REPARATION OF SULFONATED CHITOSAN AND ITS ABILITY TO PROTECT bFGF ACTIVITES

Sulfonated chitosan oligosaccharide alleviates the inhibitory effect of basic fibroblast growth factor on osteogenic differentiation of human periodontal ligament stem cells

BACKGROUND

Periodontal ligament stem cells (PDLSCs) play an essential role in periodontal tissue repair. Basic fibroblast growth factor (bFGF) has been used in the clinical treatment of periodontal disease. However, studies have shown that bFGF inhibits the osteogenic differentiation of PDLSCs, which is not conducive to alveolar bone repair. Sulfonated chitosan oligosaccharide (SCOS), a heparan-like compound, can maintain the conformation of bFGF and promote its proliferation activity. This study investigated the effects of bFGF in combination with SCOS on the osteogenic differentiation of hPDLSCs.

METHODS

hPDLSCs were isolated from healthy human periodontal ligament and identified by flow cytometry and immunofluorescence. The affinity between SCOS and bFGF was analyzed by surface plasmon resonance. Changes in osteogenic differentiation by combination of bFGF with SCOS were analyzed by alkaline phosphatase activity assay, Sirius Red staining, and Alizarin Red staining. Expression of genes and proteins was investigated by western blotting and reverse transcription-quantitative PCR.

RESULTS

Extracted hPDLSCs were mesenchymal stem cells with pluripotent differentiation potential. SCOS exhibited an affinity for bFGF. bFGF (20 ng/mL) promoted the proliferation of hPDLSCs, but inhibited their osteogenic differentiation. SCOS alleviated the inhibitory effect of bFGF on the osteogenic differentiation of hPDLSCs.

CONCLUSIONS

SCOS can reduce the inhibitory effect of bFGF on the osteogenic differentiation of hPDLSCs. This study provides evidence for the clinical use of bFGF to repair periodontal tissue.

Improving the protective effects of aFGF for peripheral nerve injury repair using sulfated chitooligosaccharides

Injury to the peripheral nerves can result in temporary or life-long neuronal dysfunction and subsequent economic or social disability. Acidic fibroblast growth factor (aFGF) promotes the growth and survival of neurons and is a possible treatment for peripheral nerve injury. Yet, the actual therapeutic utility of aFGF is limited by its short half-life and instability in vivo. In the present study, we prepared sulfated chitooligosaccharides (SCOS), which have heparin-like properties, to improve the bioactivity of aFGF. We investigated the protective effects of SCOS with or without aFGF on RSC96 cells exposed to Na₂S₂O₄ hypoxia/reoxygenation injury. Cell viability was measured by MTT assay and cytotoxicity induced by Na₂S₂O₄ was assessed by lactate dehydrogenase (LDH) release into the culture medium. Pretreatment with aFGF and SCOS dramatically decreased LDH release after injury compared to pretreatment with aFGF or SCOS alone. We subsequently prepared an aFGF/SCOS thermo-sensitive hydrogel with poloxamer and examined its effects in vivo. Paw withdrawal thresholds and thermal withdrawal latencies were measured in rats with sciatic nerve injury. Local injection of the aFGF/SCOS hydrogels (aFGF: 40, 80 µg/kg) increased the efficiency of sciatic nerve repair compared to aFGF (80 µg/kg) hydrogel alone. Especially aFGF/SCOS thermo-sensitive hydrogel decreased paw withdrawal thresholds from 117.75 ± 8.38 (g, 4 d) to 65.74 ± 3.39 (g, 10 d), but aFGF alone group were 140.58 ± 27.54 (g, 4 d) to 89.12 ± 5.60 (g, 10 d) (aFGF dose was 80 µg/kg, P < 0.05, n = 8). The thermal withdrawal latencies decreased from 11.61 ± 2.26 (s, 4 d) to 2.37 ±0.67 (s, 10 d). However, aFGF alone group were from 17.69 ± 1.47 (s, 4 d) to 4.65 ± 1.73 (s, 10 d) (P < 0.05, n = 8). Furthermore, the aFGF/SCOS hydrogels also exhibited good biocompatibility in mice. In summary, SCOS improved the protective effects of aFGF in RSC96 cells injured with Na₂S₂O₄ and increased the efficiency of nerve repair and recovery of function in rats with sciatic nerve injury. These findings pave an avenue for the development of novel prophylactic and therapeutic strategies for peripheral nerve injury.

Enhanced bioactivity of transform growth factor-β1 from sulfated chitosan microspheres for in vitro chondrogenesis of mesenchymal stem cells

Transform growth factor-β1 (TGF-β1) is an extremely powerful protein to induce the chondrogenesis of mesenchymal stem cells (MSCs) both in vitro and in vivo. However, due to the short-life of TGF-β1, the direct application of TGF-β1 may deteriorate its bioactivity and thereby the repair effect. In this study, uniform sulfated chitosan microspheres (SCMs) with a mean diameter of ∼ 2 μm were fabricated by membrane emulsification as a carrier for TGF-β1. The in vitro release study showed that TGF-β1 could be sustainedly released from the microspheres up to 16 days. Under the protection of SCMs, about 13 % TGF-β1 was preserved even after stored for 14 days. The microspheres cytotoxicity was evaluated by coculture of MSCs with different concentrations SCMs and no obvious deterioration of cell viability was observed when the concentration of SCMs is lower than 2 μg/1.0 × 104 cells. In comparison with the blank group, the addition of TGF-β1 either in free state or loaded in SCMs inhibited the proliferation trend of MSCs. Quantitative analysis of GAGs production and genes expression of COL II and aggrecan by qRT-PCR revealed that enhanced bioactivity of TGF-β1 was obtained in the group of TGF-β1/SCMs, indicating that SCMs could be functioned as a promising carrier of TGF-β1 for the in vitro chondrogenesis of MSCs.