Contribution Of Progenitor Cells Research Articles

Smad2/3 Linker Phosphorylation Is a Possible Marker of Pancreatic Stem/Progenitor Cells in the Regenerative Phase of Acute Pancreatitis.

The aims of this study are to characterize cell proliferation and differentiation during regeneration after pancreatitis and pancreatic buds during development to evaluate the role of Smad2/3, phosphorylated at the specific linker threonine residues (pSmad2/3L-Thr) in positive cells. Male C57BL/6 mice received hourly intraperitoneal injections of cerulein and were analyzed after induced pancreatitis. Pancreatitis-affected tissue sections and pancreatic buds were immunostained for pSmad2/3L-Thr, with other markers thought to be stem/progenitor markers of the pancreas. pSmad2/3L-Thr immunostaining-positive cells increased as the pancreatitis progressed. The expression of pSmad2/3L-Thr was seen in acinar cells and ductlike tubular complexes. These results suggest that pSmad2/3L-Thr is expressed during acinar-ductal metaplasia. Immunohistochemical colocalization of pSmad2/3L-Thr with Ki67 was never observed. pSmad2/3L-Thr-positive cells may remain in an undifferentiated state. During the pancreatic development process, pSmad2/3L-Thr was expressed as other markers. pSmad2/3L-Thr develops in duct structure of the undifferentiated cell population in the last part of viviparity that acinar structure is formed clearly. pSmad2/3L-Thr expression occurs during acinar-ductal metaplasia after pancreatitis and may represent the contribution of stem cells and/or progenitor cells to the differentiation of the pancreas.

Contribution of minced muscle graft progenitor cells to muscle fiber formation after volumetric muscle loss injury in wild-type and immune deficient mice.

Volumetric muscle injury (VML) causes an irrecoverable loss of muscle fibers, persistent strength deficits, and chronic disability. A crucial challenge to VML injury and possible regeneration is the removal of all of the in situ native elements necessary for skeletal muscle regeneration. Our first goal was to establish a reliable VML model in the mouse tibialis anterior (TA) muscle. In adult male wild‐type and nude mice, a non‐repaired ≈20% VML injury to the TA muscle resulted in an ≈59% loss in nerve evoked muscle strength, ≈33% loss in muscle mass, and ≈29% loss of muscle fibers at 28 day post‐injury. Our second goal was to investigate if minced muscle grafts (≈1 mm3 tissue fragments) promote recovery of muscle fibers after VML injury and to understand if the graft‐derived progenitor cells directly contribute to fiber regeneration. To assess donor cell contribution, donor muscle tissue was derived from UBC‐GFP mice in a subset of experiments. Minced grafts restored ≈34% of the lost fibers 28 days post‐injury. The number of GFP + fibers and the estimated number of regenerated fibers were similar, regardless of host mouse strain. The muscle tissue regeneration promoted by minced grafts did not improve TA muscle strength at this time post‐injury. These findings demonstrate the direct contribution of minced muscle graft‐derived myogenic stem/progenitor cells to recovery of muscle fibers after VML injury and signify the utility of autologous myogenic stem cell therapies for this indication.

