The fusion of bone-marrow-derived proinsulin-expressing cells with nerve cells underlies diabetic neuropathy

Aberrant bone marrow-derived microglia in the hypothalamus may dysregulate appetite in diabetes

Bone marrow derived cells (BMDCs) migrate into the hypothalamus, where those cells give rise to microglia to regulate food intake. Given the fact that diabetes functionally impairs BMDCs, we hypothesized that diabetic microglia would fail to exhibit physiological function, accounting for hyperphagia in diabetes. To examine the role of BMDCs, total bone marrow cells from GFP transgenic mice were transplanted into wild type mice in which diabetes was induced by streptozotocin. We first confirmed that bone marrow transplantation could be utilized to examine BMDCs in the brain parenchyma as GFP positive cells could engraft the brain parenchyma and give rise to microglia even when the BBB was intact in the recipient mice. While diabetic mice manifested hyperphagia, BMDCs were in smaller number in the hypothalamus with less response to fasting in the brain parenchyma compared to nondiabetic mice. This finding was also confirmed by examining nondiabetic chimera mice in which BMDCs were diabetic. Those mice also exhibited less response of BMDCs in response to fasting. In conclusion, diabetic BMDCs had less response of microglia to fasting, perhaps accounting for diabetic hyperphagia.

Expression of proinflammatory cytokines and proinsulin by bone marrow-derived cells for fracture healing in long-term diabetic mice

BACKGROUND

Diabetes mellitus (DM) causes bone dysfunction due to poor bone quality, leading to severe deterioration in patient of quality of life. The mechanisms of bone metabolism in DM remain unclear, although chemical and/or mechanical factors are known to disrupt the homeostasis of osteoblasts and osteoclasts. The purpose of this study was to identify the changes of osteoblasts and osteoclasts under long-term hyperglycaemic conditions, using a mouse fracture model of long-term hyperglycemia (LT-HG).

METHODS

C57BL/6J mice and green fluorescent protein (GFP) -positive bone marrow transplanted C57BL/6J mice with LT-HG, maintained under a state of hyperglycaemia for 2 months, were used in this study. After the experimental fracture, we examined the immunohistochemical expression of proinsulin and tumor necrosis factor (TNF) -α at the fracture site. C57BL/6J fracture model mice without hyperglycaemia were used as controls.

RESULTS

In the LT-HG mice, chondrocyte resorption was delayed, and osteoblasts showed an irregular arrangement at the callus site. The osteoclasts were scattered with a decrement in the number of nuclei. The expression of proinsulin was confirmed in bone marrow derived cells (BMDCs) with neovascularization 2 and 3 weeks after fracture. Immunopositivity for TNF-α was also confirmed in immature chondrocytes and BMDCs with neovascularization at 2 weeks, and the number of positive cells was not decreased at 3 weeks. Examination of GFP-grafted hyperglycaemic mice showed that the majority of cells at the fracture site were GFP-positive. Immunohistochemistry showed that the rate of double positives was 15% for GFP and proinsulin and 47% for GFP and TNF-α.

CONCLUSION

LT-HG induces an increase in the number of proinsulin and TNF-α positive cells derived from BMDCs. We suggest that proinsulin and TNF-α positive cells are involved in both bone formation and bone resorption after fracture under hyperglycaemic conditions, resulting in the delay of bone healing.

Complete remission of diabetes with a transient HDAC inhibitor and insulin in streptozotocin mice

Despite the growing epidemic worldwide, diabetes is an incurable disease. We have been focusing on why diabetes manifests refractoriness to any therapy. We recently found that abnormal bone marrow-derived cells (BMDCs), namely, Vcam-1⁺ST-HSCs, was a key mechanism for diabetic complications. We then hypothesize that those aberrant BMDCs sustainedly impair pancreatic β cells. Here we show that eliminating abnormal BMDCs using bone marrow transplantation results in controlling serum glucose in diabetic mice, in which normoglycemia is sustained even after cessation of insulin therapy. Alternatively, abnormal BMDCs exhibiting epigenetic alterations are treated with an HDAC inhibitor, givinostat, in diabetic mice. As a result, those mice are normoglycemic along with restored insulin secretion even following the cessation of both insulin and givinostat. Diabetic cell fusion between abnormal BMDCs and resident cells is significantly blocked by the combination therapy in the pancreatic islets and thymus while surgical ablation of the thymus completely eliminates therapeutic protection in diabetic mice. In conclusion, diabetes is an epigenetic stem cell disorder with thymic disturbances. The combination may be applied to patients aiming at complete remission from diabetes in clinical medicine.

Extracellular Matrix-Based Conductive Interpenetrating Network Hydrogels with Enhanced Neurovascular Regeneration Properties for Diabetic Wounds Repair

The critical effects that impair diabetic wound healing are characterized by poor vascularization and severe peripheral neuropathy. Current management strategies for diabetic wound healing are unsatisfactory, due to the paucity of neurovascular regeneration at the wound site. Importantly, conductivity in skin tissue is reported to be essential for modulating myriad biological processes especially vascular and nerve regeneration. Herein, an extracellular matrix (ECM)-based conductive dressing is synthesized from an interpenetrating polymer network hydrogel composed of gelatin methacryloyl, oxidized chondroitin sulfate (OCS), and OCS-polypyrrole conductive nanoparticles that can promote diabetic wound repairing by enhancing local neurovascular regeneration. The conductive hydrogels combine the advantageous features of water-swollen hydrogels with conductive polymers (CPs) to provide tissue-matching electrical conductivity and mechanical properties for neurovascular regeneration. In vitro and in vivo studies show that the conductive hydrogel can promote neurovascular regeneration by increasing intracellular Ca²⁺ concentration, which subsequently promotes phosphorylation of proteins in the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) and mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) pathways. Furthermore, the conductive hydrogel stimulates full-thickness diabetic wound repair on day 14 by promoting local neurovascular regeneration and collagen deposition. These findings corroborate that the ECM-based conductive interpenetrating network hydrogel dressing significantly promotes wound repairing due to its neurovascular regeneration properties, suggesting that they are suitable candidates for diabetic wound repair.

Macrophages transfer mitochondria to sensory neurons to resolve inflammatory pain

The current paradigm is that inflammatory pain passively resolves following the cessation of inflammation. Yet, in a substantial proportion of patients with inflammatory diseases, resolution of inflammation is not sufficient to resolve pain, resulting in chronic pain. Mechanistic insight into how inflammatory pain is resolved is lacking. Here, we show that macrophages actively control resolution of inflammatory pain remotely from the site of inflammation by transferring mitochondria to sensory neurons. During resolution of inflammatory pain in mice, M2-like macrophages infiltrate the dorsal root ganglia that contain the somata of sensory neurons, concurrent with the recovery of oxidative phosphorylation in sensory neurons. The resolution of pain and the transfer of mitochondria requires expression of CD200 receptor (CD200R) on macrophages and the non-canonical CD200R-ligand iSec1 on sensory neurons. Our data reveal a novel mechanism for active resolution of inflammatory pain.

Binucleated and Multinucleated Neurons are Formed by Fusion

In the era of molecular biology and atomic force microscopy, some important macroscopic issues such as simultaneous bidirectional axonal flow or neuronal multinucleosis remain unaddressed. However, these issues have to be addressed, because they distort the results of our current achievements. Using videorecording technique, we studied adhesive contacts between neurons and their processes and kinetics of anastomosis retraction between the cell bodies up to their complete fusion with introduction of neurites into the cell cytoplasm and formation of binuclear cells. Three proofs refuting the mechanism of binuclearity formation by amitosis are presented. Live trinuclear neurons without signs of amitotic division were identified. Electron microscopy showed that fusion of many living neurons into one simplest during centrifugation of isolated cells.

