Diabetic retinopathy induces retinal vascular endothelial damage resulting in ischemia, edema, and hemorrhage. Current available treatments for diabetic retinopathy are focused on end-stages of the disease. Importantly, these therapies do not address the primary pathology of retinal neurovascular degeneration during diabetes that precedes pre-retinal neovascularization and diabetic macular edema. Fresh perspective on the cellular mechanisms of DR could lead to novel and much more effective prevention / reversal strategies. We describe here a new approach to target early intermediate stages of vasodegeneration using a stem cells therapy to enhance vessel repair, reverse ischemia and prevent progression to late, sight -threatening stages of diabetic retinopathy. For patients with loss of retinal microvasculature, measures to preserve surviving vasculature and revascularize defunct capillary beds could extend the lifetime of the neuronal cells, reduce output of vasoactive and neuropathic agents and ensure retention of serviceable vision. We have developed a novel strategy to enhance endothelial progenitor cells (EPC) function both in health and in diseases such as diabetes. We recently demonstrated that a transient blockade (2-4 days) of endogenous transforming growth factor- beta type 1 (TGF-b1) in murine and human hematopoietic stem cells (HSC and EPCs ) accelerates key functions of these cells including 1) bone marrow engraftment, 2) reducing the number of HSC needed for long-term reconstitution, 3) increasing CXCR-4 expression enhancing the responsiveness of these cells to stromal derived factor (SDF)-1, a key chemokine for EPC chemotaxis including increased NO generation following SDF-1 exposure cells. And 4) increases the reparative function of human diabetic CD34 EPC in SCID mice following ischemia/ reperfusion injury. Overall Hypothesis: Transient blockade of endogenous transforming growth factor-beta type 1 (TGF-b1) using antisense phosphorodiamidate morpholino oligomers (PMO) to TGF-b1 in diabetic CD34+HSC will potentiate their ability to repair retinal vessels in diabetes. To test our hypothesis we put for the following Milestones Phase I:
AIM 1 : Our hypothesis predicts that transient TGF-2 blockade will increase homing ability and proliferation rate of CD34+ HSC in damaged retinal vessels diabetic patients with retinopathy. While this effect in the HSC is transient (2-4 days), it is sufficient to result in enhanced reparative function of these cells. The molecular mechanism of this effect will be examined in vitro by assays to assess changes in proliferation, capillary tube formation and rate of senescence.
AIM 2 : Our hypothesis predicts that TGF-b blockade enhances the reparative function of CD34+ cells by facilitating their homing to the injured retina. Either direct incorporation into blood vessels in the area of ischemia or paracrine expression of growth promoting factors could enhance the observed repair. To test this hypothesis we will use the adoptive transfer technique to deliver anti-TGF-2 PMO-modified CD34+ cells from the blood or bone marrow of patients with type II diabetes to SCID mice that have 1) undergone an ischemia/reperfusion injury model that results in vasodegeneration of retinal capillaries or 2) been made diabetic with STZ. Control CD34+ cells will be from non-diabetic age matched subjects. These proposed collaborative studies between BetaStem Therapeutics and Dr. Maria Grant's laboratory (University of Florida, Department of Pharmacology and Therapeutics) are based on the series of complementary findings summarized above. Much of the studies presented in the preliminary data section are either published1 or under review. 2 The approach proposed has been IP protected by two issued US Patents as well as pending patents. Our Phase 2 proposal will focus on clinical trials that will be based on pre- treatment of autologous diabetic CD34+ cells with anti-TGF-b1 PMOs that specifically block endogenous TGF- b1 in CD34+ cells. We hypothesize that transient TGF-b1 blockade will restore and enhance the reparative function of dysfunctional diabetic EPC and these modified EPCs will serve as a treatment for the vasodegenerative phase of diabetic retinopathy.
Our long term goal is to develop an efficient, safe clinical treatment for diabetic retinopathy using stem cells from the patient's bone marrow or blood that have been activated to repair damaged vessels in the eye. Despite advances in our understanding of how diabetic retinopathy occurs, no effective treatment exists to reverse the retinal blood vessel damage and the vision loss resulting from lack of blood/oxygen supply to the retina. Diabetic retinopathy remains the leading cause of irreversible blindness among working-age adults. We have shown that, over time, the diabetic cellular environment markedly inhibits the ability of their stem cells to repair damaged blood vessels. However, we now show that if these stem cells are treated temporarily with a drug that blocks an important regulator of stem cell activation (i.e., transforming growth factor-beta, TGF-2) vessel repair is greatly enhanced. In this proposal, we plan to test the repair capacity of stem cells obtained from diabetic patients to those from non- diabetic patients since our preliminary data suggest that stem cells from bone marrow of non-diabetic normal donors may repair better than stem cells from peripheral blood. Next, we will conduct a series of experiments to better understand the cellular mechanisms that result in the observed more efficient vascular repair. We also will test the long term safety of introducing stems cells into the eye. Once we complete these proposed studies, we will be able to plan a clinical trial to treat patients with diabetic retinopathy using their own stem cells. If this treatment proves to be safe and effective, it will be the first """"""""cure"""""""" for diabetic retinopathy.
| Bhatwadekar, Ashay D; Yan, Yuanqing; Stepps, Valerie et al. (2015) miR-92a Corrects CD34+ Cell Dysfunction in Diabetes by Modulating Core Circadian Genes Involved in Progenitor Differentiation. Diabetes 64:4226-37 |
