Paracrine Anti-inflammatory Effects of Adipose Tissue-Derived Mesenchymal Stem Cells in Human Monocytes.

The inflammatory process is an essential phenomenon in the induction of immune responses. Monocytes are key effector cells during the inflammatory process. A wide range of evidence indicates that mesenchymal stem cells from adipose tissue (ASC) are endowed with immunomodulatory capacity. However, the interaction between ASC and monocytes in the innate immune response is not well understood. The aim of this work was to investigate the possible paracrine anti-inflammatory effects of ASC in human monocytes. Monocytes were isolated from buffy coats and ASC from fat of non-obese patients. Conditioned medium (CM) from ASC in primary culture was used. We have assessed the effects of CM on the production of inflammatory mediators, degranulation, migration, phagocytic activity, senescence, oxidative stress, mitochondrial membrane potential and macrophage polarization. We have shown that ASC exert paracrine anti-inflammatory actions on human monocytes. CM significantly reduced the production of TNFα, NO and PGE2 and the activation of NF-κB. In addition, we observed a significant reduction of degranulation, phagocytic activity and their migratory ability in the presence of the chemokine CCL2. The senescence process and the production of oxidative stress and mitochondrial dysfunction were inhibited by CM which also reduced the production of TNFα by M1 macrophages while enhanced TGFß1 and IL-10 release by M2 macrophages. This study have demonstrated relevant interactions of ASC with human monocytes and macrophages which are key players of the innate immune response. Our results indicate that ASC secretome mediates the anti-inflammatory actions of these cells. This paracrine mechanism would limit the duration and amplitude of the inflammatory response.

Anti-senescence and Anti-inflammatory Effects of the C-terminal Moiety of PTHrP Peptides in OA Osteoblasts.

Osteoarthritis (OA) is characterized by degenerative changes in the whole joint leading to physical disability in the elderly population. This condition is associated with altered bone metabolism in subchondral areas suggesting that therapeutic strategies aimed at modifying bone cell metabolism may be of interest. We have investigated the effects of several parathyroid hormone-related protein (PTHrP)-derived peptides (1-37): (N-terminal), (107-111) and (107-139) (C-terminal) on senescence features induced by inflammatory stress in human OA osteoblasts. Incubation of these primary cells with interleukin(IL)-1ß led to an increased expression of senescence markers senescence-associated-ß-galactosidase activity, γH2AX foci, p16, p21, p53, and caveolin-1. PTHrP (107-111) and PTHrP (107-139) significantly reduced all these parameters. Both peptides decreased the production of IL-6 and prostaglandin E2 which was the consequence of cyclo-oxygenase-2 downregulation. PTHrP (107-139) also reduced tumor necrosis factor-α release. These anti-inflammatory effects would be related to the reduction of nuclear factor-κB activation by both peptides and activator protein-1 by PTHrP (107-139). The three PTHrP peptides favored osteoblastic function although the C-terminal domain of PTHrP was more efficient than its N-terminal domain. Our data support an anti-senescence and anti-inflammatory role for the C-terminal moiety of PTHrP with potential applications in chronic inflammatory conditions such as OA.

Paracrine effects of human adipose-derived mesenchymal stem cells in inflammatory stress-induced senescence features of osteoarthritic chondrocytes.

Aging and exposure to stress would determine the chondrocyte phenotype in osteoarthritis (OA). In particular, chronic inflammation may contribute to stress-induced senescence of chondrocytes and cartilage degeneration during OA progression. Recent studies have shown that adipose-derived mesenchymal stem cells exert paracrine effects protecting against degenerative changes in chondrocytes. We have investigated whether the conditioned medium (CM) from adipose-derived mesenchymal stem cells may regulate senescence features induced by inflammatory stress in OA chondrocytes. Our results indicate that CM down-regulated senescence markers induced by interleukin-1ß including senescence-associated ß-galactosidase activity, accumulation of γH2AX foci and morphological changes with enhanced formation of actin stress fibers. Treatment of chondrocytes with CM also decreased the production of oxidative stress, the activation of mitogen-activated protein kinases, and the expression of caveolin-1 and p21. The effects of CM were related to the reduction in p53 acetylation which would be dependent on the enhancement of Sirtuin 1 expression. Therefore, CM may exert protective effects in degenerative joint conditions by countering the premature senescence of OA chondrocytes induced by inflammatory stress.

Conditioned media from adipose-tissue-derived mesenchymal stem cells downregulate degradative mediators induced by interleukin-1ß in osteoarthritic chondrocytes.

Osteoarthritis (OA) is the most frequent joint disorder and an important cause of disability. Recent studies have shown the potential of adipose-tissue-derived mesenchymal stem cells (AD-MSC) for cartilage repair. We have investigated whether conditioned medium from AD-MSC (CM) may regulate in OA chondrocytes a number of key mediators involved in cartilage degeneration. CM enhanced type II collagen expression in OA chondrocytes while decreasing matrix metalloproteinase (MMP) activity in cell supernatants as well as the levels of MMP-3 and MMP-13 proteins and mRNA in OA chondrocytes stimulated with interleukin- (IL-) 1ß. In addition, CM increased IL-10 levels and counteracted the stimulating effects of IL-1ß on the production of tumor necrosis factor-α, IL-6, prostaglandin E2, and NO measured as nitrite and the mRNA expression of these cytokines, CCL-2, CCL-3, CCL-4, CCL-5, CCL-8, CCL-19, CCL-20, CXCL-1, CXCL-2, CXCL-3, CXCL-5, CXCL-8, cyclooxygenase-2, microsomal prostaglandin E synthase-1, and inducible NO synthase. These effects may be dependent on the inhibition of nuclear factor-κB activation by CM. Our data demonstrate the chondroprotective actions of CM and provide support for further studies of this approach in joint disease.