Effects of hydroxyapatite on endothelial network formation in collagen/fibrin composite hydrogels in vitro and in vivo

Rao, Reena; Ceccarelli, Jacob; Vigen, Marina; Gudur, Madhu Sudhan Reddy; Singh, Rahul; Deng, Cheri X.; Putnam, Andrew J.; Stegemann, Jan P.

doi:10.1016/j.actbio.2014.03.010

Cited by 37 publications

(36 citation statements)

References 30 publications

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“…4a, the cell density in the HA doped scaffolds ranged from 1.01-1.03 × 10 6 cells/mL, compared to 10 6 cells/mL in the undoped scaffolds. This biocompatibility is consistent with previous cell studies utilizing HA-doped fibrin scaffolds (Kidd, et al 2012, Rao, et al 2014). In a previous study, no significant differences in cellular metabolic activity were observed for C3H10T1/2- fLuc cells encapsulated in undoped fibrin scaffolds when exposed to 5 to 15 min continuous wave US exposures with an I SPTA of 754 W/cm 2 , compared to cells not exposed to US (Wilson, et al 2014).…”

Section: Resultssupporting

confidence: 92%

Use of Hydroxyapatite Doping to Enhance Responsiveness of Heat-Inducible Gene Switches to Focused Ultrasound

Fabiilli

Phanse

Moncion

et al. 2016

Ultrasound in Medicine & Biology

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Recently, we demonstrated that ultrasound-based hyperthermia can activate cells containing a heat-activated and ligand-inducible gene switch in a spatio-temporally controlled manner. These engineered cells can be incorporated into hydrogel scaffolds (e.g., fibrin) for in vivo implantation, where ultrasound can be used to non-invasively pattern transgene expression. Due to their high water content, the acoustic attenuation of fibrin scaffolds is low. Thus, long ultrasound exposures and high acoustic intensities are needed to generate sufficient hyperthermia for gene activation. Here, we demonstrate that the attenuation of fibrin scaffolds and the resulting hyperthermia achievable with ultrasound can be increased significantly by doping the fibrin with hydroxyapatite (HA) nanopowder. The attenuation of a 1% (w/v) fibrin scaffold with 5% (w/v) HA was similar to soft tissue. Transgene activation of cells harboring the gene switch occurred at lower acoustic intensities and shorter exposures when the cells were encapsulated in HA-doped fibrin scaffolds versus undoped scaffolds. Inclusion of HA in the fibrin scaffold did not affect the viability of the encapsulated cells.

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Section: Resultssupporting

confidence: 92%

Use of Hydroxyapatite Doping to Enhance Responsiveness of Heat-Inducible Gene Switches to Focused Ultrasound

Fabiilli

Phanse

Moncion

et al. 2016

Ultrasound in Medicine & Biology

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“…Our previous work has shown that collagen-fibrin composite matrices are well suited to cell encapsulation and have superior mechanical properties as compared to the pure protein materials [51]. In addition, we recently have shown that collagen-fibrin matrices support vasculogenesis [52, 53]. …”

Section: Introductionmentioning

confidence: 99%

Vasculogenesis and angiogenesis in modular collagen–fibrin microtissues

et al. 2014

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The process of new blood vessel formation is critical in tissue development, remodeling and regeneration. Modular tissue engineering approaches have been developed to enable the bottom-up assembly of more complex tissues, including vascular networks. In this study, collagen-fibrin composite microbeads (100-300 μm in diameter) were fabricated using a water-in-oil emulsion technique. Human endothelial cells and human fibroblasts were embedded directly in the microbead matrix at the time of fabrication. Microbead populations were characterized and cultured for 14 days either as free-floating populations or embedded in a surrounding fibrin gel. The collagen-fibrin matrix efficiently entrapped cells and supported their viability and spreading. By 7 days in culture, endothelial cell networks were evident within microbeads, and these structures became more prominent by day 14. Fibroblasts co-localized with endothelial cells, suggesting a pericyte-like function, and laminin deposition indicated maturation of the vessel networks over time. Microbeads embedded in a fibrin gel immediately after fabrication showed the emergence of cells and the coalescence of vessel structures in the surrounding matrix by day 7. By day 14, inosculation of neighboring cords and prominent vessel structures were observed. Microbeads pre-cultured for 7 days prior to embedding in fibrin gave rise to vessel networks that emanated radially from the microbead by day 7, and developed into connected networks by day 14. Lumen formation in endothelial cell networks was confirmed using confocal sectioning. These data show that collagen-fibrin composite microbeads support vascular network formation. Microbeads embedded directly after fabrication emulated the process of vasculogenesis, while the branching and joining of vessels from pre-cultured microbeads resembled angiogenesis. This modular microtissue system has utility in studying the processes involved in new vessel formation, and may be developed into a therapy for the treatment of ischemic conditions.

