Previous studies showed that human nasal chondrocytes (HNC) exhibit higher proliferation and chondrogenic capacity as compared to human articular chondrocytes (HAC). To consider HNC as a relevant alternative cell source for the repair of articular cartilage defects it is necessary to test how these cells react when exposed to environmental factors typical of an injured joint. We thus aimed this study at investigating the responses of HNC and HAC to exposure to interleukin (IL)-1β and low oxygen. For this purpose HAC and HNC harvested from the same donors (N=5) were expanded in vitro and then cultured in pellets or collagen-based scaffolds at standard (19%) or low oxygen (5%) conditions. Resulting tissues were analyzed after a short (3 days) exposure to IL-1β, mimicking the initially inflammatory implantation site, or following a recovery time (1 or 2 weeks for pellets and scaffolds, respectively). After IL-1β treatment, constructs generated by both HAC and HNC displayed a transient loss of GAG (up to 21.8% and 36.8%, respectively) and, consistently, an increased production of metalloproteases (MMP)-1 and -13. Collagen type II and the cryptic fragment of aggrecan (DIPEN), both evaluated immunohistochemically, displayed a trend consistent with GAG and MMPs production. HNC-based constructs exhibited a more efficient recovery upon IL-1β withdrawal, resulting in a higher accumulation of GAG (up to 2.6-fold) compared to the corresponding HAC-based tissues. On the other hand, HAC displayed a positive response to low oxygen culture, while HNC were only slightly affected by oxygen percentage. Collectively, under the conditions tested mimicking the postsurgery articular environment, HNC retained a tissue-forming capacity, similar or even better than HAC. These results represent a step forward in validating HNC as a cell source for cartilage tissue engineering strategies.

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Alginate was shown to be a suitable support for entrapment and cultivation of chondrocytes and bone marrow stromal cells, which under appropriate in vitro conditions synthesized cartilaginous components. The main limitation in these cultures may be low rates of mass transport through the alginate matrix governed by diffusion. In this study, we have designed and utilized a bioreactor system based on a packed bed of alginate beads with immobilized chondrogenic cells. Continuous medium perfusion provided convective mass transport through the packed bed, while small diameters of beads (2.5 mm and down to 500 μm) ensured short diffusion distances to the immobilized cells. During up to 5 weeks of cultivation, the cells synthesized extracellular matrix components merging beads together and indicating potentials of this system for precise regulation of the cellular microenvironment in cartilage tissue engineering.

Composites based on Zn-alginate hydrogels in the form of beads were produced by extrusion of a suspension containing 0.5 % w/w of alginate and 20 % w/w of activated charcoal (AC) with the intent to simultaneously release two active agents, Zn 2+ and AC particles, in a physiological-like environment. The obtained composite beads were analyzed by FE-SEM and characterized regarding textural parameters, as well as Zn 2+ and AC release kinetics in the physiological saline solution. Zn 2+ ions were quickly released reaching the equilibrium concentration within the first hour in the contrary to the release of AC particles, which was described by internal diffusion with the apparent diffusion coefficient of approximately 10-13 m 2 s-1. Potential functionality of the obtained beads was evaluated regarding antibacterial activity in suspensions of the standard bacterial strain Escherichia coli 25922. The observed strong bactericidal effects were related to the quick release of Zn 2+ that was not affected by AC. Thus, taking into account results of this study, as well as high sorption capacity of alginate hydrogel, efficiency of AC to adsorb malodor and tissue degradation products and positive effects of Zn 2+ on wound healing, the obtained composites have shown promising potentials for applications as multifunctional wound dressings.