Malfunctioning CD106-positive, short-term hematopoietic stem cells trigger diabetic neuropathy in mice by cell fusion

Diabetic neuropathy is an incurable disease. We previously identified a mechanism by which aberrant bone marrow-derived cells (BMDCs) pathologically expressing proinsulin/TNF-α fuse with residential neurons to impair neuronal function. Here, we show that CD106-positive cells represent a significant fraction of short-term hematopoietic stem cells (ST-HSCs) that contribute to the development of diabetic neuropathy in mice. The important role for these cells is supported by the fact that transplantation of either whole HSCs or CD106-positive ST-HSCs from diabetic mice to non-diabetic mice produces diabetic neuronal dysfunction in the recipient mice via cell fusion. Furthermore, we show that transient episodic hyperglycemia produced by glucose injections leads to abnormal fusion of pathological ST-HSCs with residential neurons, reproducing neuropathy in nondiabetic mice. In conclusion, we have identified hyperglycemia-induced aberrant CD106-positive ST-HSCs underlie the development of diabetic neuropathy. Aberrant CD106-positive ST-HSCs constitute a novel therapeutic target for the treatment of diabetic neuropathy.

Katagi et al. show that abnormal bone marrow-derived cells originated from hematopoietic stem cells (CD106-positive short-term HSCs) aberrantly fuse with neurons to develop diabetic neuropathy. This study suggests that the pathological abnormality is memorized in the bone marrow and that it cannot be erased by conventional therapy.

Aging and the immune response in diabetic peripheral neuropathy

A large proportion of older individuals with diabetes go on to develop diabetic peripheral neuropathy (DPN). DPN is associated with an increase in inflammatory cells within the peripheral nerve, activation of nuclear factor kappa-light-chain-enhancer of activated B cells and receptors for advanced glycation end products/advanced glycation end products pathways, aberrant cytokine expression, oxidative stress, ischemia, as well as pro-inflammatory changes in the bone marrow; all processes that may be exacerbated with age. We review the immunological features of DPN and discuss whether age-related changes in relevant immunological areas may contribute to age being a risk factor for DPN.

Protective role of neuronal and lymphoid cannabinoid CB2 receptors in neuropathic pain

Cannabinoid CB₂ receptor (CB₂) agonists are potential analgesics void of psychotropic effects. Peripheral immune cells, neurons and glia express CB₂; however, the involvement of CB₂ from these cells in neuropathic pain remains unresolved. We explored spontaneous neuropathic pain through on-demand self-administration of the selective CB₂ agonist JWH133 in wild-type and knockout mice lacking CB₂ in neurons, monocytes or constitutively. Operant self-administration reflected drug-taking to alleviate spontaneous pain, nociceptive and affective manifestations. While constitutive deletion of CB₂ disrupted JWH133-taking behavior, this behavior was not modified in monocyte-specific CB₂ knockouts and was increased in mice defective in neuronal CB₂ knockouts suggestive of increased spontaneous pain. Interestingly, CB₂-positive lymphocytes infiltrated the injured nerve and possible CB₂transfer from immune cells to neurons was found. Lymphocyte CB₂depletion also exacerbated JWH133 self-administration and inhibited antinociception. This work identifies a simultaneous activity of neuronal and lymphoid CB₂that protects against spontaneous and evoked neuropathic pain.

Neuropathy and inflammation in diabetic bone marrow

Diabetes impairs the bone marrow (BM) architecture and function as well as the mobilization of immature cells into the bloodstream and number of potential regenerative cells. Circadian regulation of bone immature cell migration is regulated by β-adrenergic receptors, which are expressed on haematopoietic stem cells, mesenchymal stem cells, and osteoblasts in the BM. Diabetes is associated with a substantially lower number of sympathetic nerve terminal endings in the BM; thus, diabetic neuropathy plays a critical role in BM dysfunction. Treatment with mesenchymal stem cells, BM mononuclear cells, haematopoietic stem cells, and stromal cells ameliorates the dysfunction of diabetic neuropathy, which occurs, in part, through secreted neurotrophic factors, growth factors, adipokines, and polarizing macrophage M2 cells and inhibiting inflammation. Inflammation may be a therapeutic target for BM stem cells to improve diabetic neuropathy. Given that angiogenic and neurotrophic effects are two major barriers to effective diabetic neuropathy therapy, targeting BM stem cells may provide a novel approach to develop these types of treatments.

A role for bone marrow-derived cells in diabetic nephropathy

Diabetes mellitus causes systemic disorders. We previously demonstrated that diabetic condition forced bone marrow-derived cells (BMDCs) to express TNF-α, leading to the development of diabetic neuropathy in mice. Here, we hypothesized that these abnormal BMDCs are also involved in diabetic nephropathy. To test our hypothesis, mice were irradiated to receive total bone marrow (BM) from the transgenic mice expressing green fluorescent protein before diabetes was induced by streptozotocin. Confocal microscopy showed that the diabetic glomerulus had more BMDCs compared with the nondiabetic glomerulus. Most of these cells exhibited endothelial phenotypes, being negative for several markers, including podocin (a maker of podocyte), α8 integrin (mesangial cell), CD68, and F4/80 (macrophage). Next, the total BM of diabetic mice was transplanted into nondiabetic mice to examine if diabetic BM per se could cause glomerular injury. The recipient mice exhibiting normal glycemia developed albuminuria and mesangial expansion with an increase in capillary area. The number of BMDCs increased in the glomerulus of the recipient mice. These cells were found to exhibit the endothelial phenotype and to express TNF-α. These data suggest that diabetic BMDCs per se could initiate glomerular disease. Finally, eNOS knockout mice were used to examine if residential endothelial injury could attract BMDCs into the glomerulus. However, endothelial dysfunction due to eNOS deficiency failed to attract BMDCs into the glomerulus. In summary, BMDCs may be involved in the development of diabetic nephropathy.-Nobuta, H., Katagi, M., Kume, S., Terashima, T., Araki, S., Maegawa, H., Kojima, H., Nakagawa, T. A role for bone marrow-derived cells in diabetic nephropathy.

Targeting tumor necrosis factor in the brain relieves neuropathic pain

Neuropathic pain is a chronic syndrome caused by direct damage to or disease of the somatosensory nervous system. The lack of safe, adequate and sustained pain relief offered by present analgesic treatments is most alarming. While many treatment options are available to manage chronic pain, such as antidepressants, non-steroidal anti-inflammatory agents, opioids, and anticonvulsants, chronic neuropathic pain remains largely unmanaged. Compounding the dilemma of ineffective chronic pain treatments is the need to provide relief from suffering and yet not contribute to the scourge of drug abuse. A recent epidemic of addiction and accidental drug prescription overdoses parallel the increased use of opioid treatment, even though opioids are rarely an effective treatment of relieving chronic pain. To make matters worse, opioids may contribute to exacerbating pain, and side-effects such as cognitive impairment, nausea, constipation, development of tolerance, as well as their potential for addiction and overdose deaths exist. Clearly, there is an urgent need for alternative, non-opiate treatment of chronic pain. Innovative discoveries of pertinent brain mechanisms and functions are key to developing effective, safe treatments. Pioneering work has revealed the essential effects of the pleiotropic mediator tumor necrosis factor (TNF) on brain functioning. These studies establish that TNF inhibits norepinephrine release from hippocampal neurons, and show that excess TNF production within the hippocampus occurs during neuropathic pain, which mobilizes additional mechanisms that further inhibit norepinephrine release. Significantly, it has been verified that elevated levels of TNF in the brain are actually required for neuropathic pain development. Since TNF decreases norepinephrine release in the brain, enhanced TNF levels would prevent engagement of the norepinephrine descending inhibitory neuronal pain pathways. Increased levels of TNF in the brain are therefore critical to the development of neuropathic pain. Therefore, strategies that decrease this enhanced TNF expression in the brain will have superior analgesic efficacy. We propose this novel approach of targeting the pathologically high levels of brain TNF as an effective strategy in the treatment of the devastating syndrome of chronic pain.

