Inigo Martinez

The secretory profiles of cultured human articular chondrocytes and mesenchymal stem cells: implications for autologous cell transplantation strategies.

This study was undertaken to compare the phenotype of human articular chondrocytes (ACs) and bone marrow-derived mesenchymal stem cells (MSCs) after cell expansion by studying the spectrum of proteins secreted by cells into the culture medium. ACs and MSCs were expanded in monolayer cultures for some weeks, as done in standard cell transplantation procedures. Initially, the expression of cartilage signature genes was compared by real-time PCR. Metabolic labeling of proteins (SILAC) in combination with mass spectrometry (LC/MS-MS) was applied to investigate differences in released proteins. In addition, multiplex assays were carried out to quantify the amounts of several matrix metalloproteases (MMPs) and their natural inhibitors (TIMPs). Expanded chondrocytes showed a slightly higher expression of cartilage-specific genes than MSCs, whereas the overall spectra of released proteins were very similar for the two cell types. In qualitative terms MSCs seemed to secrete similar number of extracellular matrix proteins (43% vs. 45% of total proteins found) and catabolic agents (9% vs. 10%), and higher number of anabolic agents (12 % vs. 7%) compared to ACs. Some matrix-regulatory agents such as serpins, BMP-1, and galectins were detected only in MSC supernatants. Quantitative analyses of MMPs and TIMPs revealed significantly higher levels of MMP-1, MMP-2, MMP-3, and MMP-7 in the medium of ACs. Our data show that after the expansion phase, both ACs and MSCs express a dedifferentiated phenotype, resembling each other. ACs hold a phenotype closer to native cartilage at the gene expression level, whereas MSCs show a more anabolic profile by looking at the released proteins pattern. Our data together with the inherent capability of MSCs to maintain their differentiation potential for longer cultivation periods would favor the use of these cells for cartilage reconstruction.

The influence of oxygen tension on the structure and function of isolated liver sinusoidal endothelial cells

BackgroundLiver sinusoidal endothelial cells (LSECs) are specialized scavenger cells, with crucial roles in maintaining hepatic and systemic homeostasis. Under normal physiological conditions, the oxygen tension encountered in the hepatic sinusoids is in general considerably lower than the oxygen tension in the air; therefore, cultivation of freshly isolated LSECs under more physiologic conditions with regard to oxygen would expect to improve cell survival, structure and function. In this study LSECs were isolated from rats and cultured under either 5% (normoxic) or 20% (hyperoxic) oxygen tensions, and several morpho-functional features were compared.ResultsCultivation of LSECs under normoxia, as opposed to hyperoxia improved the survival of LSECs and scavenger receptor-mediated endocytic activity, reduced the production of the pro-inflammatory mediator, interleukin-6 and increased the production of the anti-inflammatory cytokine, interleukin-10. On the other hand, fenestration, a characteristic feature of LSECs disappeared gradually at the same rate regardless of the oxygen tension. Expression of the cell-adhesion molecule, ICAM-1 at the cell surface was slightly more elevated in cells maintained at hyperoxia. Under normoxia, endogenous generation of hydrogen peroxide was drastically reduced whereas the production of nitric oxide was unaltered. Culture decline in high oxygen-treated cultures was abrogated by administration of catalase, indicating that the toxic effects observed in high oxygen environments is largely caused by endogenous production of hydrogen peroxide.ConclusionViability, structure and many of the essential functional characteristics of isolated LSECs are clearly better preserved when the cultures are maintained under more physiologic oxygen levels. Endogenous production of hydrogen peroxide is to a large extent responsible for the toxic effects observed in high oxygen environments.

Differences in the secretome of cartilage explants and cultured chondrocytes unveiled by SILAC technology

The main goal of our study was to analyze and compare the profiles of secreted proteins from adult human articular chondrocytes in monolayers, and cartilage explants in culture, using a de novo protein labeling approach. Stable isotope labeling of proteins in culture was used to differentiate between chondrocyte‐derived proteins and other preexisting matrix‐derived components, or proteins coming from serum or synovial fluids. Proteins in culture supernatants were resolved by one‐dimensional SDS‐PAGE electrophoresis, and analyzed in tandem with LC/MS‐MS (liquid chromatography/double mass spectrometry). Results from stable isotope labeling with amino acids in cell culture (SILAC) were validated by specific immunoblotting of four relevant proteins identified in the secretion media. After 8–10 days of culture, over 90% of proteins secreted during monolayer growth contained 13C6‐Arg and 13C6‐Lys. Nonlabeled proteins corresponded mostly to plasma‐associated proteins, indicating background contamination of medium with serum remnants. The majority of the secreted proteins in 2D cultures were extracellular matrix components and matrix regulators, along with some inflammatory agents and metabolic enzymes. In explants, only 25%–30% of proteins were labeled with heavy amino acids, corresponding to matrix regulators and carrier molecules. Nonlabeled proteins corresponded primarily to structural matrix components. In qualitative terms, all labeled proteins coming from cartilage explants were also found in chondrocytes supernatants. In summary, our results show differences in the labeling pattern of proteins found in supernatants from explants and monolayers. Most proteins found in the media of explants were subproducts of matrix turnover rather than newly synthesized. To our knowledge, this study is the first one so far applying SILAC technology in the context of cartilage and chondrocytes physiology.