Hepatic Prominin-1 expression is associated with biliary fibrosis

Intrahepatic biliary fibrosis, as seen with cholestatic liver injuries such as biliary atresia, is mechanistically distinct from fibrosis caused by hepatocyte toxicity. We previously demonstrated the expansion of cells expressing the stem/progenitor cell marker Prominin-1, within regions of developing fibrosis in biliary atresia. Thus, we hypothesized that Prominin-1 expression is biliary fibrosis-specific. Gene expression of Prominin-1 was analyzed in adult mice undergoing either cholestatic bile duct ligation or hepatotoxic carbon tetrachloride administration by quantitative polymerase chair reaction. Lineage tracing of Prominin-1-expressing cells and Collagen-1α-expressing cells was performed after bile duct ligation in Prominin-1cre-ert2-lacz;Gfplsl and Collagen-1αGfp transgenic mice, respectively. Prominin-1 expression increased significantly after bile duct ligation compared with sham (6.6±0.9-fold change at 2weeks, P<.05) but not with carbon tetrachloride (-0.7±0.5-fold change, not significant). Upregulation of Prominin-1 was observed histologically throughout the liver as early as 5days after bile duct ligation in Prominin-1cre-ert2-lacz mice by LacZ staining in nonhepatocyte cells. Lineage tracing of Prominin-1-expressing cells labeled prior to bile duct ligation in Prominin-1cre-ert2-lacz;Gfplsl mice, demonstrated increasing colocalization of GREEN FLUORESCENT PROTEIN with biliary marker CYTOKERATIN-19 within ductular reactions up to 5weeks after bile duct ligation consistent with biliary transdifferentiation. In contrast, rare colocalization of GREEN FLUORESCENT PROTEIN with mesenchymal marker α-SMOOTH MUSCLE ACTIN in Prominin-1cre-ert2-lacz;Gfplsl mice and some colocalization of GREEN FLUORESCENT PROTEIN with PROMININ-1 in Collagen-1αGfp mice, indicate minimal contribution of Prominin-1 progenitor cells to the pool of collagen-producing myofibroblasts. During biliary fibrosis Prominin-1-expressing progenitor cells transdifferentiate into cells within ductular reactions. This transdifferentiation may promote fibrosis.

The contribution of oligodendrocytes and oligodendrocyte progenitor cells to central nervous system repair in multiple sclerosis: perspectives for remyelination therapeutic strategies.

Oligodencrocytes (OLs) are the main glial cells of the central nervous system involved in myelination of axons. In multiple sclerosis (MS), there is an imbalance between demyelination and remyelination processes, the last one performed by oligodendrocyte progenitor cells (OPCs) and OLs, resulting into a permanent demyelination, axonal damage and neuronal loss. In MS lesions, astrocytes and microglias play an important part in permeabilization of blood-brain barrier and initiation of OPCs proliferation. Migration and differentiation of OPCs are influenced by various factors and the process is finalized by insufficient acummulation of OLs into the MS lesion. In relation to all these processes, the author will discuss the potential targets for remyelination strategies.

Abstract 99: IL10-inhibits Fibroblast Progenitor Cell-mediated Cardiac Fibrosis in Pressure-overloaded Myocardium

Background: Activated fibroblasts (myoFBs) play critical role in cardiac fibrosis, however, their origin in diseased heart remains uncertain. Recent studies suggest the contribution of bone marrow fibroblasts progenitor cells (BM-FPC) in pressure overload (PO)-induced cardiac fibrosis. Previously we have shown that interleukin-10 suppress PO-induced cardiac fibrosis, however, its role on inhibition of BM-FPC-mediated fibrosis is not known. Thus, we hypothesized that IL-10 inhibits PO-induced homing and transition of BM-FPC to myoFBs and therefore, attenuates cardiac fibrosis. Methods and Results: Cardiac fibrosis was induced in Wild-type (WT) and IL-10-knockout (KO) mice by transverse aortic constriction (TAC). TAC-induced left ventricular (LV) dysfunction and fibrosis were further exaggerated in KO mice. Systemic recombinant IL-10 administration markedly improved LV function and inhibited PO-induced cardiac fibrosis. PO-enhanced FPC (Prominin1 + cells) mobilization and homing in IL-10 KO mice compared to WT mice. Furthermore, bone marrow transplantation (BMT) experiment was performed wherein WT marrow from GFP mice was repopulated in IL-10 KO mice. FPC mobilization was significantly reduced in BMT-IL10 KO mice compared to IL-10 KO mice after TAC. Furthermore, immunofluorescence result in BMT mice showed that subsets of myoFBs are derived from BM after TAC. To identify the molecular mechanism, wild type BM-FPC were treated with TGFβ 2 with or without IL10. IL10 treatment significantly inhibits TGFβ 2 -induced FPC to myoFBs transition. As miRNAs are key players in cardiac fibrosis, next we performed fibrosis-associated miRNA profiling using miRNA array kit. TGFβ 2 -induced miR-208, 155, 21 and 145 expression was markedly inhibited by IL-10. Conclusion: Taken together, our findings suggest that both reduced homing to heart and transition of FPC to myofibroblasts mediate anti-fibrotic effect of IL10 during PO-induced heart failure. Ongoing investigations using molecular approaches will provide a better understanding on the mechanistic and therapeutic aspects of IL10 on PO-induced cardiac fibrosis and heart failure.