Cell-cell fusion in the nervous system: Alternative mechanisms of development, injury, and repair

Over a century ago, the seminal work of Ramón y Cajal revealed that the nervous system is made of individual units, the neurons, which are related to each other by contiguity rather than continuity. This view overturned the idea that the nervous system was a reticulum of fibers, a rete diffusa nervosa, as proposed and defined by Camillo Golgi. Although the neuron theory has been widely confirmed in every model system studied and constitutes the basis of modern neuroscience, evidence accumulated over the years suggests that neurons, similar to other types of cells, have the potential to fuse their membranes and undergo cell-cell fusion under certain conditions. This concept adds a substantial layer to our view of the nervous system and how it functions. Here, we bring together past and more recent discoveries on multiple aspects of neuronal fusion, discussing how this cellular event is generated, and what consequences it has for our understanding of nervous system development, disease, injury, and repair.

Ablation of a small subpopulation of diabetes-specific bone marrow-derived cells in mice protects against diabetic neuropathy

Diabetic peripheral neuropathy (DPN) is a major diabetic complication. Previously, we showed that hyperglycemia induces the appearance of proinsulin (PI)-producing bone marrow-derived cells (PI-BMDCs), which fuse with dorsal root ganglion neurons, causing apoptosis, nerve dysfunction, and DPN. In this study, we have devised a strategy to ablate PI-BMDCs in mice in vivo. The use of this strategy to selectively ablate TNFα-producing PI-BMDCs in diabetic mice protected these animals from developing DPN. The findings provide powerful validation for a pathogenic role of PI-BMDCs and identify PI-BMDCs as an accessible therapeutic target for the treatment and prevention of DPN.

Proinsulin-producing, hyperglycemia-induced adipose tissue macrophages underlie insulin resistance in high fat-fed diabetic mice

Adipose tissue macrophages (ATMs) play an important role in the pathogenesis of obese type 2 diabetes. High-fat diet (HFD)-induced obesity has been shown to lead to ATM accumulation in rodents; however, the impact of hyperglycemia on ATM dynamics in HFD-fed type 2 diabetic models has not been studied. We previously showed that hyperglycemia induces the appearance of proinsulin (PI)-producing proinflammatory bone marrow (BM)-derived cells (PI-BMDCs) in rodents. We fed a 60% HFD to C57BL6/J mice to produce an obese type 2 diabetes model. Absent in chow-fed animals, PI-BMDCs account for 60% of the ATMs in the type 2 diabetic mice. The PI-ATM subset expresses TNF-α and other inflammatory markers, and is highly enriched within crownlike structures (CLSs). We found that amelioration of hyperglycemia by different hypoglycemic agents forestalled PI-producing ATM accumulation and adipose inflammation in these animals. We developed a diphtheria toxin receptor-based strategy to selectively ablate PI-BMDCs among ATMs. Application of the maneuver in HFD-fed type 2 diabetic mice was found to lead to near total disappearance of complex CLSs and reversal of insulin resistance and hepatosteatosis in these animals. In sum, we have identified a novel ATM subset in type 2 diabetic rodents that underlies systemic insulin resistance.

Epidermis-dermis junction as a novel location for bone marrow-derived cells to reside in response to ionizing radiation

Bone marrow-derived cells (BMDCs) can migrate into the various organs in the mice irradiated by ionizing radiation (IR). However, it may not be the case in the skin. While IR is used for bone marrow (BM) transplantation, studying with the epidermal sheets demonstrated that the BMDC recruitment is extraordinarily rare in epidermis in the mouse. Herein, using the chimera mice with BM from green fluorescent protein (GFP) transgenic mice, we simply examined if BMDCs migrate into any layers in the total skin, as opposed to the epidermal sheets, in response to IR. Interestingly, we identified the presence of GFP-positive (GFP(+)) cells in the epidermis-dermis junction in the total skin sections although the epidermal cell sheets failed to have any GFP cells. To examine a possibility that the cells in the junction could be mechanically dissociated during separating epidermal sheets, we then salvaged such dissociated cells and examined its characteristics. Surprisingly, some GFP(+) cells were found in the salvaged cells, indicating that these cells could be derived from BM. In addition, such BMDCs were also associated with inflammation in the junction. In conclusion, BMDCs can migrate to and reside in the epidermis-dermis junction after IR.

Bone marrow-derived TNF-α causes diabetic neuropathy in mice

AIMS/HYPOTHESIS

Dysregulation of biochemical pathways in response to hyperglycaemia in cells intrinsic to the nervous system (Schwann cells, neurons, vasa nervorum) are thought to underlie diabetic peripheral neuropathy (DPN). TNF-α is a known aetiological factor; Tnf-knockout mice are protected against DPN. We hypothesised that TNF-α produced by a small but specific bone marrow (BM) subpopulation marked by proinsulin production (proinsulin-producing BM-derived cells, PI-BMDCs) is essential for DPN development.

METHODS

We produced mice deficient in TNF-α, globally in BM and selectively in PI-BMDCs only, by gene targeting and BM transplantation, and induced diabetes by streptozotocin. Motor and sensory nerve conduction velocities were used to gauge nerve dysfunction. Immunocytochemistry, fluorescence in situ hybridisation (FISH) and PCR analysis of dorsal root ganglia (DRG) were employed to monitor outcome.

RESULTS

We found that loss of TNF-α in BM only protected mice from DPN. We developed a strategy to delete TNF-α specifically in PI-BMDCs, and found that PI-BMDC-specific loss of TNF-α protected against DPN as robustly as loss of total BM TNF-α. Selective loss of PI-BMDC-derived TNF-α downregulated TUNEL-positive DRG neurons. FISH revealed PI-BMDC-neuron fusion cells in the DRG in mice with DPN; fusion cells were undetectable in non-diabetic mice or diabetic mice that had lost TNF-α expression selectively in the PI-BMDC subpopulation.

CONCLUSIONS/INTERPRETATION

BMDC-specific TNF-α is essential for DPN development; its selective removal from a small PI-BMDC subpopulation protects against DPN. The pathogenicity of PI-BMDC-derived TNF-α may have important therapeutic implications.

Mechanism of diabetic neuropathy: Where are we now and where to go?

