Human adipose tissue-derived stromal cells act as functional pericytes in mice and suppress high-glucose-induced proinflammatory activation of bovine retinal endothelial cells.

AIMS/HYPOTHESIS: The immunomodulatory capacity of adipose tissue-derived stromal cells (ASCs) is relevant for next-generation cell therapies that aim to reverse tissue dysfunction such as that caused by diabetes. Pericyte dropout from retinal capillaries underlies diabetic retinopathy and the subsequent aberrant angiogenesis. METHODS: We investigated the pericytic function of ASCs after intravitreal injection of ASCs in mice with retinopathy of prematurity as a model for clinical diabetic retinopathy. In addition, ASCs influence their environment by paracrine signalling. For this, we assessed the immunomodulatory capacity of conditioned medium from cultured ASCs (ASC-Cme) on high glucose (HG)-stimulated bovine retinal endothelial cells (BRECs). RESULTS: ASCs augmented and stabilised retinal angiogenesis and co-localised with capillaries at a pericyte-specific position. This indicates that cultured ASCs exert juxtacrine signalling in retinal microvessels. ASC-Cme alleviated HG-induced oxidative stress and its subsequent upregulation of downstream targets in an NF-κB dependent fashion in cultured BRECs. Functionally, monocyte adhesion to the monolayers of activated BRECs was also decreased by treatment with ASC-Cme and correlated with a decline in expression of adhesion-related genes such as SELE, ICAM1 and VCAM1. CONCLUSIONS/INTERPRETATION: The ability of ASC-Cme to immunomodulate HG-challenged BRECs is related to the length of time for which ASCs were preconditioned in HG medium. Conditioned medium from ASCs that had been chronically exposed to HG medium was able to normalise the HG-challenged BRECs to normal glucose levels. In contrast, conditioned medium from ASCs that had been exposed to HG medium for a shorter time did not have this effect. Our results show that the manner of HG preconditioning of ASCs dictates their immunoregulatory properties and thus the potential outcome of treatment of diabetic retinopathy.

Diet-induced obesity resistance of adult female mice selectively bred for increased wheel-running behavior is reversed by single perinatal exposure to a high-energy diet.

Female mice from independently bred lines previously selected over 50 generations for increased voluntary wheel-running behavior (S1, S2) resist high energy (HE) diet-induced obesity (DIO) at adulthood, even without actual access to running wheels, as opposed to randomly bred controls (CON). We investigated whether adult S mice without wheels remain DIO-resistant when exposed - via the mother - to the HE diet during their perinatal stage (from 2 weeks prior to conception until weaning on post-natal day 21). While S1 and S2 females subjected to HE diet either perinatally or from weaning onwards (post-weaning) resisted increased adiposity at adulthood (as opposed to CON females), they lost this resistance when challenged with HE diet during these periods combined over one single cycle of breeding. When allowed one-week access to wheels (at week 6-8 and at 10 months), however, tendency for increased wheel-running behavior of S mice was unaltered. Thus, the trait for increased wheel-running behavior remained intact following combined perinatal and post-weaning HE exposure, but apparently this did not block HE-induced weight gain. At weaning, perinatal HE diet increased adiposity in all lines, but this was only associated with hyperleptinemia in S lines irrespective of gender. Because leptin has multiple developmental effects at adolescence, we argue that a trait for increased physical activity may advance maturation in times of plenty. This would be adaptive in nature where episodes of increased nutrient availability should be exploited maximally. Associated disturbances in glucose homeostasis and related co-morbidities at adulthood are probably pleiotropic side effects.

Extracellular matrix components of adipose derived stromal cells promote alignment, organization, and maturation of cardiomyocytes in vitro.

Adipose derived stromal cells (ADSC) are relevant therapeutic agents to treat myocardial infarction (MI) in clinical trials. Soluble factors secreted by ADSC, such as growth factors and cytokines, suppress inflammation and apoptosis while promoting angiogenesis and the proliferation of cardiomyocytes (CM). Moreover, ADSC synthesize extracellular matrix (ECM) components into the intercellular space which might contribute to their therapeutic capacity. Thus, ADSC might directly modulate the post-MI microenvironment through a combination of paracrine and juxtacrine signaling. In this study, the juxtacrine role of ADSC and ADSC-derived ECM on the organization and maturation of CM was investiagated. Human ADSC synthesized and deposited a heterogenous and complex mixture of ECM components such as collagen I, III, IV, fibronectin, elastin as well as the matricellular protein periostin. Cocultures of rodent CM with human ADSC or with human ADSC-derived ECM components enhanced the cardiomyocyte alignment, their intercellular connections and the maturation of their sarcomeres, while the proliferation rate of the CM was increased and their level of hypertrophy reduced. The use of human ADSC-derived ECM could serve both to augment in vitro tissue-engineered myocardial constructs and to improve myocardial remodeling after infarction.

Adipose tissue-derived stromal cells inhibit TGF-ß1-induced differentiation of human dermal fibroblasts and keloid scar-derived fibroblasts in a paracrine fashion.

