Anne-Marie Haaparanta

Growth and Osteogenic Differentiation of Adipose Stem Cells on PLA/Bioactive Glass and PLA/β-TCP Scaffolds

The aim of this study was to compare the effects of novel three-dimensional composite scaffolds consisting of a bioactive phase (bioactive glass or beta-tricalcium phosphate [beta-TCP] 10 and 20 wt%) incorporated within a polylactic acid (PLA) matrix on viability, distribution, proliferation, and osteogenic differentiation of human adipose stem cells (ASCs). The viability and distribution of ASCs on the bioactive composite scaffolds was evaluated using Live/Dead fluorescence staining, environmental scanning electron microscopy, and scanning electron microscopy. There were no differences between the two concentrations of bioactive glass and beta-TCP in PLA scaffolds on proliferation and osteogenic differentiation of ASCs. After 2 weeks of culture, DNA content and alkaline phosphatase (ALP) activity of ASCs cultured on PLA/beta-TCP composite scaffolds were higher relative to other scaffold types. Interestingly, the cell number was significantly lower, but the relative ALP/DNA ratio of ASCs was significantly higher in PLA/bioactive glass scaffolds than in other three scaffold types. These results indicate that the PLA/beta-TCP composite scaffolds significantly enhance ASC proliferation and total ALP activity compared to other scaffold types. This supports the potential future use of PLA/beta-TCP composites as effective scaffolds for tissue engineering and as bone replacement materials.

Preparation and characterization of collagen/PLA, chitosan/PLA, and collagen/chitosan/PLA hybrid scaffolds for cartilage tissue engineering

In this study, three-dimensional (3D) porous scaffolds were developed for the repair of articular cartilage defects. Novel collagen/polylactide (PLA), chitosan/PLA, and collagen/chitosan/PLA hybrid scaffolds were fabricated by combining freeze-dried natural components and synthetic PLA mesh, where the 3D PLA mesh gives mechanical strength, and the natural polymers, collagen and/or chitosan, mimic the natural cartilage tissue environment of chondrocytes. In total, eight scaffold types were studied: four hybrid structures containing collagen and/or chitosan with PLA, and four parallel plain scaffolds with only collagen and/or chitosan. The potential of these types of scaffolds for cartilage tissue engineering applications were determined by the analysis of the microstructure, water uptake, mechanical strength, and the viability and attachment of adult bovine chondrocytes to the scaffolds. The manufacturing method used was found to be applicable for the manufacturing of hybrid scaffolds with highly porous 3D structures. All the hybrid scaffolds showed a highly porous structure with open pores throughout the scaffold. Collagen was found to bind water inside the structure in all collagen-containing scaffolds better than the chitosan-containing scaffolds, and the plain collagen scaffolds had the highest water absorption. The stiffness of the scaffold was improved by the hybrid structure compared to plain scaffolds. The cell viability and attachment was good in all scaffolds, however, the collagen hybrid scaffolds showed the best penetration of cells into the scaffold. Our results show that from the studied scaffolds the collagen/PLA hybrids are the most promising scaffolds from this group for cartilage tissue engineering.

Porous polylactide/β-tricalcium phosphate composite scaffolds for tissue engineering applications

Porous polylactide/β‐tricalcium phosphate (PLA/β‐TCP) composite scaffolds were fabricated by freeze‐drying. The aim of this study was to characterize these graded porous composite scaffolds in two different PLA concentrations (2 and 3 wt%). Also, three different β‐TCP ratios (5, 10 and 20 wt%) were used to study the effect of β‐TCP on the properties of the polymer. The characterization was carried out by determining the pH, weight change, component ratios, thermal stability, inherent viscosity and microstructure of the scaffolds in 26 weeks of hydrolysis. This study indicated that no considerable change was noticed in the structure of the scaffolds when the β‐TCP filler was added. Also, the amount of β‐TCP did not affect the pore size or the pore distribution in the scaffolds. We observed that the fabrication method improved the thermal stability of the samples. Our results suggest that, from the structural point of view, these scaffolds could have potential for the treatment of osteochondral defects in tissue engineering applications. The porous bottom surface of the scaffold and the increased osteogenic differentiation potential achieved with β‐TCP particles may encourage the growth of bone cells. In addition, the dense surface skin of the scaffold may inhibit the ingrowth of osteoblasts and bone tissue, while simultaneously encouraging the ingrowth of chondrocytes. Copyright

