title: Differentiating the extent of cartilage repair in rabbit ears using nonlinear optical microscopy.
abstract: Nonlinear optical microscopy (NLOM) was used as a noninvasive and label-free tool to detect and quantify the extent of the cartilage recovery. Two cartilage injury models were established in the outer ears of rabbits that created a different extent of cartilage recovery based on the presence or absence of the perichondrium. High-resolution NLOM images were used to measure cartilage repair, specifically through spectral analysis and image texture. In contrast to a wound lacking a perichondrium, wounds with intact perichondria demonstrated significantly larger TPEF signals from cells and matrix, coarser texture indicating the more deposition of type I collagen. Spectral analysis of cells and matrix can reveal the matrix properties and cell growth. In addition, texture analysis of NLOM images showed significant differences in the distribution of cells and matrix of repaired tissues with or without perichondrium. Specifically, the decay length of autocorrelation coefficient based on TPEF images is 11.2 ± 1.1 in Wound 2 (with perichondrium) and 7.5 ± 2.0 in Wound 1 (without perichondrium), indicating coarser image texture and faster growth of cells in repaired tissues with perichondrium (p < 0.05). Moreover, the decay length of autocorrelation coefficient based on collagen SHG images also showed significant difference between Wound 2 and 1 (16.2 ± 1.2 vs. 12.2 ± 2.1, p < 0.05), indicating coarser image texture and faster deposition of collagen in repaired tissues with perichondrium (Wound 2). These findings suggest that NLOM is an ideal tool for studying cartilage repair, with potential applications in clinical medicine. NLOM can capture macromolecular details and distinguish between different extents of cartilage repair without the need for labelling agents.
authors.affiliation: Institute of Laser and Optoelectronics Technology, Fujian Provincial Key Laboratory for Photonics Technology, Key Laboratory of OptoElectronic Science and Technology for Medicine of Ministry of Education, Fujian Normal University, Fuzhou, P. R. China.
authors.forename: X Q
authors.initials: XQ
authors.lastname: Zhu
authors.affiliation: Institute of Laser and Optoelectronics Technology, Fujian Provincial Key Laboratory for Photonics Technology, Key Laboratory of OptoElectronic Science and Technology for Medicine of Ministry of Education, Fujian Normal University, Fuzhou, P. R. China.
authors.forename: Y H
authors.initials: YH
authors.lastname: Xu
authors.affiliation: Institute of Laser and Optoelectronics Technology, Fujian Provincial Key Laboratory for Photonics Technology, Key Laboratory of OptoElectronic Science and Technology for Medicine of Ministry of Education, Fujian Normal University, Fuzhou, P. R. China.
authors.forename: C X
authors.initials: CX
authors.lastname: Liao
authors.affiliation: Department of Orthopedics, Affiliated Union Hospital of Fujian Medical University, Fuzhou, P. R. China.
authors.forename: W G
authors.initials: WG
authors.lastname: Liu
authors.affiliation: Institute of Bioproduct Development & Department of Bioprocess Engineering, Universiti Teknologi Malaysia, Johor, Malaysia.
authors.forename: K K
authors.initials: KK
authors.lastname: Cheng
authors.affiliation: Institute of Laser and Optoelectronics Technology, Fujian Provincial Key Laboratory for Photonics Technology, Key Laboratory of OptoElectronic Science and Technology for Medicine of Ministry of Education, Fujian Normal University, Fuzhou, P. R. China.
authors.forename: J X
authors.initials: JX
authors.lastname: Chen
mesh_terms: D000818:Animals; D002356:Cartilage / Q000502:physiology / Q000648:ultrastructure*; D049109:Cell Proliferation; D024042:Collagen Type I / Q000737:chemistry / Q000648:ultrastructure; D004423:Ear / Q000293:injuries; D008853:Microscopy / Q000295:instrumentation / Q000379:methods*; D011817:Rabbits; D014945:Wound Healing
chemical_list: D024042:Collagen Type I
keywords: Elastic cartilage repair; nonlinear optical microscopy; perichondrium; second harmonic generation; two-photon excited fluorescence