Rate of vascularization and exposure of silicone-capped porous polyethylene spherical implants: an animal model

In vivo vascularization of MSC-loaded porous hydroxyapatite constructs coated with VEGF-functionalized collagen/heparin multilayers

Rapid and adequate vascularization is vital to the long-term success of porous orbital enucleation implants. In this study, porous hydroxyapatite (HA) scaffolds coated with vascular endothelial growth factor (VEGF)-functionalized collagen (COL)/heparin (HEP) multilayers (porosity 75%, pore size 316.8 ± 77.1 μm, VEGF dose 3.39 ng/mm³) were fabricated to enhance vascularization by inducing the differentiation of mesenchymal stem cells (MSCs) to endothelial cells. The in vitro immunofluorescence staining, quantitative real-time polymerase chain reaction (qRT-PCR), and western blotting results demonstrated that the expression of the endothelial differentiation markers CD31, Flk-1, and von Willebrand factor (vWF) was significantly increased in the HA/(COL/HEP)₅/VEGF/MSCs group compared with the HA/VEGF/MSCs group. Moreover, the HA/(COL/HEP)₅ scaffolds showed a better entrapment of the MSCs and accelerated cell proliferation. The in vivo assays showed that the number of newly formed vessels within the constructs after 28 d was significantly higher in the HA/(COL/HEP)₅/VEGF/MSCs group (51.9 ± 6.3/mm²) than in the HA (26.7 ± 2.3/mm²) and HA/VEGF/MSCs (38.2 ± 2.4/mm²) groups. The qRT-PCR and western blotting results demonstrated that the HA/(COL/HEP)₅/VEGF/MSCs group also had the highest expression of CD31, Flk-1, and vWF at both the mRNA and protein levels.

Safety and Biocompatibility of a New High-Density Polyethylene-Based Spherical Integrated Porous Orbital Implant: An Experimental Study in Rabbits

Purpose. To evaluate clinically and histologically the safety and biocompatibility of a new HDPE-based spherical porous orbital implants in rabbits. Methods. MEDPOR (Porex Surgical, Inc., Fairburn, GA, USA), OCULFIT I, and OCULFIT II (AJL Ophthalmic S.A., Vitoria, Spain) implants were implanted in eviscerated rabbis. Animals were randomly divided into 6 groups (n = 4 each) according to the 3 implant materials tested and 2 follow-up times of 90 or 180 days. Signs of regional pain and presence of eyelid swelling, conjunctival hyperemia, and amount of exudate were semiquantitatively evaluated. After animals sacrifice, the implants and surrounding ocular tissues were processed for histological staining and polarized light evaluation. Statistical study was performed by ANOVA and Kaplan-Meier analysis. Results. No statistically significant differences in regional pain, eyelid swelling, or conjunctival hyperemia were shown between implants and/or time points evaluated. However, amount of exudate differed, with OCULFIT I causing the smallest amount. No remarkable clinical complications were observed. Histological findings were similar in all three types of implants and agree with minor inflammatory response. Conclusions. OCULFIT ophthalmic tolerance and biocompatibility in rabbits were comparable to the clinically used MEDPOR. Clinical studies are needed to determine if OCULFIT is superior to the orbital implants commercially available.

A biomimetic collagen/heparin multi-layered porous hydroxyapatite orbital implant for in vivo vascularization studies on the chicken chorioallantoic membrane

BACKGROUND

The vascularization of an orbital implant is a key issue for reducing complications, such as exposure and infection.

METHODS

Here, we developed a facile layer-by-layer assembly approach to modify porous hydroxyapatite (pHA) orbital implants with five collagen (COL)/heparin (HEP) multilayers.

RESULTS

SEM characterization showed that the average pore size of the pHA/(COL/HEP)5 scaffold was 316.8 ± 77.1 μm. After being coated with five COL/HEP multilayers, the mechanical strength was improved compared with that of the pHA scaffolds. The in vitro assay displayed that the pHA scaffolds covered with COL/HEP multilayers resulted in a larger number of human umbilical vein endothelial cells after being cultured for 14 days. The macroscopic evaluation and semi-quantitative vascular density analysis of the chicken chorioallantoic membrane assay showed that the pHA/(COL/HEP)5 scaffolds resulted in more intense angiogenesis than the pHA scaffolds.

CONCLUSIONS

These studies demonstrate that the biomembrane-mimicking coating of COL/HEP multilayers is a simple and effective strategy to endow combined biological performances of pHA orbital implants and to potentially reduce implant-related complications.

Addressing the Inflammatory Response to Clinically Relevant Polymers by Manipulating the Host Response Using ITIM Domain-Containing Receptors

Tissue contacting surfaces of medical devices initiate a host inflammatory response, characterized by adsorption of blood proteins and inflammatory cells triggering the release of cytokines, reactive oxygen species (ROS) and reactive nitrogen species (RNS), in an attempt to clear or isolate the foreign object from the body. This normal host response contributes to device-associated pathophysiology and addressing device biocompatibility remains an unmet need. Although widespread attempts have been made to render the device surfaces unreactive, the establishment of a completely bioinert coating has been untenable and demonstrates the need to develop strategies based upon the molecular mechanisms that define the interaction between host cells and synthetic surfaces. In this review, we discuss a family of transmembrane receptors, known as immunoreceptor tyrosine-based inhibitory motif (ITIM)-containing receptors, which show promise as potential targets to address aberrant biocompatibility. These receptors repress the immune response and ensure that the intensity of an immune response is appropriate for the stimuli. Particular emphasis will be placed on the known ITIM-containing receptor, Signal Regulatory Protein Alpha (SIRPhα), and its cognate ligand CD47. In addition, this review will discuss the potential of other ITIM-containing proteins as targets for addressing the aberrant biocompatibility of polymeric biomaterials.