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“…S2), and generally mirrored the values obtained from the creep deformation curve. Mechanical parameters obtained using DUE can also be combined with compositional information, for example as obtained by multispectral ultrasound imaging [41, 45], to elucidate structure-function relationships in engineered tissues.…”

Section: Resultsmentioning

confidence: 99%

“…In acellular constructs, hydroxyapatite served as a scatterer that produced ultrasound signals, while in cell-seeded constructs the cellular component served as the scatterer. HA has been used as an additive in a variety of hydrogel biomaterials, for example to potentiate bone formation and to facilitate endothelial network formation [41]. …”

Section: Methodsmentioning

confidence: 99%

“…The volume of the construct was determined by integrating the area of cross-sections obtained from 3D image data with 0.2 mm step size using a semi-automated algorithm from the VEVO 770 system. The absorption coefficient and acoustic speed of the constructs were determined from imaging an agar gel pad with and without the construct and comparing the spectral magnitude and travel time to the agar gel pad under both conditions, as described in our previous work [41]. …”

Section: Methodsmentioning

confidence: 99%

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Microscale characterization of the viscoelastic properties of hydrogel biomaterials using dual-mode ultrasound elastography

2016

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Characterization of the microscale mechanical properties of biomaterials is a key challenge in the field of mechanobiology. Dual-mode ultrasound elastography (DUE) uses high frequency focused ultrasound to induce compression in a sample, combined with interleaved ultrasound imaging to measure the resulting deformation. This technique can be used to non-invasively perform creep testing on hydrogel biomaterials to characterize their viscoelastic properties. DUE was applied to a range of hydrogel constructs consisting of either hydroxyapatite (HA)-doped agarose, HA-collagen, HA-fibrin, or preosteoblast-seeded collagen constructs. DUE provided spatial and temporal mapping of local and bulk displacements and strains at high resolution. Hydrogel materials exhibited characteristic creep behavior, and the maximum strain and residual strain were both material- and concentration-dependent. Burger’s viscoelastic model was used to extract characteristic parameters describing material behavior. Increased protein concentration resulted in greater stiffness and viscosity, but did not affect the viscoelastic time constant of acellular constructs. Collagen constructs exhibited significantly higher modulus and viscosity than fibrin constructs. Cell-seeded collagen constructs became stiffer with altered mechanical behavior as they developed over time. Importantly, DUE also provides insight into the spatial variation of viscoelastic properties at sub-millimeter resolution, allowing interrogation of the interior of constructs. DUE presents a novel technique for non-invasively characterizing hydrogel materials at the microscale, and therefore may have unique utility in the study of mechanobiology and the characterization of hydrogel biomaterials.

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Effects of hydroxyapatite on endothelial network formation in collagen/fibrin composite hydrogels in vitro and in vivo

Cited by 37 publications

References 30 publications

Use of Hydroxyapatite Doping to Enhance Responsiveness of Heat-Inducible Gene Switches to Focused Ultrasound

Use of Hydroxyapatite Doping to Enhance Responsiveness of Heat-Inducible Gene Switches to Focused Ultrasound

Vasculogenesis and angiogenesis in modular collagen–fibrin microtissues

Microscale characterization of the viscoelastic properties of hydrogel biomaterials using dual-mode ultrasound elastography

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