Tissue-resident Mesenchymal Stem Cells Research Articles

Matricellular Protein Periostin Promotes Pericyte Migration in Fibrotic Airways.

Introduction: Periostin is a matricellular protein that is currently used as a biomarker for asthma. However, its contribution to tissue remodeling in allergic asthma is currently unknown. We have previously demonstrated that tissue-resident mesenchymal stem cells known as pericytes are a key cell type involved in airway remodeling. This is thought to be caused the uncoupling of pericytes from the microvasculature supporting the large airways, facilitated by inflammatory growth factors and cytokines. It is hypothesized that periostin may be produced by profibrotic pericytes and contribute to the remodeling observed in allergic asthma.Methods: Lung sections from mice with allergic airway disease driven by exposure to house dust mite (HDM) were stained using an anti-periostin antibody to explore its involvement in fibrotic lung disease. Human pericytes were cultured in vitro and stained for periostin to assess periostin expression. Migration assays were performed using human pericytes that were pretreated with TGF-β or periostin. ELISAs were also carried out to assess periostin expression levels in bronchoalveolar lavage fluid as well as the induction of periostin production by IL-13.Results: Immunostaining indicated that pericytes robustly express periostin, with increased expression following treatment with TGF-β. Migration assays demonstrated that pericytes treated with periostin were more migratory. Periostin production was also increased in HDM exposed mice as well as in cultured pericytes treated with IL-13.Conclusion: Periostin is produced by pericytes in response to TGF-β or IL-13, and periostin plays a key role in inducing pericyte migration. The increase in periostin expression in TGF-β or IL-13 treated pericytes suggests that IL-13 may trigger periostin production in pericytes whilst TGF-β modulates periostin expression to promote pericyte migration in the context of tissue fibrosis.

Impairment of Tissue-Resident Mesenchymal Stem Cells in Chronic Ulcerative Colitis and Crohn's Disease.

Little is known about the presence and function of tissue-resident mesenchymal stem cells [MtSCs] within the gastrointestinal mucosa in health and inflammatory bowel disease [IBD]. The contribution of MtSCs to the generation of inflammatory fibroblasts during IBD is also poorly understood. We hypothesized that IBD-MtSCs are impaired and contribute to the generation of the pathological myofibroblasts in IBD. In a cohort of clinically and endoscopically active IBD patients and normal controls, we used quantitative RT-PCR and stem cell differentiation assays, as well as confocal microscopy, to characterize MtSCs. Expression of two stem cell markers, Oct4 and ALDH1A, was increased in the inflamed IBD colonic mucosa and correlated with an increase of the mesenchymal lineage marker Grem1 in ulcerative colitis [UC], but not Crohn's disease [CD]. Increased proliferation and aberrant differentiation of Oct4+Grem1+ MtSC-like cells was observed in UC, but not in CD colonic mucosa. In contrast to normal and UC-derived MtSCs, CD-MtSCs lose their clonogenic and most of their differentiation capacities. Our data also suggest that severe damage to these cells in CD may account for the pathological PD-L1low phenotype of CD myofibroblasts. In contrast, aberrant differentiation of MtSCs appears to be involved in the appearance of pathological partially differentiated PD-L1high myofibroblasts within the inflammed colonic mucosa in UC. Our data show, for the first time, that the progenitor functions of MtSCs are differentially impaired in CD vs UC, providing a scientific rationale for the use of allogeneic MSC therapy in IBD, and particularly in CD.

