Microencapsulated human mesenchymal stem cells decrease liver fibrosis in mice

Background & Aims: Mesenchymal stem cell (MSC) transplantation was shown to be effective for the treatment of liver fibrosis, but the mechanisms of action are not yet fully understood. We transplanted encapsulated human MSCs in two mouse models of liver fibrosis to determine the mechanisms behind the protective effect. Methods: Human bone marrow-derived MSCs were microencapsulated in novel alginate-polyethylene glycol microspheres. In vitro, we analyzed the effect of MSC-conditioned medium on the activation of hepatic stellate cells and the viability, proliferation, cytokine secretion, and differentiation capacity of encapsulated MSCs. The level of fibrosis induced by bile duct ligation (BDL) or carbon tetrachloride (CCl4) was assessed after intraperitoneal transplantation of encapsulated MSCs, encapsulated human fibroblasts, and empty microspheres. Results: MSC-conditioned medium inhibited hepatic stellate cell activation and release of MSC secreted anti-apoptotic (IL-6, IGFBP-2) and anti-inflammatory (IL-1Ra) cytokines. Viability, proliferation, and cytokine secretion of microencapsulated MSCs were similar to those of non-encapsulated MSCs. Within the microspheres, MSCs maintained their capacity to differentiate into adipocytes, chondrocytes, and osteocytes. 23% (5/22) of the MSC clones were able to produce anti-inflammatory IL-1Ra in vitro. Microencapsulated MSCs significantly delayed the development of BDL-and CCl4-induced liver fibrosis. Fibroblasts had an intermediate effect against CCl4-induced fibrosis. Mice transplanted with encapsulated MSCs showed lower mRNA levels of collagen type I, whereas levels of matrix metalloproteinase 9 were significantly higher. Human IL-1Ra was detected in the serum of 36% (4/11) of the mice transplanted with microencapsulated MSCs. Conclusions: MSC-derived soluble molecules are responsible for an anti-fibrotic effect in experimental liver fibrosis. (C) 2014 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

Survival of Free and Encapsulated Human and Rat Islet Xenografts Transplanted into the Mouse Bone Marrow

Redouan Mahou, Yannick Müller, Christine Wandrey

Bone marrow was recently proposed as an alternative and potentially immune-privileged site for pancreatic islet transplantation. The aim of the present study was to assess the survival and rejection mechanisms of free and encapsulated xenogeneic islets transplanted into the medullary cavity of the femur, or under the kidney capsule of streptozotocin-induced diabetic C57BL/6 mice. The median survival of free rat islets transplanted into the bone marrow or under the kidney capsule was 9 and 14 days, respectively, whereas that of free human islets was shorter, 7 days (bone marrow) and 10 days (kidney capsule). Infiltrating CD8(+) T cells and redistributed CD4(+) T cells, and macrophages were detected around the transplanted islets in bone sections. Recipient mouse splenocytes proliferated in response to donor rat stimulator cells. One month after transplantation under both kidney capsule or into bone marrow, encapsulated rat islets had induced a similar degree of fibrotic reaction and still contained insulin positive cells. In conclusion, we successfully established a small animal model for xenogeneic islet transplantation into the bone marrow. The rejection of xenogeneic islets was associated with local and systemic T cell responses and macrophage recruitment. Although there was no evidence for immune-privilege, the bone marrow may represent a feasible site for encapsulated xenogeneic islet transplantation.

Public Library of Science2014

The role of recruited bone-marrow derived mesenchymal stem cells in the establishment of the tumor stroma and a growth-supportive environment