Neuropathy is the most common complication of diabetes. As a consequence of longstanding hyperglycemia, a downstream metabolic cascade leads to peripheral nerve injury through an increased flux of the polyol pathway, enhanced advanced glycation end‐products formation, excessive release of cytokines, activation of protein kinase C and exaggerated oxidative stress, as well as other confounding factors. Although these metabolic aberrations are deemed as the main stream for the pathogenesis of diabetic microvascular complications, organ‐specific histological and biochemical characteristics constitute distinct mechanistic processes of neuropathy different from retinopathy or nephropathy. Extremely long axons originating in the small neuronal body are vulnerable on the most distal side as a result of malnutritional axonal support or environmental insults. Sparse vascular supply with impaired autoregulation is likely to cause hypoxic damage in the nerve. Such dual influences exerted by long‐term hyperglycemia are critical for peripheral nerve damage, resulting in distal‐predominant nerve fiber degeneration. More recently, cellular factors derived from the bone marrow also appear to have a strong impact on the development of peripheral nerve pathology. As evident from such complicated processes, inhibition of single metabolic factors might not be sufficient for the treatment of neuropathy, but a combination of several inhibitors might be a promising approach to overcome this serious disorder. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2010.00070.x, 2010)

Mesenchymal stem cell therapy ameliorates diabetic hepatocyte damage in mice by inhibiting infiltration of bone marrow-derived cells

Although mesenchymal stem cells (MSCs) have been implicated in hepatic injury, the mechanism through which they contribute to diabetic liver disease has not been clarified. In this study, we investigated the effects of MSC therapy on diabetic liver damage with a focus on the role of bone-marrow-derived cells (BMDCs), which infiltrate the liver, and elucidated the mechanism mediating this process. Rat bone-marrow (BM)-derived MSCs were administered to high-fat diet (HFD)-induced type 2 diabetic mice and streptozotocin (STZ)-induced insulin-deficient diabetic mice. MSC-conditioned medium (MSC-CM) was also administered to examine the trophic effects of MSCs on liver damage. Therapeutic effects of MSCs were analyzed by assessing serum liver enzyme levels and histological findings. Kinetic and molecular profiles of BMDCs in the liver were evaluated using BM-chimeric mice. Curative effects of MSC and MSC-CM therapies were similar because both ameliorated the aggravation of aspartate aminotransferase and alanine aminotransferase at 8 weeks of treatment, despite persistent hyperlipidemia and hyperinsulinemia in HFD-diabetic mice and persistent hyperglycemia in STZ-diabetic mice. Furthermore, both therapies suppressed the abnormal infiltration of BMDCs into the liver, reversed excessive expression of proinflammatory cytokines in parenchymal cells, and regulated proliferation and survival signaling in the liver in both HFD- and STZ-diabetic mice. In addition to inducing hepatocyte regeneration in STZ-diabetic mice, both therapies also prevented excessive lipid accumulation and apoptosis of hepatocytes and reversed insulin resistance (IR) in HFD-diabetic mice.

CONCLUSION

MSC therapy is a powerful tool for repairing diabetic hepatocyte damage by inhibiting inflammatory reactions induced by BMDCs and IR. These effects are likely the result of humoral factors derived from MSCs.

Emerging roles of hematopoietic cells in the pathobiology of diabetic complications

Diabetic complications encompass macrovascular events, mainly the result of accelerated atherosclerosis, and microvascular events that strike the eye (retinopathy), kidney (nephropathy), and nervous system (neuropathy). The traditional view is that hyperglycemia-induced dysregulated biochemical pathways cause injury and death of cells intrinsic to the organs affected. There is emerging evidence that diabetes compromises the function of the bone marrow (BM), producing a stem cell niche-dependent defect in hematopoietic stem cell mobilization. Furthermore, dysfunctional BM-derived hematopoietic cells contribute to diabetic complications. Thus, BM cells are not only a victim but also an accomplice in diabetes and diabetic complications. Understanding the underlying molecular mechanisms may lead to the development of new therapies to prevent and/or treat diabetic complications by specifically targeting these perpetrators.

Hyperglycemia induces abnormal gene expression in hematopoietic stem cells and their progeny in diabetic neuropathy

Diabetic peripheral neuropathy is a major chronic diabetic complication. We have previously shown that in type 1 diabetic streptozotocin-treated mice, insulin- and TNF-α co-expressing bone marrow-derived cells (BMDCs) induced by hyperglycemia travel to nerve tissues where they fuse with nerve cells, causing premature apoptosis and nerve dysfunction. Here we show that similar BMDCs also occur in type 2 diabetic high-fat diet (HFD) mice. Furthermore, we found that hyperglycemia induces the co-expression of insulin and TNF-α in c-kit(+)Sca-1(+)lineage(-) (KSL) progenitor cells, which maintain the same expression pattern in the progeny, which in turn participates in the fusion with neurons when transferred to normoglycemic animals.

Mesenchymal stem cell-like cells derived from mouse induced pluripotent stem cells ameliorate diabetic polyneuropathy in mice

Background. Although pathological involvements of diabetic polyneuropathy (DPN) have been reported, no dependable treatment of DPN has been achieved. Recent studies have shown that mesenchymal stem cells (MSCs) ameliorate DPN. Here we demonstrate a differentiation of induced pluripotent stem cells (iPSCs) into MSC-like cells and investigate the therapeutic potential of the MSC-like cell transplantation on DPN. Research Design and Methods. For induction into MSC-like cells, GFP-expressing iPSCs were cultured with retinoic acid, followed by adherent culture for 4 months. The MSC-like cells, characterized with flow cytometry and RT-PCR analyses, were transplanted into muscles of streptozotocin-diabetic mice. Three weeks after the transplantation, neurophysiological functions were evaluated. Results. The MSC-like cells expressed MSC markers and angiogenic/neurotrophic factors. The transplanted cells resided in hindlimb muscles and peripheral nerves, and some transplanted cells expressed S100β in the nerves. Impairments of current perception thresholds, nerve conduction velocities, and plantar skin blood flow in the diabetic mice were ameliorated in limbs with the transplanted cells. The capillary number-to-muscle fiber ratios were increased in transplanted hindlimbs of diabetic mice. Conclusions. These results suggest that MSC-like cell transplantation might have therapeutic effects on DPN through secreting angiogenic/neurotrophic factors and differentiation to Schwann cell-like cells.

Transplantation of Neural Crest-Like Cells Derived from Induced Pluripotent Stem Cells Improves Diabetic Polyneuropathy in Mice

Impaired vascularity and nerve degeneration are the most important pathophysiological abnormalities of diabetic polyneuropathy (DPN). Therefore, regeneration of both the vascular and nervous systems is required for the treatment of DPN. The neural crest (NC) is a transient embryonic structure in vertebrates that differentiates into a vast range of cells, including peripheral neurons, Schwann cells, and vascular smooth muscle cells. In this study, we investigated the ability of transplantation of NC-like (NCL) cells derived from aged mouse induced pluripotent stem (iPS) cells in the treatment of DPN. iPS cells were induced to differentiate into neural cells by stromal cell-derived inducing activity (SDIA) and subsequently supplemented with bone morphogenetic protein 4 to promote differentiation of NC lineage. After the induction, p75 neurotrophin receptor-positive NCL cells were purified using magnetic-activated cell sorting. Sorted NCL cells differentiated to peripheral neurons, glial cells, and smooth muscle cells by additional SDIA. NCL cells were transplanted into hind limb skeletal muscles of 16-week streptozotocin-diabetic mice. Nerve conduction velocity, current perception threshold, intraepidermal nerve fiber density, sensitivity to thermal stimuli, sciatic nerve blood flow, plantar skin blood flow, and capillary number-to-muscle fiber ratio were evaluated. Four weeks after transplantation, the engrafted cells produced growth factors: nerve growth factor, neurotrophin 3, vascular endothelial growth factor, and basic fibroblast growth factor. It was also confirmed that some engrafted cells differentiated into vascular smooth muscle cells or Schwann cell-like cells at each intrinsic site. The transplantation improved the impaired nerve and vascular functions. These results suggest that transplantation of NCL cells derived from iPS cells could have therapeutic effects on DPN through paracrine actions of growth factors and differentiation into Schwann cell-like cells and vascular smooth muscle cells.

