Regulation of Adult Hematopoietic Stem Cells Fate for Enhanced Tissue-specific Repair

Abstract

The ability to control the differentiation of adult hematopoietic stem cells (HSCs) would promote development of new cell-based therapies to treat multiple degenerative diseases. Systemic injection of NaIO(3) was used to ablate the retinal pigment epithelial (RPE) layer in C57Bl6 mice and initiate neural retinal degeneration. HSCs infected ex vivo with lentiviral vector expressing the RPE-specific gene RPE65 restored a functional RPE layer, with typical RPE phenotype including coexpression of another RPE-specific marker, CRALBP, and photoreceptor outer segment phagocytosis. Retinal degeneration was prevented and visual function, as measured by electroretinography (ERG), was restored to levels similar to that found in normal animals. None of the controls (no HSCs, HSCs alone and HSCs infected with lentiviral vector expressing LacZ) showed these effects. In vitro gene array studies demonstrated that infection of HSC with RPE65 increased adenylate cyclase mRNA. In vitro exposure of HSCs to a pharmacological agonist of adenylate cyclase also led to in vitro differentiation of HSCs to RPE-like cells expressing pigment granules and the RPE-specific marker, CRALBP. Our data confirm that expression of the cell-specific gene RPE65 promoted fate determination of HSCs toward RPE for targeted tissue repair, and did so in part by activation of adenylate cyclase signaling pathways. Expression by HSCs of single genes unique to a differentiated cell may represent a novel experimental paradigm to influence HSC plasticity, force selective differentiation, and ultimately lead to identification of pharmacological alternatives to viral gene delivery.

Studying melanin and lipofuscin in RPE cell culture models

“…Since ARPE19 cells lack melanin but recapitulate most of the biological functions attributed to RPE cells in vivo, the extent to which melanosomes augment facets of RPE differentiation or function is likely to be modest. Interestingly, RPE cells derived from bone marrow cells are poorly pigmented in vitro but when transplanted into the retina they rapidly repigment with typical melanosomes emphasizing the importance of the niche environment (Sengupta et al, 2009). …”

Circulating Mononuclear Progenitor Cells: Differential Roles for Subpopulations in Repair of Retinal Vascular Injury

“…3,[5][6][7][8] These cells have been implicated in the formation of normal, functioning ocular vasculature during development of the newborn eye and in restoration of retinal function when injected into eyes of animal models with retinal degeneration, thus supporting the therapeutic potential of these cells. [9][10][11] However, the degree of progenitor cell involvement in vascular repair appears to vary with vascular bed, local growth stimuli, and disease state (e.g., diabetes). 3,4,[12][13][14] Bone marrow-derived cells that express the inflammatory monocyte marker CD14 are known to exhibit endothelial characteristics under certain conditions.…”

Stemming vision loss with stem cells

“…Other, less common diseases of the retina such as macular telangiectasia (MacTel) and retinal angiomatous proliferation (RAP) involve focal vascular abnormalities that may also be associated with neuronal (e.g., cone photoreceptor) loss. "Crosstalk" between local vascular networks and the tissues they supply may help maintain physiological homeostasis and function in a variety of tissues including the retina (35)(36)(37). In fact, endothelial cells are known to provide trophic substances that greatly stimulate self renewal and directed differentiation of neural stem cells in the central nervous system (38) as well as hepatocytes during liver regeneration in response to injury (39).…”

“…These freshly differentiated cells could then serve as "replacement cells" for damaged local cells and/or exert paracrine functions by producing cytokines, growth factors, and other trophic molecules (37). Two other advantages to generating these replacement cells locally from injected progenitor cells are that less ex vivo manipulation of the donor cell population is required and that there is greater likelihood that the appropriately differentiated cells would be generated as a result of being in the appropriate microenvironment.…”