Bone Marrow Stem Cell Abnormality and Diabetic Complications

Noncanonical Mechanisms for Direct Bone Marrow Generating Ang II (Angiotensin II) Predominate in CD68 Positive Myeloid Lineage Cells

Bone marrow (BM) Ang II (angiotensin II) is a major participant in the regulation of hematopoiesis and immunity. The novel tissue substrate Ang-(1-12) [angiotensin-(1-12)] and its cleaving enzyme chymase are an essential source of Ang II production in cardiac tissue. We hypothesized this noncanonical chymase-mediated Ang II-producing mechanism exists in the BM tissue. Immunohistostaining and flow cytometry confirmed the presence of Ang-(1-12) immunoreaction in the BM of SD (Sprague Dawley) rats. Chymase-mediated Ang II-producing activity in BM was ≈1000-fold higher than ACE (angiotensin-converting enzyme)-mediated Ang II-producing activity (4531±137 and 4.2±0.3 fmol/min per mg, respectively; n=6; P<0.001) and 280-fold higher than chymase activity in the left ventricle of 16.3±1.7 fmol/min per mg (P<0.001). Adding a selective chymase inhibitor, TEI-F00806, eliminated almost all 125I-Ang II production. Flow cytometry demonstrated that delta median fluorescence intensity of chymase in cluster of differentiation 68 positive cells was significantly higher than that in cluster of differentiation 68 negative cells (1546±157 and 222±48 arbitrary units, respectively; P=0.0021). Cluster of differentiation 68 positive and side scatter low subsets, considered to be myeloid progenitors, express the highest chymase fluorescence intensity in rat BM. Chymase activity and cellular expression was similar in both male and female rats. In conclusion, myeloid lineage cells, especially myeloid progenitors, have an extraordinary Ang II-producing activity by chymase in the BM.

Implanted Muscle-Derived Stem Cells Ameliorate Erectile Dysfunction in a Rat Model of Type 2 Diabetes, but Their Repair Capacity Is Impaired by Their Prior Exposure to the Diabetic Milieu

INTRODUCTION

Muscle-derived stem cells (MDSCs) and other SCs implanted into the penile corpora cavernosa ameliorate erectile dysfunction in type 1 diabetic rat models by replenishing lost corporal smooth muscle cells (SMCs) and decreasing fibrosis. However, there are no conclusive data from models of type 2 diabetes (T2D) and obesity.

AIM

To determine whether MDSCs from obese Zucker (OZ) rats with T2D at an early stage of diabetes (early diabetic SCs isolated and cultured in low-glucose medium [ED-SCs]) counteract corporal veno-occlusive dysfunction and corporal SMC loss or lipo-fibrosis when implanted in OZ rats at a late stage of diabetes and whether MDSCs from these OZ rats with late diabetes (late diabetic SCs isolated and cultured in high-glucose medium [LD-SC]) differ from ED-SCs in gene transcriptional phenotype and repair capacity.

METHODS

ED-SCs and LD-SCs were compared by DNA microarray assays, and ED-SCs were incubated in vitro under high-glucose conditions (ED-HG-SC). These three MDSC types were injected into the corpora cavernosa of OZ rats with late diabetes (OZ/ED, OZ/LD, and OZ/ED-HG rats, respectively). Untreated OZ and non-diabetic lean Zucker rats functioned as controls. Two months later, rats were subjected to cavernosometry and the penile shaft and corporal tissues were subjected to histopathology and DNA microarray assays.

MAIN OUTCOME MEASURES

In vivo erectile dysfunction assessment by Dynamic Infusion Cavernosometry followed by histopathology marker analysis of the penile tissues.

RESULTS

Implanted ED-SCs and ED-HG-SCs improved corporal veno-occlusive dysfunction, counteracted corporal decreases in the ratio of SMCs to collagen and fat infiltration in rats with long-term T2D, and upregulated neuronal and endothelial nitric oxide. LD-SCs acquired an inflammatory, pro-fibrotic, oxidative, and dyslipidemic transcriptional phenotype and failed to repair the corporal tissue.

CONCLUSION

MDSCs from pre-diabetic rats injected into the corpora cavernosa of rats with long-term T2D improve corporal veno-occlusive dysfunction and the underlying histopathology. In contrast, MDSCs from rats with long-term uncontrolled T2D are imprinted by the hyperglycemic and dyslipidemic milieu with a noxious phenotype associated with an impaired tissue repair capacity. SCs affected by diabetes could lack tissue repair efficacy as autografts and should be reprogrammed in vitro or substituted by SCs from allogenic non-diabetic sources.

Status of stem cells in diabetic nephropathy: predictive and preventive potentials

BACKGROUND

Recruitment of stem cells to sites of tissue injury constitutes an important mechanism aimed at tissue repair and regeneration. However, it is not clear how the diabetic milieu affects the viability of endogenous stem cells. Thus, we tested the hypothesis that diabetes mellitus is associated with increased apoptosis which, in turn, contributes to reduction in stem cells and the manifestation of type 2 diabetic nephropathy.

METHODS

Sixteen-week-old male obese type 2 diabetic db/db mice, and their appropriate controls, were used for assessment of the status of endothelial progenitor cells (EPCs), mesenchymal stem cells (MSCs), and hematopoetic stem cells (HSCs) in the peripheral blood and renal tissue using specific cell markers. Further, we explored whether diabetic animals display greater apoptosis of stem cell subsets.

RESULTS

The peripheral blood cells of db/db mice displayed reduction in EPCs (p < 0.05) compared to those of db/m controls. Further, kidney cells prepared from experimental groups also showed reductions in EPCs, MSCs, and HSCs. We also observed increased apoptosis of stem cell subsets in cells prepared from kidneys of db/db than those of db/m mice.

CONCLUSIONS

The present study shows a similar pattern of decline in stem cell subsets in peripheral blood and kidneys of db/db mice, an effect likely related to increased apoptosis. Collectively, the results suggest that apoptosis of stem cells likely contributes to eventual manifestation of renal failure in diabetes mellitus. Monitoring of blood levels of stem cell subsets could predict failure of their reparative and protective effects and eventual manifestations of diabetic complications.

Diabetes impairs adipose tissue-derived stem cell function and efficiency in promoting wound healing

Adipose tissue-derived stem cells (ASCs) are gaining increasing consideration in tissue repair therapeutic application. Recent evidence indicates that ASCs enhance skin repair in animal models of impaired wound healing. To assess the therapeutic activity of autologous vs. allogeneic ASCs in the treatment of diabetic ulcers, we functionally characterized diabetic ASCs and investigated their potential to promote wound healing with respect to nondiabetic ones. Adipose tissue-derived cells from streptozotocin-induced type 1 diabetic mice were analyzed either freshly isolated as stromal vascular fraction (SVF), or following a single passage of culture (ASCs). Diabetic ASCs showed decreased proliferative potential and migration. Expression of surface markers was altered in diabetic SVF and cultured ASCs, with a reduction in stem cell marker-positive cells. ASCs from diabetic mice released lower amounts of hepatocyte growth factor, vascular endothelial growth factor (VEGF)-A, and insulin-like growth factor-1, growth factors playing important roles in skin repair. Accordingly, the supernatant of diabetic ASCs manifested reduced capability to promote keratinocyte and fibroblast proliferation and migration. Therapeutic potential of diabetic SVF administered to wounds of diabetic mice was blunted as compared with cells isolated from nondiabetic mice. Our data indicate that diabetes alters ASC intrinsic properties and impairs their function, thus affecting therapeutic potential in the autologous treatment for diabetic ulcers.