1690-P: In Vitro Differentiation of Pancreas-Derived Mesenchymal Stem Cells into Insulin-Producing Beta Cells

Differentiation of insulin-producing cells (IPCs) from stem cells has been widely studied as an alternative source for cell transplantation therapy in diabetes. Mesenchymal stem cells (MSCs) are a useful therapeutic option for islet transplants due to their immunomodulatory properties and differentiation potential. In this study, we introduce a method for in vitro differentiation of pancreatic MSCs into IPCs. Research-grade pancreas from cadaveric donors was used to isolate islets, and the COBE remnant after islet purification was used for the generation of pancreatic MSCs. The remnant tissue was cultured in RPMI medium and plastic to isolate tissue-resident MSCs. Surface marker expression analysis and differentiation assays were performed to characteristically confirm that the cells obtained were in fact MSCs. Osteogenic, adipogenic and chondrogenic differentiation of MSCs were induced by StemPro® differentiation kits. The protocol for the differentiation of IPCs from stem cells was adopted from Pagliuca et al. 2014. Similarly, we have treated the pancreatic MSCs with molecules and growth factors at different stages of development to produce IPCs. The insulin secretion from differentiated IPCs also analyzed at all stages. The culture of remnant tissue after islet isolation resulted in plastic-adherent cells of fibroblast-like morphology after 3 passages. Flow cytometry analysis showed homogeneous expression of markers (CD90, CD73, CD29, CD105) and negative expression of CD14, CD34, and CD45 as classically characterized by cultured MSCs. Interestingly, there was a significant increase in insulin levels up to 5 and 100 folds in the media at developmental stages S5 (P= 0.0686) and S6 (P <0.0001) respectively. Our results reveal that MSCs can be directly differentiated into IPCs. Human pancreas-derived MSCs may serve as an alternative source of insulin-producing beta cells that can be transplanted to type 1 diabetes patients. Disclosure J. Kalivarathan: None. P. Saravanan: None. M.F. Levy: None. M.A. Kanak: None.

Genetic and epigenetic stability of stem cells: Epigenetic modifiers modulate the fate of mesenchymal stem cells

Stem cell research has progressed widely and has been receiving a considerable attention for its advantages and drawbacks. Despite their extensive therapeutic potential in regenerative medicine, they are debatable for their genetic and epigenetic stability. In fact lineage specific differentiation is mediated via epigenetic changes in DNA methylation, acetylation, histone modifications etc. Thus epigenetics plays an important role in stem cell biology. For therapeutic interventions stem cells need to be genetically and epigenetically stable for their maximum paracrine secretions for bringing about expected tissue repair and regeneration. In this review we have focused on the current status of genetic and epigenetic stability in stem cells and their importance in regenerative medicine. We have also touched upon the possibility of considering tissue resident mesenchymal stem cells as epigenetic modifiers. This is likely to open a new era in stem cell therapeutic intervention by reversing disease inducing epigenetic changes.

Improved Isolation of Human Vascular Wall-Resident Mesenchymal Stem Cells.

Niches for tissue-resident mesenchymal stem cells (MSCs) have been identified in many adult tissues. In particular, MSCs residing in the vascular stem cell niche came into focus: the so-called vascular wall-resident MSCs (VW-MSCs) were, based upon their anatomic location, (1) distributed throughout the adult organism, and (2) supposed to be the first line cells which could be addressed in response to a pathologic trigger acting on or in close vicinity to the vascular system. Like tissue-resident MSCs in general, VW-MSC contribute to organ integrity and harbor the capacity to suppress inflammation and promote repair during normal vessel homeostasis, although resident MSCs present in the healthy situation of an individual seems not to bear sufficient for protection or repair following injury. In contrast, injury affected MSCs could contribute to disease induction and progression. A detailed understanding of the molecular repertoire as well as of the signaling pathways controlling stem cell fate of VW-MSCs is prerequisite to understand how (1) endogenous VW-MSCs contribute to normal vessel homeostasis as well as diseases that include the vascular system, (2) a potential on-site manipulation of these cells directly within their endogenous niche could be used for therapeutically benefits, and (3) isolated and therapeutically applied VW-MSCs in terms of exogenous MSCs with superior repair capabilities might be logically more efficient to address vascular diseases than MSCs derived from other tissues. This chapter describes a straightforward protocol for the improved isolation of human VW-MSCs.

