Testosterone may increase rat anterior cruciate ligament strength.

BACKGROUND: Women are more likely than men to injure the anterior cruciate ligament (ACL). Human and animal trials have linked circulating estradiol to injury rate and ligament strength. Fewer studies have examined the role of testosterone. The purpose of this study was to determine if male rats with normal testosterone levels would have stronger ACLs than castrated rats. METHODS: Eight castrated (group C) and eight normal (group N) 12-week-old, male Sprague-Dawley rats were used for the study. Mean testosterone levels were 0.14ng/mL (95% CI: 0.10 to 0.17) in group C and 3.54ng/mL (95% CI: 1.32 to 5.76) in group N. After euthanasia, ACL cross-sectional area was calculated, and a servohydraulic material testing unit was used to measure ligament properties. RESULTS: Specimens from both groups had similar cross-sectional area, but N specimens showed greater mean load-to-failure (34.5N [95% CI: 31.6 to 37.4] vs 29.2N [95% CI: 27.9 to 30.6]) and ultimate stress (38.7MPa [95% CI: 34.1 to 43.3] vs 31.8MPa [95% CI: 29.8 to 33.8]). Mean energy was 27.7mJ (95% CI: 23.1 to 32.2) in the N group and 23.4mJ (95% CI: 18.2 to 28.6) in the C group. CONCLUSIONS: Rats with normal circulating testosterone had higher ACL load-to-failure and ultimate stress, indicating that testosterone may influence ACL strength and the injury rate of the ligament.

Synthesis and properties of regenerated cellulose-based hydrogels with high strength and transparency for potential use as an ocular bandage.

Cellulose is a biologically derived material with excellent wound-healing properties. The high strength of cellulose fibers and the ability to synthesize gels with high optical transparency make these materials suitable for ocular applications. In this study, cellulose materials derived from wood pulp, cotton, and bacterial sources were dissolved in lithium chloride/N,N-dimethylacetamide to form regenerated cellulose hydrogels. Material properties of the resulting hydrogels, including water content, optical transparency, and tensile and tear strengths, were evaluated. Synthesis parameters, including activation time, dissolution time, relative humidity, and cellulose concentration, were found to impact the material properties of the resulting hydrogels. Overnight activation time improves the optical transparency of the hydrogels from 77% to 97% at 550 nm, whereas controlling cellulose concentration improves their tear strength by as much as 200%. On the basis of the measured transmittance and strength values of the regenerated hydrogels prepared via the optimized synthesis parameters, Avicel PH 101, Sigma-Aldrich microcrystalline cellulose 435236, and bacterial cellulose types were prioritized for future biocompatibility testing and potential clinical investigation.

Glucosamine modulates chondrocyte proliferation, matrix synthesis, and gene expression.

OBJECTIVE: To investigate the effects of glucosamine (GlcN) on chondrocyte proliferation, matrix production, and gene expression for providing insights into the biochemical basis of its reported beneficial effects in osteoarthritis (OA). METHODS: Dose-dependent effect of GlcN on cell morphology, proliferation, cartilage matrix production and gene expression was examined by incubating primary bovine chondrocytes with various amounts of GlcN in monolayers (2D) and in cell-laden hydrogels (3D constructs). Histology, immunofluorescent staining and biochemical analyses were used to determine the effect of GlcN on cartilage matrix production in 3D constructs. The impact of GlcN on gene expression was evaluated with real-time polymerase chain reaction (PCR). RESULTS: GlcN concentration and culture conditions significantly affected the cell behavior. Quantitative detection of matrix production in cell-laden hydrogels indicated a relatively narrow window of GlcN concentration that promotes matrix production (while limiting cellular proliferation, but not cell viability). Notably, GlcN enhanced cartilage specific matrix components, aggrecan and collagen type II, in a dose-dependent manner up to 2 mM but the effect was lost by 15 mM. Additionally, GlcN treatment up-regulated transforming growth factor-beta1 (TGF-beta1) mRNA levels. CONCLUSION: Results indicate that culture conditions play a significant role in determining the effect of GlcN on chondrocytes, explaining both the previously reported beneficial and deleterious effects of this sugar. The ability of GlcN to alter TGF-beta1 signaling provides a biochemical mechanism for GlcN activity on chondrocytes that up to now has remained elusive. The observed anabolic effect of optimal GlcN concentrations on chondrocytes may be useful in formulating effective cartilage repair strategies.

Experimental model for cartilage tissue engineering to regenerate the zonal organization of articular cartilage.

OBJECTIVE: Regeneration of the zonal organization of articular cartilage may be an important advancement for cartilage tissue engineering. The first goal of this study was to validate our surgical technique as a method to selectively isolate chondrocytes from different zones of bovine articular cartilage. The second goal was to confirm that chondrocytes from different zones would have different proliferative and metabolic activities in two-dimensional (2-D) and 3-D cultures. Finally, to regenerate the zonal organization, we sought to make multi-layered constructs by encapsulating chondrocytes from different zones of articular cartilage. DESIGN: Cartilage slices were removed from three (upper, middle, and lower) zones of articular cartilage of young bovine legs. Histology and biochemical composition of the cartilage slices were analyzed to confirm that they had been obtained from the proper zone. Growth kinetics and gene expression in monolayer culture and matrix formation in photopolymerizing hydrogels were evaluated. Multi-layered photopolymerizing hydrogels were constructed with chondrocytes from each zone of native cartilage encapsulated. Cell viability and maintenance of the cells in the respective layer were evaluated using the Live/Dead Viability kit and cell tracking protocols, respectively. After 3 weeks, the multi-layered constructs were harvested for histologic examination including immunohistochemistry for type II collagen. RESULTS: Analysis of histology and biochemical composition confirmed that the cartilage slices had been obtained from the specific zone. Chondrocytes from different zones differed in growth kinetics and gene expression in monolayer and in matrix synthesis in 3-D culture. Cells encapsulated in each of the three layers of the hydrogel remained viable and remained in the respective layer in which they were encapsulated. After 3-week culture, each zone of multi-layered constructs had similar histologic findings to that of native articular cartilage. CONCLUSION: We present this as an experimental model to regenerate zonal organization of articular cartilage by encapsulating chondrocytes from different layers in multi-layered photopolymerizing gels.

Biological response of chondrocytes to hydrogels.

Primary bovine chondrocytes were encapsulated in alginate and alginate combined with cartilage matrix extract, Cartrigel, for the purpose of cartilage tissue engineering. The cell constructs were incubated in vitro and gene expression of cartilage-specific extracellular matrix molecules was quantitated and localized with in situ hybridization with a decrease in expression observed in the alginate-Cartrigel constructs. Further understanding of cell response to scaffolds will allow rational design and development of hydrogels for cartilage tissue engineering.