DNMT1 is a required genomic regulator for murine liver histogenesis and regeneration.

DNA methyltransferase 1 (DNMT1) is an essential regulator maintaining both epigenetic reprogramming during DNA replication and genome stability. We investigated the role of DNMT1 in the regulation of postnatal liver histogenesis under homeostasis and stress conditions. We generated Dnmt1 conditional knockout mice (Dnmt1(Δalb) ) by crossing Dnmt1(fl/fl) with albumin-cyclization recombination transgenic mice. Serum, liver tissues, and primary hepatocytes were collected from 1-week-old to 20-week old mice. The Dnmt1(Δalb) phenotype was assessed by histology, confocal and electron microscopy, biochemistry, as well as transcriptome and methylation profiling. Regenerative growth was induced by partial hepatectomy and exposure to carbon tetrachloride. The impact of Dnmt1 knockdown was also analyzed in hepatic progenitor cell lines; proliferation, apoptosis, DNA damage, and sphere formation were assessed. Dnmt1 loss in postnatal hepatocytes caused global hypomethylation, enhanced DNA damage response, and initiated a senescence state causing a progressive inability to maintain tissue homeostasis and proliferate in response to injury. The liver regenerated through activation and repopulation from progenitors due to lineage-dependent differences in albumin-cyclization recombination expression, providing a basis for selection of less mature and therefore less damaged hepatic progenitor cell progeny. Consistently, efficient knockdown of Dnmt1 in cultured hepatic progenitor cells caused severe DNA damage, cell cycle arrest, senescence, and cell death. Mx1-cyclization recombination-driven deletion of Dnmt1 in adult quiescent hepatocytes did not affect liver homeostasis. These results establish the indispensable role of DNMT1-mediated epigenetic regulation in postnatal liver growth and regeneration; Dnmt1(Δalb) mice provide a unique experimental model to study the role of senescence and the contribution of progenitor cells to physiological and regenerative liver growth. (Hepatology 2016;64:582-598).

A Subpopulation of Label-Retaining Cells of the Kidney Papilla Regenerates Injured Kidney Medullary Tubules.

SummaryTo determine whether adult kidney papillary label-retaining cells (pLRCs) are specialized precursors, we analyzed their transcription profile. Among genes overexpressed in pLRCs, we selected candidate genes to perform qPCR and immunodetection of their encoded proteins. We found that Zfyve27, which encodes protrudin, identified a subpopulation of pLRCs. With Zfyve27-CreERT2 transgenic and reporter mice we generated bitransgenic animals and performed cell-lineage analysis. Post tamoxifen, Zfyve27-CreERT2 marked cells preferentially located in the upper part of the papilla. These cells were low cycling and did not generate progeny even after long-term observation, thus they did not appear to contribute to kidney homeostasis. However, after kidney injury, but only if severe, they activated a program of proliferation, migration, and morphogenesis generating multiple and long tubular segments. Remarkably these regenerated tubules were located preferentially in the kidney medulla, indicating that repair of injury in the kidney is regionally specified. These results suggest that different parts of the kidney have different progenitor cell pools.

