New autoimmune genes and the pathogenesis of type 1 diabetes

An important step towards a prevascularized islet microencapsulation device: in vivo prevascularization by combination of mesenchymal stem cells on micropatterned membranes

Extrahepatic transplantation of islets of Langerhans could aid in better survival of islets after transplantation. When islets are transfused into the liver 60-70% of them are lost immediately after transplantation. An important factor for a successful extrahepatic transplantation is a well-vascularized tissue surrounding the implant. There are many strategies known for enhancing vessel formation such as adding cells with endothelial potential, the combination with angiogenic factors and / or applying surface topography at the exposed surface of the device. Previously we developed porous, micropatterned membranes which can be applied as a lid for an islet encapsulation device and we showed that the surface topography induces human umbilical vein endothelial cell (HUVEC) alignment and interconnection. This was achieved without the addition of hydrogels, often used in angiogenesis assays. In this work, we went one step further towards clinical implementation of the device by combining this micropatterned lid with Mesenchymal Stem Cells (MSCs) to facilitate prevascularization in vivo. As for HUVECs, the micropatterned membranes induced MSC alignment and organization in vitro, an important contributor to vessel formation, whereas in vivo (subcutaneous rat model) they contributed to improved implant prevascularization. In fact, the combination of MSCs seeded on the micropatterned membrane induced the highest vessel formation score in 80% of the sections.

Mycobacterium avium subsp. paratuberculosis as a trigger of type-1 diabetes: destination Sardinia, or beyond?

Type 1 diabetes mellitus (T1DM) is a multifactorial autoimmune disease in which the insulin producing beta cell population is destroyed by the infiltrated T lymphocytes. Even though the exact cause of T1DM is yet to be ascertained, varying degree of genetic susceptibility and environmental factors have been linked to the disease progress and outcome. Mycobacterium avium subsp. paratuberculosis (MAP) is an obligate zoonotic pathogen that causes chronic infection of intestines in ruminants, the Johne's disease. MAP that can even survive pasteurization and chlorination has also been implicated to cause similar type of enteritis in humans called Crohn's disease. With the increasing recognition of the link between MAP and Crohn's disease, it has been postulated that MAP is an occult antigen which besides Crohn's could as well be thought to trigger T1DM. Epitope homologies between mycobacterial proteins (Hsp 65) and pancreatic glutamic acid decarboxylase (GAD 65) and infant nutrition studies implicate MAP as one of the triggers for T1DM. PCR and ELISA analyses in diabetic patients from Sardinia suggest that MAP acts as a possible trigger for T1DM. Systematic mechanistic insights are needed to prove this link. Unfortunately, no easy animal model(s) or in-vitro systems are available to decipher the complex immunological network that is triggered in MAP infection leading to T1DM.

Effects of intrahepatic bone-derived mesenchymal stem cells autotransplantation on the diabetic Beagle dogs

BACKGROUND

To assess the effects of intrahepatic autotransplantation of bone-derived Beagle canine mesenchymal stem cells (BcMSCs) containing human insulin and EGFP in diabetic Beagle dogs.

MATERIALS AND METHODS

BcMSCs were isolated from Beagle canine bone marrow, expanded, and transfected with a recombinant retrovirus MSCV carrying human insulin and EGFP. Animals were made diabetic by an intravenous administration of streptozotocin (STZ, 30 mg/kg) and alloxan (50 mg/kg), followed by intrahepatic autotransplantation of transfected BcMSCs. The variations of body weight, blood glucose, serum insulin levels, and plasma C-peptide were determined after autotransplantation. BcMSCs' survival and human insulin expression in liver and serum were examined by fluorescent microscopy, radioimmunoassay (RIA), and immunohistochemistry (IHC).

RESULTS

The body weight of diabetic Beagle dogs received BcMSCs transplantation increased by 11.09% within 16 wk after treatment, and the average blood glucose levels were 19.80±3.13 mmol/L (d 7) and 9.78±3.11 mmol/L (d 112), while in untreated animals, the average values were 21.20±3.26 mmol/L (d 7) and 22.5±3.22 mmol/L (d 112), showing a significant difference (P<0.05). The detection of C-peptide excluded the possible function of regenerative β cells. However, glucose tolerance test revealed BcMSCs group response was not as efficient as that of normal islets, although they could respond to the glucose challenge.

CONCLUSION

Experimental diabetes could be relieved effectively for up to 16 wk by intrahepatic autotransplantation of BcMSCs expressing human insulin, which implies a novel approach of gene therapy for type I diabetes.

