Cyclic Stretch Effects on Adipose-Derived Stem Cell Stiffness, Morphology and Smooth Muscle Cell Gene Expression

Recent investigations consider adipose-derived stemcells (ASCs) as a promising source of stemcells for clinical therapies. To obtain functional cells with enhanced cytoskeleton and aligned structure, mechanical stimuli are utilized during differentiation of stem cells to the target cells. Since function of muscle cells is associated with cytoskeleton, enhanced structure is especially essential for these cells when employed in tissue engineering. In this study by utilizing a custom-made device, effects of uniaxial tension (1Hz, 10% stretch) on cytoskeleton, cell alignment, cell elastic properties, and expression of smooth muscle cell (SMC) genes in ASCs are investigated.Due to proper availability ofASCs, results can be employed in cardiovascular engineeringwhen production of functional SMCs in arterial reconstruction is required. Results demonstrated that cells were oriented after 24 hours of cyclic stretch with aligned pseudo-podia. Staining of actin filaments confirmed enhanced polymerization and alignment of stress fibers. Such phenomenon resulted in stiffening of cell body which was quantified by atomic force microscopy (AFM). Expression of SM α-actin and SM22 α-actin as SMC associated genes were increased after cyclic stretch while GAPDH was considered as internal control gene. Finally, it was concluded that application of cyclic stretch on ASCs assists differentiation to SMC and enhances functionality of cells.

Fabrication of chitosan silk-based tracheal scaffold using freeze-casting method

Background: Since the treatments of long tracheal lesions are associated with some limitations, tissue engineered trachea is considered as an alternative option. This study aimed at preparing a composite scaffold, based on natural and synthetic materials for tracheal tissue engineering

Methods: Nine chitosan silk-based scaffolds were fabricated using three freezing rates [0.5, 1, and 2[degree]C/min] and glutaraldehyde [GA] concentrations [0, 0.4, and 0.8 wt%]. Samples were characterized, and scaffolds having mechanical properties compatible with those of human trachea and proper biodegradability were selected for chondrocyte cell seeding and subsequent biological assessments

Results: The pore sizes were highly influenced by the freezing rate and varied from 135.3x372.1 to 37.8x83.4 micro m. Swelling and biodegradability behaviors were more affected by GA rather than freezing rate. Tensile strength raised from 120 kPa to 350 kPa by an increment of freezing rate and GA concentration. In addition, marked stiffening was demonstrated by increasing elastic modulus from 1.5 MPa to 12.2 MPa. Samples having 1 and 2[degree]C/min of freezing rate and 0.8 wt% GA concentration made a non-toxic, porous structure with tensile strength and elastic modulus in the range of human trachea, facilitating the chondrocyte proliferation. The results of 21-day cell culture indicated that glycosaminoglycans content was significantly higher for the rate of 2[degree]C/min [12.04 micro g/min] rather than the other [9.6 micro g/min]

Conclusion: A homogenous porous structure was created by freeze drying. This allows the fabrication of a chitosan silk scaffold cross-linked by GA for cartilage tissue regeneration with application in tracheal regeneration

Effects of Uniaxial Cyclic Stretch Loading on Morphology of Adipose Derived Stem Cells

Adipose derived stem cells (ADSC) are good candidates for the replacement of bone marrow derived mesenchymal stem cells due to their abundance, multipotency property, and easier accessibility. In order to explore the behavior of these cells in response to mechanical stimulation, in this study we have investigated the effects of uniaxial dynamic mechanical loading on ADSC's morphology. Stem cells derived from the fat tissue of human and after an overnight culture were seeded on a silicone rubber strips. Afterwards, cells were subjected to a uniaxial dynamic loading in three different groups. Cell images were evaluated considering different morphological parameters. Fractal dimension decreased significantly after loading while in control groups there were a significant increase (p<0.05), approving that cyclic strain would lead to more aligned and organized cells. Cell orientation also increased significantly (p<0.05). Moreover cells' orientation angle, 24 hour after loading does not change compared to the observations immediately after loading, which attests to the practicality of the cyclic strain in functional tissue engineering. Cell width decreased and cell length increased which led to a significant increase in cell shape index (p<0.05). Results confirmed that uniaxial dynamic loading affects cell morphological parameters comparing their values before and after loading. In addition, the number of cycles are also an important factor since different number of cycles lead to different amounts of certain morphological parameters. Conclusively, cyclic strain can be a practical method in the field of functional tissue engineering.

Numerical modeling of primary thoracic traumabecause of blast

Since explosive blasts continue to cause casualties in both civil and military environments, there is a need for an understanding of the mechanisms of blast trauma at the human organ level, plus a more detailed predictive methodology. The primary goal of this research was to develop a finite element model capable of predicting primary blast injury to the lung so as to assist in the development of personal protective equipment. Numerical simulation of thorax blast loading consisted of the following components: 3D thorax modeling reconstruction, meshing and assembly of various thorax parts, blast and boundary loading, numerical solution, result extraction and data analysis. By comparing the models to published experimental data, local extent of injury in the lung was correlated to the peak pressure measured in each finite element, categorized as no injury [< 60 kPa], trace [60-100 kPa], slight [100-140 kPa], moderate [140-240 kPa] and severe [> 240 kPa]. It seemed that orienting the body at an angle of 45 degrees provides the lowest injury. The level and type of trauma inflicted on a human organ by a blast overpressure is related to many factors including: blast characteristics, body orientation, equipment worn and the number of exposures to blast loading