Akademik Veri Yönetim Sistemi
Tezin Türü: Doktora
Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Fen Bilimleri Enstitüsü, Fen Bilimleri Enstitüsü, Türkiye
Tezin Onay Tarihi: 2018
Öğrenci: GÖKHAN BAHÇECİOĞLU
Danışman: VASIF NEJAT HASIRCI
Özet:Three dimensional (3D) printing has recently been in the spotlight of tissue engineering field, because it enables production of patient-specific tissue engineered scaffolds with desired shapes, porosities and pore sizes. In the current study, the aim was to develop a meniscal construct via tissue engineering that would serve as a functional replacement for the damaged tissues. The scaffold involves 3D printed polycaprolactone (PCL) structure embedded in different hydrogels; the hydrogel used at the inner region induces glycosaminoglycan (GAG) production similar to the cartilage-like tissues, and the hydrogel used at the outer region induces collagen production similar to fibrocartilage-like tissue. Various hydrogels such as agarose (Ag), methacrylated gelatin (GelMA), methacrylated hyaluronic acid (MeHA) and GelMA-MeHA were prepared and their effect on cell activities were studied by using two different cells, porcine fibrochondrocytes and human fibrochondrocytes. Constructs were tested in vitro using porcine fibrochondrocytes in order to investigate their performance before any animal experimentation. Different hydrogels (Ag, GelMA, MeHA and GelMA-MeHA) were seeded with the cells and tested under static (no load) or dynamic (compression, 5-15% strain) culture conditions. Ag (which promoted GAG production) and GelMA (which promoted collagen production) were selected to embed the 3D printed PCL scaffolds. After 56 days of culture, PCL scaffolds embedded in Ag resulted in 2-fold higher collagen and 3-fold higher GAG production, and the ones embedded in GelMA resulted in a 10-fold higher collagen production compared to untreated PCL. Mechanical properties of the PCL did not change after embedding in Ag or GelMA. PCL scaffolds with meniscus-shapes were 3D printed and embedded in Ag and GelMA at the inner and outer regions, respectively. The inner region of the constructs that was embedded in Ag produced high amounts of GAG, and the outer region that was embedded in GelMA produced high amounts of collagen after 56 days of incubation. Thus, the meniscus-shaped constructs mimicking the biochemical content of the meniscal tissue were produced. In order to investigate the performance of the constructs in vitro before any clinical applications, human fibrochondrocytes were used to engineer the meniscus. To this end, square prism-shaped PCL scaffolds having different designs were printed with various interior (with or without shifting of the consecutive layers) and exterior (with or without circumferential strands) architectures, and studied for their suitability as human meniscus substitutes. Shifting of the strands led to lower mechanical properties while introduction of the circumferential strands enhanced mechanical properties in all combinations. The compressive modulus of the scaffolds when the scaffolds were produced in shifted architecture and with circumferential strands (~0.4 MPa) was close to that of the human meniscus (0.3-2 MPa), while the tensile modulus (18 MPa) was lower than that of the meniscus (70-130 MPa). The 3D printed PCL scaffolds were produced in shifted architecture and with circumferential strands, embedded in the human fibrochondrocyte-carrying Ag, GelMA or GelMA-Ag, and incubated for 42 days under static culture conditions. The order of collagen deposition on the hydrogel-embedded scaffolds from the highest to the lowest was GelMA > GelMA-Ag > Ag. When the meniscus-shaped constructs with the circumferential strands were embedded in GelMA-Ag at the inner region instead of agarose alone, collagen deposition was increased. At the end, a zonal difference in the biochemical content of the constructs, high COL I at the outer region and high COL II at the inner region, was created, mimicking the native meniscus. The structural organization of the meniscus was also mimicked with introducing circumferential strands to the engineered constructs.