Diabetes impairs the interactions between long-term hematopoietic stem cells and osteopontin-positive cells in the endosteal niche of mouse bone marrow

Hematopoietic stem cells (HSCs) are maintained, and their division/proliferation and quiescence are regulated in the microenvironments, niches, in the bone marrow. Although diabetes is known to induce abnormalities in HSC mobilization and proliferation through chemokine and chemokine receptors, little is known about the interaction between long-term HSCs (LT-HSCs) and osteopontin-positive (OPN) cells in endosteal niche. To examine this interaction, LT-HSCs and OPN cells were isolated from streptozotocin-induced diabetic and nondiabetic mice. In diabetic mice, we observed a reduction in the number of LT-HSCs and OPN cells and impaired expression of Tie2, β-catenin, and N-cadherin on LT-HSCs and β1-integrin, β-catenin, angiopoietin-1, and CXCL12 on OPN cells. In an in vitro coculture system, LT-HSCs isolated from nondiabetic mice exposed to diabetic OPN cells showed abnormal mRNA expression levels of Tie2 and N-cadherin. Conversely, in LT-HSCs derived from diabetic mice exposed to nondiabetic OPN cells, the decreased mRNA expressions of Tie2, β-catenin, and N-cadherin were restored to normal levels. The effects of diabetic or nondiabetic OPN cells on LT-HSCs shown in this coculture system were confirmed by the coinjection of LT-HSCs and OPN cells into bone marrow of irradiated nondiabetic mice. Our results provide new insight into the treatment of diabetes-induced LT-HSC abnormalities and suggest that the replacement of OPN cells may represent a novel treatment strategy.

Review of the history and current status of cell-transplant approaches for the management of neuropathic pain

Treatment of sensory neuropathies, whether inherited or caused by trauma, the progress of diabetes, or other disease states, are among the most difficult problems in modern clinical practice. Cell therapy to release antinociceptive agents near the injured spinal cord would be the logical next step in the development of treatment modalities. But few clinical trials, especially for chronic pain, have tested the transplant of cells or a cell line to treat human disease. The history of the research and development of useful cell-transplant-based approaches offers an understanding of the advantages and problems associated with these technologies, but as an adjuvant or replacement for current pharmacological treatments, cell therapy is a likely near future clinical tool for improved health care.

It is all in the blood: the multifaceted contribution of circulating progenitor cells in diabetic complications

Diabetes mellitus (DM) is a worldwide growing disease and represents a huge social and healthcare problem owing to the burden of its complications. Micro- and macrovascular diabetic complications arise from excess damage through well-known biochemical pathways. Interestingly, microangiopathy hits the bone marrow (BM) microenvironment with features similar to retinopathy, nephropathy and neuropathy. The BM represents a reservoir of progenitor cells for multiple lineages, not limited to the hematopoietic system and including endothelial cells, smooth muscle cells, cardiomyocytes, and osteogenic cells. All these multiple progenitor cell lineages are profoundly altered in the setting of diabetes in humans and animal models. Reduction of endothelial progenitor cells (EPCs) along with excess smooth muscle progenitor (SMP) and osteoprogenitor cells creates an imbalance that promote the development of micro- and macroangiopathy. Finally, an excess generation of BM-derived fusogenic cells has been found to contribute to diabetic complications in animal models. Taken together, a growing amount of literature attributes to circulating progenitor cells a multi-faceted role in the pathophysiology of DM, setting a novel scenario that puts BM and the blood at the centre of the stage.

Pathogenesis of diabetic neuropathy: bad to the bone

Insulin and proinsulin are normally produced only by the pancreas and thymus. We detected in diabetic rodents the presence of extra pancreatic proinsulin-producing bone marrow-derived cells (PI-BMDCs) in the BM, liver, and fat. In mice and rats with diabetic neuropathy, we also found proinsulin-producing cells in the sciatic nerve and neurons of the dorsal root ganglion (DRG). BM transplantation experiments using genetically marked donor and recipient mice showed that the proinsulin-producing cells in the DRG, which morphologically resemble neurons, are actually polyploid proinsulin-producing fusion cells formed between neurons and PI-BMDCs. Additional experiments indicate that diabetic neuropathy is not simply the result of nerve cells being damaged directly by hyperglycemia. Rather, hyperglycemia induces fusogenic PI-BMDCs that travel to the peripheral nervous system, where they fuse with Schwann cells and DRG neurons, causing neuronal dysfunction and death, the sine qua non for diabetic neuropathy. Poorly controlled diabetes is indeed bad to the bone.

Fusion of bone marrow-derived cells with renal tubules contributes to renal dysfunction in diabetic nephropathy

Although diabetic nephropathy (DN) is a major cause of end-stage renal disease, the mechanism of dysfunction has not yet been clarified. We previously reported that in diabetes proinsulin-producing bone marrow-derived cells (BMDCs) fuse with hepatocytes and neurons. Fusion cells are polyploidy and produce tumor necrosis factor (TNF)-α, ultimately causing diabetic complications. In this study, we assessed whether the same mechanism is involved in DN. We performed bone marrow transplantation from male GFP-Tg mice to female C57BL/6J mice and produced diabetes by streptozotocin (STZ) or a high-fat diet. In diabetic kidneys, massive infiltration of BMDCs and tubulointerstitial injury were prominent. BMDCs and damaged tubular epithelial cells were positively stained with proinsulin and TNF-α. Cell fusion between BMDCs and renal tubules was confirmed by the presence of Y chromosome. Of tubular epithelial cells, 15.4% contain Y chromosomes in STZ-diabetic mice, 8.6% in HFD-diabetic mice, but only 1.5% in nondiabetic mice. Fusion cells primarily expressed TNF-α and caspase-3 in diabetic kidney. These in vivo findings were confirmed by in vitro coculture experiments between isolated renal tubular cells and BMDCs. It was concluded that cell fusion between BMDCs and renal tubular epithelial cells plays a crucial role in DN.

Inactivation of TNF-α ameliorates diabetic neuropathy in mice

Tumor necrosis factor (TNF)-α is a potent proinflammatory cytokine involved in the pathogenesis of diabetic neuropathy. We inactivated TNF-α to determine if it is a valid therapeutic target for the treatment of diabetic neuropathy. We effected the inactivation in diabetic neuropathy using two approaches: by genetic inactivation of TNF-α (TNF-α(-/-) mice) or by neutralization of TNF-α protein using the monoclonal antibody infliximab. We induced diabetes using streptozotocin in wild-type and TNF-α(-/-) mice. We measured serum TNF-α concentration and the level of TNF-α mRNA in the dorsal root ganglion (DRG) and evaluated nerve function by a combination of motor (MNCV) and sensory (SNCV) nerve conduction velocities and tail flick test, as well as cytological analysis of intraepidermal nerve fiber density (IENFD) and immunostaining of DRG for NF-κB p65 serine-276 phosphorylated and cleaved caspase-3. Compared with nondiabetic mice, TNF-α(+/+) diabetic mice displayed significant impairments of MNCV, SNCV, tail flick test, and IENFD as well as increased expression of NF-κB p65 and cleaved caspase-3 in their DRG. In contrast, although nondiabetic TNF-α(-/-) mice showed mild abnormalities of IENFD under basal conditions, diabetic TNF-α(-/-) mice showed no evidence of abnormal nerve function tests compared with nondiabetic mice. A single injection of infliximab in diabetic TNF-α(+/+) mice led to suppression of the increased serum TNF-α and amelioration of the electrophysiological and biochemical deficits for at least 4 wk. Moreover, the increased TNF-α mRNA expression in diabetic DRG was also attenuated by infliximab, suggesting infliximab's effects may involve the local suppression of TNF-α. Infliximab, an agent currently in clinical use, is effective in targeting TNF-α action and expression and amelioration of diabetic neuropathy in mice.