Foxp3 and Treg cells in HIV-1 infection and immuno-pathogenesis

FoxP3(+)CD4(+)CD25(+) regulatory T (Treg) cells are implicated in a number of pathologic processes including elevated levels in cancers and infectious diseases, and reduced levels in autoimmune diseases. Treg cells are activated to modulate immune responses to avoid over-reactive immunity. However, conflicting findings are reported regarding relative levels of Treg cells during HIV-1 infection and disease progression. The role of Treg cells in HIV-1 diseases (aberrant immune activation) is poorly understood due to lack of a robust model. We summarize here the regulation and function of Foxp3 in Treg cells and in modulating HIV-1 replication. Based on recent findings from SIV/monkey and HIV/humanized mouse models, a model of the dual role of Treg cells in HIV-1 infection and immuno-pathogenesis is discussed.

Reversal of diabetes in mice by intrahepatic injection of bone-derived GFP-murine mesenchymal stem cells infected with the recombinant retrovirus-carrying human insulin gene

BACKGROUND

The objective of this study was to assess the effect of intrahepatic injection of bone-derived green fluorescent protein (GFP)-transgenic murine mesenchymal stem cells (GFP-mMSCs) containing the human insulin(ins) gene in streptozotocin-induced diabetic mice.

METHODS

GFP-mMSCs were isolated from the bone marrow of GFP transgenic mice, expanded, and transfected with a recombinant retrovirus MSCV carrying the human insulin gene. C57BL/6J mice were made diabetic by an intraperitoneal administration of 160 mg/kg streptozotocin (STZ), followed by intrahepatic injection of transfected GFP-mMSCs. The variations in body weight and the blood glucose and serum insulin levels were determined after cell transplantation. GFP-mMSCs survival and human insulin expression in liver tissues were examined by fluorescent microscopy and immunohistochemistry.

RESULTS

The body weight in diabetic mice that received GFP-mMSCs harboring the human insulin gene was increased by 6% within 6 weeks after treatment, and the average blood glucose levels in these animals were 10.40 +/- 2.80 mmol/l (day 7) and 6.50 +/- 0.89 mmol/l (day 42), respectively, while the average values of blood glucose in diabetic animals without treatment were 26.80 +/- 2.49 mmol/l (day 7) and 25.40 +/- 4.10 mmol/l (day 42), showing a significant difference (p < 0.05). Moreover, secretion of human insulin of GFP-mMSCs in serum and animal liver was detected by radioimmunoassay (RIA) and immunohistochemistry (IHC).

CONCLUSIONS

Experimental diabetes could be relieved effectively for up to 6 weeks by intrahepatic transplantation of murine mesenchymal stem cells expressing human insulin. This study implies a novel approach of gene therapy for type I diabetes.

FoxP3 enhances HIV-1 gene expression by modulating NFkappaB occupancy at the long terminal repeat in human T cells

FoxP3 determines the development of CD4+CD25+ regulatory T (Treg) cells and represses interleukin-2 (IL-2) expression in Treg cells. However, human immunodeficiency virus type 1 (HIV-1) infects and replicates efficiently in FoxP3+ Treg cells. We report that, while inhibiting IL-2 gene expression, FoxP3 enhances gene expression from HIV-1 long terminal repeat (LTR). This FoxP3 activity requires both the N- and C-terminal domains and is inactivated by human IPEX (immunodysregulation, polyendocrinopathy, enteropathy, X-linked syndrome) mutations. FoxP3 enhances HIV-1 LTR via its specific NFkappaB binding sequences in an NFkappaB-dependent fashion in T cells but not in HEK293 cells. FoxP3 decreases level of histone acetylation at the interleukin-2 locus but not at the HIV-1 LTR. Although NFkappaB nuclear translocation is not altered, FoxP3 enhances NFkappaB-p65 binding to HIV-1 LTR. These data suggest that FoxP3 modulates gene expression in a promoter sequence-dependent fashion by modulating chromatin structure and NFkappaB activity. HIV-1 LTR has evolved to both highjack the T-cell activation pathway for expression and to resist FoxP3-mediated suppression of T-cell activation.

Paratuberculosis and Type I diabetes: is this the trigger?

