-
H Deplaine,
M Lebourg, P Ripalda,
A Vidaurre,
P Sanz-Ramos,
G Mora,
F Prósper,
I Ochoa,
M Doblaré,
J L Gómez Ribelles,
I Izal-Azcárate,
G Gallego Ferrer
[show abstract]
[hide abstract]
ABSTRACT: Polymer-ceramic composites obtained as the result of a mineralization process hold great promise for the future of tissue engineering. Simulated body fluids (SBFs) are widely used for the mineralization of polymer scaffolds. In this work an exhaustive study with the aim of optimizing the mineralization process on a poly(L-lactic acid) (PLLA) macroporous scaffold has been performed. We observed that when an air plasma treatment is applied to the PLLA scaffold its hydroxyapatite nucleation ability is considerably improved. However, plasma treatment only allows apatite deposition on the surface of the scaffold but not in its interior. When a 5 wt % of synthetic hydroxyapatite (HAp) nanoparticles is mixed with PLLA a more abundant biomimetic hydroxyapatite layer grows inside the scaffold in SBF. The morphology, amount, and composition of the generated biomimetic hydroxyapatite layer on the pores' surface have been analyzed. Large mineralization times are harmful to pure PLLA as it rapidly degrades and its elastic compression modulus significantly decreases. Degradation is retarded in the composite scaffolds because of the faster and extensive biomimetic apatite deposition and the role of HAp to control the pH. Mineralized scaffolds, covered by an apatite layer in SBF, were implanted in osteochondral lesions performed in the medial femoral condyle of healthy sheep. We observed that the presence of biomimetic hydroxyapatite on the pore's surface of the composite scaffold produces a better integration in the subchondral bone, in comparison to bare PLLA scaffolds. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2012.
Journal of Biomedical Materials Research Part B Applied Biomaterials 11/2012; · 2.15 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The aim of this work was to determine the pathways implicated in the mechanosensing of chondrocytes.
Rat chondrocytes were cultured in collagen hydrogels of different stiffness (2-20 Pa) in normoxia and hypoxia, in monolayer and embedded inside hydrogels. First, chondrocyte were cultured on hydrogels in the presence of antibodies to block integrins. Second, custom RT-PCR array plates and western blot were used to detect changes in expression of genes implicated in downstream signalling pathways.
The results allowed us to demonstrate the mechanosensing of chondrocytes for changes in stiffness in the range of Pascals. We also identified Non-Muscle Myosin II (NMMII) and integrins α1, β1 and β3 as participants in the mechanosensing, since their blockade inhibits the sensing of the stiffness, and they are up-regulated in the process. RT-PCR arrays and western blot detected up-regulation of Paxillin, RhoA, Fos, Jun and Sox9. We detected no expression of Src in the monolayer cultures, but we found a role for this protein in 3D. The expression of HIF-1α was not modified under normoxia but was found to participate under hypoxia. Focal Adhesion Kinase (FAK), showed a direct relationship with the expression of Aggrecan in hypoxia and an inverse one in normoxia. Finally, immunofluorescence analysis located the expression of factors AP-1, Sox-9 and HIF-1α inside the cell nuclei and RhoA, Src, Paxillin and FAK close to the cytoplasmic membrane.
We determined here some of the genes that are up-regulated during the process of chondrocyte mechanosensing.
Osteoarthritis and Cartilage 05/2012; 20(8):931-9. · 3.90 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We performed a morphological and histomorphometric analysis of the use of either autografts, or of frozen or freeze-dried cancellous bone allografts in sheep. A cancellous bone defect was created in the lateral portion of the distal epiphysis of the left femur. Four groups of six animals were monitored for 3 months. In the first group, the cavity was filled with autograft, in the second with frozen allograft and in the third with freeze-dried allograft. In the last group, the cavity was not filled and served as control. A study of the host bone showed that the mean trabecular width of the peripheral osteoid was greatest in the control group, while the number of osteoblasts and osteoclasts was significantly lower in the freeze-dried allograft group. However, the different bone grafts that were used to fill the cavity showed a greater trabecular width and area in the autografts. Among the frozen allografts, these measurements were also greater than in the freeze-dried allograft group. The "erosion surface" of the freeze-dried allograft group was also found to be three times greater, and there were a larger number of osteoclasts and osteoclastic nuclei. We concluded that the "lyophilised" allografts were re-absorbed rapidly and that there were no major morphological differences between the frozen allografts and the autograft groups.
International Orthopaedics 03/2004; 28(1):2-6. · 2.03 Impact Factor
