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

Abstract

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.

Toward zonally tailored scaffolds for osteochondral differentiation of synovial mesenchymal stem cells

“…Similarly, the “Bone” scaffolds—which contained the highest levels of osteoinductive PDMS and BMP2—induced the greatest expression of osteogenic markers TNAP and OPN, in agreement with previous bone marrow MSC studies. 43 Overall, these results suggest that a graded transition from PEG-CSC-TGFβ1 to PEG-PDMS-BMP2 scaffolds elicits a gradual SMSC phenotypic shift from chondrocyte to hypertrophic chondrocyte to osteoblast-like. As such, further development of these scaffold formulations for use in SMSC-based OCD repair is warranted.…”

“…In contrast, the “Bone” scaffold formulation was associated with a clear osteogenic response relative to “PEG” controls (↑TNAP, ↑OPN, ↑mineralization, with ↔Sox9 and ↔Col II; Figure 1) While we did not control for donor variability in all of our scaffold development studies due to practical reasons, we observed minimal effect of donor with our osteogenic scaffolds (Supporting Information Figure S4), as was observed previously for bone marrow derived MSCs. 43 …”

“…Furthermore, PDMS was increased to 4 wt % from the 2 wt % utilized in previous bone marrow MSC studies based upon the increased osteopontin (OPN) production and mineralization associated with PDMS incorporation. 43 …”

“…Moreover, growth factors tethered into PEG-based scaffolds are effectively inhibited from being internalized by cells, 40,42 allowing for repeated signaling by a single growth factor molecule and use of lower growth factor doses. 43,44 …”

“…Similarly, PEG-scaffolds incorporating hydrophobic, inorganic poly(dimethylsiloxane) (PDMS) along with low-dose BMP2 stimulate bone marrow MSC osteoblastic differentiation while maintaining a non-brittle, elastomeric structure for physiological loading. 43,59 …”