This is consistent with previously reported micropatterning studies as well as matrix elasticity studies observing cell size to be a regulator of lineage commitment.[17, 21, 40] When looking at cells on 2,500 and 5,000 m2 patterns with different shape and elasticity we found a more mixed populace of adipocytes and osteoblasts. stem cell behavior for future tissue engineering strategies. when evaluating lineage commitment and differentiation of cells.[35-37] To address this concern of diminished differentiation capability, trials to assess the ability of MSCs to commit to adipocytes and osteoblasts under passage 6 were first run with lineage specific medium and soluble cues for 7 days. In strictly adipogenic medium, we observed 80.3% and 81.9% adipogenic lineage commitment at 5,000 cells/cm2 and 25,000 cells/cm2. Alternatively, in osteogenic medium we observed 100% and 80.9% osteogenic lineage commitment (Determine 2). Further evaluations were done using MSCs in a 1:1 mixture of adipogenic and osteogenic medium for 7 days on unpatterned substrates. As previously shown, [21, 38] we confirmed cell density contributed to lineage commitment when looking at the differentiation of MSCs at a density of 5,000 cells/cm2 and 25,000 cells/cm2. Our findings show that on glass coverslips, cells continued to show 100% osteogenic differentiation with 5,000 cm2 density while only 40.6% osteogenic differentiation with 25,000 cells/cm2. We then coated coverslips with 10% PEG (~7 kPa) and found the softer substrate contributed to 40.4% greater adipogenic differentiation in low plating densities and similar adipogenic differentiation in higher plating densities (Determine 2). Open in a separate window Physique 2 MSCs showed multilineage capabilities when cultured in medium containing growth factors promoting osteogenesis and adipogenesis. Dual staining of MSCs after 1 week for osteogenesis (alkaline phosphatase-purple/blue) and adipogenesis (lipids-red). Each line of images and graphs represents a differing culture condition with both 5,000 cells/cm2 and 25,000 cells/cm2. Conditions tested were adipogenic medium alone on glass, osteogenic medium alone on glass, mixed medium on glass, and mixed medium on 7 kPa extracellular matrix. Pie charts show the percentage of differentiation to each lineage (red-adipocyte, blue-osteoblast). These results compare similarly to previous studies using differing cell densities and show the effects of cell density and substrate stiffness around the differentiation potential of MSCs in mixed medium. As cell density increases, cell adhesion and spreading are decreased and cell-cell contact is usually increased which leads to enhanced signaling. This aspect has been confirmed by several studies to control cell behavior[21, 39] and we further show that substrate elasticity along with cell density can control lineage commitment of MSCs. To address the interplay between cell size, shape, and substrate elasticity remaining experiments were conducted using patterned cells cultured in mixed media conditions. Micropatterning and Adhesion of Mesenchymal Cells UV lithography techniques were used to restrict the shape of individual cells into circles, squares, and rectangles onto coverslips (Physique 3). A photomask was utilized to control size and shape of the islands with a mixture of PEG-SH and PEG-DA used as the precursor answer for the hydrogels. UV light was employed to selectively crosslink hydrogels into circles, squares, and rectangles on a gold coated glass coverslip through the photomask (Physique 4A-C). The remaining regions of the coverslip were then rendered non-adhesive with a tri(ethylene glycol)-terminated monolayer to prevent non-specific binding of protein or cells. Patterns were incubated in maleimide-modified fibronectin answer to absorb protein exclusively to hydrogel islands to allow cell attachment as seen in Physique 4D and 4E. MSCs were then able to attach to the hydrogel islands and spread to assume distinct shapes of the underlying islands (Physique 4F-I). Cells were able to attach and spread on patterns while remaining viable and constrained to hydrogel islands for one week in culture to determine the lineage commitment effects due to size, shape and elasticity of the microenvironment. MSCs were plated onto hydrogel islands using MSC growth medium initially, switched to a 50:50 mixture of adipogenic and osteogenic differentiation media, and cultured for 7 days. Cells were then analyzed by staining for lineage specific markers Oil Cd22 Red O and alkaline phosphatase for adipogenic and osteogenic differentiation respectively. Open in a separate window Physique 3 Schematic showing UV lithography process used to produce hydrogel shapes of varying elasticity. Hydrogel shapes were functionalized.Our interpretation shows that cell size was responsible for lineage commitment choices at 1,000 m2 in all cases regardless of matrix elasticity or shape. of cells.