Thermoplastic bioactive composite – with special reference to dissolution behaviour and tissue response

Bioactive glasses are surface-active ceramic materials which support and accelerate bone growth in the body. During the healing of a bone fracture or a large bone defect, fixation is often needed. The aim of this thesis was to determine the dissolution behaviour and biocompatibility of a composite consisting of poly(ε-caprolactone-co-DL-lactide) and bioactive glass (S53P4). In addition the applicability as an injectable material straight to a bone defect was assessed. In in vitro tests the dissolution behaviour of plain copolymer and composites containing bioactive glass granules was evaluated, as well as surface reactivity and the material’s capability to form apatite in simulated body fluid (SBF). The human fibroblast proliferation was tested on materials in cell culture. In in vivo experiments, toxicological tests, material degradation and tissue reactions were tested both in subcutaneous space and in experimental bone defects. The composites containing bioactive glass formed a unified layer of apatite on their surface in SBF. The size and amount of glass granules affected the degradation of polymer matrix, as well the material’s surface reactivity. In cell culture on the test materials the human gingival fibroblasts proliferated and matured faster compared with control materials. In in vitro tests a connective tissue capsule was formed around the specimens, and became thinner in the course of time. Foreign body cell reactions in toxicological tests were mild. In experimental bone defects the specimens with a high concentration of small bioactive glass granules (<45 μm) formed a dense apatite surface layer that restricted the bone ingrowth to material. The range of large glass granules (90-315 μm) with high concentrations formed the best bonding with bone, but slow degradation on the copolymer restricted the bone growth only in the superficial layers. In these studies, the handling properties of the material proved to be good and tissue reactions were mild. The reactivity of bioactive glass was retained inside the copolymer matrix, thus enabling bone conductivity with composites. However, the copolymer was noticed to degradate too slowly compared with the bone healing. Therefore, the porosity of the material should be increased in order to improve tissue healing.

Role of fibroblast growth factors and their receptors in prostate cancer

Prostate cancer (PCa) is the most common non-cutaneous malignant disease among males in the developed countries. Radical prostatectomy (RP) is an effective therapy for most PCa patients with localized or locally invaded tumors but in some cases the cancer recurs after RP. PCa is a heterogeneous disease, which is regulated by many factors, such as androgen receptor (AR), estrogen receptors and  (ER and ER), fibroblast growth factors (FGFs) and their receptors (FGFRs). In this study, the role of ERβ, FGF8, FGF13 and FGFRL1 was investigated in PCa. Previous studies have suggested that ER is protective against PCa whereas FGF8 has been shown to induce PCa in transgenic mice. FGF13 and FGFRL1 are poorly understood members of the FGF and FGFR families, respectively. Transgenic mouse models were used to investigate the ability of inactivated ERβ to facilitate FGF8-induced prostate tumorigenesis. Human PCa tissue microarrays (TMAs) were used to study the expression pattern of FGF13 and FGFRL1 in PCa and the results were correlated to corresponding patient data. The targets and biological functions of FGF13 and FGFRL1 were characterized using experimental in vivo and in vitro models. The results show that deficiency of ERβ, which had been expected to have tumor suppressing capacity, seemed to influence epithelial differentiation but did not affect FGF8-induced prostate tumorigenesis. Analysis of the TMAs showed increased expression of FGF13 in PCa. The level of cytoplasmic FGF13 was associated with the PCa biochemical recurrence (BCR), demonstrated by increasing serum PSA value, and was able to act as an independent prognostic biomarker for PCa patients after RP. Expression of FGFRL1, the most recently identified FGFR, was also elevated in PCa. Cytoplasmic and nuclear FGFRL1 was associated with high Gleason score and Ki67 level whereas the opposite was true for the cell membrane FGFRL1. Silencing of FGFRL1 in PC-3M cells led to a strongly decreased growth rate of these cells as xenografts in nude mice and the experiments with PCa cell lines showed that FGFRL1 is able to modulate the FGF2- and FGF8-induced signaling pathways. The next generation sequencing (NGS) experiments with FGFRL1-silenced PC-3M cells revealed candidates for FGFRL1 target genes. In summary, these studies provide new data on the FGF/FGFR signaling pathways in normal and malignant prostate and suggest a potential role for FGF13 and FGFRL1 as novel prognostic markers for PCa patients. Keywords: FGF8, FGF13, FGFRL1, ERβ, prostate cancer, prognostic marker