The Mechanisms Involved In The Islet Regeneration Of Bone Marrow Mesenchymal Stem Cells

Diabetes mellitus is one of the most common chronic metabolic diseasesworldwide, and with the change of lifestyles, the incidence continues to increaseyear by year. It is not only a serious impact on human health, but also anenormous burden to the social and economy. Type1diabetic patients are insulindependent as a result of autoimmune destruction of pancreatic beta cells. Incontrast, type2diabetes is mainly caused by a combination of insulin resistanceand inadequate insulin secretion. The global incidence of diabetes mellitus hasincreased dramatically over the past few years and continues to rise.Furthermore, diabetes mellitus is costly in terms of healthcare resources and isassociated with considerable morbidity and mortality. Diabetes mellitus isprimary disorder of carbohydrate metabolism with multiple etiologic factors andserious complications can occur even under the most careful supervision.Currently, the primary treatment methods are oral hypoglyceimic agents andexternal insulin injections. For all this we cannot prevent the occurrence anddevelopment of chronic complication because of glycemic control cannotachieve the desired state, such as microangiopathy, nephropathy, oculopathy.Due to the complex operation, donor shortage, immune rejection and other factors, it is limited greatly that the wide application of islet transplantation inclinical.With the development of regenerative medicine, recently, the use of stemcells transplantation or gene therapy has been considered as a new therapeuticstrategy for diabetes mellitus. Compared with embryonic stem cells (ESCs) andother tissue-specific stem cells such as hematological and pancreatic stem cells,MSCs have several advantages, such as easy availability as well as few ethicalconcerns and low immunogenicity. In addition, they also have extensivelyproliferative properties in vitro while maintaining their undifferentiatedmulti-potent status. When transplanted into the body of receptors, MSCs alsoshow an important paracrine and immunomodulatory effects. These propertiesmake MSCs an ideal candidate cell type for tissue engineering, regenerativemedicine and autoimmune disease treatment. Based on these, we have raisedseveral potential concerns that should be clarified or resolved in the futurebefore MSC transplantation could be considered a routine therapeutic approachin the clinic. Lack of clinical data to support the long-term safety of MSCs,requires efficient signaling to achieve the recruitment of sufficient amounts ofcells. Although we are beginning to clarify the role of these signals, furtherunderstanding of the molecular mechanisms involved is required. Recently,many studies have proven that MSC migration was regulated by numerouscytokines, growth factors, and their receptors. Stromal cell-derived factor-1(SDF-1), which is also known as CXCL12, belongs to the CXC subfamily andwas first cloned from bone marrow stromal cells. SDF-1is expressed in a widerange of normal tissues, and is a potent chemoattractant for hematopoietic cellsfacilitating their transmigration through endothelial cell barriers. Mostimportantly, SDF-1is thought to regulate hematopoietic stem cell (HSC) migration into and out of the bone marrow. Its receptor, CXCR4, aseven-transmembrane G protein-coupled receptor (GPCR) is highly conservedacross species and expressed in numerous types of embryonic and adult stemcells. The SDF-1/CXCR4interaction may play a crucial role in the homing ofMSC and exhibit enhanced migratory capacity toward diabetes.Objective:Stem cell homing signals play an important role in stem cell migration to theischemic environment and are therefore crucial for injury tissue repair. To date,the most important stem cell homing factor is the stromal cell derived factor l(SDF-1) and its receptor CXCR4. It has been demonstrated, CXCR4, express inmesenchymal stem cells. So, in this study, we aimed to investigate the effect ofSDF-1and pancreas extract from diabetes mellitus on the migration of MSCsMethods:MSCs were isolated, cultured, purified by the whole bone marrow culturefrom SD rat, and then identified by detecting the phenotypes with flowcytometry (FCM) and observing the morphology with optical microscope.After fasting for12hours, diabetic rat model was established by a singleintraperitoneal injection of streptozotocin (65mg/kg). For confirmation thediabetes rat model, the blood glucose monitoring through the tail venous and thepancreatic tissue stained with HE (Hematoxylin and Eosin). Preparation oftissue extracts from normal and diabetic pancreases.The use of Transwell chamber migration assay system, in vitro, to observethe effects of different concentrations of SDF-1and pancreas tissue extracts onthe migration of MSCs. In brief, cells were suspended in low serum medium andseeded into the upper well, and containing SDF-1or pancreatic extract medium was placed in the lower well of Transwell. Following incubation for24h at37℃, cells that had not migrated from the upper side of the filter were scraped offwith a cotton swab, and filters were stained.The number of cells that hadmigrated to the lower side of the filter was counted under a light microscope inthree randomly-selected fields.Results:Mesenchymal stem cells can adherent to the plastic surface, after the cellswere separated from the bone marrow. When they were subcultured to the threepassages, MSCs were successfully purified. The result of Flow cytometry aboutthe phenotypes of MSCs were98.6%、99.7%、1.8%and5.0%, indicate CD29+,CD90+, CD34-and CD45-, That accord with the standard of mesenchymal stemcells. Diabetes model was successfully induced, when the glucose levels≥16.7mmol/L and last for more than a week.Under the different concentration of SDF-1(10,50,100,200ng/ml), theresult of Transwell respectively were (13.33±1.15,19.67±3.06,25.33±2.89,25.67±4.04) significantly than that of the control group(9.00±3.00)（P＜0.05).Under the different pancreatic tissue extracts (NP: normal pancreas DP: diabetespancreas), the number of MSCs were (26.33±3.79,19.67±3.79) respectively.Conclusions:SDF-1had a concentration-dependent chemotaxis effect on MSCs.Pancreatic tissue extracts from diabetic rat model can induce the migration ofMSCs obviously, and this effect could be partially suppressed by AMD3100. Sowe demonstrated that pancreatic tissue extracts from diabetic rat model caninduce the migration of bone marrow mesenchymal stem cells, and SDF-1/CXCR4axis may play an important role in this process.