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- Aulin, Cecilia, 1979-
(författare)
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Extracellular Matrix Based Materials for Tissue Engineering
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The extracellular matrix is (ECM) is a network of large, structural proteins and polysaccharides, important for cellular behavior, tissue development and maintenance. Present thesis describes work exploring ECM as scaffolds for tissue engineering by manipulating cells cultured in vitro or by influencing ECM expression in vivo. By culturing cells on polymer meshes under dynamic culture conditions, deposition of a complex ECM could be achieved, but with low yields. Since the major part of synthesized ECM diffused into the medium the rate limiting step of deposition was investigated. This quantitative analysis showed that the real rate limiting factor is the low proportion of new proteins which are deposited as functional ECM. It is suggested that cells are pre-embedded in for example collagen gels to increase the steric retention and hence functional deposition. The possibility to induce endogenous ECM formation and tissue regeneration by implantation of growth factors in a carrier material was investigated. Bone morphogenetic protein-2 (BMP-2) is a growth factor known to be involved in growth and differentiation of bone and cartilage tissue. The BMP-2 processing and secretion was examined in two cell systems representing endochondral (chondrocytes) and intramembranous (mesenchymal stem cells) bone formation. It was discovered that chondrocytes are more efficient in producing BMP-2 compared to MSC. The role of the antagonist noggin was also investigated and was found to affect the stability of BMP-2 and modulate its effect. Finally, an injectable gel of the ECM component hyaluronan has been evaluated as delivery vehicle in cartilage regeneration. The hyaluronan hydrogel system showed promising results as a versatile biomaterial for cartilage regeneration, could easily be placed intraarticulary and can be used for both cell based and cell free therapies.
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| 2. |
- Paidikondala, Maruthibabu, 1985-
(författare)
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Regulating Gene Expression to Promote Osteoblastic Differentiation of Stem Cells
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bone is a tissue that heals by itself, unless the defect is too large (critical size). Today, novel regenerative medicine approaches have emerged as an alternative to treat such defects. This thesis explores alternative therapeutic strategies for bone tissue engineering which are biocompatible and clinically translatable. Many types of scaffolds that can act as reservoirs for growth factors such as rh-BMP-2 have been developed for bone tissue engineering in the past. However, the role of cross-linking chemistries that are employed to make hydrogels on the integrity and function of the loaded growth factors is not well understood. In this thesis, we have explored the influence of cross-linking chemistry on rh-BMP-2 integrity and bioactivity both in-vitro and in-vivo. These studies have demonstrated that thiol-Michael addition cross-linking chemistry greatly affects the integrity and bio-functionality of the loaded protein BMP-2 and leads to poor bone formation in an in-vivo rat model. On the other hand, hydrogels employing hydrazone chemistry did not significantly affect the integrity and bioactivity of BMP-2, which lead to a superior bone formation in-vivo. Since the high dose of rh-BMP-2 is known to confer many side effects, alternative ex-vivo strategies involving transient transfection of BMP-2 expressing plasmid DNA and silencing of anti-osteogenic genes using siRNA are developed. Our optimized method involves rapid transfection of hMSCs in suspension (5 minutes) with plasmid DNA followed by centrifugation and encapsulation in a hydrogel not only reduced cytotoxicity but also lead to efficient osteoblast differentiation of stem cells. Furthermore, this thesis presents the role of ECM-derived polymer HA in interacting with siRNA and trafficking across the plasma membrane, presumably through CD44 receptors and successfully silencing the target gene in-vitro. We explored the potential of such a non-cationic transfection method to deliver functional siRNA (anti-Pleckho-1 siRNA) in MSCs and compared it with commercially available cationic lipid LipofectamineTMRNAiMAX, using our optimized suspension transfection method. Our novel ex-vivo strategy employing HA hydrogels enabled efficient silencing of BMP-2 signaling pathway antagonist Pleckho-1 while avoiding the cytotoxicity issues in 3D, which further qualifies them for potential clinical application for cell-based therapies.
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