Redifferentiation of in vitro expanded adult articular chondrocytes by combining the hanging-drop cultivation method with hypoxic environment.

The main purpose of this work has been to establish a new culturing technique to improve the chondrogenic commitment of isolated adult human chondrocytes, with the aim of being used during cell-based therapies or tissue engineering strategies. By using a rather novel technique to generate scaffold-free three-dimensional (3D) structures from in vitro expanded chondrocytes, we have explored the effects of different culture environments on cartilage formation. Three-dimensional chondrospheroids were developed by applying the hanging-drop technique. Cartilage tissue formation was attempted after combining critical factors such as serum-containing or serum-free media and atmospheric (20%) or low (2.5%) oxygen tensions. The quality of the formed microtissues was analyzed by histology, immunohistochemistry, electron microscopy, and real-time PCR, and directly compared with native adult cartilage. Our results revealed highly organized, 3D tissue-like structures developed by the hanging-drop method. All culture conditions allowed formation of 3D spheroids; however, cartilage generated under low oxygen tension had a bigger size, enhanced matrix deposition, and higher quality of cartilage formation. Real-time PCR demonstrated enhanced expression of cartilage-specific genes such us collagen type II and aggrecan in 3D cultures when compared to monolayers. Cartilage-specific matrix proteins and genes expressed in hanging-drop-developed spheroids were comparable to the expression obtained by applying the pellet culture system. In summary, our results indicate that a combination of 3D cultures of chondrocytes in hanging drops and a low oxygen environment represent an easy and convenient way to generate cartilage-like microstructures. We also show that a new specially tailored serum-free medium is suitable for in vitro cartilage tissue formation. This new methodology opens up the possibility of using autogenously produced solid 3D structures with redifferentiated chondrocytes as an attractive alternative to the currently used autologous chondrocyte transplantation for cartilage repair.

Cancer associated fibroblasts in stage I-IIIA NSCLC: Prognostic impact and their correlations with tumor molecular markers

Background Cancer Associated Fibroblasts (CAFs) are thought to regulate tumor growth and metastasis. Fibroblast Activating Protein 1 (FAP-1) is a marker for fibroblast activation and by many recognized as the main marker of CAFs. Alpha Smooth Muscle Actin (α-SMA) is a general myofibroblast marker, and can be used to identify CAFs. This study investigates the prognostic impact of FAP-1 and α-SMA in non-small cell lung cancer (NSCLC) patients and correlates their expression to 105 proteins investigated in the same cohort. Methods Tumor specimens from 536 NSCLC patients were obtained and tissue micro-arrays were constructed. Immunohistochemistry was used to evaluate the expression of FAP-1 and α-SMA and explore their impact on survival and association with other tumor molecular markers in NSCLC patients. Results High expression of FAP-1, but not α-SMA, in squamous cell carcinoma (SCC, P = 0.043, HR = 0.63 95% CI 0.40–0.99) was significantly associated with increased disease-specific survival. FAP-1 and α-SMA were not significantly correlated to each other. Analyses of FAP-1 and α-SMA associated with other tumor-related proteins revealed histotype-specific correlation patterns. Conclusion The presence of FAP-1 expressing CAFs is an indicator of positive outcome for NSCLC-SCC patients. In addition, correlation analyses suggest FAP-1 and α-SMA to label different subsets of fibroblasts and their associations with other tumor-related proteins diverge according to histological subtype.

Development of a new method to harvest chondroprogenitor cells from underneath cartilage defects in the knees

