Cell-secreted matrices perpetuate the bone-forming phenotype of differentiated mesenchymal stem cells

Abstract

Prior to transplantation, mesenchymal stem/stromal cells (MSCs) can be induced toward the osteoblastic phenotype using a cocktail of soluble supplements. However, there is little evidence of differentiated MSCs directly participating in bone formation, suggesting that MSCs may either die or revert in phenotype upon transplantation. Cell-secreted decellularized extracellular matrices (DMs) are a promising platform to confer bioactivity and direct cell fate through the presentation of a complex and physiologically relevant milieu. Therefore, we examined the capacity of biomimetic DMs to preserve the mineral-producing phenotype upon withdrawal of the induction stimulus. Regardless of induction duration, ranging up to 6 weeks, MSCs exhibited up to a 5-fold reduction in osteogenic markers within 24 hours following stimulus withdrawal. We show that seeding osteogenically induced MSCs on DMs yields up to 2-fold more calcium deposition than tissue culture plastic, and this improvement is at least partially mediated by increasing actin cytoskeletal tension via the ROCK II pathway. MSCs on DMs also secreted 25% more vascular endothelial growth factor (VEGF), a crucial endogenous proangiogenic factor that is abrogated during MSC osteogenic differentiation. The deployment of DMs into a subcutaneous ectopic site enhanced the persistence of MSCs 5-fold, vessel density 3-fold, and bone formation 2-fold more than MSCs delivered without DMs. These results underscore the need for deploying MSCs using biomaterial platforms such as DMs to preserve the in vitro-acquired mineral-producing phenotype and accelerate the process of bone repair.

Bone Morphogenetic Protein‐2 Promotes Human Mesenchymal Stem Cell Survival and Resultant Bone Formation When Entrapped in Photocrosslinked Alginate Hydrogels

“…For in vivo studies, MSCs genetically modified to express firefly luciferase (UC Davis Center of Excellence in Gene Therapy) were expanded in α-MEM and used at passages 9–10. [10] Culture media was refreshed every 3 days.…”

“…[3] MSCs are multipotent cells that, among other phenotypes, can participate in bone formation directly by differentiating toward the osteoblastic phenotype [4–6] or indirectly by secreting paracrine acting trophic factors that stimulate angiogenesis and regulate local inflammation. [7–10] Regardless of their contribution, long-term survival and engraftment of MSCs to defect sites is poor, [11, 12] drastically decreasing the therapeutic potential of MSC-based treatments. Strategies that boost cell retention will likely translate into greater functional benefit, motivating the need for improved methods to retain cells at the defect site while promoting their survival and function to achieve the desired clinical outcome.…”

Measurement of oxygen tension within mesenchymal stem cell spheroids

“…However, as the MSC spheroids adjusted their packing density to allow for the transport of oxygen and nutrients, this came at the expense of ECM deposition and available integrin sites for cell adhesion. Cellderived matrix enhances cell survival and function [53,54], and MSC spheroid formation can enhance the production of ECM proteins such as laminin, elastin, type 1 collagen and fibronectin [31,55,56]. Furthermore, we recently demonstrated that MSC spheroids containing 15 000 cells per spheroid deposit a collagen-rich ECM, and that the MSCs' integrin-ECM interactions drive cell fate [57].…”

<i>In vivo</i> evaluation of chitosan-glycerol gel scaffolds seeded with stem cells for full-thickness mandibular bone regeneration

“…On the other hand, allografts, xenografts, or artificial bone substitutes may expose the patient to severe risks of foreign body reactions and infections (5). Stem cells represent the new frontier in the field of regenerative medicine and are seen as a promising and suitable means to overcome the aforementioned drawbacks (6)(7)(8). Numerous studies report that adult stem cells can be isolated from several organs and tissues.…”