Bone marrow expression of poly(ADP-ribose) polymerase underlies diabetic neuropathy via hematopoietic-neuronal cell fusion

Diabetic neuropathy is the most common diabetic complication. The pathogenetic pathways include oxidative stress, advanced glycation end product (AGE) formation, protein kinase C, and NF-κB activation, as well as increased polyol flux. These metabolic perturbations affect neurons, Schwann cells, and vasa nervorum, which are held to be the primary cell types involved. We hypothesize that diabetes induces the appearance of abnormal bone marrow-derived cells (BMDCs) that fuse with neurons in the dorsal root ganglia (DRG) of mice, leading to diabetic neuropathy. Neuronal poly(ADP-ribose) polymerase-1 (PARP-1) activation in diabetes is known to generate free radical and oxidant-induced injury and poly(ADP-ribose) polymer formation, resulting in neuronal death and dysfunction, culminating in neuropathy. We further hypothesize that BM-specific PARP expression plays a determining role in disease pathogenesis. Here we show that bone marrow transplantation (BMT) of PARP-knockout (PARPKO) cells to wild-type mice protects against, whereas BMT of wild-type cells to PARPKO mice, which are normally "neuropathy-resistant," confers susceptibility to, diabetic neuropathy. The pathogenetic process involving hyperglycemia, BMDCs, and BMDC-neuron fusion can be recapitulated in vitro. Incubation in high, but not low, glucose confers fusogenicity to BMDCs, which are characterized by proinsulin (PI) and TNF-α coexpression; coincubation of isolated DRG neurons with PI-BMDCs in high glucose leads to spontaneous fusion between the 2 cell types, while the presence of a PARP inhibitor or use of PARPKO BMDCs in the incubation protects against BMDC-neuron fusion. These complementary in vivo and in vitro experiments indicate that BMDC-PARP expression promotes diabetic neuropathy via BMDC-neuron fusion.

Interleukin-7 induces recruitment of monocytes/macrophages to endothelium

AIMS

Interleukin-7 (IL-7) is a master regulator of T-cell development and homoeostasis. Increased IL-7 levels are associated with inflammatory diseases. The aims of this study were to determine whether IL-7 is a biomarker for inflammatory conditions or an active participant in atherogenesis.

METHODS AND RESULTS

Advanced atherosclerotic lesions in Apoe(-/-) mice were regressed by long-term cholesterol lowering through treatment with a helper-dependent adenovirus expressing apolipoprotein E (n= 6-10). Using this model, gene expression patterns in the aorta were analysed at an early phase of regression by microarray. After stringent statistical analysis, we found that IL-7 expression is significantly reduced in response to lowering of cholesterol (n= 6). To understand the importance of IL-7 down-regulation for atherosclerotic regression, we studied the effects and mechanisms of action of IL-7 on endothelial cells (ECs) in vitro as well as in vivo. Our major findings are: (i) IL-7 up-regulates cell adhesion molecules and monocyte chemoattractant protein-1 in ECs and promotes monocyte adhesion to ECs; (ii) this regulation is mediated by phosphatidylinositol 3-kinase (PI3K)/AKT-dependent and -independent activation of NF-κB; (iii) elevation of plasma IL-7 induces recruitment of monocytes/macrophages to endothelium without affecting plasma cholesterol (n= 5, 6); and (4) lack of IL-7 in bone marrow-derived cells reduces migration of monocytes/macrophages to the lesions (n= 5, 6).

CONCLUSION

These results suggest that IL-7 inflames endothelium via PI3K/AKT-dependent and -independent activation of NF-κB and recruits monocytes/macrophages to the endothelium, thus playing an active role in atherogenesis.

Homing of the bone marrow-derived interstitial cells of Cajal is decreased in diabetic mouse intestine

BACKGROUND

Interstitial cells of Cajal (ICCs), which express c-Kit receptor tyrosine kinase (KIT), play an important role in gastrointestinal motility. Loss of ICCs likely contributes to diabetic gastrointestinal motility disorder, however, the mechanism of attrition remains unknown. Here, we test the hypothesis that the bone marrow-derived progenitors are an important source of intestinal ICCs and that decreased homing of these progenitors in diabetes contributes to ICC diminution.

METHODS

Wild type mice were X-ray irradiated, transplanted with bone marrow (BMT) from green fluorescence protein (GFP)-transgenic (TG)-mice and subsequently made diabetic by streptozotocin (STZ) injection. Intestinal homing of GFP-positive bone marrow-derived cells was examined 2 or 5 months after STZ treatment.

RESULTS

In the BMT-mice, we found many GFP-positive bone marrow-derived cells (BMDCs) in most parts of the intestinal area, the number of BMDCs was significantly decreased in diabetic mice compared with nondiabetic controls. As a representative area, we further examined the myenteric plexus of the proximal small intestine, and found that the cell numbers of ICCs marked by c-Kit-positive immunoreactivity were decreased by more than 40% in diabetic versus nondiabetic mice. Furthermore, numbers of c-Kit+/GFP+ and c-Kit+/GFP- cells were similar in nondiabetic mice, and decreased by 45.8% and 42.0%, respectively, in diabetic mice.

CONCLUSION

These results suggest that the decreased homing from the bone marrow is a major cause of ICC loss in the intestine in diabetes mellitus.

Identification and isolation from either adult human bone marrow or G-CSF-mobilized peripheral blood of CD34(+)/CD133(+)/CXCR4(+)/ Lin(-)CD45(-) cells, featuring morphological, molecular, and phenotypic characteristics of very small embryonic-like (VSEL) stem cells

OBJECTIVE

Recently, we demonstrated that normal human bone marrow (hBM)-derived CD34(+) cells, released into the peripheral blood after granulocyte colony-stimulating factor mobilization, contain cell subpopulations committed along endothelial and cardiac differentiation pathways. These subpopulations could play a key role in the regeneration of post-ischemic myocardial lesion after their direct intracardiac delivery. We hypothesized that these relevant cells might be issued from very small embryonic-like stem cells deposited in the BM during ontogenesis and reside lifelong in the adult BM, and that they could be mobilized into peripheral blood by granulocyte colony-stimulating factor.

MATERIALS AND METHODS

Samples of normal hBM and leukapheresis products harvested from cancer patients after granulocyte colony-stimulating factor mobilization were analyzed and sorted by multiparameter flow cytometry strategy. Immunofluorescence and reverse transcription quantitative polymerase chain reaction assays were performed to analyze the expression of typical pluripotent stem cells markers.

RESULTS

A population of CD34(+)/CD133(+)/CXCR4(+)/Lin(-) CD45(-) immature cells was first isolated from the hBM or from leukapheresis products. Among this population, very small (2-5 μm) cells expressing Oct-4, Nanog, and stage-specific embryonic antigen-4 at protein and messenger RNA levels were identified.

CONCLUSIONS

Our study supports the hypothesis that very small embryonic-like stem cells constitute a "mobile" pool of primitive/pluripotent stem cells that could be released from the BM into the peripheral blood under the influence of various physiological or pathological stimuli. In order to fully support that hBM- and leukapheresis product-derived very small embryonic-like stem cells are actually pluripotent, we are currently testing their ability to differentiate in vitro into cells from all three germ layers.

Malfunction of bone marrow-derived osteoclasts and the delay of bone fracture healing in diabetic mice

It is well known that bone fracture healing is delayed in diabetes mellitus, but the mechanism remains to be elucidated. Since several studies have demonstrated that diabetes causes abnormalities in bone marrow-derived cells, we used the streptozotocin (STZ)-induced diabetic mouse model after bone marrow transfer from green fluorescent protein (GFP) transgenic mice, and examined fracture healing. Compared with nondiabetic mice, diabetic mice at 3 weeks after fracture showed a decrease in mineralized callus, with the remainder consisting of cartilage. Bone formation parameters and mineralization rate were not altered in the STZ mice, but bone resorption parameters were significantly decreased. Therefore, the delayed bone formation in the STZ mice may have resulted from an impairment of cartilage resorption. Interestingly, we found that 80% of the osteoclasts in the callus were derived from bone marrow and the sizes of the osteoclasts as well as the resorption pits formed were significantly smaller in the diabetic mice. Moreover, transcript analysis using RNA isolated by laser capture microdissection (LCM) showed that the expression of DC-STAMP, a putative pivotal gene for osteoclast fusion, was decreased in osteoclasts from diabetic mice. Since the sustainability of osteoclast function depends on the controlled renewal of multinuclear osteoclasts, impaired osteoclast function in diabetes may contribute to decreased cartilage resorption and delayed endochondral ossification.

