Mangir, N, Eke, G, Hasirci, N, Chapple, CR, Hasirci, V, MacNeil, S. (2019). An estradiol releasing, proangiogenic hydrogel as a candidate material for use in soft tissue interposition. Neurourology and Urodynamics, 1(8). DOI: 10.1002/nau.23971

Soft tissue interposition (STI) using local and/or regional flaps is often necessary in urogenital reconstruction to stimulate wound healing and prevent recurrence. Harvesting STI flaps can cause donor site morbidity and may not be available in some patients. In this study, we designed estradiol (E2) releasing hydrogel that could be used as an alternative to a STI flap and to investigate its ability to stimulate tissue production and angiogenesis. A hydrogel was constructed by crosslinking a solution of estradiol, methacrylated gelatin (15%, w/v), and methacrylated hyaluronic acid (1%, w/v). The release of estradiol was measured using a UV-spectrophotometer (λ_max = 220 nm). Angiogenesis was evaluated by an ex ovo chicken embryo chorioallantoic membrane (CAM) assay. Estradiol was gradually released from the hydrogel over 21 days. The hydrogels could be easily manipulated with surgical forceps without any deformation. The hydrogels significantly increased collagen production of human dermal fibroblasts (HDFs). Scanning electron microscopic examination demonstrated that HDFs produced significantly more extracellular matrix (ECM) on estradiol releasing hydrogels compared with the controls. Estradiol releasing hydrogels doubled the number of blood vessels growing toward the hydrogel compared with the controls (vasculogenic index, 59.6 [±6.4] and 25.6 [±4.0], respectively; [P < 0.05]). We present a proangiogenic, degradable hydrogel that can be used as an off-the-shelf available substitute to traditional STI flaps. This is achieved by using estradiol as a potent stimulator of new tissue production and new blood vessel formation.

Hasturk, O., Ermis, M., Demirci, U., Hasirci, N., and Hasirci, V. (2019). Square prism micropillars on poly (methyl methacrylate) surfaces modulate the morphology and differentiation of human dental pulp mesenchymal stem cells. Colloids and Surfaces B: Biointerfaces, 178, 44-55. DOI: 10.1016/j.colsurfb.2019.02.037

Use of soluble factors is the most common strategy to induce osteogenic differentiation of mesenchymal stem cells (MSCs) in vitro, but it may raise potential side effects in vivo. The topographies of the substrate surfaces affect cell behavior, and this could be a promising approach to guide stem cell differentiation. Micropillars have been reported to modulate cellular and subcellular shape, and it is particularly interesting to investigate whether these changes in cell morphology can modulate gene expression and lineage commitment without chemical induction. In this study, poly(methyl methacrylate) (PMMA) films were decorated with square prism micropillars with different lateral dimensions (4, 8 and 16 μm), and the surface wettability of the substrates was altered by oxygen plasma treatment. Both, pattern dimensions and hydrophilicity, were found to affect the attachment, proliferation, and most importantly, gene expression of human dental pulp mesenchymal stem cells (DPSCs). Decreasing the pillar width and interpillar spacing of the square prism pillars enhanced cell attachment, cell elongation, and deformation of nuclei, but reduced early proliferation rate. Surfaces with 4 or 8 μm wide pillars/gaps upregulated the expression of early bone-marker genes and mineralization over 28 days of culture. Exposure to oxygen plasma increased wettability and promoted cell attachment and proliferation but delayed osteogenesis. Our findings showed that surface topography and chemistry are very useful tools in controlling cell behavior on substrates and they can also help create better implants. The most important finding is that hydrophobic micropillars on polymeric substrate surfaces can be exploited in inducing osteogenic differentiation of MSCs without any differentiation supplements.