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Concept: Stroma


In myeloid malignancies, the neoplastic clone outgrows normal hematopoietic cells toward BM failure. This event is also sustained by detrimental stromal changes, such as BM fibrosis and osteosclerosis, whose occurrence is harbinger of a dismal prognosis. We show that the matricellular protein SPARC contributes to the BM stromal response to myeloproliferation. The degree of SPARC expression in BM stromal elements, including CD146(+) mesenchymal stromal cells, correlates with the degree of stromal changes, and the severity of BM failure characterizing the prototypical myeloproliferative neoplasm primary myelofibrosis. Using Sparc(-/-) mice and BM chimeras, we demonstrate that SPARC contributes to the development of significant stromal fibrosis in a model of thrombopoietin-induced myelofibrosis. We found that SPARC deficiency in the radioresistant BM stroma compartment impairs myelofibrosis but, at the same time, associates with an enhanced reactive myeloproliferative response to thrombopoietin. The link betwen SPARC stromal deficiency and enhanced myeloid cell expansion under a myeloproliferative spur is also supported by the myeloproliferative phenotype resulting from the transplantation of defective Apc(min) mutant hematopoietic cells into Sparc(-/-) but not WT recipient BM stroma. Our results highlight a complex influence of SPARC over the stromal and hematopoietic BM response in myeloproliferative conditions.

Concepts: Gene, Cancer, Fibrosis, Mesenchymal stem cell, Stromal cell, Myeloproliferative disease, Myelofibrosis, Stroma


Pre-clinical evidence indicates that autologous bone marrow-derived mesenchymal stromal cell (BM-MSC) transplantation improves motor function in patients with central nervous system disorders.

Concepts: Central nervous system, Nervous system, Brain, Stem cell, Mesenchymal stem cell, Bone marrow, Stromal cell, Stroma


Mesenchymal Stromal Cells (MSC), as advanced therapy products, must satisfy all the requirements for human use of medicinal products, aiming to maintain the quality and safety of the cells. The MSC manufacturing process for clinical use should comply with the principles of Good Manufacturing Practice (GMP). This ensures that cell preparations are produced and controlled, from the collection and manipulation of raw materials, through the processing of intermediate products, to the quality controls, storage, labelling and packaging, and release. The objective of this document is to provide the minimal quality requirements for the MSC production and its delivery for clinical use, so the safety of the final cell therapy product will not be compromised. For this purpose, the document evaluates the most important steps of GMP-compliant MSC production: the isolation and expansion process; the validation phase of the process, including all quality controls for the characterization, functionality, potency and safety of MSCs; the quality control at the batch release to guarantee the safety of patient infusion. This opinion paper reflects the consensus viewpoint of the authors and scientists participating the GISM Working Group*. * GISM Working Group includes the following individual investigators: Biagi E, Del Bue M, Frigerio S, Lisini D, Marazzi M, Mareschi K, Nava S, Parolini O, Riccobon A, Romagnoli L, Viganò M.

Concepts: Stem cell, Mesenchymal stem cell, Quality control, Management, Stromal cell, Stroma of ovary, Stroma, Production and manufacturing


The extracellular matrix (ECM) provides structural and biochemical signals that regulate cell function. A well-controlled balance between cells and surroundings (i.e., dynamic reciprocity) is crucial for regulating ECM architecture. During cancer progression, epithelial cells undergo genetic alterations which, together with stromal changes including ECM remodeling, disturb the homeostatic dynamics of the epithelium. A parallel organization of stromal ECM fibrils is associated with tumorigenic responses. In an emerging paradigm, continuous and progressive regulation via mechanical forces and aberrant signaling are believed to be responsible for tumor-associated ECM remodeling. In this review we discuss the discrete biomechanical and biochemical mechanisms that underlie these architectural changes and highlight their particular relevance to the regulation of the alignment of ECM in the mesenchymal stroma.

Concepts: DNA, Epithelium, Basement membrane, Carcinoma, Regulation, Stroma


Pancreatic ductal adenocarcinomas (PDAs) are desmoplastic and can undergo epithelial-to-mesenchymal transition to confer metastasis and chemoresistance. Studies have demonstrated that phenotypically and functionally distinct stromal cell populations exist in PDAs. Fibroblast activation protein-expressing (FAP-expressing) cells act to enhance PDA progression, while α-smooth muscle actin myofibroblasts can restrain PDA. Thus, identification of precise molecular targets that mediate the protumorigenic activity of FAP+ cells will guide development of therapy for PDA. Herein, we demonstrate that FAP overexpression in the tumor microenvironment correlates with poor overall and disease-free survival of PDA patients. Genetic deletion of FAP delayed onset of primary tumor and prolonged survival of mice in the KPC mouse model of PDA. While genetic deletion of FAP did not affect primary tumor weight in advanced disease, FAP deficiency increased tumor necrosis and impeded metastasis to multiple organs. Lineage-tracing studies unexpectedly showed that FAP is not only expressed by stromal cells, but can also be detected in a subset of CD90+ mesenchymal PDA cells, representing up to 20% of total intratumoral FAP+ cells. These data suggest that FAP may regulate PDA progression and metastasis in cell-autonomous and/or non-cell-autonomous fashions. Together, these data support pursuing FAP as a therapeutic target in PDA.