BACKGROUND: Adipose tissue-derived stromal cells augment wound healing and skin regeneration. It is unknown whether and how they can also influence dermal scarring. The authors hypothesized that adipose tissue-derived stromal cells inhibit adverse differentiation of dermal fibroblasts induced by the pivotal factor in scarring, namely, transforming growth factor (TGF)-ß. METHODS: TGF-ß1-treated adult human dermal fibroblasts and keloid scar-derived fibroblasts were incubated with adipose tissue-derived stromal cell-conditioned medium and assessed for proliferation and differentiation, particularly the production of collagen, expression of SM22α, and development of hypertrophy and contractility. RESULTS: TGF-ß1-induced proliferation of adult human dermal fibroblasts was abolished by adipose tissue-derived stromal cell-conditioned medium. Simultaneously, the medium reduced SM22α gene and protein expression of TGF-ß1-treated adult human dermal fibroblasts, and their contractility was reduced also. Furthermore, the medium strongly reduced transcription of collagen I and III genes and their corresponding proteins. In contrast, it tipped the balance of matrix turnover to degradation through stimulating gene expression of matrix metalloproteinase (MMP)-1, MMP-2, and MMP-14, whereas MMP-2 activity was up-regulated also. Even in end-stage myofibroblasts (i.e., keloid scar-derived fibroblasts), adipose tissue-derived stromal cell-conditioned medium suppressed TGF-ß1-induced myofibroblast contraction and collagen III gene expression. CONCLUSION: The authors show that adipose tissue-derived stromal cells inhibit TGF-ß1-induced adverse differentiation and function of adult human dermal fibroblasts and TGF-ß1-induced contraction in keloid scar-derived fibroblasts, in a paracrine fashion.

Pericytes in the eye.

Pericytes in the retina differ from pericytes in many other organs by their high density and their cooperative role in the neurovascular unit. Their diverse ontogeny and the fact that not one pericyte marker identifies the entire population suggest also functional plurality in the retina, including invading cells of mesenchymal origin. Further, to establish factors determining pericyte recruitment, modifiers of pericyte adhesion and homeostasis, such as notch-3 and angptl-4, have been recently identified, expanding the understanding of pericyte function in the retina. Also, the role of pericytes as part of the neurovascular unit has been appreciated, given that the neuroglia determines pericyte survival and motility under disease conditions. Pericyte dropout is not unique in the diabetic retina, and non-diabetic animal models may prove useful in the search for mechanisms involved in disease-associated dysfunction of the neurovascular unit.

Mesenchymal stem cells: promising for myocardial regeneration?

The pandemic of cardiovascular disease is continuously expanding as the result of changing life styles and diets throughout the Old and New World. Immediate intervention therapy saves the lives of many patients after acute myocardial infarction (MI). However, for many this comes at the price of adverse cardiac remodeling and heart failure. Currently, no conventional therapy can prevent the negative aftermath of MI and alternative treatments are warranted. Therefore, cardiac stem cell therapy has been put forward over the past decade, albeit with modest successes. Mesenchymal Stem Cells (MSC) are promising because these are genuine cellular factories of a host of secreted therapeutic factors. MSC are obtained from bone marrow or adipose tissue (ADSC). However, the heart itself also contains mesenchymal- like stem cells, though more difficult to acquire than ADSC. Interestingly, mesenchymal cells such as fibroblasts can be directly or indirectly reprogrammed to all myocardial cell types that require replacement after MI. To date, the paracrine and juxtacrine mechanisms of ADSC and other MSC on vessel formation are best understood. The preconditioning of, otherwise naive, stem cells is gaining more interest: previously presumed deleterious stimuli such as hypoxia and inflammation, i.e. causes of myocardial damage, have the opposite effect on mesenchymal stem cells. MSC gain a higher therapeutic capacity under hypoxia and inflammatory conditions. In this review, mesenchymal stem cells and their working mechanisms are put into the perspective of clinical cardiac stem cell therapy.

Adipose stromal cells primed with hypoxia and inflammation enhance cardiomyocyte proliferation rate in vitro through STAT3 and Erk1/2.

BACKGROUND: Experimental clinical stem cell therapy has been used for more than a decade to alleviate the adverse aftermath of acute myocardial infarction (aMI). The post-infarcted myocardial microenvironment is characterized by cardiomyocyte death, caused by ischemia and inflammation. These conditions may negatively affect administered stem cells. As postnatal cardiomyocytes have a poor proliferation rate, while induction of proliferation seems even more rare. Thus stimulation of their proliferation rate is essential after aMI. In metaplastic disease, the pro-inflammatory cytokine interleukin-6 (IL-6) has been identified as potent mediators of the proliferation rate. We hypothesized that IL-6 could augment the proliferation rate of (slow-)dividing cardiomyocytes. METHODS: To mimic the behavior of therapeutic cells in the post-infarct cardiac microenvironment, human Adipose Derived Stromal Cells (ADSC) were cultured under hypoxic (2% O2) and pro-inflammatory conditions (IL-1ß) for 24h. Serum-free conditioned medium from ADSC primed with hypoxia and/or IL-1ß was added to rat neonatal cardiomyocytes and adult cardiomyocytes (HL-1) to assess paracrine-driven changes in cardiomyocyte proliferation rate and induction of myogenic signaling pathways. RESULTS: We demonstrate that ADSC enhance the proliferation rate of rat neonatal cardiomyocytes and adult HL-1 cardiomyocytes in a paracrine fashion. ADSC under hypoxia and inflammation in vitro had increased the interleukin-6 (IL-6) gene and protein expression. Similar to conditioned medium of ADSC, treatment of rat neonatal cardiomyocytes and HL-1 with recombinant IL-6 alone also stimulated their proliferation rate. This was corroborated by a strong decrease of cardiomyocyte proliferation after addition of IL-6 neutralizing antibody to conditioned medium of ADSC. The stimulatory effect of ADSC conditioned media or IL-6 was accomplished through activation of both Janus Kinase-Signal Transducer and Activator of Transcription (JAK/STAT) and Mitogen-Activated Protein (MAP) kinases (MAPK) mitogenic signaling pathways. CONCLUSION: ADSC are promising therapeutic cells for cardiac stem cell therapy. The inflammatory and hypoxic host post-MI microenvironment enhances the regenerative potential of ADSC to promote the proliferation rate of cardiomyocytes. This was achieved in paracrine manner, which warrants the development of ADSC conditioned medium as an "of-the-shelf" product for treatment of post-myocardial infarction complications.