Immunobiology of stromal cells

Lucie PEDUTO, Team leader
Selene Di CARLO, Postdoc
Sarah ENOUZ, Postdoc
Sophie DULAUROY, Technician

Stromal cells in immunity and pathogenesis


Our team is interested in the cellular and molecular basis of tissue remodeling and inflammation, with a particular focus on the immunomodulatory role of stromal cells in the context of inflammatory diseases, fibrosis and tumor microenvironment.

Activated stromal cells are organizers in lymphoid tissue development and essential players in immunity. However chronic activation of stromal cells leads also to pathologies, through the generation of tertiary lymphoid tissues in chronic inflammatory disease, or production of excessive extracellular matrix and pro-inflammatory cytokines in fibrosis and tumors. To investigate the contribution of stromal cells to these pathologies, we are generating BAC-transgenic mice expressing reporter genes under control of particular chemokines, cytokines, cytokine receptors or proteases expressed by subsets of stromal cells with roles in immune development and chronic diseases. The transgenes we use also allow for the fate mapping of stromal cell subsets, their specific ablation in vivo, as well as gene manipulation in these stromal subsets.

Activated stromal cells are essential players in the development and organization of lymphoid tissues/ immunity. However persistent activation of stromal cells contribute to disease pathogenesis in chronic inflammatory diseases, fibrosis and tumors.


Stromal cells in immune development and inflammation

The immune system is composed of lymphoid and myeloid cells of hematopoietic origin that patrol the body for infection or injury. These immune mobile cells rely on signals produced by non-hematopoietic sessile cells, such as endothelial cells and a variety of ill-defined stromal cells including fibroblasts, perivascular cells and pericytes, to gain access to lymphoid tissues or injured/infected sites, and to form inflammatory aggregates. A distinct subset of stromal cells, called Lymphoid stromal (LS) cells, express structural chemokines, adhesion molecules and cytokines that are required to stabilize lymphoid tissues and play a central organizing role in the guidance and survival of leukocytes in lymphoid tissues. We have shown that LS cells are programmed during the fetal development of lymphoid tissues as well as in lymphocyte-rich organs such as the gut, and are re-induced by injury to organize lymphocyte recruitment in inflammatory lesions and tumors. They express the marker gp38 (podoplanin) and produce critical signals for leucocyte recruitment, survival and lymphangiogenesis. We are currently studying the cellular and molecular mechanisms that induce LS cells activation and expansion during inflammation, as well as the crosstalk with immune cells.

The generation of lymphoid stromal cells during ontogeny, inflammation and tumor progression. Lymph node anlagen were imaged at E16.5; LTi cells are in green. Inflammation is shown in the ear 3 days after injection of Complete Freund's Adjuvant. A pancreatic tumor is shown in 12 weeks old RIP-Tag mice. Gp38 is expressed by lymphoid stromal cells and Lyve1 by lymphatic endothelial cells (Peduto et al., J. Immunol., 2009).

Stromal cells in acute injury and fibrosis

Activated stromal cells are required for efficient tissue repair, however they are also the main collagen-overproducing cells involved in the scarring and fibrotic processes, which foster inflammation and eventually compromise organ recovery. The transition from activated stroma to profibrotic stroma remains poorly understood. Based on ADAM12 (A Disintegrin And Metalloprotease 12) re-expression in a number of human diseases with a fibrotic component, we investigated the identity and role of ADAM12+ cells during injury. Using BAC transgenic mice generated in the lab, we showed that ADAM12+ cells are normally programmed during vascular wall development and are re-induced by acute muscle and dermis injury as a distinct subset of PDGFRa+ gp38+ pro-inflammatory stromal cells with a specific pro-fibrotic fate and function. Accordingly, such cells can be specifically targeted to limit the generation of pro-fibrotic cells and collagen accumulation during the scarring process. Injury-induced ADAM12+ cells have initially a perivascular location, even though they are not embedded within the vascular basement membrane (the location of pericytes at steady-state), indicating that they are activated pericytes detaching upon injury, or mesenchymal cells in close proximity to vessels.

Injury-induced ADAM12+ cells are not embedded within the vascular basement membrane, in contrast to ADAM12+ cells during postnatal muscle growth. Capillaries are in blue; ColIV stains for vascular basement membrane; NG2 is a marker for pericytes. (Dulauroy et al, Nature Medicine 2012).

The detachment of pericytes from endothelium has been reported during vascular remodelling occurring in chronic pathologies, such as tumorigenesis, diabetic retinopathy and kidney disease.
These results are consistent with work in liver fibrosis, kidney fibrosis and spinal cord injury, showing that subsets of perivascular mesenchymal cells/pericytes are a major source of myofibroblasts and scar tissue. We are currently studying the cellular and molecular mechanism(s) underlying activation and differentiation of subsets of perivascular cells toward a profibrotic fate. Using mouse models for fibrosis, we are determining the contribution of such populations to inflammation and disease pathogenesis in fibrotic diseases.

