Properties and clinical relevance of osteoinductive biomaterials

This thesis had two main goals: (¿) to investigate parameters influencing osteoinductive potential of biomaterials in order to unravel the mechanism underlying osteoinduction and (¿¿) to investigate performance of osteoinductive biomaterials orthotopically in order to get insight into their clinical relevance

Effect of high content nanohydroxyapatite composite scaffolds prepared via melt extrusion additive manufacturing on the osteogenic differentiation of human mesenchymal stromal cells

The field of bone tissue engineering seeks to mimic the bone extracellular matrix composition, balancing the organic and inorganic components. In this regard, additive manufacturing (AM) of high content calcium phosphate (CaP)-polymer composites holds great promise towards the design of bioactive scaffolds. Yet, the biological performance of such scaffolds is still poorly characterized. In this study, melt extrusion AM (ME-AM) was used to fabricate poly(ethylene oxide terephthalate)/poly(butylene terephthalate) (PEOT/PBT)-nanohydroxyapatite (nHA) scaffolds with up to 45 wt% nHA, which presented significantly enhanced compressive mechanical properties, to evaluate their in vitro osteogenic potential as a function of nHA content. While osteogenic gene upregulation and matrix mineralization were observed on all scaffold types when cultured in osteogenic media, human mesenchymal stromal cells did not present an explicitly clear osteogenic phenotype, within the evaluated timeframe, in basic media cultures (i.e. without osteogenic factors). Yet, due to the adsorption of calcium and inorganic phosphate ions from cell culture media and simulated body fluid, the formation of a CaP layer was observed on PEOT/PBT-nHA 45 wt% scaffolds, which is hypothesized to account for their bone forming ability in the long term in vitro, and osteoconductivity in vivo.We are grateful to H2020-NMP-PILOTS-2015 (GA n. 685825) for financial support. PH gratefully acknowledges the Gravitation Program ‘Materials-Driven Regeneration’, funded by the Netherlands Organization for Scientific Research (NWO) (024.003.013). Some of the materials used in this work were provided by the Texas A&M Health Science Center College of Medicine Institute for Regenerative Medicine at Scott & White through a grant from NCRR of the NIH (Grant #P40RR017447). We would also like to thank Eva Gubbins from MERLN Institute for performing the ICP-MS measurements

Microfluidic gradient generator for drug testing on a colorectal tumor-on-a-chip disease model

Statement of Purpose: Colorectal cancer is the third most common cancer and its incidence increases with ageing. Understanding the mechanisms of tumour growth rely in further advances to unveil cancer-causing agents, drug screening and in the development of personalized therapies. Standard 2D in vitro models and in vivo animal models have undoubtedly contributed to the development of anti-cancer drug candidates. Yet their translation into successful clinical trials is critically low, which reinforces the need of a deeper understanding of tumorigenesis (1). Therefore, 3D models integrating tissue engineering (TE) strategies with microfluidic technology have sparked the expectation on physiologically relevant microfluidic in vitro models (2). The aim of this work is to establish a 3D microfluidic model that enables the reconstitution of physiological functions of microvascular tissue that emulates the human colorectal tumor microenvironment. This model will be established via a microfluidic device with an encapsulating hydrogel compartment comprising a co-culture system of HCT-116 colorectal cancer cells and human intestinal microvascular endothelial cells

Cranioplasty with patient-specific implants in repeatedly reconstructed cases

Objective: Cranioplasty is indicated to restore form and function of bone defects of the neurocranium. Autografts are the gold standard, alloplastic materials are used when autologous bone is unavailable or unsuitable, and increasing evidence supports the use of patient-specific implants (PSIs) for reconstruction. We reviewed our own patient data to assess pre- and intraoperative aspects, complications and costs in patients that were treated with PSIs from titanium or polyetheretherketone (PEEK) for skull bone reconstruction. Methods: We retrospectively evaluated all patients receiving a PSI as at least a secondary reconstruction between 2004 and 2016 at Maastricht University Medical Center. These cases were analyzed for demographics, perioperative surgical and medical aspects, as well as costs. Results: In total 30 patients received PSIs, of which 20 were included in this study. Duration of PSI placement was not statistically different between group I, where previously placed reconstruction material was still in situ, and group II, where no remaining previously placed reconstruction material was present (group I: 104 +/- 27 mins, group II: 86 +/- 36 mins; p = 0.27). Postoperatively, 2 patients experienced complications (10%). Costs of obtaining the PSIs were not significantly different between group I and group II (group I: mean EUR 7536 +/- 2759, group II: mean EUR 8351 +/- 2087, p = 0.51). Conclusion: Treatment of skull bone defects in repeated reconstruction requires an optimal preoperative planning and intraoperative procedure. In this retrospective study comparing repeatedly reconstructed cases with and without remaining previously placed reconstruction material present at the surgical site, we could not find significant differences in the duration of the surgical procedure nor costs of obtaining the PSIs. The protocol followed at MUMC for preoperative planning, manufacturing, and surgery, represents the current state-of-the-art treatment. (C) 2019 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved

Microfluidic collagen patterning for tendon regeneration

We present a microfluidic approach to align collagen fibers for tendon regeneration. Collagen fibers with a specific orientation were patterned in a microfluidic channel by introducing collagen solution through integrated microstructures. The fluid flow in the pillar array was evaluated by computational modeling, and the aligned collagen fibers were analyzed quantitatively. Then, primary rat tenocytes were cultured on oriented and not-oriented collagen micropatterns, and their phenotypical commitment was evaluated. We believe that such a platform would be useful to replicate in vivo microenvironment for the study of regenerative processes

Elucidating the individual effects of calcium and phosphate ions on hMSCs by using composite materials

Prova tipográficaThe biological performance of bone graft substitutes based on calcium phosphate bioceramics is dependent on a number of properties including chemical composition, porosity and surface micro- and nanoscale structure. However, in contemporary bioceramics these properties are interlinked, therefore making it difficult to investigate the individual effects of each property on cell behavior. In this study we have attempted to investigate the effects of calcium and inorganic phosphate ions independent from one another by preparing composite materials with polylactic acid (PLA) as a polymeric matrix and calcium carbonate or sodium phosphate salts as fillers. Clinically relevant bone marrow derived human mesenchymal stromal cells (hMSCs) were cultured on these composites and proliferation, osteogenic differentiation and ECM mineralization were investigated with time and were compared to plain PLA control particles. In parallel, cells were also cultured on conventional cell culture plates in media supplemented with calcium or inorganic phosphate to study the effect of these ions independent of the 3D environment created by the particles. Calcium was shown to increase proliferation of cells, whereas both calcium and phosphate positively affected alkaline phosphatase enzyme production. QPCR analysis revealed positive effects of calcium and of inorganic phosphate on the expression of osteogenic markers, in particular bone morphogenetic protein-2 and osteopontin. Higher levels of mineralization were also observed upon exposure to either ion. Effects were similar for cells cultured on composite materials and those cultured in supplemented media, although ion concentrations in the composite cultures were lower. The approach presented here may be a valuable tool for studying the individual effects of a variety of soluble compounds, including bioinorganics, without interference from other material properties.TeRM Smart Mix Program of the Netherlands Ministry of Education, Culture and Science Netherlands Science Organisation TA-COAST Grant # 05321104 Portuguese Foundation for Science and Technology (FCT) Grant # SFRH/BD69962/201