Regulation of mesenchymal stem cell chondrogenesis by glucose through protein kinase C/transforming growth factor signaling.

OBJECTIVE: Effective induction of human mesenchymal stem cell (hMSC) differentiation for regenerative medicine applications remains a great challenge. While much research has studied hMSC activity during differentiation, it is unclear whether pre-differentiation culture can modulate differentiation capacity. We investigate the effect of glucose concentration in pre-differentiation/expansion culture on modulating chondrogenic capacity of hMSCs, and explore the underlying molecular mechanism. DESIGN: The extent of chondrogenesis of hMSCs previously cultured with different concentrations of glucose was evaluated. Transforming growth factor-beta (TGF-ß) signaling molecules and protein kinase C (PKC) were analyzed to identify the role of these molecules in the regulation of glucose on chondrogenesis. In addition, hMSCs in high-glucose expansion culture were treated with the PKC inhibitor to modulate the activity of PKC and TGF-ß signaling molecules. RESULTS: High-glucose maintained hMSCs were less chondrogenic than low-glucose maintained cells upon receiving differentiation signals. Interestingly, we found that high-glucose culture increased the phosphorylation of PKC and expression of type II TGF-ß receptor (TGFßRII) in pre-differentiation hMSCs. However, low-glucose maintained hMSCs became more responsive to chondrogenic induction with increased PKC activation and TGFßRII expression than high-glucose maintained hMSCs during differentiation. Inhibiting the PKC activity of high-glucose maintained hMSCs during expansion culture upregulated the TGFßRII expression of chondrogenic cell pellets, and enhanced chondrogenesis. CONCLUSION: Our findings demonstrate the effect of glucose concentration on regulating the chondrogenic capability of pre-differentiation hMSCs, and provide insight into the mechanism of how glucose concentration regulates PKC and TGF-ß signaling molecules to prime pre-differentiation hMSCs for subsequent chondrogenesis.

Prospectus. Future trends in transfusion.

There are several emerging trends in perioperative transfusion that are promising in terms of clinical practice. These include modifications in transfusion practice, changes in blood bank procedures and philosophy, the use of autologous transfusion methods, and the development of new artificial blood substitutes. Refinement of current techniques will continue, and will be driven by several factors. The most significant recent changes in surgical practice relating to blood transfusion include a decreased reliance on the use of arbitrary transfusion triggers, and the increased use of various forms of autologous transfusion. Other clinical changes have been less obvious, such as changes in blood bank management practice. Similar factors drive the development of blood conservation strategies and artificial blood substitutes or O2 carriers. Both will play a role in reducing perioperative blood loss. The most likely scenarios involve use of blood substitutes in conjunction with various methods of blood conservation. Recent advances in blood banking have made the donor blood supply safer than ever before. Progress in the clinical setting and in the laboratory have widened the possibilities for treatment of perioperative blood loss, with attention to minimizing risk and cost, and maintaining safety for the patient.