BackgroundMesenchymal progenitor cells from bone marrow hold great potential as a cell source for cartilage repair. Aspiration from the iliac crest is the most widely used method to harvest bone marrow cells for cartilage repair. The objective of our study was to establish a new method to isolate mesenchymal progenitor cells by direct aspiration of bone marrow from the subchondral spongious bone underneath cartilage defects during microfracture treatment and to confirm the chondrogenic potential of the resulting cell cultures.MethodsBone marrow was aspirated arthroscopically from patients treated for isolated cartilage defects. Adherent stromal cells were isolated, expanded in monolayer cultures, and characterized by flow cytometry. Chondrogenic induction of cells was achieved by combination of spheroid cultures in hanging drops and the concomitant use of transforming growth factor-β (TGFβ). Articular chondrocytes established in three-dimensional (3D) cultures were used as positive cartilage-forming units, and skin fibroblasts were used as negative controls. Three-dimensional constructs were stained for immunohistochemical and histological examination, and a real-time polymerase chain reaction (PCR) was performed to quantify the expression of aggrecan, collagen types 1 and 2, and Sox9.ResultsMesenchymal stem cell-like progenitor cells (MSCs) displaying chondrogenic differentiation capacity were harvested arthroscopically from underneath cartilage lesions on distal femurs using the one-hole technique. Stem cell-related surface antigens analyzed by flow cytometry confirmed the nature of the isolated adherent cells. MSC spheroids stained positive for glycosaminoglycans and collagen type 2. Realtime PCR showed that MSCs in 3D spheroids significantly increased gene expression of collagen type 2, aggrecan, and Sox 9 and down-regulated expression of collagen type 1 when compared to the mRNA levels measured in MSCs monolayers.ConclusionsWe describe a new technique that may be applied for harvesting bone marrow cells from cartilage defects during arthroscopic intervention of the knee. Cells harvested in this way hold full chondrogenic differentiation potential. Our data imply that MSC storage may be established by using marrow from this approach, bypassing the need for cell aspiration from the iliac crest.

Comparative Analyses of the Secretome from Dedifferentiated and Redifferentiated Adult Articular Chondrocytes

Objective: The main goal of this study was to compare the secretion products derived from human articular chondrocytes established in either long-term monolayer cultures or in scaffold-free 3-dimensional (3-D) cultures. Methods: Stable isotope labeling of amino acids in cell culture (SILAC) was applied to investigate quantitatively the differences between proteins secreted from dedifferentiated and redifferentiated chondrocytes. Proteins in cell supernatants were resolved by 1-D gel electrophoresis and analyzed by mass spectrometry. The results from the proteomic analyses were validated by immunoblotting. Additionally, antibody arrays were used to screen culture supernatants for 79 different morphogens. Results: Quantitative SILAC showed that some relevant growth factors such as CTGF or GAS6 were elevated in monolayers, along with proteins characteristic of a dedifferentiated phenotype such as collagen type I and tenascin. In spheroids, data showed overexpression of some cartilage-specific proteins such as aggrecan, together with important matrix regulators such as chitinase-3–like protein and stromelysin-1. Antibody arrays revealed that chondrocytes in monolayer secrete higher levels of leukocyte-activating agents such as MCP-1 and GRO, whereas the spheroid configuration favors the production of cell morphogens such as MCSF and VEGF. Conclusion: Our results show that some classic dedifferentiation and redifferentiation markers are differentially expressed in 2-D or 3-D culture configurations. Other cell/matrix regulatory molecules are also found to be differentially expressed by chondrocytes in 2-D and 3-D conditions by SILAC and antibody arrays. Our data bring new information for understanding the biology of chondrocytes in general and the process of cartilage tissue reconstruction in particular.

LAG-3 in non-small cell lung cancer: expression in primary tumors and metastatic lymph nodes is associated with improved survival

Micro‐Abstract The immune checkpoint lymphocyte activation gene‐3 (LAG‐3) is a novel target for the treatment of non–small‐cell lung cancer (NSCLC). We evaluated the prognostic significance of LAG‐3 expression in a large, unselected cohort of 553 primary NSCLC tumors and 143 metastatic lymph nodes. In both primary tumors and metastatic lymph nodes, LAG‐3 expression was associated with significantly improved survival. Background Lymphocyte activation gene‐3 (LAG‐3) is an immune checkpoint receptor and a putative therapeutic target in non–small‐cell lung cancer (NSCLC). We explored the prognostic effect of LAG‐3+ tumor‐infiltrating lymphocytes (TILs) in primary tumors and metastatic lymph nodes in NSCLC and its potential for inclusion in an immunoscore, supplementing the TNM classification. Materials and Methods Primary tumor tissue from 553 stage I‐IIIB NSCLC patients and 143 corresponding metastatic lymph nodes were collected. The expression of LAG‐3 was evaluated by immunohistochemistry on tissue microarrays. Results On univariate analysis, LAG‐3+ TILs in the intraepithelial and stromal compartments of primary tumors and in the intraepithelial and extraepithelial compartments of metastatic lymph nodes were associated with improved disease‐specific survival (DSS). On multivariate analysis, stromal LAG‐3+ TILs were a significant independent predictor of improved DSS (hazard ratio [HR], 0.59; 95% confidence interval [CI], 0.43‐0.82; P = .002). Stromal LAG‐3+ TILs did not have prognostic impact across all pathologic stages. In the metastatic lymph nodes, intraepithelial (HR, 0.61; 95% CI, 0.38‐0.99; P = .049) and extraepithelial (HR, 0.54; 95% CI, 0.29‐0.70; P < .001) LAG‐3+ TILs were independently associated with favorable DSS. Conclusion LAG‐3+ TILs are an independent positive prognostic factor in stage I‐IIIB NSCLC. LAG‐3 in metastatic lymph nodes is a candidate marker for an immunoscore in NSCLC.