In acutely injured skeletal muscle, a major fraction of profibrotic myofibroblasts (blue) accumulating in collagen-rich scar tissue (red) is derived from ADAM12+ cells (the cellular progeny of ADAM12+ cells is in green). M: muscle; CD: collagen deposit. (Dulauroy et al, Nature Medicine 2012).

Tumor microenvironment

It is increasingly recognized that tumor progression, invasion and ultimately metastasis result from interactions between cancer cells and their supporting stromal microenvironment. The tumor stromal microenvironment share many similarities with fibrotic stroma and comprises extracellular matrix components, as well as cellular components such as stromal cells (fibroblasts and myofibroblasts), blood and lymphatic vessels, and immune cells, which are collectively modulated by the tumor to allow progression and invasion. Our team is interested in the stromal crosstalk with tumor cells and immune cells, and how dysregulation of these interactions contribute to disease pathogenesis.

Our previous investigations highlighted the critical role of ADAM9 (A Disintegrin And Metalloprotease 9) in prostate tumor progression, possibly by altering the tumor-stromal crosstalk through shedding of growth factors essential in tumor proliferation and differentiation (such as EGF and FGFR2iiib). A similar role was found for ADAM12, highly expressed by a subset of carcinoma-associated stromal cells.

(A) Stromal cells (red) supportive of leucocytes (green) developing in the periphery of a neuroendocrine pancreatic tumor (blue), (B) stromal cells (red) infiltrating a poorly differentiated prostatic carcinoma (gray) and producing collagen (blue) and proteases (green). (credit: L. Peduto, Institut Pasteur)

Stromal cells developing in tumors can be visualized by staining with antibodies against PDGFRa, aSMA, FAP, gp38, desmin, vimentin, and other stromal markers. A major current focus of our team is to understand the mechanisms by which functionally distinct subsets of stromal cells develop, differentiate and affect tumor progression/immunity. We are investigating different tumor microenvironment, including prostate cancer, pancreatic cancer and melanoma, as well as metastasis in the lymph node, lung and liver to assess stromal organ specificities. Using transgenic mice generated in the lab, we are currently identifying mechanisms underlying the contribution of subsets of stromal cells to tumor angiogenesis, immune responses and therapeutic resistance, as increasing evidence indicates that stromal cells may contribute to a lack of response/ resistance to anti-cancer therapies.

Selected publications:

Dulauroy S, Di Carlo SE, Vives FL, Eberl G, and Peduto L. 2012. Lineage tracing and genetic ablation of ADAM12+ perivascular cells identify a major source of profibrotic cells during acute tissue injury. Nature Medicine, 18: 1262-1270.

Biot C, Rentsch C, Gsponer J, Birkhaeuser F, Jusforgues-Saklani H, Lemaître F, Bachmann A, Bousso P, Demangel A, Peduto L, Thalmann G, and Albert ML. 2012. Intravesical BCG immunotherapy: characterization of the bladder immune response identifies a strategy for improving anti-tumor activity. Science Translational Medicine, 4(137): 137ra72.

Schilte C, Couderc T, Chretien F, Sourisseau M, Gangneux N, Guivel-Benhassine F, Kraxner A, Tschopp J, Higgs S, Michault A, Arenzana-Seisdedos F, Colonna M, Peduto L, Schwartz O, Lecuit M, and Albert ML. 2010. Type I IFN controls chikungunya virus via its action on non-hematopoietic cells. J Exp Med, 207 (2): 429-442.

Peduto L, Dulauroy S, Lochner M, Spaeth G, Morales MA, Cumano A, and Eberl G. 2009. Inflammation recapitulates the ontogeny of lymphoid stromal cells. J Immunol, 182 (9): 5789-5799.

Alves N, Richard-Le Goff O, Huntington N, Sousa AP, Ribeiro VS, Bordack A, Vives FL, Peduto L, Chidgey A, Cumano A, Boyd R, Eberl G, and Di Santo JP. 2009. Characterization of the thymic IL-7 niche in vivo. PNAS, 106 (5): 1512-1517.

Peduto L. ADAM9 as a potential target molecule in cancer. 2009. Curr Pharm Des, 15 (20): 2282-2287.

Lochner M, Peduto L, Cherrier M, Sawa S, Langa F, Varona R, Riethmacher D, Si-Tahar M, Di Santo JP, and Eberl G. 2008. In vivo equilibrium of proinflammatory IL-17+ and regulatory IL-10+ Foxp3+ RORgamma t+ T cells. J Exp Med, 205(6): 1381-1393.

Peduto L, Reuter VE, Sehara-Fujisara A, Shaffer DR, Scher HI, and Blobel CP. 2006. ADAM12 is highly expressed in carcinoma-associated stroma and is required for prostate tumor progression. Oncogene, 25(39): 5462-5466.

Peduto L, Reuter VE, Shaffer DR, Scher HI, and Blobel CP. 2005. Critical function for ADAM9 in mouse prostate cancer. Cancer Research, 65(20): 9312-9319.