Elevated BMP and Mechanical Signaling Through YAP1/RhoA Poises FOP Mesenchymal Progenitors for Osteogenesis.

Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disease characterized by the formation of extraskeletal bone, or heterotopic ossification (HO), in soft connective tissues such as skeletal muscle. All familial and sporadic cases with a classic clinical presentation of FOP carry a gain-of-function mutation (R206H; c.617 G > A) in ACVR1, a cell surface receptor that mediates bone morphogenetic protein (BMP) signaling. The BMP signaling pathway is recognized for its chondro/osteogenic-induction potential, and HO in FOP patients forms ectopic but qualitatively normal endochondral bone tissue through misdirected cell fate decisions by tissue-resident mesenchymal stem cells. In addition to biochemical ligand-receptor signaling, mechanical cues from the physical environment are transduced to activate intracellular signaling, a process known as mechanotransduction, and can influence cell fates. Utilizing an established mesenchymal stem cell model of mouse embryonic fibroblasts (MEFs) from the Acvr1R206H/+ mouse model that mimics the human disease, we demonstrated that activation of the mechanotransductive effectors Rho/ROCK and YAP1 are increased in Acvr1R206H/+ cells. We show that on softer substrates, a condition associated with low mechanical signaling, the morphology of Acvr1R206H/+ cells is similar to the morphology of control Acvr1+/+ cells on stiffer substrates, a condition that activates mechanotransduction. We further determined that Acvr1R206H/+ cells are poised for osteogenic differentiation, expressing increased levels of chondro/osteogenic markers compared with Acvr1+/+ cells. We also identified increased YAP1 nuclear localization in Acvr1R206H/+ cells, which can be rescued by either BMP inhibition or Rho antagonism. Our results establish RhoA and YAP1 signaling as modulators of mechanotransduction in FOP and suggest that aberrant mechanical signals, combined with and as a result of the increased BMP pathway signaling through mutant ACVR1, lead to misinterpretation of the cellular microenvironment and a heightened sensitivity to mechanical stimuli that promotes commitment of Acvr1R206H/+ progenitor cells to chondro/osteogenic lineages.

Impact of HIV/simian immunodeficiency virus infection and viral proteins on adipose tissue fibrosis and adipogenesis

HIV-infected patients receiving antiretroviral treatment (ART) often present adipose tissue accumulation and/or redistribution. adipose tissue has been shown to be an HIV/SIV reservoir and viral proteins as Tat or Nef can be released by infected immune cells and exert a bystander effect on adipocytes or precursors. Our aim was to demonstrate that SIV/HIV infection per se could alter adipose tissue structure and/or function. Morphological and functional alterations of subcutaneous (SCAT) and visceral adipose tissue (VAT) were studied in SIV-infected macaques and HIV-infected ART-controlled patients. To analyze the effect of Tat or Nef, we used human adipose stem cells (ASCs) issued from healthy donors, and analyzed adipogenesis and extracellular matrix component production using two dimensional (2D) and three-dimensional (3D) culture models. Adipocyte size and index of fibrosis were determined on Sirius red-stained adipose tissue samples. Proliferating and adipocyte 2D-differentiating or 3D-differentiating ASCs were treated chronically with Tat or Nef. mRNA, protein expression and secretion were examined by RT-PCR, western-blot and ELISA. SCAT and VAT from SIV-infected macaques displayed small adipocytes, decreased adipogenesis and severe fibrosis with collagen deposition. SCAT and VAT from HIV-infected ART-controlled patients presented similar alterations. In vitro, Tat and/or Nef induced a profibrotic phenotype in undifferentiated ASCs and altered adipogenesis and collagen production in adipocyte-differentiating ASCs. We demonstrate here a specific role for HIV/SIV infection per se on adipose tissue fibrosis and adipogenesis, probably through the release of viral proteins, which could be involved in adipose tissue dysfunction contributing to cardiometabolic alterations of HIV-infected individuals.

