Recombinant Collagen I Peptide Microcarriers for Cell Expansion and Their Potential Use As Cell Delivery System in a Bioreactor Model.

Tissue engineering is a promising field, focused on developing solutions for the increasing demand on tissues and organs regarding transplantation purposes. The process to generate such tissues is complex, and includes an appropriate combination of specific cell types, scaffolds, and physical or biochemical stimuli to guide cell growth and differentiation. Microcarriers represent an appealing tool to expand cells in a three-dimensional (3D) microenvironment, since they provide higher surface-to volume ratios and mimic more closely the in vivo situation compared to traditional two-dimensional methods. The vascular system, supplying oxygen and nutrients to the cells and ensuring waste removal, constitutes an important building block when generating engineered tissues. In fact, most constructs fail after being implanted due to lacking vascular support. In this study, we present a protocol for endothelial cell expansion on recombinant collagen-based microcarriers under dynamic conditions in spinner flask and bioreactors, and we explain how to determine in this setting cell viability and functionality. In addition, we propose a method for cell delivery for vascularization purposes without additional detachment steps necessary. Furthermore, we provide a strategy to evaluate the cell vascularization potential in a perfusion bioreactor on a decellularized biological matrix. We believe that the use of the presented methods could lead to the development of new cell-based therapies for a large range of tissue engineering applications in the clinical practice.

Matrix dimensions, stiffness, and structural properties modulate spontaneous chondrogenic commitment of mouse embryonic fibroblasts.

Experimental models for cartilage and bone development have been studied in order to understand the biomechanical and biological parameters that regulate skeletal tissue formation. We have previously described that when mouse embryonic fibroblasts (MEFs) were cultured in a three-dimensional (3D)-soft self-assembling peptide nanofiber, the system engaged in a spontaneous process of cartilage-like formation evidenced by the expression of Sox9, Collagen type II, and proteoglycans. In the present work, we studied the influence that matrix mechanical properties have in modulating lineage commitment in an in vitro model of chondrogenesis. This effect was observed only when MEFs were cultured at low elastic modulus values (∼ 0.1 kPa). Interestingly, under these conditions, the system expressed the chondrogenic inductor BMP4 and its antagonist Noggin. On the other hand, at higher elastic modulus values (∼ 5 kPa), the system expressed Noggin but not BMP4, and did not engage in chondrogenesis, which suggest that the balance between bone morphogenetic protein/Noggin could be implicated in the chondrogenic process. Finally, no evidence of hypertrophy was detected under the conditions tested (by assessing expression of Collagen type X and Runx2) unless we challenged the system by co-culturing it with endothelial cells. Importantly, under these new conditions, the system underwent spontaneous matrix calcium mineralization. These results suggest that the 3D-system described here is sensitive to respond to environmental changes such as biomechanical and biological cues.