Abstract
Tissue engineering is a branch of regenerative medicine, which comprises the combination of biomaterials, cells and other bioactive molecules to regenerate tissues. Biomaterial scaffolds act as substrate and as physical support for cells and they can also reproduce the extracellular matrix cues. Although tissue engineering applications in cellular therapy tend to focus on the use of specialized cells from particular tissues or stem cells, little attention has been paid to endothelial progenitors, an important cell type in tissue regeneration. We combined 3D printed poly(lactic acid) scaffolds comprising two different pore sizes with human adipose-derived stromal cells (hASCs) and expanded CD133+ cells to evaluate how these two cell types respond to the different architectures. hASCs represent an ideal source of cells for tissue engineering applications due to their low immunogenicity, paracrine activity and ability to differentiate. Expanded CD133+ cells were isolated from umbilical cord blood and represent a source of endothelial-like cells with angiogenic potential. Fluorescence microscopy and scanning electron microscopy showed that both cell types were able to adhere to the scaffolds and maintain their characteristic morphologies. The porous PLA scaffolds stimulated cell cycle progression of hASCs but led to an arrest in the G1 phase and reduced proliferation of expanded CD133+ cells. Also, while hASCs maintained their undifferentiated profile after 7 days of culture on the scaffolds, expanded CD133+ cells presented a reduction of the von Willebrand factor (vWF), which affected the cells’ angiogenic potential. We did not observe changes in cell behavior for any of the parameters analyzed between the scaffolds with different pore sizes, but the 3D environment created by the scaffolds had different effects on the cell types tested. Unlike the extensively used mesenchymal stem cell types, the 3D PLA scaffolds led to opposite behaviors of the expanded CD133+ cells in terms of cytotoxicity, proliferation and immunophenotype. The results obtained reinforce the importance of studying how different cell types respond to 3D culture systems when considering the scaffold approach for tissue engineering.
Highlights
As tissue engineering techniques evolve, the need for understanding three-dimensional (3D) microenvironments becomes more pronounced, considering that two-dimensional (2D) cultures are not an ideal model to predict cell behavior in the 3D environment of the biological tissues (Jensen and Teng, 2020)
As we initially aimed to study the behavior of human adipose-derived stromal cells (hASCs) and CD133 + cells in the poly(lactic acid) (PLA) scaffolds without favoring a specific differentiation path, we used 3D scaffolds with larger pore sizes (>500 um) to favor initial cell adhesion and nutrient distribution
Since von Willebrand factor (vWF) is associated with angiogenesis, playing an important role in controlling the formation of new blood vessels, we investigated whether the reduction in vWF observed in the immunophenotypic profiling could affect the angiogenic potential of the expanded CD133+ cells
Summary
As tissue engineering techniques evolve, the need for understanding three-dimensional (3D) microenvironments becomes more pronounced, considering that two-dimensional (2D) cultures are not an ideal model to predict cell behavior in the 3D environment of the biological tissues (Jensen and Teng, 2020). A 3D system differs from a 2D culture flask mostly due to the fact that the cells can experience a surrounding network in which they are exposed to a gradient of nutrients and to a surface that can present heterogeneous composition and stiffness (Baker and Chen, 2012). In the classical approach of tissue engineering, 3D culture is performed on scaffolds made of biomaterials (Gaharwar et al, 2020) In this case, the scaffold acts as a support for cells to proliferate and secrete the extracellular matrix (Abbot and Kaplan, 2016; Gaharwar et al, 2020). PLA is a good biomaterial option because it can be produced from renewable sources, it can be combined with other biomaterials, and compared to other biomaterials, its processing methods are more straightforward (Casalini et al, 2019)
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