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| 2. |
- Pulliainen, Outi, et al.
(författare)
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Poly-L-D-lactic acid scaffold in the repair of porcine knee cartilage lesions.
- 2007
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Ingår i: Tissue engineering. - : Mary Ann Liebert Inc. - 1076-3279 .- 1557-8690. ; 13:6, s. 1347-55
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Tidskriftsartikel (refereegranskat)abstract
- Articular cartilage injuries cause a major clinical problem because of the negligible repair capacity of cartilage. Autologous chondrocyte transplantation is a surgical method developed to repair cartilage lesions. In the operation, cartilage defect is covered with a periosteal patch and the suspension of cultured autologous chondrocytes is injected into the lesion site. The method can form good repair tissue, but new techniques are needed to make the operation easier and to increase the postoperative biomechanical properties of the repair tissue. In this study, we investigated poly-L,D-lactic acid (PLDLA) scaffolds alone or seeded with autologous chondrocytes in the repair of circular 6-mm cartilage lesions in immature porcine knee joints. Spontaneous repair was used as a reference. Histologic evaluation of the repair tissue showed that spontaneous repair exhibited higher scores than either PLDLA scaffold group (with or without seeded chondrocytes). The scaffold material was most often seen embedded in the subchondral bone underneath the defect area, probably because of the hardness of the PLDLA material. However, some of the cell-seeded and nonseeded scaffolds contained cartilaginous tissue, suggesting that invasion of mesenchymal cells inside nonseeded scaffolds had occurred. Hyaluronan deposited in the scaffold had possibly acted as a chemoattractant for the cell recruitment. In conclusion, the PLDLA scaffold material used in this study was obviously mechanically too hard to be used for cartilage repair in immature animals.
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| 3. |
- Vasara, Anna I, et al.
(författare)
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Subchondral bone reaction associated with chondral defect and attempted cartilage repair in goats.
- 2004
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Ingår i: Calcified tissue international. - : Springer Science and Business Media LLC. - 0171-967X .- 1432-0827. ; 74:1, s. 107-14
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Tidskriftsartikel (refereegranskat)abstract
- Repair of cartilage damage with autologous chondrocyte transplantation (ACT) has become popular in clinical use during the past few years. Although clinical results have mostly been successful, several unanswered questions remain regarding the biological mechanism of the repair process. The aim of this study was to develop a goat model for ACT. The repair was not successful due to the graft delamination, but we characterize the subchondral changes seen after the procedure. A chondral lesion was created in 14 goat knees, operated on 1 month later with ACT, and covered with periosteum or a bioabsorbable poly-L/D-lactide scaffold. After 3 months, only two of the five lesions repaired with ACT showed partly hyaline-like repair tissue, and all lesions (n = 4) with the scaffold failed. Even though the lesions did not extend through the calcified cartilage, the bone volume and collagen organization of bone structure were decreased when assessed by quantitative polarized light microscopy. There was a significant loss of bone matrix and distortion of the trabecular structure of subchondral bone, which extended several millimeters into the bone. The subchondral bone demonstrated strong hyaluronan staining in the bone marrow and cartilaginous areas with signs of endochondral ossification, suggesting structural remodeling of the bone. The goat model used here proved not to be an optimal model for ACT. The changes in subchondral bone may alter the biomechanical properties of the subchondral plate and thus the long-term survival of the repair tissue after ACT.
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| 4. |
- Vasara, Anna I, et al.
(författare)
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Immature porcine knee cartilage lesions show good healing with or without autologous chondrocyte transplantation.
- 2006
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Ingår i: Osteoarthritis and cartilage / OARS, Osteoarthritis Research Society. - : Elsevier BV. - 1063-4584 .- 1522-9653. ; 14:10, s. 1066-74
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: The purpose of this study was to find out how deep chondral lesions heal in growing animals spontaneously and after autologous chondrocyte transplantation. METHODS: A 6mm deep chondral lesion was created in the knee joints of 57 immature pigs and repaired with autologous chondrocyte transplantation covered with periosteum or muscle fascia, with periosteum only, or left untreated. After 3 and 12 months, the repair tissue was evaluated with International Cartilage Repair Society (ICRS) macroscopic grading, modified O'Driscoll histological scoring, and staining for collagen type II and hyaluronan, and with toluidine blue and safranin-O staining for glycosaminoglycans. The repair tissue structure was also examined with quantitative polarized light microscopy and indentation analysis of the cartilage stiffness. RESULTS: The ICRS grading indicated nearly normal repair tissue in 65% (10/17) after the autologous chondrocyte transplantation and 86% (7/8) after no repair at 3 months. At 1 year, the repair tissue was nearly normal in all cases in the spontaneous repair group and in 38% (3/8) in the chondrocyte transplantation group. In most cases, the cartilage repair tissue stained intensely for glycosaminoglycans and collagen type II indicating repair tissue with true constituents of articular cartilage. There was a statistical difference in the total histological scores at 3 months (P=0.028) with the best repair in the spontaneous repair group. A marked subchondral bone reaction, staining with toluidine blue and collagen type II, was seen in 65% of all animals. CONCLUSIONS: The spontaneous repair ability of full thickness cartilage defects of immature pigs is significant and periosteum or autologous chondrocytes do not bring any additional benefits to the repair.
