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Additional file 1: Fig. S1. Effect of siH19-2 on the expression levels of collagens, osteogenic markers and other H19-target candidates, assessed through RT-qPCR, 3 days after culture under osteogenic-inducing conditions (N = 6). Fig. S2. Decellularization of MSCs matrices. Primary MSCs from osteoporotic patients were differentiated for 10 days under osteogenic-inducing conditions before decellularization. After treatment with the decellularization buffer (urea 2 M), samples were stained with a) DAPI (blue) to visualize nuclei (scale: 100 μm) and b) hematoxylin (blue-purple color) to visualize nuclei and matrix integrity (scale: 100 μm). c) DNA and sGAGs content were measured. Non-decellularized matrices were used as a control. Fig. S3. In silico predictions for the binding site between miR-29-a/b/c and lncRNA H19. Fig. S4. Expression profile of H19 during early osteogenic differentiation stages in MSCs from healthy donors (N = 4) and osteoporotic patients (N = 4). Fig. S5. miR-29c-3p expression after transfection of MSCs with miR-29c-3p mimics, miR-29c-3p inhibitor or respective controls (NC-mimics and NC-inhibitor), and cultured for 3 days in osteogenic-inducing conditions (N = 6). Table SI. Donors of Human Mesenchymal Stem/Stromal Cells. Table SII. Primers used for reverse transcription quantitative real-time PCR. Table SIII. Mature miRNAs sequences according to miRbase annotations ( http://www.mirbase.org/ ). Table SIV. Antibodies used for immunocytochemistry stainings.

Additional file 3: Figure S3. Histological grading applied in semi-quantification of immune cells prevalence and distribution in tissues retrieved from OA and AL patients.

Additional file 1: Figure S1. Histological grading applied in semi-quantification of OA synovial tissues inflammation and tissue fibrosis, necrosis, innervation (NF200) and TGF-β1 in tissues collected from OA and AL patients.

Additional file 2: Figure S2. Histological grading applied in semi-quantification regarding the accumulation of prosthetic debris in synovial membrane-like interface tissues.

Despite the importance of immune cell–biomaterial interactions for the regenerative outcome, few studies have investigated how distinct three-dimensional biomaterials modulate the immune cell-mediated mesenchymal stem/stromal cells (MSC) recruitment and function. Thus, this work compares the response of varied primary human immune cell populations triggered by different model scaffolds and describes its functional consequence on recruitment and motility of bone marrow MSC. It was found that poly-lactic acid (PLA) and chitosan scaffolds lead to an increase in the metabolic activity of macrophages but not of peripheral blood mononuclear cells (PBMC), natural killer (NK) cells or monocytes. PBMC and NK cells increase their cell number in PLA scaffolds and express a secretion profile that does not promote MSC recruitment. Importantly, chitosan increases IL-8, MIP-1, MCP-1 and RANTES secretion by macrophages while PLA stimulates IL-6, IL-8 and MCP-1 production, all chemokines that can lead to MSC recruitment. This secretion profile of macrophages in contact with biomaterials correlates with the highest MSC invasion. Furthermore, macrophages enhance stem cell motility within chitosan scaffolds by 44% but not in PLA scaffolds. Thus, macrophages are the cells that in contact with engineered biomaterials become activated to secrete bioactive molecules that stimulate MSC recruitment.

We have developed a new carrier system for bone morphogenetic protein 2 (BMP-2). This agent has been successfully incorporated into biomimetic calcium phosphate implant coatings without losing its osteoinductive potency. Numerous materials have been tested for their efficiency in carrying BMP-2 and in promoting its osteoinductive effects at both ectopic and orthotopic sites. In the present study, we compare the osteoinductive effects of BMP-2 delivered by biomimetic coatings and by classical collagen sponges in vivo using an ectopic rat model. Titanium-alloy discs, either bearing a co-precipitated layer of calcium phosphate and BMP-2 (1.7 μg/disc) or inserted into collagen sponges impregnated with the same drug (10 μg/sponge), were implanted subcutaneously in the dorsal region of rats and the bone-formation process monitored after 2 and 5 weeks. After 2 weeks, the net volume of bone formed in the biomimetic coating group (5.8 mm3/disc) was greater (p < 0.01) than in the collagen sponge one (2.3 mm3/sponge). By the end of the fifth week, the net volume of bone deposited had increased significantly (p < 0.001) in the biomimetic coating group (11.6 mm3/disc), whereas in the collagen sponge one it remained unchanged. (3.0 mm3/sponge; p = 0.82). As a carrier for BMP-2 and in facilitating its osteogenic effects, biomimetic calcium phosphate coatings offer a distinct advantage over the classical collagen sponge.

Crystal growth of calcium hydrogenphosphate dihydrate (DCPD), in the presence of polyaspartic acid or calcium phytate (system A), as well as nucleation and growth of octacalcium phosphate (OCP), in the presence of poly-l-lysine, poly-l- glutamic acid or polystyrene sulfonate (system B) have been investigated. In system A crystallization of DCPD was inhibited and the crystal growth morphology was specifically modified by preferential interaction of the respective additive with the dominant (010) crystal face. In system B crystals were formed via precursor phase(s) and polyelectrolytes exhibited dual action, at low concentrations inducing and at high concentrations inhibiting nucleation of the crystalline phase. Crystal/additive interactions controlling growth were nonspecific and resulted in smaller crystals with rounded edges, but with the same basic orientation as in the controls.