Osteogenesis on nanoparticulate mineralized collagen scaffolds via autogenous activation of the canonical BMP receptor signaling pathway

Abstract

Skeletal regenerative medicine frequently incorporates deliverable growth factors to stimulate osteogenesis. However, the cost and side effects secondary to supraphysiologic dosages of growth factors warrant investigation of alternative methods of stimulating osteogenesis for clinical utilization. In this work, we describe growth factor independent osteogenic induction of human mesenchymal stem cells (hMSCs) on a novel nanoparticulate mineralized collagen glycosaminoglycan scaffold (MC-GAG). hMSCs demonstrated elevated osteogenic gene expression and mineralization on MC-GAG with minimal to no effect upon addition of BMP-2 when compared to non-mineralized scaffolds (Col-GAG). To investigate the intracellular pathways responsible for the increase in osteogenesis, we examined the canonical and non-canonical pathways downstream from BMP receptor activation. Constitutive Smad1/5 phosphorylation with nuclear translocation occurred on MC-GAG independent of BMP-2, whereas Smad1/5 phosphorylation depended on BMP-2 stimulation on Col-GAG. When non-canonical BMPR signaling molecules were examined, ERK1/2 phosphorylation was found to be decreased in MC-GAG but elevated in Col-GAG. No differences in Smad2/3 or p38 activation were detected. Collectively, these results demonstrated that MC-GAG scaffolds induce osteogenesis without exogenous BMP-2 addition via endogenous activation of the canonical BMP receptor signaling pathway.

Synergistic intrafibrillar/extrafibrillar mineralization of collagen scaffolds based on a biomimetic strategy to promote the regeneration of bone defects

“…However, because collagen possesses poor mechanical properties and too high a degradation rate in vivo when used alone, many studies have attempted to modify it through mineralization. 1,[44][45][46][47][48] In the present work, we fabricated a novel synergistically intra-and extrafibrillar mineralized collagen scaffold using precursors of ACP stabilized by CMC, a negatively charged polymer. Type 1 collagen self-assembles into fibrils with a triple-helical molecular structure, which is known as tropocollagen, and thus, we Notes: There is a statistically significant difference on cell proliferation between BMC scaffolds and the other two scaffolds at each testing time.…”

“…49,50 Hence, we provided a new method for biomimetic mineralization based on the PILP strategy, in which collagen gels after self-assembly, but not dry collagen scaffolds, were immersed into the CMC/ ACP nanocomplex solution. Compared with the direct mixing of collagen solution and mineral ions 11,46,47 or immersing the dry collagen scaffolds in the mineral solution, 13,23,51 the mineralized method described in this study can cause the collagen scaffold to have a water oversaturated status after self-assembly. This status may make the nanocomplexes of CMC/ACP more easily intercalate into the interstices of the collagen fibrils, which is the crux of intrafibrillar mineralization of collagen scaffolds.…”

Biomimetic Scaffolds for Osteogenesis

“…Similarly, we have previously utilized a novel nano-particulate mineralized collagen glycosaminoglycan scaffold (MC-GAG) to demonstrate growth factor independent osteogenic induction of hMSCs [9] . This work is significant as it may ultimately lead to methods of osteogenesis that minimize or eliminate reliance on artificial implants and growth factors.…”

“…These scaffolds have variable osteogenic properties depending on their REVIEW material composition, porosity, and the incorporation of osteoblasts or mesenchymal stem cells into the scaffold prior to implantation [9,12] . The function of these scaffolds is to augment bone regeneration via osteoinduction of the seeded progenitor cells as well as osteoconduction.…”

“…Growth factors including BMP-2 and BMP-7 continue to be of interest in bone tissue engineering. However, barriers associated with the use of these agents include substantial cost and an unfavorable side effect profile, including the risk of heterotopic ossification and decreased maxillary growth following treatment [9][10][11][12] . Additionally, the use of BMP-2 and other similar proteins has traditionally been limited by their short half-life, which prevents the controlled and sustained release of these agents into the site of injury.…”