Characterizing and optimizing poly-l-lactide-co-ε-caprolactone membranes for urothelial tissue engineering

Different synthetic biomaterials such as polylactide (PLA), polycaprolactone and poly-l-lactide-co-ε-caprolactone (PLCL) have been studied for urothelial tissue engineering, with favourable results. The aim of this research was to further optimize the growth surface for human urothelial cells (hUCs) by comparing different PLCL-based membranes: smooth (s) and textured (t) PLCL and knitted PLA mesh with compression-moulded PLCL (cPLCL). The effects of topographical texturing on urothelial cell response and mechanical properties under hydrolysis were studied. The main finding was that both sPLCL and tPLCL supported hUC growth significantly better than cPLCL. Interestingly, tPLCL gave no significant advantage to hUC attachment or proliferation compared with sPLCL. However, during the 14 day assessment period, the majority of cells were viable and maintained phenotype on all the membranes studied. The material characterization exhibited potential mechanical characteristics of sPLCL and tPLCL for urothelial applications. Furthermore, the highest elongation of tPLCL supports the use of this kind of texturing. In conclusion, in light of our cell culture results and mechanical characterization, both sPLCL and tPLCL should be further studied for urothelial tissue engineering.

Comparison of a poly-l-lactide-co-ɛ-caprolactone and human amniotic membrane for urothelium tissue engineering applications

The reconstructive surgery of urothelial defects, such as severe hypospadias is susceptible to complications. The major problem is the lack of suitable grafting materials. Therefore, finding alternative treatments such as reconstruction of urethra using tissue engineering is essential. The aim of this study was to compare the effects of naturally derived acellular human amniotic membrane (hAM) to synthetic poly-l-lactide-co-ε-caprolactone (PLCL) on human urothelial cell (hUC) viability, proliferation and urothelial differentiation level. The viability of cells was evaluated using live/dead staining and the proliferation was studied using WST-1 measurement. Cytokeratin (CK)7/8 and CK19 were used to confirm that the hUCs maintained their phenotype on different biomaterials. On the PLCL, the cell number significantly increased during the culturing period, in contrast to the hAM, where hUC proliferation was the weakest at 7 and 14 days. In addition, the majority of cells were viable and maintained their phenotype when cultured on PLCL and cell culture plastic, whereas on the hAM, the viability of hUCs decreased with time and the cells did not maintain their phenotype. The PLCL membranes supported the hUC proliferation significantly more than the hAM. These results revealed the significant potential of PLCL membranes in urothelial tissue engineering applications.

Improved dimensional stability with bioactive glass fibre skeleton in poly(lactide-co-glycolide) porous scaffolds for tissue engineering

Bone tissue engineering requires highly porous three-dimensional (3D) scaffolds with preferable osteoconductive properties, controlled degradation, and good dimensional stability. In this study, highly porous 3D poly(d,l-lactide-co-glycolide) (PLGA) - bioactive glass (BG) composites (PLGA/BG) were manufactured by combining highly porous 3D fibrous BG mesh skeleton with porous PLGA in a freeze-drying process. The 3D structure of the scaffolds was investigated as well as in vitro hydrolytic degradation for 10weeks. The effect of BG on the dimensional stability, scaffold composition, pore structure, and degradation behaviour of the scaffolds was evaluated. The composites showed superior pore structure as the BG fibres inhibited shrinkage of the scaffolds. The BG was also shown to buffer the acidic degradation products of PLGA. These results demonstrate the potential of these PLGA/BG composites for bone tissue engineering, but the ability of this kind of PLGA/BG composites to promote bone regeneration will be studied in forthcoming in vivo studies.