Endoglin is required in Pax3-derived cells for embryonic blood vessel formation

Mutations in endoglin, a TGFβ/BMP coreceptor, are causal for hereditary hemorrhagic telangiectasia (HHT). Endoglin-null (Eng-/-) mouse embryos die at embryonic day (E)10.5–11.5 due to defects in angiogenesis. In part, this is due to an absence of vascular smooth muscle cell differentiation and vessel investment. Prior studies from our lab and others have shown the importance of endoglin expression in embryonic development in both endothelial cells and neural crest stem cells. These studies support the hypothesis that endoglin may play cell-autonomous roles in endothelial and vascular smooth muscle cell precursors. However, the requirement for endoglin in vascular cell precursors remains poorly defined. Our objective was to specifically delete endoglin in neural crest- and somite-derived Pax3-positive vascular precursors to understand the impact on somite progenitor cell contribution to embryonic vascular development. Pax3Cre mice were crossed with Eng+/− mice to obtain compound mutant Pax3Cre/+;Eng+/− mice. These mice were then crossed with homozygous endoglin LoxP-mutated (EngLoxP/LoxP) mice to conditionally delete the endoglin gene in specific lineages that contribute to endothelial and smooth muscle constituents of developing embryonic vessels. Pax3Cre/+;EngLoxP/− mice showed a variety of vascular defects at E10.5, and none of these mice survived past E12.5. Embryos analyzed at E10.5 showed malformations suggestive of misdirection of the intersomitic vessels. The dorsal aorta showed significant dilation with associated vascular smooth muscle cells exhibiting disorganization and enhanced expression of smooth muscle differentiation proteins, including smooth muscle actin. These results demonstrate a requirement for endoglin in descendants of Pax3-expressing vascular cell precursors, and thus provides new insight into the cellular basis underlying adult vascular diseases such as HHT.

Abstract 4725: Hematopoietic stem cell niche activation and progenitor mobilization mediate cancer-associated immunosuppression and metastasis

Abstract Metastatic tumors have been shown to establish microenvironments in distant tissues that are permissive to disseminated tumor cells. Hematopoietic cells are essential components of this microenvironment, yet the events that initiate the hematopoietic response remain unclear. Further, the functional contribution of hematopoietic stem and progenitor cells (HSPCs) to metastatic progression has not been addressed. Here, we utilized two highly metastatic C57bl/6 murine cell lines capable of spontaneous metastasis following orthotopic injection to study how the hematopoietic response is initiated and can function to promote metastatic progression in immune competent tumor-bearing mice. In both the E0771 breast carcinoma model and M3-9-M rhabdomyosarcoma model we found that a primary tumor drove expansion of HSPCs within the bone marrow prior to establishment of metastatic lesions. To detect changes within the bone marrow microenvironment that accounted for the observed HSPC expansion in tumor-bearing mice, we performed qPCR analysis of whole femur lysate from control or pre-metastatic tumor-bearing mice. We found the bone marrow microenvironment of tumor-bearing mice expressed a transcriptional program of hematopoietic niche activation that promoted expansion as well as mobilization of hematopoietic progenitors, including downregulation of the HSPC homing cytokine CXCR4. Consistent with this, we detected elevated HSPCs in the circulation of newly diagnosed cancer patients as well as pre-metastatic tumor-bearing mice. By using a pharmacological antagonist of CXCR4 to mobilize HSPCs as seen in the tumor bearing setting, we demonstrated that circulating HSPCs were functionally capable of significantly enhancing metastasis in mice. To determine the mechanisms by which circulating HSPCs can promote metastatic progression, we tracked the developmental fate of flow cytometry-sorted HSPCs injected into the circulation of control or tumor-bearing pre-metastatic mice. We found that HSPCs localized within pre-metastatic tissues preferentially differentiated into the myeloid lineage. Further, depletion of these myeloid cells abrogated the metastasis-promoting effects of HSPC mobilization. Together, these data establish bone marrow niche activation as one of the earliest steps of the metastatic process and identify circulating HSPCs as a potential indicator of metastatic niche initiation. Citation Format: Amber J. Giles, Meera Murgai, Yorleny Vicioso, Steven Highfill, Miki Kasai, Linda Vahdat, Leonard Wexler, Crystal Mackall, David Lyden, Rosandra Kaplan. Hematopoietic stem cell niche activation and progenitor mobilization mediate cancer-associated immunosuppression and metastasis. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4725. doi:10.1158/1538-7445.AM2015-4725

