Collagen hydrogel scaffold promotes mesenchymal stem cell and endothelial cell coculture for bone tissue engineering

Abstract

The generation of functional, vascularized tissues is a key challenge for the field of tissue engineering. Before clinical implantations of such tissue engineered bone constructs can succeed, tactics to promote neovascularization need to be strengthened. We have previously demonstrated that the tubular perfusion system (TPS) bioreactor is an effective culturing method to augment osteogenic differentiation and maintain viability of human mesenchymal stem cells (hMSC). Here, we devised a strategy to address the need for a functional microvasculature by designing an in vitro coculture system that simultaneously cultures osteogenic differentiating hMSCs with endothelial cells (ECs). We utilized the TPS bioreactor as a dynamic coculture environment, which we hypothesize will encourage prevascularization of endothelial cells and early formation of bone tissue and could aid in anastomosis of the graft with the host vasculature after patient implantation. To evaluate the effect of different natural scaffolds for this coculture system, the cells were encapsulated in alginate and/or collagen hydrogel scaffolds. We discovered the necessity of cell-to-cell proximity between the two cell types as well as preference for the natural cell binding capabilities of hydrogels like collagen. We discovered increased osteogenic and angiogenic potential as seen by amplified gene and protein expression of ALP, BMP-2, VEGF, and PECAM. The TPS bioreactor further augmented these expressions, indicating a synergistic effect between coculture and applied shear stress. The development of this dynamic coculture platform for the prevascularization of engineered bone, emphasizing the importance of the construct microenvironments and will advance the clinical use of tissue engineered constructs.

Efficiency of coculture with angiogenic cells or physiological BMP‐2 administration on improving osteogenic differentiation and bone formation of MSCs

“…It is well recognized that a vascular network is crucial for cell‐based bone constructs. Combining angiogenic cells with MSCs to improve vascularization has been proven effective . The efficiency of angiogenic cells on improving osteogenic differentiation of co‐cultured MSCs in three‐dimensional constructs in vitro and bone formation in vivo , however, remains unknown compared to MSC monoculture and well‐developed strategy by MSCs with BMP‐2 supplementation.…”

“…A variety of materials have been utilized as 3D scaffolds for MSCs in the context of bone repair. Collagen I, which is one the abundant components of native bone, has been widely used . Although collagen matrices have weak mechanical properties, the smooth microgeometry, transmural permeability, preserved Arg‐Gly‐Asp (RGD) cell binding sites, as well as easy application, make them suitable to model biological response .…”

“…Collagen I, which is one the abundant components of native bone, has been widely used. 21,22 Although collagen matrices have weak mechanical properties, the smooth microgeometry, transmural permeability, preserved Arg-Gly-Asp (RGD) cell binding sites, as well as easy application, make them suitable to model biological response. 23 Likewise, collagen is the only FDA-approved carrier for BMP-2 based bone regeneration.…”

Physical confinement alters cytoskeletal contributions towards human mesenchymal stem cell migration

“…Such trials include systemic or targeted delivery of MSCs in patients for the treatment of a variety of conditions such as graft‐versus‐host disease, osteoarthritis, and myocardial infarction. Additionally, tissue‐engineered constructs that incorporate MSCs are becoming increasingly viable and complex (Dolatshahi‐Pirouz et al, ; Nguyen, Moriarty, Kamalitdinov, Etheridge, & Fisher, ; Nguyen, Jeon, Krebs, Schapira, & Alsberg, ). The in vivo or the in vitro stem cell microenvironment is critical for providing signaling cues to regulate the balance between quiescence and activation or differentiation of stem cells and to control tissue formation and repair (Teo et al, ; Winer, Janmey, McCormick, & Funaki, ).…”

Hydrogels in Regenerative Medicine

“…Researchers have discovered increased osteogenic and angiogenic potential, as evidenced by increased protein and protein expression of ALP, BMP-2, VEGF, and PECAM [107].…”