Chemical and topographical patterning of hydrogels for neural cell guidance in vitro

This review focuses on hydrogels and their patterning techniques in relation to central nervous system applications, with emphasis on synthetic and natural materials and chemical and topographical patterning techniques. We describe the properties of hydrogel materials and various techniques used in hydrogel patterning methods. Also, the applicability and utilization of patterned hydrogels with neural cells is discussed. Surface chemistry and topography significantly affect cell behaviour, including cell attachment, migration and maturation. Although several patterning techniques are described in the literature, a review of techniques applicable to hydrogel materials is needed. Use of these patterned cell–hydrogel constructs might provide novel ways to treat central nervous system deficits in the future. Copyright

Articular cartilage repair with recombinant human type II collagen/polylactide scaffold in a preliminary porcine study

The purpose of this study was to investigate the potential of a novel recombinant human type II collagen/polylactide scaffold (rhCo‐PLA) in the repair of full‐thickness cartilage lesions with autologous chondrocyte implantation technique (ACI). The forming repair tissue was compared to spontaneous healing (spontaneous) and repair with a commercial porcine type I/III collagen membrane (pCo). Domestic pigs (4‐month‐old, n = 20) were randomized into three study groups and a circular full‐thickness chondral lesion with a diameter of 8 mm was created in the right medial femoral condyle. After 3 weeks, the chondral lesions were repaired with either rhCo‐PLA or pCo together with autologous chondrocytes, or the lesion was only debrided and left untreated for spontaneous repair. The repair tissue was evaluated 4 months after the second operation. Hyaline cartilage formed most frequently in the rhCo‐PLA treatment group. Biomechanically, there was a trend that both treatment groups resulted in better repair tissue than spontaneous healing. Adverse subchondral bone reactions developed less frequently in the spontaneous group (40%) and the rhCo‐PLA treated group (50%) than in the pCo control group (100%). However, no statistically significant differences were found between the groups. The novel rhCo‐PLA biomaterial showed promising results in this proof‐of‐concept study, but further studies will be needed in order to determine its effectiveness in articular cartilage repair.

Analysis of Different Natural and Synthetic Biomaterials to Support Cardiomyocyte Growth

The aim of this study was to scan through several biomaterials to find an optimal biomaterial to support the growth of cardiomyocytes. Neonatal rat cardiomyocytes were cultured on polylactide, chitosan, poly (1,8-octanediolco-citric acid), copolymer of poly(ethylene oxide terephthalate) and poly (butylene terephthalate), PuraMatrix™ and collagen. The suitability of biomaterials for cardiomyocyte culture was evaluated based on several parameters. The cells were characterized with time-lapse imaging, immunocytochemistry and LIVE/DEAD® staining. Collagen gel was the best biomaterial. It supported well the growth, survival and functionality of the cardiomyocytes. Polylactide and chitosan membranes supported the cell growth and survival, but these biomaterials were too stiff for further cardiac applications. In conclusion, collagen gel is a good biomaterial to obtain a 3D structure to model heart tissue.

µCT Based Characterization of Biomaterial Scaffold Microstructure Under Compression

Scaffolds are often designed with progressive degradation to make way for cell proliferation of seeded cells for native tissue. The viability of the scaffold has been shown to depend on, among other things, the microstructure. Common parameters, that are used to describe microstructure, are porosity, material thickness, pore size and surface area. These properties quantify the suitability of the scaffold as a substrate for cell adhesion, fluid exchange and nutrient transfer. Bone and cartilage scaffolds are often placed or operated under loads (predominantly compression). This can alter the structural parameters depending on the stiffness of the scaffold and applied deformation. It is important to know, how scaffolds’ parameters change under deformation. In this study, two scaffolds (PLCL-TCP and collagen-PLA) intended for use in bone and cartilage applications, were studied through micro computed tomography based imaging and in situ mechanical testing. The scaffolds were subjected to uniaxial compressive deformation up to 50% of the original size. The corresponding changes in the individual scaffold bulk characteristics were analyzed. Our results show an expected decrease in porosity with increasing deformation (with PLCL-TCP scaffold 52% deformation resulted in 56% decrease in porosity). Especially in the sandwich constructs of collagen-PLA, but also in PLCL-TCP composites, it was evident that different materials are affected differently which may be of significance in applications with mechanical loading. Our results are a step towards understanding the changes in the structure of these scaffolds under loading.