Radiation-induced sensitivity of tissue-resident mesenchymal stem cells in the head and neck region.

Tissue-resident mesenchymal stem cells (MSCs) possess the ability to migrate to areas of inflammation and promote the regeneration of damaged tissue. However, it remains unclear how radiation influences this capacity of MSC in the head and neck region. Two types of MSCs of the head and neck region (mucosa [mMSC] and parotid gland [pMSC]) were isolated, cultured and exposed to single radiation dosages of 2 Gy/day up to 10 days. Effects on morphology, colony forming ability, apoptosis, chemokine receptor expression, cytokine secretion, and cell migration were analyzed. Although MSC preserved MSC-specific regenerative abilities and immunomodulatory properties following irradiation in our in vitro model, we found a deleterious impact on colony forming ability, especially in pMSC. MSC exhibited robustness and activation upon radiation for the support of tissue regeneration, but lost their potential to replicate, thus possibly leading to depletion of the local MSC-pool after irradiation.

Characterisation and immunosuppressive activity of human cartilage-derived mesenchymal stem cells.

Mesenchymal stem cells (MSCs) exert potent immuno-regulatory activities on various immune cells and also differentiate into various mesodermal lineages besides retaining a distinct self-renewal ability. Such exclusive characteristics had enabled MSCs to be recognised as an ideal source for cell-based treatment in regenerative medicine and immunotherapy. Thus, considering MSCs for treating degenerative disease of organs with limited regenerative potential such as cartilage would serve as an ideal therapy. This study explored the feasibility of generating human cartilage-derived MSCs (hC-MSCs) from sports injured patients and characterised based on multipotent differentiation and immunosuppressive activities. Cartilage tissues harvested from a non-weight bearing region during an arthroscopy procedure were used to generate MSCs. Despite the classic morphology of fibroblast-like cells and a defined immunophenotyping, MSCs expressed early embryonic transcriptional markers (SOX2, REX1, OCT4 and NANOG) and differentiated into chondrocytes, adipocytes and osteocytes when induced accordingly. Upon co-culture with PHA-L activated T-cells, hC-MSCs suppressed the proliferation of the T-cells in a dose-dependent manner. Although, hC-MSCs did not alter the activation profile of T cells significantly, yet prevented the entering of activated T cells into S phase of the cell cycle by cell cycle arrest. The present study has strengthened the evidence of tissue-resident mesenchymal stem cells in human cartilage tissue. The endogenous MSCs could be an excellent tool in treating dysregulated immune response that associated with cartilage since hC-MSCs exerted both immunosuppressive and regenerative capabilities.

Significance of CD34 Negative Hematopoietic Stem Cells and CD34 Positive Mesenchymal Stem Cells - A Valuable Dimension to the Current Understanding.

The strategy to expand CD34+ hematopoietic stem cells (HSCs) is being increasingly practiced to meet the demand for a higher cell dose. This is for hematopoietic reconstitution in patients with higher body weights. Interestingly, literature reports show that CD34- (CD34 negative) cell population also possesses the potential to reconstitute the bone marrow & in a certain phase, converts them into CD34+ phenotype. The current practice of positive selection of CD34+ HSCs by eliminating rest of the (CD34-) population for expansion could probably pose a risk of losing valuable HSCs with good reconstitution potentials. MSCs (Mesenchymal Stem Cells) hold great promise for use in various regenerative medicine applications. International Society for Cellular Therapy (ISCT) defined MSCs to be CD34 negative; tissue resident MSCs and peripheral blood-derived MSCs express CD34 on their surface even in vitro, though up to limited passages. This interesting observation of CD34 positive expression displayed in vivo by non-hematopoietic cell types such as MSCs was intriguing, thus prompting a detailed review of its significance, if any. Based on an extensive review, we strongly believe that CD34 expression in MSCs has some significant role in hematopoietic reconstitution & in regeneration of degenerated tissues. The concept of poor CD34 expression or stunted expression by certain MSCs should not be ignored. Several interesting research findings are in agreement with our assumption. However, it still leaves behind several unanswered questions that can only be addressed through detailed studies of phenotypic developmental pathways of MSCs.