Mesenchymal stem cells derived from bone marrow of diabetic patients portrait unique markers influenced by the diabetic microenvironment

Cellular microenvironment is known to play a critical role in the maintenance of human bone marrow-derived mesenchymal stem cells (BM-MSCs). It was uncertain whether BM-MSCs obtained from a 'diabetic milieu' (dBM-MSCs) offer the same regenerative potential as those obtained from healthy (non-diabetic) individuals (hBM-MSCs). To investigate the effect of diabetic microenvironment on human BM-MSCs, we isolated and characterized these cells from diabetic patients (dBM-MSCs). We found that dBM-MSCs expressed mesenchymal markers such as vimentin, smooth muscle actin, nestin, fibronectin, CD29, CD44, CD73, CD90, and CD105. These cells also exhibited multilineage differentiation potential, as evident from the generation of adipocytes, osteocytes, and chondrocytes when exposed to lineage specific differentiation media. Although the cells were similar to hBM-MSCs, 6% (3/54) of dBM-MSCs expressed proinsulin/C-peptide. Emanating from the diabetic microenvironmental milieu, we analyzed whether in vitro reprogramming could afford the maturation of the islet-like clusters (ICAs) derived from dBM-MSCs. Upon mimicking the diabetic hyperglycemic niche and the supplementation of fetal pancreatic extract, to differentiate dBM-MSCs into pancreatic lineage in vitro, we observed rapid differentiation and maturation of dBM-MSCs into islet-like cell aggregates. Thus, our study demonstrated that diabetic hyperglycemic microenvironmental milieu plays a major role in inducing the differentiation of human BM-MSCs in vivo and in vitro.

Cell fusion of bone marrow cells and somatic cell reprogramming by embryonic stem cells

Bone marrow transplantation is a curative treatment for many diseases, including leukemia, autoimmune diseases, and a number of immunodeficiencies. Recently, it was claimed that bone marrow cells transdifferentiate, a much desired property as bone marrow cells are abundant and therefore could be used in regenerative medicine to treat incurable chronic diseases. Using a Cre/loxP system, we studied cell fusion after bone marrow transplantation. Fused cells were chiefly Gr-1(+), a myeloid cell marker, and found predominantly in the bone marrow; in parenchymal tissues. Surprisingly, fused cells were most abundant in the kidney, Peyer's patches, and cardiac tissue. In contrast, after cell fusion with embryonic stem cells, bone marrow cells were reprogrammed into new tetraploid pluripotent stem cells that successfully differentiated into beating cardiomyocytes. Together, these data suggest that cell fusion is ubiquitous after cellular transplants and that the subsequent sharing of genetic material between the fusion partners affects cellular survival and function. Fusion between tumor cells and bone marrow cells could have consequences for tumor malignancy.

DRG-targeted helper-dependent adenoviruses mediate selective gene delivery for therapeutic rescue of sensory neuronopathies in mice

Dorsal root ganglion (DRG) neuron dysfunction occurs in a variety of sensory neuronopathies for which there are currently no satisfactory treatments. Here we describe the development of a strategy to target therapeutic genes to DRG neurons for the treatment of these disorders. We genetically modified an adenovirus (Ad) to generate a helper virus (HV) that was detargeted for native adenoviral tropism and contained DRG homing peptides in the adenoviral capsid fiber protein; we used this HV to generate DRG-targeted helper-dependent Ad (HDAd). In mice, intrathecal injection of this HDAd produced a 100-fold higher transduction of DRG neurons and a markedly attenuated inflammatory response compared with unmodified HDAd. We also injected HDAd encoding the beta subunit of beta-hexosaminidase (Hexb) into Hexb-deficient mice, a model of the neuronopathy Sandhoff disease. Delivery of the DRG-targeted HDAd reinstated neuron-specific Hexb production, reversed gangliosidosis, and ameliorated peripheral sensory dysfunction. The development of DRG neuron-targeted HDAd with proven efficacy in a preclinical model may have implications for the treatment of sensory neuronopathies of diverse etiologies.

[Pathophysiology and treatment for diabetic neuropathy]

Diabetic neuropathy (DN) is the most frequent among peripheral neuropathies. Since its pathophysiology is so complicated, neither classification nor therapeutic management of DN has been established. Sensory/autonomic polyneuropathy (DP) is the main type of DN. Since diabetic patients occasionally have one or more subtypes of DN and/or other polyneuropathy including treatable neuropathy like CIDP, the treatment for DP has to be conducted after excluding the possibility of other conditions. Glycemic control is most essential to prevent the development of DP. However, it is practically difficult to keep HbA1c under 6.5% so that drinking and smoking better be restricted and blood pressure be properly maintained to retard the progression of DP. Aldose reductase inhibitor is only one commercially available drug for DP and its efficacy must be evaluated by nerve function tests along with subjective symptoms. More vigorous therapeutic procedure is expected by obtaining not only more potential drugs based on pathogenic mechanisms but also the technique targeting of DNA/siRNA of given peptides at dorsal root ganglion neurons.

Isolation of specific peptides that home to dorsal root ganglion neurons in mice

We isolated peptides that home to mouse dorsal root ganglion (DRG) from a phage library expressing random 7-mer peptides fused to a minor coat protein (pIII) of the M13 phage. An in vitro biopanning procedure yielded 113 phage plaques after five cycles of enrichment by incubation with isolated DRG neurons and two cycles of subtraction by exposure to irrelevant cell lines. Analyses of the sequences of this collection identified three peptide clones that occurred repeatedly during the biopanning procedure. Phage-antibody staining revealed that the three peptides bound to DRG neurons of different sizes. To determine if the peptides would recognize neuronal cells in vivo, we injected individual GST-peptide-fusion proteins into the subarachnoid space of mice and observed the appearance of immunoreactive GST in the cytosol of DRG neurons with a similar size distribution as that observed in vitro, indicating that the GST-peptide-fusion proteins were recognized and taken up by different DRG neurons in vivo. The identification of homing peptide sequences provides a powerful tool for future studies on DRG neuronal function in vitro and in vivo, and opens up the possibility of neuron-specific drug and gene delivery in the treatment of diseases affecting DRG neurons.

Extra-pancreatic insulin production in RAt lachrymal gland after streptozotocin-induced islet β-cells destruction

Previous work has revealed that insulin is secreted in the tear film; its mRNA is expressed in the lachrymal gland (LG) and its receptor in tissues of the ocular surface. To test the hypothesis of insulin production in the LG, we compared normal and diabetic rats for: (1) the presence of insulin and C-peptide, (2) glucose- and carbachol-induced insulin secretion ex-vivo, and (3) biochemical and histological characteristics of diabetic LG that would support this possibility. Four weeks after streptozotocin injection, blood and tears were collected from streptozotocin-diabetic male Wistar rats. Insulin levels in the tear film rose after glucose stimulation in diabetic rats, but remained unchanged in the blood. Ex vivo static secretion assays demonstrated that higher glucose and 200 microM carbachol significantly increased mean insulin levels from LG samples of both groups. Insulin and C-peptide were expressed in LG of diabetic rats as determined by RIA. Comparable synaptophysin immune staining and peroxidase activity in the LG of both groups suggest that the structure and function of these tissues were maintained. These findings provide evidence of insulin production by LG. Higher expression of reactive oxygen species scavengers may prevent oxidative damage to LG compared to pancreatic beta-cells.