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| 5. |
- Belay, B, et al.
(författare)
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Optical projection tomography as a quantitative tool for analysis of cell morphology and density in 3D hydrogels
- 2021
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Ingår i: Scientific reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 11:1, s. 6538-
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Tidskriftsartikel (refereegranskat)abstract
- Assessing cell morphology and function, as well as biomaterial performance in cell cultures, is one of the key challenges in cell biology and tissue engineering (TE) research. In TE, there is an urgent need for methods to image actual three-dimensional (3D) cell cultures and access the living cells. This is difficult using established optical microscopy techniques such as wide-field or confocal microscopy. To address the problem, we have developed a new protocol using Optical Projection Tomography (OPT) to extract quantitative and qualitative measurements from hydrogel cell cultures. Using our tools, we demonstrated the method by analyzing cell response in three different hydrogel formulations in 3D with 1.5 mm diameter samples of: gellan gum (GG), gelatin functionalized gellan gum (gelatin-GG), and Geltrex. We investigated cell morphology, density, distribution, and viability in 3D living cells. Our results showed the usability of the method to quantify the cellular responses to biomaterial environment. We observed that an elongated morphology of cells, thus good material response, in gelatin-GG and Geltrex hydrogels compared with basic GG. Our results show that OPT has a sensitivity to assess in real 3D cultures the differences of cellular responses to the properties of biomaterials supporting the cells.
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| 6. |
- Krieger, Ulrich K., et al.
(författare)
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A reference data set for validating vapor pressure measurement techniques : homologous series of polyethylene glycols
- 2018
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Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 11:1, s. 49-63
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Tidskriftsartikel (refereegranskat)abstract
- To predict atmospheric partitioning of organic compounds between gas and aerosol particle phase based on explicit models for gas phase chemistry, saturation vapor pressures of the compounds need to be estimated. Estimation methods based on functional group contributions require training sets of compounds with well-established saturation vapor pressures. However, vapor pressures of semivolatile and low-volatility organic molecules at atmospheric temperatures reported in the literature often differ by several orders of magnitude between measurement techniques. These discrepancies exceed the stated uncertainty of each technique which is generally reported to be smaller than a factor of 2. At present, there is no general reference technique for measuring saturation vapor pressures of atmospherically relevant compounds with low vapor pressures at atmospheric temperatures. To address this problem, we measured vapor pressures with different techniques over a wide temperature range for intercomparison and to establish a reliable training set. We determined saturation vapor pressures for the homologous series of polyethylene glycols (H-(O-CH2-CH2)(n)-OH) for n = 3 to n = 8 ranging in vapor pressure at 298 K from 10(-7) to 5 x 10(-2) Pa and compare them with quantum chemistry calculations. Such a homologous series provides a reference set that covers several orders of magnitude in saturation vapor pressure, allowing a critical assessment of the lower limits of detection of vapor pressures for the different techniques as well as permitting the identification of potential sources of systematic error. Also, internal consistency within the series allows outlying data to be rejected more easily. Most of the measured vapor pressures agreed within the stated uncertainty range. Deviations mostly occurred for vapor pressure values approaching the lower detection limit of a technique. The good agreement between the measurement techniques (some of which are sensitive to the mass accommodation coefficient and some not) suggests that the mass accommodation coefficients of the studied compounds are close to unity. The quantum chemistry calculations were about 1 order of magnitude higher than the measurements. We find that extrapolation of vapor pressures from elevated to atmospheric temperatures is permissible over a range of about 100 K for these compounds, suggesting that measurements should be performed best at temperatures yielding the highest-accuracy data, allowing subsequent extrapolation to atmospheric temperatures.
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