What can target kidney fibrosis?

Fibrosis, a characteristic of all chronic kidney diseases, is now recognized to be an independent predictor of disease progression. Deposition of pathological matrix in the walls of glomerular capillaries, the interstitial space and around arterioles both predicts and contributes to functional demise of the nephron and its surrounding vasculature. Recent identification of the major cell populations of fibroblast precursors in the kidney interstitium as pericytes and tissue-resident mesenchymal stem cells, and in the glomerulus as podocytes, parietal epithelial and mesangial cells, has enabled the study of the fibrogenic process in much greater depth directly in the fibroblast precursors. These cells are not only matrix-producing cells, but are also important innate immune surveillance cells that regulate the inflammatory process, exacerbate tissue damage by release of radicals and cytokines, and contribute to parenchymal and microvascular dysfunction by aberrant wound-healing responses. Innate immune signaling in fibroblasts and their precursors is intimately intertwined with the process of fibrogenesis. In addition, genomic and genetic studies also point to defective responses in loci close to genes involved in solute transport, metabolism, autophagy, protein handling and vascular homeostasis, principally in the epithelium and endothelium, as upstream drivers of the fibrotic process, indicating that cellular crosstalk is vital for development of fibrosis. As we move beyond TGFβ inhibition as a central target for fibrosis, targeting innate immune signaling and metabolic dysfunction appear increasingly tenable alternative targets for novel therapies.

The Potential for Resident Lung Mesenchymal Stem Cells to Promote Functional Tissue Regeneration: Understanding Microenvironmental Cues

Tissue resident mesenchymal stem cells (MSCs) are important regulators of tissue repair or regeneration, fibrosis, inflammation, angiogenesis and tumor formation. Bone marrow derived mesenchymal stem cells (BM-MSCs) and endothelial progenitor cells (EPC) are currently being considered and tested in clinical trials as a potential therapy in patients with such inflammatory lung diseases including, but not limited to, chronic lung disease, pulmonary arterial hypertension (PAH), pulmonary fibrosis (PF), chronic obstructive pulmonary disease (COPD)/emphysema and asthma. However, our current understanding of tissue resident lung MSCs remains limited. This review addresses how environmental cues impact on the phenotype and function of this endogenous stem cell pool. In addition, it examines how these local factors influence the efficacy of cell-based treatments for lung diseases.

Positional Identity of Murine Mesenchymal Stem Cells Resident in Different Organs Is Determined in the Postsegmentation Mesoderm

Although mesenchymal stem cells (MSCs) of distinct tissue origin have a large number of similarities and differences, it has not been determined so far whether tissue-resident MSCs are the progenies of one ancestor cell lineage or the results of parallel cell developmental events. Here we compared the expression levels of 177 genes in murine MSCs derived from adult and juvenile bone marrow and adult adipose tissue, as well as juvenile spleen, thymus, and aorta wall by quantitative real-time polymerase chain reaction and the results were partially validated at protein level. All MSC lines uniformly expressed a large set of genes including well-known mesenchymal markers, such as α-smooth muscle actin, collagen type I α-chain, GATA6, Mohawk, and vimentin. In contrast, pluripotency genes and the early mesodermal marker T-gene were not expressed. On the other hand, different MSC lines consistently expressed distinct patterns of Hox genes determining the positional identity of a given cell population. Moreover, MSCs of different origin expressed a few other transcription factors also reflecting their topological identity and so the body segment or organ to which they normally contributed in vivo: (1) thymus-derived cells specifically expressed Tbx5 and Pitx2; (2) spleen-derived MSCs were characterized with Tlx1 and Nkx2.5; (3) Pitx1 designated femoral bone marrow cells and (4) En2 appeared in aorta wall-derived MSCs. Thus, MSCs exhibited topographic identity and memory even after long-term cultivation in vitro. On the basis of these results, we suggest that postnatal MSCs isolated from different anatomical sites descend from precursor cells developing in the postsegmentation mesoderm.

