Detrimental Effects of Chlorhexidine on Articular Cartilage Viability, Matrix, and Mechanics.

BACKGROUND: Chlorhexidine gluconate (CHG) solution is commonly used as an antiseptic irrigation for bacterial decontamination during orthopaedic surgery. Although the chondrotoxicity of CHG on articular cartilage has been reported, the full extent of CHG-related chondrotoxicity and its effects on the extracellular matrix and mechanical properties are unknown. PURPOSE: To investigate the in vitro effects of a single 1-minute CHG exposure on the viability, biochemical content, and mechanics of native articular cartilage explants. STUDY DESIGN: Controlled laboratory study. METHODS: Articular cartilage explants (6 per group) were harvested from femoral condyles of the porcine stifle and sectioned at tidemark. Explants were bathed in CHG solution (0.05% CHG in sterile water) at varying concentrations (0% control, 0.01% CHG, and 0.05% CHG) for 1 minute, followed by complete phosphate-buffered saline wash and culture in chondrogenic medium. At 7 days after CHG exposure, cell viability, matrix content (collagen and glycosaminoglycan [GAG]), and compressive mechanical properties (creep indentation testing) were assessed. RESULTS: One-minute CHG exposure was chondrotoxic to explants, with both 0.05% CHG (2.6% ± 4.1%) and 0.01% CHG (76.3% ± 8.6%) causing a decrease in chondrocyte viability compared with controls (97.5% ± 0.6%; P < .001 for both). CHG exposure at either concentration had no significant effect on collagen content, while 0.05% CHG exposure led to a significant decrease in mean GAG per wet weight compared with the control group (2.6% ± 1.7% vs 5.2% ± 1.9%; P = .029). There was a corresponding weakening of mechanical properties in explants treated with 0.05% CHG compared with controls, with decreases in mean aggregate modulus (177.8 ± 90.1 kPa vs 280.8 ± 19.8 kPa; P < .029) and shear modulus (102.6 ± 56.5 kPa vs 167.9 ± 16.2 kPa; P < .020). CONCLUSION: One-minute exposure to CHG for articular cartilage explants led to dose-dependent decreases in chondrocyte viability, GAG content, and compressive mechanical properties. This raises concern for the risk of mechanical failure of the cartilage tissue after CHG exposure. CLINICAL RELEVANCE: Clinicians should be judicious regarding the use of CHG irrigation at these concentrations in the presence of native articular cartilage.

Tissue anisotropy and collagenomics in porcine penile tunica albuginea: Implications for penile structure-function relationships and tissue engineering.

The tunica albuginea (TA) of the penis is an elastic layer that serves a structural role in penile erection. Disorders affecting the TA cause pain, deformity, and erectile dysfunction. There is a substantial clinical need for engineered replacements of TA, but data are scarce on the material properties and biochemical composition of healthy TA. The objective of this study was to assess tissue organization, protein content, and mechanical properties of porcine TA to establish structure-function relationships and design criteria for tissue engineering efforts. TA was isolated from six pigs and subjected to histomorphometry, quantification of collagen content and pyridinoline crosslinks, bottom-up proteomics, and tensile mechanical testing. Collagen was 20 ± 2%/wet weight (WW) and 53 ± 4%/dry weight (DW). Pyridinoline content was 426 ±131 ng/mg WW, 1011 ± 190 ng/mg DW, and 45 ± 8 mmol/mol hydroxyproline. Bottom-up proteomics identified 14 proteins with an abundance of >0.1% of total protein. The most abundant collagen subtype was type I, representing 95.5 ± 1.5% of the total protein in the samples. Collagen types III, XII, and VI were quantified at 1.7 ± 1.0%, 0.8 ± 0.2%, and 0.4 ± 0.2%, respectively. Tensile testing revealed anisotropy: Young's modulus was significantly higher longitudinally than circumferentially (60 ± 18 MPa vs. 8 ± 5 MPa, p < 0.01), as was ultimate tensile strength (16 ± 4 MPa vs. 3 ± 3 MPa, p < 0.01). Taken together, the tissue mechanical and compositional data obtained in this study provide important benchmarks for the development of TA biomaterials. STATEMENT OF SIGNIFICANCE: The tunica albuginea of the penis serves an important structural role in physiologic penile erection. This tissue can become damaged by disease or trauma, leading to pain and deformity. Treatment options are limited. Little is known about the precise biochemical composition and biomechanical properties of healthy tunica albuginea. In this study, we characterize the tissue using proteomic analysis and tensile testing to establish design parameters for future tissue engineering efforts. To our knowledge, this is the first study to quantify tissue anisotropy and to use bottom-up proteomics to characterize the composition of penile tunica albuginea.

Knee orthopedics as a template for the temporomandibular joint.

Although the knee joint and temporomandibular joint (TMJ) experience similar incidence of cartilage ailments, the knee orthopedics field has greater funding and more effective end-stage treatment options. Translational research has resulted in the development of tissue-engineered products for knee cartilage repair, but the same is not true for TMJ cartilages. Here, we examine the anatomy and pathology of the joints, compare current treatments and products for cartilage afflictions, and explore ways to accelerate the TMJ field. We examine disparities, such as a 6-fold higher article count and 2,000-fold higher total joint replacement frequency in the knee compared to the TMJ, despite similarities in osteoarthritis incidence. Using knee orthopedics as a template, basic and translational research will drive the development and implementation of clinical products for the TMJ. With more funding opportunities, training programs, and federal guidance, millions of people afflicted with TMJ disorders could benefit from novel, life-changing therapeutics.