Diverse contribution of bone marrow-derived late-outgrowth endothelial progenitor cells to vascular repair under pulmonary arterial hypertension and arterial neointimal formation

AimsIt is still controversial whether bone marrow (BM)-derived endothelial progenitor cells (EPCs) can contribute to vascular repair and prevent the progression of vascular diseases. We aimed to characterize BM-derived EPC subpopulations and to evaluate their therapeutic efficacies to repair injured vascular endothelium of systemic and pulmonary arteries. Methods and resultsBM mononuclear cells of Fisher-344 rats were cultured under endothelial cell-conditions. Early EPCs appeared on days 3–6. Late-outgrowth and very late-outgrowth EPCs (LOCs and VLOCs) were defined as cells forming cobblestone colonies on days 9–14 and 17–21, respectively. Among EPC subpopulations, LOCs showed the highest angiogenic capability with enhanced proliferation potential and secretion of proangiogenic proteins. To investigate the therapeutic effects of these EPCs, Fisher-344 rats underwent wire-mediated endovascular injury in femoral artery (FA) and were concurrently injected intraperitoneally with 60mg/kg monocrotaline (MCT). Injured rats were then treated with six injections of one of three EPCs (1×106 per time). After 4weeks, transplanted LOCs, but not early EPCs or VLOCs, significantly attenuated neointimal lesion formation in injured FAs. Some of CD31+ LOCs directly replaced the injured FA endothelium (replacement ratio: 11.7±7.0%). In contrast, any EPC treatment could neither replace MCT-injured endothelium of pulmonary arterioles nor prevent the progression of pulmonary arterial hypertension (PAH). LOCs modified protectively the expression profile of angiogenic and inflammatory genes in injured FAs, but not in MCT-injured lungs. ConclusionBM-derived LOCs can contribute to vascular repair of injured systemic artery; however, even they cannot rescue injured pulmonary vasculature under MCT-induced PAH.

Insulin-Like Growth Factor Binding Protein-2 Promotes Adhesion of Endothelial Progenitor Cells to Endothelial Cells via Integrin α5β1.

The contribution of endothelial progenitor cells (EPCs) to new vessel formation has been studied in different physiological and pathological conditions for decades. As previously suggested, insulin-like growth factor binding protein-2 (IGFBP-2) may interact with integrins and promote cell migration. However, the role of IGFBP-2 in regulation of EPC functions remains largely unknown. In this present study, we found that overexpression of IGFBP-2 in human umbilical vein endothelial cells (HUVECs) promoted EPC-endothelial adhesion. Conversely, siRNA-mediated depletion of IGFBP-2 inhibited oxygen-glucose deprivation (OGD)-induced EPC-endothelial adhesion. Further, we demonstrated that the arginine-glycine-aspartic acid (RGD) motif in its C-domain is required for interaction with integrin α5β1. In addition, treatment with IGFBP-2 significantly enhanced incorporation of EPCs into tubule networks formed by HUVECs. Thus, our findings suggest that exogenous administration of IGFBP-2 may facilitate neovascularization and improve treatment of ischemic conditions.

Stem and progenitor cells: advancing bone tissue engineering.