Aging alters tissue resident mesenchymal stem cell properties

Tissue resident mesenchymal stem cells (MSCs) are known to participate in tissue regeneration that follows cell turnover, apoptosis, or necrosis. It has been long known that aging impedes an organism's repair/regeneration capabilities. In order to study the age associated changes, the molecular characteristics of adipose tissue derived MSCs (ASCs) from three age groups of healthy volunteers i.e., young, middle aged, and aged were investigated. The number and multilineage differentiation potential of ASCs declined with age. Aging reduces the proliferative capacity along with increases in cellular senescence. A significant increase in quiescence of G2 and S phase was observed in ASCs from aged donors. The expression of genes related to senescence such as CHEK1 and cyclin-dependent kinase inhibitor p16 ink4a was increased with age, however genes of apoptosis were downregulated. Further, an age-dependent abnormality in the expression of DNA break repair genes was observed. Global microRNA analysis revealed an abnormal expression of mir-27b, mir-106a, mir-199a, and let-7. In ubiquitously distributed adipose tissue (and ASCs), aging brings about important alterations, which might be critical for tissue regeneration and homeostasis. Our findings therefore provide a better understanding of the mechanism(s) involved in stem cell aging and regenerative potential, and this in turn may affect tissue repair that declines with aging.

Isolation & characterization of Hoechst(low) CD45(negative) mouse lung mesenchymal stem cells.

Tissue resident mesenchymal stem cells (MSC) are important regulators of tissue repair or regeneration, fibrosis, inflammation, angiogenesis and tumor formation. Taken together these studies suggest that resident lung MSC play a role during pulmonary tissue homeostasis, injury and repair during diseases such as pulmonary fibrosis (PF) and arterial hypertension (PAH). Here we describe a technology to define a population of resident lung MSC. The definition of this population in vivo pulmonary tissue using a define set of markers facilitates the repeated isolation of a well-characterized stem cell population by flow cytometry and the study of a specific cell type and function.

Isolation & Characterization of Hoechst<sup>low</sup> CD45<sup>negative</sup> Mouse Lung Mesenchymal Stem Cells

Tissue resident mesenchymal stem cells (MSC) are important regulators of tissue repair or regeneration, fibrosis, inflammation, angiogenesis and tumor formation. Taken together these studies suggest that resident lung MSC play a role during pulmonary tissue homeostasis, injury and repair during diseases such as pulmonary fibrosis (PF) and arterial hypertension (PAH). Here we describe a technology to define a population of resident lung MSC. The definition of this population in vivo pulmonary tissue using a define set of markers facilitates the repeated isolation of a well-characterized stem cell population by flow cytometry and the study of a specific cell type and function.

Identification of Mesenchymal Stem Cells in Perinodular Fat and Skin in Dupuytren's Disease: A Potential Source of Myofibroblasts with Implications for Pathogenesis and Therapy

