Hypothyroidism Exacerbates Thrombophilia in Female Rats Fed with a High Fat Diet.

Clotting abnormalities are discussed both in the context with thyroid dysfunctions and obesity caused by a high fat diet. This study aimed to investigate the impact of hypo-, or hyperthyroidism on the endogenous thrombin potential (ETP), a master indicator of clotting activation, on Sprague Dawley rats fed a normal or high fat diet. Female Sprague Dawley rats (n = 66) were grouped into normal diet (ND; n = 30) and high-fat diet (HFD; n = 36) groups and subdivided into controls, hypothyroid and hyperthyroid groups, induced through propylthiouracil or triiodothyronine (T3) treatment, respectively. After 12 weeks of treatment ETP, body weight and food intake were analyzed. Successfully induced thyroid dysfunction was shown by T3 levels, both under normal and high fat diet. Thyroid dysfunction was accompanied by changes in calorie intake and body weight. In detail, compared to euthyroid controls, hypothyroid rats showed significantly increased-and hyperthyroid animals significantly decreased-ETP levels. High fat diet potentiated these effects in both directions. In summary, we are the first to show that hypothyroidism and high fat diet potentiate the thrombotic capacity of the clotting system in Sprague Dawley rats. This effect may be relevant for cardiovascular disease where thyroid function is poorly understood as a pathological contributor in the context of clotting activity and obesogenic nutrition.

Vocal fold fibroblast response to growth factor treatment is age dependent: results from an in vitro study.

INTRODUCTION: Vocal fold (VF) fibroblasts (VFFs) are the central target in developing new strategies for treatment of VF injury and scarring. Nevertheless, only little is known about the basic biological characteristics of these cells. The aim of this study was to explore the impact of age of VFFs on the response to external growth factor stimulation. STUDY DESIGN: In vitro cell study using a rat model. METHODS: VFFs were extracted from young and aged rat VF 3 months after establishing unilateral injury. Resulting scar fibroblasts (SFs) and normal fibroblasts (NFs) were subsequently cultured separately with or without the addition of hepatocyte growth factor (HGF). After 24 and 72 hours, the production of hyaluronic acid (HA) was examined in the supernatant culture media using enzyme-linked immunosorbent assay. RESULTS: Only cultured SF and NF from young animals could be stimulated significantly in the production of HA by HGF. Within these, average percentage increase was higher in NF compared with SF. CONCLUSION: The response of VFFs in cell culture to growth factors stimulation is highly depending on the age of the animals. This is another step in a nearer characterization of scar VFF and could furthermore be an important point when estimating the success of an intervention. Age-depending effects must be considered as an important factor in developing possible therapeutic agents for VF scarring.

Age effects on extracellular matrix production of vocal fold scar fibroblasts in rats.

Vocal fold (VF) fibroblasts are the central subject of interest in fibrogenesis and wound healing after VF injury. Scar fibroblasts (SF) exhibit an aberrant production of several extracellular matrix (ECM) components which lead either to VF fibrosis or scarless wound healing. This study aimed to investigate the role of age at the time of injury on ECM production of SF. This is designed as an animal study. VF injury was established unilaterally in eight male Sprague-Dawley rats [3 months of age (n = 4), 11 months of age (n = 4)], while the other side was left intact. Three months after injury the larynges were excised and fibroblasts were extracted from VF [normal fibroblasts (NF)­scar fibroblasts (SF)] and cultured in vitro. After first passage, VF fibroblasts were plated in 24-well plates and levels of hyaluronic acid (HA) and collagen type I were determined enzymatically from supernatant after 24 and 72 h. Cultured SF from younger animals produced significantly higher levels of HA compared to NF fibroblasts from the same animals. HA concentrations of the older animals did not differ significantly between the NF and SF cultures, but the range in SF cultures was large. In contrast to previous studies, we found that even 3 months after VF injury cultured SF from young animals expressed higher levels of HA in comparison to SF from older animals. No difference in collagen levels were observed between the younger and older animals. Age of animals is an essential factor during VF healing and has to be considered for study design.

Multiaxial mechanical response and constitutive modeling of esophageal tissues: Impact on esophageal tissue engineering.

Congenital defects of the esophagus are relatively frequent, with 1 out of 2500 babies suffering from such a defect. A new method of treatment by implanting tissue engineered esophagi into newborns is currently being developed and tested using ovine esophagi. For the reconstruction of the biological function of native tissues with engineered esophagi, their cellular structure as well as their mechanical properties must be considered. Since very limited mechanical and structural data for the esophagus are available, the aim of this study was to investigate the multiaxial mechanical behavior of the ovine esophagus and the underlying microstructure. Therefore, uniaxial tensile, biaxial tensile and extension-inflation tests on esophagi were performed. The underlying microstructure was examined in stained histological sections through standard optical microscopy techniques. Moreover, the uniaxial ultimate tensile strength and residual deformations of the tissue were determined. Both the mucosa-submucosa and the muscle layers showed nonlinear and anisotropic mechanical behavior during uniaxial, biaxial and inflation testing. Cyclical inflation of the intact esophageal tube caused marked softening of the passive esophagi in the circumferential direction. The rupture strength of the mucosa-submucosa layer was much higher than that of the muscle layer. Overall, the ovine esophagus showed a heterogeneous and anisotropic behavior with different mechanical properties for the individual layers. The intact and layer-specific multiaxial properties were characterized using a well-known three-dimensional microstructurally based strain-energy function. This novel and complete set of data serves the basis for a better understanding of tissue remodeling in diseased esophagi and can be used to perform computer simulations of surgical interventions or medical-device applications.

Esophagus tissue engineering: hybrid approach with esophageal epithelium and unidirectional smooth muscle tissue component generation in vitro.

PURPOSE: The aim of this study was to engineer the two main components of the esophagus in vitro: (a) esophageal epithelium and (b) smooth muscle tissue. Furthermore, (a) survivability of esophageal epithelial cells (EEC) on basement membrane matrix (BMM)-coated scaffolds and (b) oriented smooth muscle tissue formation on unidirectional BMM-coated collagen scaffolds was investigated. METHODS: Both EEC and smooth muscle cells (SMC) were sourced from Sprague-Dawley rats. The EEC were maintained in vitro and seeded onto BMM-coated 2-D collagen scaffolds. Similarly, smooth muscle cells were obtained using an explants technique and seeded on unidirectional 3-D BMM-coated collagen scaffolds. Cell-polymer constructs for EEC and SMC were maintained in vitro for 8 weeks. RESULTS: Protocols to obtain higher yield of EEC were established. EEC formed a layer of differentiated epithelium after 14 days. EEC survivability on polymers was observed up to 8 weeks. Unidirectional smooth muscle tissue strands were successfully engineered. CONCLUSION: Esophageal epithelium generation, survivability of EEC on BMM-coated scaffolds, and engineering of unidirectional smooth muscle strands were successful in vitro. The hybrid approach of assembling individual tissue components in vitro using BMM-coated scaffolds and later amalgamating them to form composite tissue holds promises in the tissue engineering of complex organ systems.