Unlike many other postnatal tissues, bone can regenerate and repair itself; nevertheless, this capacity can be overcome. Traditionally, surgical reconstructive strategies have implemented autologous, allogeneic, and prosthetic materials. Autologous bone--the best option--is limited in supply and also mandates an additional surgical procedure. In regenerative tissue engineering, there are myriad issues to consider in the creation of a functional, implantable replacement tissue. Importantly, there must exist an easily accessible, abundant cell source with the capacity to express the phenotype of the desired tissue, and a biocompatible scaffold to deliver the cells to the damaged region. A literature review was performed using PubMed; peer-reviewed publications were screened for relevance in order to identify key advances in stem and progenitor cell contribution to the field of bone tissue engineering. In this review, we briefly introduce various adult stem cells implemented in bone tissue engineering such as mesenchymal stem cells (including bone marrow- and adipose-derived stem cells), endothelial progenitor cells, and induced pluripotent stem cells. We then discuss numerous advances associated with their application and subsequently focus on technological advances in the field, before addressing key regenerative strategies currently used in clinical practice. Stem and progenitor cell implementation in bone tissue engineering strategies have the ability to make a major impact on regenerative medicine and reduce patient morbidity. As the field of regenerative medicine endeavors to harness the body's own cells for treatment, scientific innovation has led to great advances in stem cell-based therapies in the past decade.

Multipotent glia-like stem cells mediate stress adaptation.

The neural crest-derived adrenal medulla is closely related to the sympathetic nervous system; however, unlike neural tissue, it is characterized by high plasticity which suggests the involvement of stem cells. Here, we show that a defined pool of glia-like nestin-expressing progenitor cells in the adult adrenal medulla contributes to this plasticity. These glia-like cells have features of adrenomedullary sustentacular cells, are multipotent, and are able to differentiate into chromaffin cells and neurons. The adrenal is central to the body's response to stress making its proper adaptation critical to maintaining homeostasis. Our results from stress experiments in vivo show the activation and differentiation of these progenitors into new chromaffin cells. In summary, we demonstrate the involvement of a new glia-like multipotent stem cell population in adrenal tissue adaptation. Our data also suggest the contribution of stem and progenitor cells in the adaptation of neuroendocrine tissue function in general.

0171 : Contribution of progenitor cells sharing some serotonergic proteins in the pathophysiology of human aortic and mitral valves degeneration

Many compounds (pergolide, fenfluramine, ectasy) were described as inducers of fibrotic valvular lesions. All these compounds share in common to activate the 5HT2B serotonergic receptor. This observation leads to the hypothesis that cardiac valves express a « serotonergic system » that could be activated by serotonin (5-HT) or 5-HT receptor (5-HTR) agonists. In this work, we characterized the expression pattern of 5-HT2A, 2B, 4 R and the 5- HT transporter (SERT) in whole and cell subpopulations of 30 human mitral and aortic valves collected at the time of surgical valve replacement (Aortic: 11 calcified, 5 sclerotic, 4 bicuspid; Mitral: 12 dystrophic). All samples express 5HT2A, 2B, 4 R and SERT, the amount of 5HT2B R mRNA being higher than the 5HT2A R whatever the valve and etiology. 5HT2BR expression is found in endothelial cells (CD31+) at the valve surface, but also inside valve lesions, expressed by interstitial cells (smooth muscle α-actin and vimentin positive cells) located in an abundant glycosaminoglycan matrix. In fact, fibromyxoid lesions and calcified aortic valves express a high amount of CD34+ cells. These cells are endothelial progenitors because they express VEGFR2 and eNOS together with 5-HT2R. After collagenase treatment, valve samples were labeled with CD31 and CD34 antibodies: 60.1 (± 11) % of all mitral valvular cells are CD34+ compared to 36.1 (±8) % of aortic valvular cells (FACS analysis and sorting). To summarize, 5HT2A, 2B, 4 receptors and SERT are expressed in aortic and mitral diseased valves. The amounts of 5HT2A, 2B R mRNA are equivalent between mitral and aortic valves. High amount of CD34+ endothelial progenitors, expressing 5HT2AR and 5HT2BR, are found in degenerated valves. The contribution of the two 5-HT2 receptors and endothelial progenitors in valve degeneration is now under investigation.

