Application of Hematopoietic Cells to Therapeutic Angiogenesis

Silencing of eIF3e promotes blood perfusion recovery after limb ischemia through stabilization of hypoxia-inducible factor 2α activity

OBJECTIVE

We previously observed that silencing of eukaryotic translation initiation factor 3 subunit e (eIF3e), a hypoxia-independent downregulator of hypoxia-inducible factor 2α (HIF-2α), led to neoangiogenesis by promoting HIF-2α activity under normoxic conditions. In the current study, we investigated whether temporary silencing of eIF3e in muscles affects blood flow recovery in a mouse ischemic limb model.

METHODS

eIF3e silencing was performed using small interfering RNA (siRNA), and changes in gene transcription and protein expression were analyzed in vitro using murine primary skeletal muscle myoblast and human primary skeletal muscle myoblast cell cultures. In unilateral femoral artery ligation experiments, eIF3e siRNA-expressing plasmids were injected into the muscles of BALB/c mice near the ligation sites, and tissue damage and loss of limb function were scored for 28 days while serial measurements of limb perfusions were performed with laser Doppler perfusion imaging.

RESULTS

Silencing of eIF3e in murine primary skeletal muscle myoblasts led to stabilization of HIF-2α and upregulation of angiogenic transcripts, including basic fibroblast growth factor and platelet-derived growth factor B (P < .05), and the supernatant of eIF3e-silenced human primary skeletal muscle myoblasts triggered the tube formation of human umbilical vein endothelial cells. The in vivo mouse model of hindlimb ischemia revealed that single intramuscular injections of eIF3e siRNA-expressing plasmids significantly enhanced perfusion of ischemia-damaged limbs (P < .05) at days 7 and 14 and functional recovery at days 7, 14, and 21 (P < .05).

CONCLUSIONS

eIF3e is an angiogenesis suppressor and may be a therapeutic target for promoting angiogenesis after ischemic injuries.

Cell therapy for multiple sclerosis: an evolving concept with implications for other neurodegenerative diseases

Multiple sclerosis is a major cause of neurological disability, and particularly occurs in young adults. It is characterised by conspicuous patches of damage throughout the brain and spinal cord, with loss of myelin and myelinating cells (oligodendrocytes), and damage to neurons and axons. Multiple sclerosis is incurable, but stem-cell therapy might offer valuable therapeutic potential. Efforts to develop stem-cell therapies for multiple sclerosis have been conventionally built on the principle of direct implantation of cells to replace oligodendrocytes, and therefore to regenerate myelin. Recent progress in understanding of disease processes in multiple sclerosis include observations that spontaneous myelin repair is far more widespread and successful than was previously believed, that loss of axons and neurons is more closely associated with progressive disability than is myelin loss, and that damage occurs diffusely throughout the CNS in grey and white matter, not just in discrete, isolated patches or lesions. These findings have introduced new and serious challenges that stem-cell therapy needs to overcome; the practical challenges to achieve cell replacement alone are difficult enough, but, to be useful, cell therapy for multiple sclerosis must achieve substantially more than the replacement of lost oligodendrocytes. However, parallel advances in understanding of the reparative properties of stem cells--including their distinct immunomodulatory and neuroprotective properties, interactions with resident or tissue-based stem cells, cell fusion, and neurotrophin elaboration--offer renewed hope for development of cell-based therapies. Additionally, these advances suggest avenues for translation of this approach not only for multiple sclerosis, but also for other common neurological and neurodegenerative diseases.

Sertoli cells enhance formation of capillary-like structures in vitro

Sertoli cells isolated from the testis (referred to as extratesticular Sertoli cells) have been shown to facilitate allo- and xenogeneic cell transplantations. It appears likely that the ability of these cells to enhance the success of cell engraftment is due, in part, to the retention of their intratesticular functions of trophic support and immunoprotection. Sertoli cells also are involved in the regulation of angiogenesis in the testis, which may also contribute to enhanced cell engraftment success facilitated by extratesticular Sertoli cells. Because the maintenance of the cell's intratesticular angiogenic function has not yet been evaluated for extratesticular Sertoli cells, this study examined the cell's ability to enhance angiogenesis in vitro. Sertoli cell conditioned media were derived from isolated rat Sertoli cell cultures and used in a rat aortic model of induced angiogenesis, in endothelial and smooth muscle cell monocultures, and in endothelial smooth muscle cocultures. An angiogenic rat cytokine array identified angiogenic factors in the control and conditioned media. Aorta sections incubated with Sertoli cell conditioned media showed a marked increase in the formation of capillary-like structures when compared to controls. Likewise, endothelial cells incubated in conditioned media organized into capillary-like structures not observed when incubated in control media. In coculture, smooth muscle cells were associated with endothelial cell-derived capillary-like structures only when incubated in conditioned media. Cytokine arrays indicated the presence and a qualitative increase of specific angiogenic growth factors in Sertoli cell conditioned media not observed in control media. Results indicate that extratesticular Sertoli cells retain their intratesticular angiogenic function in vitro.