Type 1 diabetes mellitus (T1DM) is an autoimmune disease. The etiology of T1DM is incompletely understood but environmental agent(s) are thought to trigger T1DM in the genetically at risk. Exposure to cow's milk early in life is a recognized risk factor in the development of T1DM. Mycobacterium avium ss. paratuberculosis (MAP) is the cause of bovine Johne's disease and also is thought to act as an immune antigen in Crohn's disease and other granulomatous diseases. MAP is shed in cow's milk and has been shown to survive pasteurization. Genetic susceptibilities, epitope homologies and epidemiologic studies are presented that support MAP as a causative agent of T1DM in the genetically at risk.

The stages of type 1A diabetes

We can now predict the development of type 1 diabetes in man because it is a chronic autoimmune disorder with defined stages of disease. We can also readily prevent the disorder in animal models. A major goal is safe prevention in man, and for this we will almost certainly need a better understanding of pathogenesis, coupled with rigorous clinical trials.

Delayed functional maturation of natural regulatory T cells in the medulla of postnatal thymus: role of TSLP

BACKGROUND

Generation of functional (CD4+)(CD8-)CD25+ regulatory T cells (Treg) in the murine thymus depends on FoxP3. Removal of the thymus from neonatal mice has been shown to result in a multiple organ autoimmune disease phenotype that can be prevented by introducing the FoxP3+ Treg population to the animal. It has therefore, been proposed that functional FoxP3+ Treg cells are not made in the neonatal thymus; however, it remains unclear when and where functional (FoxP3+)(CD4+)(CD8-)CD25+ thymocytes are generated in postnatal thymus.

RESULTS

We report that neither FoxP3 mRNA nor protein is expressed in (CD4+)(CD8-)CD25+, or (CD4+)(CD8-)CD25- thymocytes until 3-4 days post birth, despite the presence of mature (CD4+)(CD8-)CD25+/- thymocytes in the thymus by 1-2 days after birth. (FoxP3-)(CD4+)(CD8-)CD25+ thymocytes from day 2 newborn mice show no Treg activity. Interestingly, we are able to detect low numbers of FoxP3+ thymocytes dispersed throughout the medullary region of the thymus as early as 3-4 days post birth. Expression of FoxP3 is induced in embryonic day 17 fetal thymus organ culture (FTOC) after 4-6 days of in vitro culture. Treatment of FTOCs with thymic stromal derived lymphopoietin (TSLP) enhanced expression of FoxP3, and blocking the TSLP receptor reduces FoxP3 expression in FTOC. Furthermore, TSLP stimulates FoxP3 expression in purified (CD4+)CD8- thymocytes, but not in (CD4+)CD8+, (CD4-)CD8+ and (CD4-)CD8- thymocytes.

CONCLUSION

Expression of FoxP3 or Treg maturation is ontogenically distinct and kinetically delayed from the generation of (CD4+)(CD8-)CD25+ or (CD4+)(CD8-)CD25- thymocytes in the postnatal thymus. TSLP produced from medullary thymic epithelia cells (mTEC) contributes to the expression of FoxP3 and the maturation of natural regulatory T cells. Overall, these results suggest that the development of Treg cells requires paracrine signaling during late stages of thymocyte maturation that is distinct from signaling during positive or negative selection.

An innately interesting decade of research in immunology

"Nature has provided, in the white corpuscles as you call them-in the phagocytes as we call them-a natural means of devouring and destroying all disease germs. There is at bottom only one genuinely scientific treatment for all diseases, and that is to stimulate the phagocytes." So opined B.B. in G.B. Shaw's The Doctor's Dilemma in a dramatic restatement of a key portion of Ilya Metchnikoff's Nobel Prize address: "Whenever the organism enjoys immunity, the introduction of infectious microbes is followed by the accumulation of mobile cells, of white corpuscles of the blood in particular which absorb the microbes and destroy them. The white corpuscles and the other cells capable of doing this have been designated 'phagocytes,' (i.e., devouring cells) and the whole function that ensures immunity has been given the name of 'phagocytosis'". Based on these insights into the foundation of resistance to infectious disease, Metchnikoff was awarded the 1908 Nobel Prize in Physiology or Medicine together with Paul Ehrlich (Fig. 1). Although both were cited for discoveries in immunity, the contributions of the two men seem worlds apart. Ehrlich's studies did not deal with generic responses to infection, but rather with the highly specific nature of antibodies and their relationship to the cells producing them: "As the cell receptor is obviously preformed, and the artificially produced antitoxin only the consequence, i.e. secondary, one can hardly fail to assume that the antitoxin is nothing else but discharged components of the cell, namely receptors discharged in excess". But biological systems are just that-systems-and the parts need to work together. And so we arrive, a century later, at an appreciation for just how intimately related these two seemingly disparate aspects of host defense really are.