Low immunogenicity of allogeneic human umbilical cord blood-derived mesenchymal stem cells in vitro and in vivo

Evaluation of the immunogenicity of human mesenchymal stem cells (MSCs) in an allogeneic setting during therapy has been hampered by lack of suitable models due to technical and ethical limitations. Here, we show that allogeneic human umbilical cord blood derived-MSCs (hUCB-MSCs) maintained low immunogenicity even after immune challenge in vitro. To confirm these properties in vivo, a humanized mouse model was established by injecting isolated hUCB-derived CD34+ cells intravenously into immunocompromised NOD/SCID IL2γnull (NSG) mice. After repeated intravenous injection of human peripheral blood mononuclear cells (hPBMCs) or MRC5 cells into these mice, immunological alterations including T cell proliferation and increased IFN-γ, TNF-α, and human IgG levels, were observed. In contrast, hUCB-MSC injection did not elicit these responses. While lymphocyte infiltration in the lung and small intestine and reduced survival rates were observed after hPBMC or MRC5 transplantation, no adverse events were observed following hUCB-MSC introduction. In conclusion, our data suggest that allogeneic hUCB-MSCs have low immunogenicity in vitro and in vivo, and are therefore “immunologically safe” for use in allogeneic clinical applications.     

Role of antigen presentation in the production of pro-inflammatory cytokines in obese adipose tissue

Type II diabetes regroups different physiological anomalies that ultimately lead to low-grade chronic inflammation, insulin resistance and loss of pancreatic β-cells. Obesity is one of the best examples of such a condition that can develop into Metabolic Syndrome, causing serious health problems of great socio-economic consequences. The pathological outcome of obesity has a genetic basis and depends on the delicate balance between pro- and anti-inflammatory effectors of the immune system. The causal link between obesity and inflammation is well established. While innate immunity plays a key role in the development of a pro-inflammatory state in obese adipose tissues, it has now become clear that adaptive immune cells are also involved and participate in the cascade of events that lead to metabolic perturbations. The efficacy of some immunotherapeutic protocols in reducing the symptoms of obesity-driven metabolic syndrome in mice implicated all arms of the immune response. Recently, the production of pathogenic immunoglobulins and pro-inflammatory cytokines by B and T lymphocytes suggested an auto-immune basis for the establishment of a non-healthy obese state. Understanding the cellular landscape of obese adipose tissues and how immune cells sustain chronic inflammation holds the key to the development of targeted therapies. In this review, we emphasize the role of antigen-presenting cells and MHC molecules in obese adipose tissue and the general contribution of the adaptive arm of the immune system in inflammation-induced insulin resistance.     

Fine structural properties of natural and synthetic glycogens

Glycogen, highly branched (1→4)(1→6)-linked α-d-glucan, can be extracted from natural sources such as animal tissues or shellfish (natural source glycogen, NSG). Glycogen can also be synthesized in vitro from glucose-1-phosphate using the cooperative action of α-glucan phosphorylase (GP, EC 2.4.1.1) and branching enzyme (BE, EC 2.4.1.18), or from short-chain amylose by the cooperative action of BE and amylomaltase (AM, EC 2.4.1.25). It has been shown that enzymatically synthesized glycogen (ESG) has structural and physicochemical properties similar to those of NSG. In this study, the fine structures of ESG and NSG were analyzed using isoamylase and α-amylase. Isoamylase completely hydrolyzed the α-1,6 linkages of ESG and NSG. The unit-chain distribution (distribution of degrees of polymerization (DP) of α-1,4 linked chains) of ESG was slightly narrower than that of NSG. α-Amylase treatment revealed that initial profiles of hydrolyses of ESG and NSG were almost the same: both glycogens were digested slowly, compared with starch. The final products from NSG by α-amylase hydrolysis were glucose, maltose, maltotriose, branched oligosaccharides with DP ? 4, and highly branched macrodextrin molecules with molecular weights of up to 10,000. When ESG was digested with excess amounts of α-amylase, much larger macrodextrins (molecular weight > 10⁶) were detected. In contrast, oligosaccharides with DP 4-7 could not be detected from ESG. These results suggest that the α-1,6 linkages in ESG molecules are more regularly distributed than those in NSG molecules.     

Optimization of the therapeutic efficacy of human umbilical cord blood–mesenchymal stromal cells in an NSG mouse xenograft model of graft-versus-host disease

Background aimsAlthough in vitro studies have demonstrated the immunosuppressive capacity of mesenchymal stromal cells (MSCs), most in vivo studies on graft-versus-host disease (GVHD) have focused on prevention, and the therapeutic effect of MSCs is controversial. Moreover, optimal time intervals for infusing MSCs have not been established.MethodsWe attempted to evaluate whether human umbilical cord blood–MSCs (hUCB-MSCs) could either prevent or treat GVHD in an NSG mouse xenograft model by injection of MSCs before or after in vivo clearance. Mice were infused with either a single dose or multiple doses of 5 × 10⁵ hUCB-MSCs (3- or 7-day intervals) before or after GVHD onset.ResultsBefore onset, hUCB-MSCs significantly improved the survival rate only when repeatedly injected at 3-day intervals. In contrast, single or repeated injections after GVHD onset significantly increased the survival rate and effectively attenuated tissue damage and inflammation. Furthermore, the levels of prostaglandin E₂ and transforming growth factor-β1 increased significantly, whereas the level of interferon-γ decreased significantly in all MSC treatment groups.ConclusionsThese data establish the optimal time intervals for preventing GVHD and show that hUCB-MSCs effectively attenuated symptoms and improved survival rate when administered after the onset of GVDH.