Stem cell review series: regulating highly potent stem cells in aging: environmental influences on plasticity

Significant advances in the past decade have revealed that a large number of highly plastic stem cells are maintained in humans through adulthood and are present even in older adults. These findings are notable in light of the reduced capacity for repair and regeneration in older tissues. The apparent dichotomy can be reconciled through an appreciation of the age-associated changes in the microenvironmental pathways that govern adult stem cell plasticity and differentiation patterns. Specifically, the recent identification of the age-related loss of the local platelet-derived growth factor signals that promote the induction of cardiac myocytes from Oct-3/4+ bone marrow stem cells, rather than impairment in the stem cells themselves, provides a template for understanding and targeting the environmental pathways underlying the regenerative capacity of older tissues and organs. It is projected that this paradigm extends to the overall regulation of adult stem cell biology, shifting the balance from tissue generation during development and maturation to the prevention of untoward stem cell differentiation with aging.

Redox signals in wound healing

Physical trauma represents one of the most primitive challenges that threatened survival. Healing a problem wound requires a multi-faceted comprehensive approach. First and foremost, the wound environment will have to be made receptive to therapies. Second, the appropriate therapeutic regimen needs to be identified and provided while managing systemic limitations that could secondarily limit the healing response. Unfortunately, most current solutions seem to aim at designing therapeutic regimen with little or no consideration of the specific details of the wound environment and systemic limitations. One factor that is centrally important in making the wound environment receptive is correction of wound hypoxia. Recent work have identified that oxygen is not only required to disinfect wounds and fuel healing but that oxygen-dependent redox-sensitive signaling processes represent an integral component of the healing cascade. Over a decade ago, it was proposed that in biological systems oxidants are not necessarily always the triggers for oxidative damage and that oxidants such as H2O2 could actually serve as signaling messengers and drive several aspects of cellular signaling. Today, that concept is much more developed and mature. Evidence supporting the role of oxidants such as H2O2 as signaling messenger is compelling. A complete understanding of the continuum between the classical and emergent roles of oxygen requires a thorough consideration of current concepts in redox biology. The objective of this review is to describe our current understanding of how redox-sensitive processes may drive dermal tissue repair.

Redox regulation of the VEGF signaling path and tissue vascularization: Hydrogen peroxide, the common link between physical exercise and cutaneous wound healing

Vascularization, under physiological or pathophysiological conditions, typically takes place by one or more of the following processes: angiogenesis, vasculogenesis, arteriogenesis, and lymphangiogenesis. Although all of these mechanisms of vascularization have sufficient contrasting features to warrant consideration under separate cover, one common feature shared by all is their sensitivity to the VEGF signaling pathway. Conditions such as wound healing and physical exercise result in increased production of reactive oxygen species such as H(2)O(2), and both are associated with increased tissue vascularization. Understanding these two scenarios of adult tissue vascularization in tandem offers the potential to unlock the significance of redox regulation of the VEGF signaling pathway. Does H(2)O(2) support tissue vascularization? H(2)O(2) induces the expression of the most angiogenic form of VEGF, VEGF-A, by a HIF-independent and Sp1-dependent mechanism. Ligation of VEGF-A to VEGFR2 results in signal transduction leading to tissue vascularization. Such ligation generates H(2)O(2) via an NADPH oxidase-dependent mechanism. Disruption of VEGF-VEGFR2 ligation-dependent H(2)O(2) production or decomposition of such H(2)O(2) stalls VEGFR2 signaling. Numerous antioxidants exhibit antiangiogenic properties. Current evidence lends firm credence to the hypothesis that low-level endogenous H(2)O(2) supports vascular growth.

Quality of Life Improvement and Long-Term Effects of Peripheral Blood Mononuclear Cell Transplantation for Severe Arteriosclerosis Obliterans in Diabetic Patients on Dialysis

BACKGROUND

Severe arteriosclerosis obliterans (ASO) can be intractable, especially in diabetic patients on hemodialysis (HD). Recently, the transplantation of autologous peripheral blood mononuclear cells (PBMNCs) has been reported to have beneficial effects, but the long-term effects and impact on quality of life (QOL) have not been studied.

METHODS AND RESULTS

Autologous PBMNCs were transplanted into 7 diabetic patients on HD who had severe ASO (5 cases with Fontaine IV and 2 with Fontaine III) after administration of 5 microg/kg granulocyte colony stimulating factor; QOL and degree of ischemia was assessed by measuring skin temperature, skin perfusion pressure (SPP), ankle-brachial index (ABI), and ulcer size, and from angiographic findings. At 4 weeks after the procedure, skin temperature was significantly improved, and SPP and ABI also were increased. These beneficial effects persisted for up to 24 weeks. Angiographic findings and ulcer size improved in 3 of 7 and 3 of 4 patients, respectively. SF-36v2 analysis revealed significant improvements in pain scores. No serious complications were detected.

CONCLUSION

Transplantation of PBMNCs resulted in improvement in pain and leg ischemia for over 6 months without serious complications. This therapy is safe and effective for severe ASO in diabetic patients on HD.