[35-37] To address this concern of diminished differentiation capability, trials to assess the ability of MSCs to commit to adipocytes and osteoblasts under passage 6 were first run with lineage specific medium and soluble cues for 7 days. In strictly adipogenic medium, we observed 80.3% and 81.9% adipogenic lineage commitment at 5,000 cells/cm2 and 25,000 cells/cm2. Alternatively, in osteogenic medium we observed 100% and 80.9% osteogenic lineage commitment (Figure 2). Further evaluations were done using MSCs in a 1:1 mixture of adipogenic and osteogenic medium for 7 days on unpatterned substrates. As previously shown, [21, 38] we confirmed cell density contributed to lineage commitment when looking at the differentiation of MSCs at a density of 5,000 cells/cm2 and 25,000 cells/cm2. Our findings show that on glass coverslips, cells continued to show 100% osteogenic differentiation with 5,000 cm2 density while only 40.6% osteogenic differentiation with 25,000 cells/cm2. We O6BTG-octylglucoside then coated coverslips with 10% PEG (~7 kPa) and found the softer substrate contributed to 40.4% greater adipogenic differentiation in low plating densities and similar adipogenic differentiation in higher plating densities (Figure 2). Open in a separate window Figure 2 MSCs showed multilineage capabilities when cultured in medium containing growth factors promoting osteogenesis and adipogenesis. Dual staining of MSCs after 1 week for osteogenesis (alkaline phosphatase-purple/blue) and adipogenesis (lipids-red). Each line of O6BTG-octylglucoside images and graphs represents a differing culture condition with both 5,000 cells/cm2 and 25,000 cells/cm2. Conditions tested were adipogenic medium alone on glass, osteogenic medium alone on glass, mixed medium on glass, and mixed medium on 7 kPa extracellular matrix. Pie charts show the percentage of differentiation to each lineage (red-adipocyte, blue-osteoblast). These results compare similarly to previous studies using differing cell densities and show the effects of cell density and substrate stiffness on the differentiation potential of MSCs in mixed medium. As cell density increases, cell adhesion and spreading are decreased and cell-cell contact is increased which leads to enhanced signaling. This aspect has been confirmed by several studies to control cell behavior[21, 39] and we further show that substrate elasticity along with cell density can control lineage commitment of MSCs. To address the interplay between cell size, shape, and substrate elasticity remaining experiments were conducted using patterned cells cultured in mixed media conditions. Micropatterning and Adhesion of Mesenchymal Cells UV lithography O6BTG-octylglucoside techniques were used to restrict the shape of individual cells into circles, squares, and rectangles onto coverslips (Figure 3). A photomask was utilized to control size and shape of the islands with a mixture of PEG-SH and PEG-DA used as the precursor solution for the hydrogels. UV light was employed to selectively crosslink hydrogels into circles, squares, and rectangles on a gold coated glass coverslip through the photomask (Figure 4A-C). The remaining regions of the coverslip were then rendered non-adhesive with a tri(ethylene glycol)-terminated monolayer to prevent non-specific binding of protein or cells. Patterns were incubated in maleimide-modified fibronectin solution to absorb protein exclusively to hydrogel islands to allow cell attachment as seen in Figure 4D and 4E. MSCs were then able to attach to the hydrogel islands and spread to assume distinct shapes of the underlying islands (Figure 4F-I). Cells were able to attach and spread on patterns while remaining viable and constrained to hydrogel islands for one week in culture to determine the lineage commitment effects due to size, shape and elasticity of the microenvironment. MSCs were plated onto hydrogel islands using MSC growth medium initially, switched to a 50:50 mixture of adipogenic and osteogenic.