Inflammatory cytokines present during bone healing have been suggested to enhance osteogenic differentiation of mesenchymal stem cells (MSCs). However, little is known about the effects of anti-inflammatory cytokines (e.g. IL-4) on MSCs differentiation, although these are also produced during the bone healing process. We hypothesised that both pro- and anti-inflammatory cytokines enhance osteogenic differentiation of MSCs. Human adipose tissue-derived mesenchymal stem cells (hASCs) were cultured in αMEM containing 2% platelet-lysate, 50 μM ascorbic acid-2-phosphate, 5 mM β-glycerophosphate and 10 nM 1,25-(OH)2 vitamin D3. TNF-α, IL-6, IL-8, IL-17F and IL-4 (10 ng/mL) were present during the first 72h of culture. Gene expression was quantified by real-time quantitative PCR. Significant effects (P<0.05) are mentioned below. TNF-α decreased expression of osteogenic differentiation markers RUNX2 (6-fold), ALP (2-fold), and COL1 (4-fold) at day 4. IL-6 increased expression of the proliferation marker Ki67 (2-fold) at 6 h, but decreased expression of COL1 (2-fold) at 48h and RUNX2 (6-fold) at day 4. IL-8 decreased expression of OCN (5-fold) at 48h, and expression of RUNX2 (4-fold) at day 4. Similarly, IL-17F decreased expression of RUNX2 by 4-fold at day 4. IL-17F increased expression of OCN (3-fold), albeit only at 6h. Finally, IL-4 decreased expression of RUNX2 at day 4 (10-fold) and day 7 (6-fold). In contrast to the other cytokines, IL-4 enhanced expression of OCN at day 4 (3-fold) and day 7 (5-fold). Our findings suggest that pro-inflammatory cytokines TNF-α, IL-6, IL-8, and IL-17F, and the anti-inflammatory cytokine IL-4, exert different effects on the expression of osteogenic markers by hASCs. The pro-inflammatory cytokines are unlikely to enhance osteogenic differentiation of MSCs, but IL-4 might, since it enhanced expression of the late osteogenic marker osteocalcin. The modulation of inflammation after bone fracture may be useful to enhance bone repair in patients with inflammatory diseases or for tissue engineering strategies.
Disclosure: The authors declared no competing interests.