Human adipose stem/stromal cell (ASC) spheroids were used as a serum‐free in vitro model to recapitulate the molecular events and extracellular matrix organization that orchestrate a hypertrophic cartilage phenotype. Induced‐ASC spheroids (ø = 450 µm) showed high cell viability throughout the period of culture. The expression of collagen type X alpha 1 chain (COLXA1) and matrix metallopeptidase 13 (MMP‐13) was upregulated at week 2 in induced‐ASC spheroids compared with week 5 (P < .001) evaluated by quantitative real‐time PCR. In accordance, secreted levels of IL‐6 (P < .0001), IL‐8 (P < .0001), IL‐10 (P < .0001), bFGF (P < .001), VEGF (P < .0001), and RANTES (P < .0001) were the highest at week 2. Strong in situ staining for collagen type X and low staining for TSP‐1 was associated with the increase of hypertrophic genes expression at week 2 in induced‐ASC spheroids. Collagen type I, osteocalcin, biglycan, and tenascin C were detected at week 5 by in situ staining, in accordance with the highest expression of alkaline phosphatase (ALPL) gene and the presence of calcium deposits as evaluated by Alizarin Red O staining. Induced‐ASC spheroids showed a higher force required to compression at week 2 (P < .0001). The human ASC spheroids under serum‐free inducer medium and normoxic culture conditions were induced to a hypertrophic cartilage phenotype, opening a new perspective to recapitulate endochondral ossification in vivo.

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This study was developed based on in vivo investigation of microporous granular biomaterials based on calcium phosphates, involving matrices of β-tricalcium phosphate (β-TCP), hydroxyapatite (HA), biphasic compositions of both phases and a control group. The physicochemical characterization of materials was carried out by X-Ray diffraction (DRX) and mercury porosimetry. Biodegradability, bioactivity and neoformation processes were investigated by Raman spectroscopy, scanning electron microscopy (SEM) and polarized light conducted on biopsies obtained from in vivo tests for periods of 90 and 180 days. These were performed to evaluate the behavior of granular microporous compositions in relation to bone neoformation. Through the performance obtained from in vivo assays, excellent osseointegration and bone tissue neoformation were observed. The results are encouraging and show that the microporous granular biomaterials of HA, β-TCP and biphasic compositions show similar results with perfect osseointegration. Architectures simulating a bone structure can make the difference between biomaterials for bone tissue replacement and repair.

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