A canine in vitro model for evaluation of marrow-derived mesenchymal stromal cell-based bone scaffolds.

Tissue engineered bone grafts based on bone marrow mesenchymal stromal cells (MSCs) are being actively developed for craniomaxillofacial (CMF) applications. As for all tissue engineered implants, the bone-regenerating capacity of these MSC-based grafts must first be evaluated in animal models prior to human trials. Canine models have traditionally resulted in improved clinical translation of CMF grafts relative to other animal models. However, the utility of canine CMF models for evaluating MSC-based bone grafts rests on canine MSCs (cMSCs) responding in a similar manner to scaffold-based stimuli as human MSCs (hMSCs). Herein, cMSC and hMSC responses to polyethylene glycol (PEG)-based scaffolds were therefore compared in the presence or absence of osteoinductive polydimethylsiloxane (PDMS). Notably, the conjugation of PDMS to PEG-based constructs resulted in increases in both cMSC and hMSC osteopontin and calcium deposition. Based on these results, cMSCs were further used to assess the efficacy of tethered bone morphogenic protein 2 (BMP2) in enhancing PEG-PDMS scaffold osteoinductivity. Addition of low doses of tethered BMP2 (100 ng/mL) to PEG-PDMS systems increased cMSC expression of osterix and osteopontin compared to both PEG-PDMS and PEG-BMP2 controls. Furthermore, these increases were comparable to effects seen with up to five-times higher BMP2 doses noted in literature. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A:2382-2393, 2018.

Characterization of sequential collagen-poly(ethylene glycol) diacrylate interpenetrating networks and initial assessment of their potential for vascular tissue engineering.

Collagen hydrogels have been widely investigated as scaffolds for vascular tissue engineering due in part to the capacity of collagen to promote robust cell adhesion and elongation. However, collagen hydrogels display relatively low stiffness and strength, are thrombogenic, and are highly susceptible to cell-mediated contraction. In the current work, we develop and characterize a sequentially-formed interpenetrating network (IPN) that retains the benefits of collagen, but which displays enhanced mechanical stiffness and strength, improved thromboresistance, high physical stability and resistance to contraction. In this strategy, we first form a collagen hydrogel, infuse this hydrogel with poly(ethylene glycol) diacrylate (PEGDA), and subsequently crosslink the PEGDA by exposure to longwave UV light. These collagen-PEGDA IPNs allow for cell encapsulation during the fabrication process with greater than 90% cell viability via inclusion of cells within the collagen hydrogel precursor solution. Furthermore, the degree of cell spreading within the IPNs can be tuned from rounded to fully elongated by varying the time delay between the formation of the cell-laden collagen hydrogel and the formation of the PEGDA network. We also demonstrate that these collagen-PEGDA IPNs are able to support the initial stages of smooth muscle cell lineage progression by elongated human mesenchymal stems cells.