Concepts: DNA, Gene, Genetics, Gene expression, Chromosome, Therapy, Stromal cell, Stroma


: Age-related osteoporosis is driven by defects in the tissue-resident mesenchymal stromal cells (MSCs), a heterogeneous population of musculoskeletal progenitors that includes skeletal stem cells (SSCs). MSC decline leads to reduced bone formation, causing loss of bone volume and the breakdown of bony microarchitecture crucial to trabecular strength. Furthermore, the low-turnover state precipitated by MSC loss leads to low-quality bone that is unable to perform remodeling-mediated maintenance-replacing old damaged bone with new healthy tissue. Using minimally expanded exogenous MSCs injected systemically into a mouse model of human age-related osteoporosis, we show long-term engraftment and markedly increased bone formation. This led to improved bone quality and turnover and, importantly, sustained microarchitectural competence. These data establish proof of concept that MSC transplantation may be used to prevent or treat human age-related osteoporosis.

Concepts: Osteoporosis, Bone, Stem cell, Mesenchymal stem cell, Bone marrow, Stromal cell, Stroma of ovary, Stroma


The tumor microenvironment is a critical modulator of carcinogenesis; however, in many tumor types, the influence of the stroma during preneoplastic stages is unknown. Here we explored the relationship between pre-tumor cells and their surrounding stroma in malignant progression of the cerebellar tumor medulloblastoma (MB). We show that activation of the vascular regulatory signalling axis mediated by Norrin (an atypical Wnt)/Frizzled4 (Fzd4) inhibits MB initiation in the Ptch(+/-) mouse model. Loss of Norrin/Fzd4-mediated signalling in endothelial cells, either genetically or by short-term blockade, increases the frequency of pre-tumor lesions and creates a tumor-permissive microenvironment at the earliest, preneoplastic stages of MB. This pro-tumor stroma, characterized by angiogenic remodelling, is associated with an accelerated transition from preneoplasia to malignancy. These data expose a stromal component that regulates the earliest stages of tumorigenesis in the cerebellum, and a novel role for the Norrin/Fzd4 axis as an endogenous anti-tumor signal in the preneoplastic niche.

Concepts: Gene, Cancer, Oncology, Evolution, Angiogenesis, Blood vessel, Endothelium, Stroma


Emerging studies have begun to demonstrate that reprogrammed stromal cells play pivotal roles in tumor growth, metastasis, and resistance to therapy. However, the contribution of stromal cells to non-small-cell lung cancer (NSCLC) has remained underexplored. We used an orthotopic model of Kras-driven NSCLC to systematically dissect the contribution of specific hematopoietic stromal cells in lung cancer. RNA deep-sequencing analysis of individually sorted myeloid lineage and tumor epithelial cells revealed cell-type-specific differentially regulated genes, indicative of activated stroma. We developed a computational model for crosstalk signaling discovery based on ligand-receptor interactions and downstream signaling networks and identified known and novel tumor-stroma paracrine and tumor autocrine crosstalk-signaling pathways in NSCLC. We provide cellular and molecular insights into components of the lung cancer microenvironment that contribute to carcinogenesis. This study has the potential for development of therapeutic strategies that target tumor-stroma interactions and may complement conventional anti-cancer treatments.

Concepts: Cancer, Metastasis, Lung cancer, Non-small cell lung carcinoma, Carcinoma, Stromal cell, Stroma of ovary, Stroma


Therapeutic antibodies that block the programmed death-1 (PD-1)-programmed death-ligand 1 (PD-L1) pathway can induce robust and durable responses in patients with various cancers, including metastatic urothelial cancer. However, these responses only occur in a subset of patients. Elucidating the determinants of response and resistance is key to improving outcomes and developing new treatment strategies. Here we examined tumours from a large cohort of patients with metastatic urothelial cancer who were treated with an anti-PD-L1 agent (atezolizumab) and identified major determinants of clinical outcome. Response to treatment was associated with CD8+T-effector cell phenotype and, to an even greater extent, high neoantigen or tumour mutation burden. Lack of response was associated with a signature of transforming growth factor β (TGFβ) signalling in fibroblasts. This occurred particularly in patients with tumours, which showed exclusion of CD8+T cells from the tumour parenchyma that were instead found in the fibroblast- and collagen-rich peritumoural stroma; a common phenotype among patients with metastatic urothelial cancer. Using a mouse model that recapitulates this immune-excluded phenotype, we found that therapeutic co-administration of TGFβ-blocking and anti-PD-L1 antibodies reduced TGFβ signalling in stromal cells, facilitated T-cell penetration into the centre of tumours, and provoked vigorous anti-tumour immunity and tumour regression. Integration of these three independent biological features provides the best basis for understanding patient outcome in this setting and suggests that TGFβ shapes the tumour microenvironment to restrain anti-tumour immunity by restricting T-cell infiltration.

Concepts: Immune system, Cancer, Oncology, Tumor, Neoplasm, Stromal cell, Stroma of ovary, Stroma


Mesenchymal stromal cell (MSC) infusion could be a mean to establish tolerance in solid organ recipients. The aim of this prospective, controlled, phase-1 study was to evaluate the feasibility, safety and tolerability of a single infusion of MSCs in liver transplant recipients.

Concepts: Mesenchymal stem cell, Cirrhosis, Liver, Organ, Organ transplant, Stromal cell, Stroma of ovary, Stroma