A multipotent stem cell population in the adult adrenal medulla mediates stress response

The neural crest derived adrenal medulla is closely related to the sympathetic nervous system; however, unlike neural tissue, it is characterized by high plasticity which suggests the involvement of stem cells. In this study, by using two transgenic mouse models, Nestin-GFP and the inducible Nestin-CreER:Rosa26YFP, we define a pool of multipotent glia-like nestin-GFP expressing progenitor cells in the adult adrenal medulla, which contribute to its plasticity. The adrenal plays a central role in response to stress. However, the role of adrenomedullary progenitor cells in stress adaptation has not been studied so far. Our results from stress experiments in vivo show the activation and differentiation of these progenitors into new chromaffin cells. In summary, we demonstrate the involvement of a new glia-like multipotent stem cell population in adrenal tissue adaptation. Our data also suggest the contribution of stem and progenitor cells in the adaptation of neuroendocrine tissue function in general.

Prospective heterotopic ossification progenitors in adult human skeletal muscle

Skeletal muscle has strong regenerative capabilities. However, failed regeneration can lead to complications where aberrant tissue forms as is the case with heterotopic ossification (HO), in which chondrocytes, osteoblasts and white and brown adipocytes can arise following severe trauma. In humans, the various HO cell types likely originate from multipotent mesenchymal stromal cells (MSCs) in skeletal muscle, which have not been identified in humans until now. In the present study, adherent cells from freshly digested skeletal muscle tissue were expanded in defined culture medium and were FACS-enriched for the CD73+CD105+CD90− population, which displayed robust multilineage potential. Clonal differentiation assays confirmed that all three lineages originated from a single multipotent progenitor. In addition to differentiating into typical HO lineages, human muscle resident MSCs (hmrMSCs) also differentiated into brown adipocytes expressing uncoupling protein 1 (UCP1). Characterizing this novel multipotent hmrMSC population with a brown adipocyte differentiation capacity has enhanced our understanding of the contribution of non-myogenic progenitor cells to regeneration and aberrant tissue formation in human skeletal muscle.

Progenitor/stem cells in renal regeneration and mass lesions.

Adult kidneys have limited regenerative capacity following a prominent acute kidney injury. As understanding regenerative mechanisms is the key to discovering therapeutic strategies for preventing and treating renal diseases, in recent years, researchers have hotly debated whether progenitor/stem cells offer a support system for renal repair. The Romagnani-led group identified CD133 stem cells in the parietal epithelium and renal tubules, and their data indicate that these progenitor/stem cells support renal repair in the glomeruli and renal tubules. The Humphreys and Bonventre group used the lineage-tracing technique. They observed no contribution of progenitor cells to tubular repair, but they later reported that the differentiated tubular cells responsible for tubular repair actually gained some characteristics of progenitor cells. This review article will focus on major updates regarding the controversial progenitor/stem cells in renal regeneration and highlight some new progenitor cell issues in renal mass lesions.

A34 Session 10: Adjunctive Therapeutic Approaches: Vascular targeting approaches to enhance thermal therapy applications

