold to enhance ligament healing.
authors.affiliation: Musculoskeletal Research Center, Department of Bioengineering, University of Pittsburgh, 405 Center for Bioengineering, 300 Technology Drive, Pittsburgh, Pennsylvania 15219, USA.
authors.forename: Rui
authors.initials: R
authors.lastname: Liang
authors.forename: Savio L-Y
authors.initials: SL
authors.lastname: Woo
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Takakura
authors.forename: Daniel K
authors.initials: DK
authors.lastname: Moon
authors.forename: Fengyan
authors.initials: F
authors.lastname: Jia
authors.forename: Steven D
authors.initials: SD
authors.lastname: Abramowitch
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D024042:Collagen Type I / Q000032:analysis; D024062:Collagen Type V / Q000032:analysis; D005260:Female; D007413:Intestinal Mucosa / Q000502:physiology*; D007421:Intestine, Small / Q000502:physiology*; D017888:Medial Collateral Ligament, Knee / Q000293:injuries* / Q000503:physiopathology; D011817:Rabbits; D023822:Tissue Engineering; D014945:Wound Healing
chemical_list: D024042:Collagen Type I; D024062:Collagen Type V