Publications

Most of the conventional in vitro models to test biomaterial-driven vascularization are too simplistic to recapitulate the complex interactions taking place in the actual cell microenvironment, which results in a poor prediction of the in vivo performance of the material. However, during the last decade, cell culture models based on microfluidic technology have allowed attaining unprecedented levels of tissue biomimicry. In this work, we propose a microfluidic-based 3D model to evaluate the effect of bioactive biomaterials capable of releasing signalling cues (such as ions or proteins) in the recruitment of endogenous endothelial progenitor cells, a key step in the vascularization process. The usability of the platform is demonstrated using experimentally-validated finite element models and migration and proliferation studies with rat endothelial progenitor cells (rEPCs) and bone marrow-derived rat mesenchymal stromal cells (BM-rMSCs). As a proof of concept of biomaterial evaluation, the response of rEPCs to an electrospun composite made of polylactic acid with calcium phosphates nanoparticles (PLA+CaP) was compared in a co-culture microenvironment with BM-rMSC to a regular PLA control. Our results show a significantly higher rEPCs migration and the upregulation of several pro-inflammatory and proangiogenic proteins in the case of the PLA+CaP. The effects of osteopontin (OPN) on the rEPCs migratory response were also studied using this platform, suggesting its important role in mediating their recruitment to a calcium-rich microenvironment. This new tool could be applied to screen the capacity of a variety of bioactive scaffolds to induce vascularization and accelerate the preclinical testing of biomaterials. STATEMENT OF SIGNIFICANCE: : For many years researchers have used neovascularization models to evaluate bioactive biomaterials both in vitro, with low predictive results due to their poor biomimicry and minimal control over cell cues such as spatiotemporal biomolecule signaling, and in vivo models, presenting drawbacks such as being highly costly, time-consuming, poor human extrapolation, and ethically controversial. We describe a compact microphysiological platform designed for the evaluation of proangiogenesis in biomaterials through the quantification of the level of sprouting in a mimicked endothelium able to react to gradients of biomaterial-released signals in a fibrin-based extracellular matrix. This model is a useful tool to perform preclinical trustworthy studies in tissue regeneration and to better understand the different elements involved in the complex process of vascularization.Copyright © 2022. Published by Elsevier Ltd.

JTD Keywords: angiogenesis, bioactive materials, bone regeneration, bone-formation, calcium-phosphate, extracellular calcium, in-vitro, interstitial flow, ion release, microfluidic model, signalling gradient, substitutes, tissue engineering, vascularization, vegf, Ion release, Mesenchymal stem-cells, Tissue engineering, Vascularization

Solution-mediated surface reactions occur for most calcium phosphate-based biomaterials and may influence cellular response. A reasonable extrapolation of such processes observed in vitro to in vivo performance requires a deep understanding of the underlying mechanisms. We therefore systematically investigated the nature of ion reactivity of calcium-deficient hydroxyapatite (CDHA) by exposing it for different periods of time to standard cell culture media of different chemical composition (DMEM and McCoy medium, with and without osteogenic supplements and serum proteins). Kinetic ion interaction studies of principal extracellular ions revealed non-linear sorption of Ca2+ (∼50% sorption) and K+ (∼8%) as well as acidification of all media during initial contact with CDHA (48 h). Interestingly, inorganic phosphorus (Pi) was sorbed from McCoy medium (∼50%) or when using osteogenic media containing β-glycerophosphate, but not from DMEM medium. Non-linear sorption data could be perfectly described by pseudo-first-order and pseudo-second-order sorption models. At longer contact time (21 days), and with frequent renewal of culture medium, sorption of Ca2+ remained constant throughout the experiment, while sorption of Pi gradually decreased in McCoy medium. In great contrast, CDHA began to release Pi slowly with time when using DMEM medium. Infrared spectra showed that CDHA exposed to culture media had a carbonated surface chemistry, suggesting that carbonate plays a key role in the ion reactivity of CDHA. Our data show that different compositions of the aqueous environment may provoke opposite ion reactivity of CDHA, and this must be carefully considered when evaluating the osteoinductive potential of the material.

JTD Keywords: Hydroxyapatite, Bioactive materials, Cell culture medium, Ion exchange, Sorption models

At present, strong requirements in orthopaedics are still to be met, both in bone and joint substitution and in the repair and regeneration of bone defects. In this framework, tremendous advances in the biomaterials field have been made in the last 50 years where materials intended for biomedical purposes have evolved through three different generations, namely first generation (bioinert materials), second generation (bioactive and biodegradable materials) and third generation (materials designed to stimulate specific responses at the molecular level). In this review, the evolution of different metals, ceramics and polymers most commonly used in orthopaedic applications is discussed, as well as the different approaches used to fulfil the challenges faced by this medical field.

JTD Keywords: Biomaterials, Orthopaedics, Tissue engineering, Bioactive materials, Biodegradable materials, Bioinert materials