Rapid fabrication of vascularized and innervated cell-laden bone models with biomimetic intrafibrillar collagen mineralization

Abstract

Bone tissue, by definition, is an organic–inorganic nanocomposite, where metabolically active cells are embedded within a matrix that is heavily calcified on the nanoscale. Currently, there are no strategies that replicate these definitive characteristics of bone tissue. Here we describe a biomimetic approach where a supersaturated calcium and phosphate medium is used in combination with a non-collagenous protein analog to direct the deposition of nanoscale apatite, both in the intra- and extrafibrillar spaces of collagen embedded with osteoprogenitor, vascular, and neural cells. This process enables engineering of bone models replicating the key hallmarks of the bone cellular and extracellular microenvironment, including its protein-guided biomineralization, nanostructure, vasculature, innervation, inherent osteoinductive properties (without exogenous supplements), and cell-homing effects on bone-targeting diseases, such as prostate cancer. Ultimately, this approach enables fabrication of bone-like tissue models with high levels of biomimicry that may have broad implications for disease modeling, drug discovery, and regenerative engineering.

Elastin-derived scaffolding associated or not with bone morphogenetic protein (BMP) or hydroxyapatite (HA) in the repair process of metaphyseal bone defects

“…Von Kossa staining revealed intense calcium deposits distributed in all experimental groups. These results demonstrate that hydroxyapatite or morphogenetic protein-loaded elastin matrices can be mineralized in order to mimic the intra and extrafibrillary mineralization profile of native bone, making it a favorable microenvironment for osteogenic proliferation and osteogenesis differentiation, as well as structural support for vascular growth [38].…”

Three-dimensional Structural Interrelations between Cells, Extracellular Matrix and Mineral in Vertebrate Mineralization

“…Nucleation of mineral in association with collagen surfaces or within collagen fibrils has been conceptualized through different mechanisms. One such proposal involves calcium ion transport to collagen by binding to a negatively charged polyelectrolyte, such as phosphorylated osteopontin (40). Alternatively, ions may diffuse or be actively or passively transported as described above.…”

Progress and Challenges in Microengineering the Dental Pulp Vascular Microenvironment

“…Of note, these conduits establish the communication between the highly vascularized apex with the long axis of the engineered pulp tissue throughout the root canal space and enable the improved oxygenation of the cells embedded in the construct. Importantly, as we described above, endothelialized vessel-like structures such as these have been shown to anastomose with the host vasculature and form chimeric vessels in animal models 40 . Moreover, preliminary data (not shown) from our team have shown that much like engineered conduits that facilitate nerve guidance in regenerated spinal cord injuries and other neural regeneration approaches, the dental pulp conduits can also facilitate and guide the projection of neurites from the apex of a tooth model into the core of the engineered pulp.…”

“…It is also noteworthy that when hydrogels are engineered with adequate vasculature formation and substantial perivascular support in vitro before implantation, these human cell-derived vessels go on to anastomose with the host vasculature and enable blood transport without apparent leakage for at least 3 weeks in vivo after implantation 40 . Recent data from our group show that vessels expressing human-specific CD31, a marker for endothelial cell communication in the vasculature, and alpha smooth muscle actin, as a marker for pericytelike phenotype, are distributed across the thickness of a cell-laden hydrogel and show traces of red blood cells, which indicate the anastomosis with the host.…”