Evaluating Oxygen Tensions Related to Bone Marrow and Matrix for MSC Differentiation in 2D and 3D Biomimetic Lamellar Scaffolds.

The physiological O2 microenvironment of mesenchymal stem cells (MSCs) and osteoblasts and the dimensionality of a substrate are known to be important in regulating cell phenotype and function. By providing the physiologically normoxic environments of bone marrow (5%) and matrix (12%), we assessed their potential to maintain stemness, induce osteogenic differentiation, and enhance the material properties in the micropatterned collagen/silk fibroin scaffolds that were produced in 2D or 3D. Expression of osterix (OSX) and vascular endothelial growth factor A (VEGFA) was significantly enhanced in the 3D scaffold in all oxygen environments. At 21% O2, OSX and VEGFA expressions in the 3D scaffold were respectively 13,200 and 270 times higher than those of the 2D scaffold. Markers for assessing stemness were significantly more pronounced on tissue culture polystyrene and 2D scaffold incubated at 5% O2. At 21% O2, we measured significant increases in ultimate tensile strength (p < 0.0001) and Young's modulus (p = 0.003) of the 3D scaffold compared to the 2D scaffold, whilst 5% O2 hindered the positive effect of cell seeding on tensile strength. In conclusion, we demonstrated that the 3D culture of MSCs in collagen/silk fibroin scaffolds provided biomimetic cues for bone progenitor cells toward differentiation and enhanced the tensile mechanical properties.

Human adipose derived stem cells are superior to human osteoblasts (HOB) in bone tissue engineering on a collagen-fibroin-ELR blend.

The ultrastructure of the bone provides a unique mechanical strength against compressive, torsional and tensional stresses. An elastin-like recombinamer (ELR) with a nucleation sequence for hydroxyapatite was incorporated into films prepared from a collagen - silk fibroin blend carrying microchannel patterns to stimulate anisotropic osteogenesis. SEM and fluorescence microscopy showed the alignment of adipose-derived stem cells (ADSCs) and the human osteoblasts (HOBs) on the ridges and in the grooves of microchannel patterned collagen-fibroin-ELR blend films. The Young's modulus and the ultimate tensile strength (UTS) of untreated films were 0.58 ± 0.13 MPa and 0.18 ± 0.05 MPa, respectively. After 28 days of cell culture, ADSC seeded film had a Young's modulus of 1.21 ± 0.42 MPa and UTS of 0.32 ± 0.15 MPa which were about 3 fold higher than HOB seeded films. The difference in Young's modulus was statistically significant (p: 0.02). ADSCs attached, proliferated and mineralized better than the HOBs. In the light of these results, ADSCs served as a better cell source than HOBs for bone tissue engineering of collagen-fibroin-ELR based constructs used in this study. We have thus shown the enhancement in the tensile mechanical properties of the bone tissue engineered scaffolds by using ADSCs.

Osteogenic differentiation of adipose derived stem cells on high and low aspect ratio micropatterns.

Adipose derived stem cells (ADSCs) were cultured on collagen-silk fibroin films with microchannel and micropillar patterns to investigate the effects of cell morphology changes on osteogenic differentiation. Channel and pillar micropatterned films were prepared from collagen type I and silk fibroin. While higher ADSC proliferation profiles were obtained on micropillar blend film, microchannel blend films, however, caused twice higher aspect ratio and effective orientation of cells. Alkaline phosphatase activity of ADSCs was several times higher on microchannel surface when the measured activities were normalized to cell number. Effective deposition of collagen type I and mineral by the cells were observed for patterned and unpatterned films, and these extracellular matrix components were oriented along the axis of the microchannels. In conclusion, the use of collagen-fibroin blend film with microchannel topography increased the aspect ratio and alignment of cells significantly, and was also effective in the differentiation of ADSCs into osteogenic lineage.

Protein-based materials in load-bearing tissue-engineering applications.

Proteins such as collagen and elastin are robust molecules that constitute nanocomponents in the hierarchically organized ultrastructures of bone and tendon as well as in some of the soft tissues that have load-bearing functions. In the present paper, the macromolecular structure and function of the proteins are reviewed and the potential of mammalian and non-mammalian proteins in the engineering of load-bearing tissue substitutes are discussed. Chimeric proteins have become an important structural biomaterial source and their potential in tissue engineering is highlighted. Processing of proteins challenge investigators and in this review rapid prototyping and microfabrication are proposed as methods for obtaining precisely defined custom-built tissue engineered structures with intrinsic microarchitecture.

Systemic inflammation and metabolic syndrome in stable COPD patients.

INTRODUCTION: Chronic obstructive pulmonary disease (COPD) has extrapulmonary effects that seems to be related with systemic inflammation. The relationship between metabolic syndrome which is an important determinant of systemic inflammation in general population and COPD is still not clear. The aim of the current study was to investigate the frequency of metabolic syndrome and C-reactive protein (CRP) levels, as a marker of systemic inflammation in stable COPD patients with different severity levels and in age and sex matched control group. PATIENTS AND METHODS: Ninety-one stable COPD patients and 42 control subjects were included in the study. The severity level in patients with COPD were determined according to GOLD (Global Initiative for Chronic Obstructive Lung Disease) criteria. ATP III (The National Cholesterol Education Program's Adult Treatment Panel III) was used in diagnosis of metabolic syndrome. Hs-CRP levels were measured in venous samples of patients and control subjects. RESULTS: The frequency of metabolic syndrome was found higher in patient group than control subjects, especially in GOLD stages I, II (p= 0.004). Abdominal obesity, hypertension, hyperglycemia components of metabolic syndrome were significantly more prevalent in patient group (p< 0.0001). Increased CRP levels were higher in control and patient groups in all GOLD stages, with metabolic syndrome than without metabolic syndrome (p= 0.047, p= 0.217, p< 0.001, p= 0.05, p= 0.467). CONCLUSION: The study showed that frequency of metabolic syndrome was higher in stable COPD patients than control subjects and general Turkish population. Abdominal obesity, hypertension and hyperglycemia were significantly more prevalent in patient group. Systemic inflammation was more intense in COPD patients with metabolic syndrome than without metabolic syndrome.