The physiological reaction of tumor tissue and the progression of normal vascular and cellular repair processes in the body after thermal ablation suggest specific ways that adjuvant therapies may improve tumor control. This is a topic of growing importance as thermal ablation techniques are being used more than ever yet continue to have significant and unpredictable recurrence rates in clinical settings. We hypothesized that incomplete ablation of tumor tissue near the margin and around major blood vessels allows re-oxygenation and repopulation of the tumor. Microvessel functionality after partial thermal ablation of experimental murine tumors has been investigated after both high and low temperature thermal ablations. Interestingly, the oxygenation in the tumor margin increased from 1.2 ± 0.98 mmHg to 10.4 ± 6.3 mmHg during and for the first 20–30 min after a typical hot or cold ablation session, suggesting that the vascular response is a common feature to all of ablative medicine. Vessels with active blood flow in the peripheral regions of the tumor were seen to persist at varying levels from 24–72 h post-ablation. The level of hypoxia detected by pimonidazole binding was inversely related to the number of functional vessels detected. Our results suggest that simultaneous or tightly sequenced ablation and ionizing radiation therapy may have merit as an efficient means to completely sterilize tumor volume since radiation is most cytotoxic in areas of improved oxygenation and ablation most effectively debulks volumes with low or impaired perfusion. Furthermore, nanomedicine or other vascular-targeted drugs that can selectively impair the vasculature of the tumor may significantly increase the volume of complete ablation obtained and improve reproducibility of the ablation zone from tumor to tumor. A vascular sensitizing/damaging agent may also increase the overall effect of radiotherapy and thus improve tumor control. We have also documented a contribution of progenitor cells in repairing sublethally damaged tissue after ablation and promoting establishment of a vascular niche capable of regenerating the tumor mass which suggests agents that block the mobilization of bone marrow derived cells could also serve to improve the results of thermal ablative therapy for a variety of tumor types. These aspects of combined treatments will be discussed for both high temperature ablations and cryosurgery. Supported by NCI CA44114, Arkansas Breast Cancer Research Program and the Winthrop P. Rockefeller Cancer Institute at UAMS.

Endothelial progenitor cells contribute to the development of ovarian carcinoma tumor blood vessels.

Only a few studies in the literature have reported the contribution of endothelial progenitor cells (EPCs) in ovarian tumors, and with regard to malignant tumors, the data on the pre-existing endothelium insertion rate and the extent to which these cells contribute to tumor angiogenesis is controversial. The present study demonstrated the existence of EPCs and evaluated the expression of two markers, AC133 (also known as cluster of differentiation 133 or prominin) and tyrosine kinase with immunoglobulin-like and EGF-like domains 2 (Tie2), signaling the presence of EPCs in the pre-existing endothelium. In total, 62 female patients who were diagnosed with ovarian tumors were retrospectively selected over a four-year period. Immunohistochemical analyses used Tie2 and AC133 as primary antibodies. In total, 27.4% of ovarian tumor cases expressed AC133 and Tie2 in blood vessel endothelial cells. The expression of these two markers did not correlate with the clinicopathological prognostic parameters, histological type, vascular microdensity or vessel type. The expression of AC133 and Tie2 in blood vessel endothelial cells contributes to angiogenesis progression in cases where the budding process is reduced or absent, as shown by the inverse correlation with the rate of proliferation of the endothelial cells.

Skin Progenitor Cells Contribute to Bleomycin‐Induced Skin Fibrosis

The origin of the cells that contribute to skin fibrosis is unclear. We undertook the present study to assess the contribution of Sox2-expressing skin progenitor cells to bleomycin-induced scleroderma. Scleroderma was induced, by bleomycin administration, in wild-type mice and in mice in which CCN2 was deleted from Sox2-expressing cells. Lineage tracing analysis was performed to assess whether cells expressing Sox2 are recruited to fibrotic lesions in response to bleomycin-induced scleroderma. In response to bleomycin, Sox2-positive/α-smooth muscle actin-positive cells were recruited to fibrotic tissue. CCN2-conditional knockout mice in which CCN2 was deleted from Sox2-expressing cells exhibited resistance to bleomycin-induced skin fibrosis. Collectively, these results indicate that CCN2 is required for the recruitment of progenitor cells and that CCN2-expressing progenitor cells are essential for bleomycin-induced skin fibrosis. Lineage tracing analysis using mice in which a tamoxifen-dependent Cre recombinase was expressed under the control of the Sox2 promoter confirmed that progenitor cells were recruited to the fibrotic lesion in response to bleomycin, and that this did not occur in CCN2-knockout mice. The ability of serum to induce α-smooth muscle actin expression in skin progenitor cells required the presence of CCN2. Sox2-positive skin progenitor cells are required in order for bleomycin-induced skin fibrosis to occur, and CCN2 is required for the recruitment of these cells to the fibrotic lesion. Targeting stem cell recruitment or CCN2 may therefore represent a useful therapeutic approach in combating fibrotic skin disease.