Dupuytren's disease (DD) is a fibroproliferative disorder characterized by aberrant proliferation of myofibroblasts, the source of which remains unknown. Recent studies indicate that circulating and tissue-resident mesenchymal stem cells (MSCs) can differentiate into myofibroblasts. Therefore, the aim of this study was to profile MSCs from phenotypically distinct DD sites including cord, nodule, skin overlying nodule (SON), and perinodular fat (PNF) compared with unaffected internal controls, that is, distant palmar fat (DPF) and transverse palmar fascia (Skoog's fibers) as well as external control carpal tunnel (CT) tissue including skin, fat, and fascia. Freshly isolated primary fibroblasts as well as cells grown up to passage 5 (P5) from DD (n=27) and CT (n=14) samples were analyzed for the presence of established MSC markers CD73, CD90, and CD105 and absence of hematopoietic marker CD34 using fluorescence-activated cell sorting, in-cell quantitative western blotting, immunohistochemistry, and immunocytochemistry. Freshly isolated cells from SON, PNF, and cord biopsies had a higher number of CD34(-)73(+)90(+)105(+) cells compared with Skoog's fibers and CT controls. P3 cells obtained from all DD biopsies compared with CT samples differentiated into osteocytes, adipocytes, and chondrocytes. P3 cord and nodule cells expressed intense α-smooth muscle actin staining compared with skin and fat cells. Stem cell markers including stem cell factor, MSC-homing marker CXCR4, and Wnt/β-catenin downregulator Dkk-1 were all upregulated in SON and PNF compared with CT skin and CT fat, respectively, as shown by real-time quantitative polymerase chain reaction. However, osteogenic marker OSF-1 had a significantly higher expression in the PNF (P=0.002) and cord (P=0.01) compared with the nodule. In conclusion, we have shown the presence of MSCs in specific DD tissue phenotypes compared with internal and external control tissue. These findings provide preliminary support for a potential alternative source of disease myofibroblasts originating from sites such as SON and PNF as opposed to palmar fascia alone.

Mesenchymal stem cells in transplantation and tissue regeneration

Mesenchymal stem cells in transplantation and tissue regeneration

Characterization of hematopoietic potential of mesenchymal stem cells

Mesenchymal and hematopoietic tissues are important reservoirs of adult stem cells. The potential of tissue resident mesenchymal stem cells (MSCs) to differentiate into cells of mesodermal and ectodermal lineages has been reported previously. We examined the hypothesis that adherent adipose tissue resident mesenchymal stem cells (ASCs) are capable of generating cells with hematopoietic characteristics. When cultured in differentiation media, clonally isolated ASCs develop into cells with hematopoietic attributes. The hematopoietic differentiated cells (HD) express early hematopoietic (c-kit, PROM1, CD4) as well as monocyte/macrophage markers (CCR5, CD68, MRC1, CD11b, CSF1R). Additionally, HD cells display functional characteristics of monocyte/macrophages such as phagocytosis and enzymatic activity of α-Naphthyl Acetate Esterase. HD cells are also responsive to stimulation by IL-4 and LPS as shown by increased CD14 and HLA-DRB1 expressions and release of IL-2, IL10, and TNF. Taken together, this study characterizes the potential of ASCs to generate functional macrophages in vitro, and therefore paves way for their possible use in cell therapy applications.

Tissue-resident mesenchymal stem cells attract peripheral blood neutrophils and enhance their inflammatory activity in response to microbial challenge

Human MSCs may respond to TLR ligation, and recent research has suggested that many tissues contain tissue-specific MSCs, possibly located in periendothelial and perivascular regions. At present, the functional consequences of these findings are unclear. We hypothesized that tissue-specific MSCs could play an instructional role during early phases of bacterial challenge. To investigate this hypothesis further, we set up a coculture system of glandular MSCs and peripheral blood neutrophils so that we could analyze the cellular interactions of these cells in response to LPS challenge. We found that stimulation with bacterial endotoxin induced chemokine receptor expression and mobility of MSCs. Activated MSCs secreted large amounts of inflammatory cytokines and recruited neutrophils in an IL-8- and MIF-dependent manner. Recruited and activated neutrophils showed a prolonged lifespan, an increased expression of inflammatory chemokines, and an enhanced responsiveness toward subsequent challenge with LPS. Our findings demonstrate a complex, functional interaction between tissue-resident MSCs and peripheral blood neutrophils upon bacterial challenge and suggest a role for MSCs in the early phases of pathogen challenge, when classical immune cells have not been recruited yet.