Jean-Paul Abbühl

The Mesenchymal Stem Cell (MSC) is a self-renewing multipotent progenitor originally found in the bone marrow. It has drawn strong interest from translational research because of the multipotency of MSCs, their immunosuppression, their intrinsic homing and their promotion of wound healing in human patients. Currently available methods rely on in vitro culture for the isolation and expansion of MSCs and most studies used these cells for their investigation. Fibroblasts constitute the connective tissue and support epithelial or hematopoietic cells. Although they have already been extensively investigated, it is not clear whether stem cells exist in vivo which specifically regenerate fibroblasts. MSCs are a potential candidate, because of their fibroblastic shape in vitro, their differentiation towards several mesodermal lineages and their supportive function. We aim to characterize the in vivo differentiation potential of MSCs toward fibroblasts in normal and tumor tissues. A new transplantation approach was developed in order to transfer labeled MSCs in the bone marrow and assess their recruitment and lineage contribution in vivo. Long-term engraftment was accomplished by isolating and transplanting these cells within one day. To this end, strategies for their purification, preconditioning of the host and transplantation methodologies were established during this thesis. We were able to enrich MSCs over 1000 fold by combining a new extraction protocol, a negative selection by MACS and a positive selection by FACS. Cloning of sorted MSCs was performed to confirm their multipotency at single cell level. GFP-expressing MSCs were able to engraft in host mice tolerant for GFP and their expansion in vivo was stimulated by block of GSK3 activity. Altogether, the chimeric MSC model was used to track the recruitment of bone-marrow derived MSCs into spontaneous breast tumors. The tumor microenvironment encompasses several non-tumorigenic cells interacting with cancer cells. Among them, cancer-associated fibroblasts are known to participate in carcinogenesis. Whilst this heterogeneous stromal population has been extensively investigated, their source(s) remain elusive. I now propose tumoral MSCs as one source of cancer-associated fibroblast, based on their ability to self-renew and reconstitute stromal heterogeneity upon serial transplantation. Finally, I introduced the new concept that the multipotency of MSCs is subjugated by cancer cells to meet their requirements for enhanced tumor progression and prepare for metastasis. I found MSCs present in the tumor microenvironment to differentiate into cancer-associated osteoblasts and produce hydroxyapatite-mineralization in vivo. Microcalcification is an accepted poor prognostic feature in breast cancer patients but its function and origin is not documented. I showed that hydroxyapatite was able to promote proliferation of tumor cells and increased intracellular calcium concentration. Lastly, cancer-associated osteoblast and hydroxyapatite were able to promote tumor growth and metastasis in vivo. To conclude, bone marrow derived MSCs are circulating stem cells that participate in the establishment of the pathogenic stroma in breast cancer. Owing to their multipotency, MSCs give rise to cancer-associated osteoblasts that induce pro-malignant mineralization in situ. Subsequently, cancer cells harbor increased intracellular calcium concentration, enhanced proliferation and metastasis. We foresee the development of new stroma-targeted therapies that prevent the mineralization of tumor tissue and reduce metastasis in breast cancer patients.

EPFL2014

Long-Term Engraftment of Primary Bone Marrow Stromal Cells Repairs Niche Damage and Improves Hematopoietic Stem Cell Transplantation

Zuzana Tatárová

Hematopoietic stem cell (HSC) transplantation represents a curative treatment for various hematological disorders. However, delayed reconstitution of innate and adaptive immunity often causes fatal complications. HSC maintenance and lineage differentiation are supported by stromal niches, and we now find that bone marrow stroma cells (BMSCs) are severely and permanently damaged by the pre-conditioning irradiation required for efficient HSC transplantation. Using mouse models, we show that stromal insufficiency limits the number of donor-derived HSCs and B lymphopoiesis. Intra-bone transplantation of primary, but not cultured, BMSCs quantitatively reconstitutes stroma function in vivo, which is mediated by a multipotent NT5E(+) (CD73)(+) ENG(-) (CD105)(-) LY6A(+) (SCA1)(+) BMSC subpopulation. BMSC co-transplantation doubles the number of functional, donor-derived HSCs and significantly reduces clinically relevant side effects associated with HSC transplantation including neutropenia and humoral immunodeficiency. These data demonstrate the potential of stroma recovery to improve HSC transplantation.

Cell Press2017

The role of recruited bone-marrow derived mesenchymal stem cells in the establishment of the tumor stroma and a growth-supportive environment

Jean-Paul Abbühl

EPFL2014