Intravenous mononuclear marrow cells reverse neuropathic pain from experimental mononeuropathy

BACKGROUND

Stem cells mediate neuroprotection in a variety of nervous system injury models. In this study, we evaluated a potential role for stem cells in pain therapies. Marrow mononuclear cells containing mixed stem cell populations were used because of wide experience with these cells in experimental and clinical transplantation.

METHODS

After sciatic nerve chronic constriction injury (CCI), adult male Sprague Dawley rats were treated with freshly isolated marrow mononuclear cells (10(7) cells in 0.5 mL IV) from the same strain, or with carrier. The major end points of analysis were thermal and mechanical hypersensitivity using paw withdrawal latency (PWL) to a calibrated heat source and paw withdrawal response to von Frey filaments, evaluated by a blinded investigator.

RESULTS

Marrow transplantation did not prevent pain, and 5 days after CCI all animals were equivalently lesioned. However, 10 days after CCI, rats that received marrow transplants demonstrated paw withdrawal response and PWL patterns indicating recovery from pain, whereas untreated rats continued to have significant pain behavior patterns. For example, PWL values for marrow-treated animals were similar to baseline pre-CCI values (P = 0.54) but significantly shorter latency to withdrawal indicative of continuing pain was seen in untreated rats compared with pre-CCI values (P < 0.001).

CONCLUSIONS

These studies suggest that stem or progenitor cell-mediated therapies may be useful for the treatment of pain after nerve injury, and deserve further study to elucidate the mechanisms of analgesia.

Fusion of proinsulin-producing bone marrow-derived cells with hepatocytes in diabetes

We previously reported that diabetes in mice is associated with the appearance of proinsulin-producing (Proins-P) cells in the liver. It was unclear, however, whether these Proins-P bone marrow-derived cells (BMDC) merely transit through the liver or undergo fusion with hepatocytes, normally an extremely rare event. In this study, we found that, in diabetes, BMDC in the liver produce not only Proins but also TNF-alpha, suggesting that diabetes reprograms gene expression in BMDC, turning on "inappropriate" genes. Bone marrow transplantation using genetically marked donor and recipient mice showed that fusion occurs between Proins-P BMDC and hepatocytes. Cell fusion is further supported by the presence of the Y chromosome in Proins-P cells in female mice that received male bone marrow transplantation cells. Morphologically, Proins-P fusion cells are albumin-producing hepatocytes that constitute approximately 2.5% of the liver section area 5 months after diabetes induction. An extensive search failed to reveal any fusion cells in nondiabetic mice. Thus, diabetes causes fusion between Proins-P BMDC and hepatocytes in vivo, an observation that has implications for the pathophysiology of diabetes as well as the fundamental biology of heterotypic cell fusion.

Extrapancreatic proinsulin/insulin-expressing cells in diabetes mellitus: is history repeating itself?

Insulin is a key regulator of life. Until 25 years ago, the pancreatic beta-cell was thought to be the only organ that produces insulin in the body. Insulin deficiency, whether absolute (in type 1) or relative (in type 2 diabetes), underlies the metabolic derangements in diabetes mellitus, and investigations on insulin have concentrated on pancreatic insulin production, its regulation and the metabolic consequences of insulin deficiency. The thymus was the next organ that was found to also produce insulin, a process that may tolerize the body to the molecule, protecting the host from developing autoimmune beta-cell destruction and (type 1) diabetes. However, now and then there were descriptions of promiscuous insulin production outside the pancreas. During our investigations on diabetes gene therapy in rodents, we serendipitously came across the presence of mysterious cells marked by proinsulin production in unexpected organs, some of which cells may underlie certain chronic diabetic complications. Starting with a historical perspective on insulin expression in brain and thymus, this review focuses mainly on unraveling the mystery of extrapancreatic extrathymic proinsulin/insulin expression in diabetes mellitus.

Morphological and molecular characterization of novel population of CXCR4+ SSEA-4+ Oct-4+ very small embryonic-like cells purified from human cord blood: preliminary report

Recently, we purified from adult murine bone marrow (BM) a population of CXCR4(+), Oct-4(+) SSEA-1(+), Sca-1(+) lin(-) CD45(-) very small embryonic-like (VSEL) stem cells and hypothesized that similar cells could be also present in human cord blood (CB). Here, we report that by employing a novel two-step isolation procedure -- removal of erythrocytes by hypotonic lysis combined with multiparameter sorting -- we could isolate from CB a population of human cells that are similar to murine BM-derived VSELs, described previously by us. These CB-isolated VSELs (CB-VSEL) are very small (3-5 micro m) and highly enriched in a population of CXCR4(+)AC133(+)CD34(+)lin(-) CD45(-) CB mononuclear cells, possess large nuclei containing unorganized euchromatin and express nuclear embryonic transcription factors Oct-4 and Nanog and surface embryonic antigen SSEA-4. Further studies are needed to see if human CB-isolated VSELs similar to their murine BM-derived counterparts are endowed with pluripotent stem cell properties.

The pleiotropic effects of the SDF-1–CXCR4 axis in organogenesis, regeneration and tumorigenesis

Proper response of normal stem cells (NSC) to motomorphogens and chemoattractants plays a pivotal role in organ development and renewal/regeneration of damaged tissues. Similar chemoattractants may also regulate metastasis of cancer stem cells (CSC). Growing experimental evidence indicates that both NSC and CSC express G-protein-coupled seven-transmembrane span receptor CXCR4 and respond to its specific ligand alpha-chemokine stromal derived factor-1 (SDF-1), which is expressed by stroma cells from different tissues. In addition, a population of very small embryonic-like (VSEL) stem cells that express CXCR4 and respond robustly to an SDF-1 gradient was recently identified in adult tissues. VSELs express several markers of embryonic and primordial germ cells. It is proposed that these cells are deposited early in the development as a dormant pool of embryonic/pluripotent NSC. Expression of both CXCR4 and SDF-1 is upregulated in response to tissue hypoxia and damage signal attracting circulating NSC and CSC. Thus, pharmacological modulation of the SDF-1-CXCR4 axis may lead to the development of new therapeutic strategies to enhance mobilization of CXCR4+ NSC and their homing to damaged organs as well as inhibition of the metastasis of CXCR4+ cancer cells.

Imaging pancreatic beta-cells in the intact pancreas

We have developed a method to visualize fluorescent protein-labeled beta-cells in the intact pancreas through combined reflection and confocal imaging. This method provides a 3-D view of the beta-cells in situ. Imaging of the pancreas from mouse insulin I promoter (MIP)-green (GFP) and red fluorescent protein (RFP) transgenic mice shows that islets, beta-cell clusters, and single beta-cells are not evenly distributed but are aligned along the large blood vessels. We also observe the solitary beta-cells in both fetal and adult mice and along the pancreatic and common bile ducts. We have imaged the developing endocrine cells in the embryos using neurogenin-3 (Ngn3)-GFP mice crossed with MIP-RFP mice. The dual-color-coded pancreas from embryos (E15.5) shows a large number of green Ngn3-expressing proendocrine cells with a smaller number of red beta-cells. The imaging technique that we have developed, coupled with the transgenic mice in which beta-cells and beta-cell progenitors are labeled with different fluorescent proteins, will be useful for studying pancreatic development and function in normal and disease states.