Michela Pierini

The Posterior Iliac Crest Outperforms the Anterior Iliac Crest When Obtaining Mesenchymal Stem Cells from Bone Marrow

BACKGROUND The clinical application of freshly isolated connective-tissue progenitors, as well as the potential preparation of culture-expanded mesenchymal stem cell populations for therapeutic applications, will benefit from clinical methods that maximize the yield of the starting population. We compared the number of cells, concentration, and prevalence of colony-founding connective-tissue progenitors from the anterior and posterior iliac crest. In addition, we compared the expansion kinetics and multilineage differentiation potential of their culture-expanded progeny when processed to form mesenchymal stem cells. METHODS Marrow aspirate was collected from both the anterior and posterior iliac crest of twenty-two patients. The concentration and prevalence of colony-founding connective-tissue progenitors were estimated with use of a colony formation assay. The expansion kinetics and multilineage differentiation potential of the culture-expanded mesenchymal stem cell populations derived from these starting samples were compared. RESULTS The yield of colony-founding connective-tissue progenitors was 1.6 times greater in the posterior compared with the anterior iliac crest. No differences were found with respect to the viability, phenotype, expansion kinetics, or multilineage differentiation potential of mesenchymal stem cell populations derived from these two sites. CONCLUSIONS The concentration and yield of colony-founding connective-tissue progenitors were greater when aspirate was obtained from the posterior compared with the anterior iliac crest, whereas the biological potential of the cells derived from these sites appeared comparable. CLINICAL RELEVANCE The harvesting of bone marrow from the posterior iliac crest appears to be preferred, as it provided a modestly higher concentration of colony-founding connective-tissue progenitors than comparable aspirate from the anterior iliac crest.

Efficient isolation and enrichment of mesenchymal stem cells from bone marrow

BACKGROUND AIMS Bone marrow (BM) mesenchymal stromal cells (MSC) have been identified as a source of pluripotent stem cells used in clinical practice to regenerate damaged tissues. BM MSC are commonly isolated from BM by density-gradient centrifugation. This process is an open system that increases the risk of sample contamination. It is also time consuming and requires technical expertise that may result in variability regarding cellular recovery. The BD Vacutainer® Cell Preparation Tube™ (CPT) was conceived to separate mononuclear cells from peripheral blood. The main goal of this study was to verify whether MSC could be isolated from BM using the CPT. METHODS BM was harvested, divided into two equal aliquots and processed using either CPT or a Ficoll-Paque™ PREMIUM density gradient. Both methods were compared regarding cell recovery, viability, proliferation, differentiation capacities and the presence of MSC progenitors. RESULTS Similar numbers of mononuclear cells were isolated from BM when comparing the two methods under study. No differences were found in terms of phenotypic characterization, viability, kinetics and lineage differentiation potential of MSC derived by CPT or Ficoll. Surprisingly, a fibroblast-colony-forming unit (CFU-F) assay indicated that, with CPT, the number of MSC progenitors was 1.8 times higher compared with the Ficoll gradient separation. CONCLUSIONS The CPT method is able to isolate MSC efficiently from BM, allowing the enrichment of MSC precursors.

The Pro/Pro genotype of the p53 codon 72 polymorphism modulates PAI-1 plasma levels in ageing.

Plasminogen activator inhibitor 1 (PAI-1) is over-expressed during ageing and it has been linked to cellular senescence. Recently, PAI-1 has been also identified in vitro as a critical downstream target of p53. TP53, the p53 gene, has a common functional polymorphism at codon 72 which influences the capability to modulate both apoptosis and cell senescence. In the attempt to demonstrate an in vivo role of p53 in the relationship between PAI-1 and age, we studied PAI-1 on 570 healthy subjects (aged from 18 to 92yrs.). PAI-1 showed significant relationship with age (r=0.12, p=0.02). Stratifying by genotype, it became evident that the association between PAI-1 and age was mainly due to Pro/Pro subjects (partial r=0.75, p<0.01). These results have been confirmed by a validation study on an independent sample population of 496 subjects (aged from 18 to 94yrs.). This is the first demonstration of an in vivo role of TP53 polymorphism in PAI-1 regulation, supporting the hypothesis that the effects of this polymorphism are age-dependent. In particular, our results indicate that Pro/Pro genotype plays a pivotal role in determining PAI-1 levels in aged subjects, while in Arg carriers PAI-1 levels are associated to the known insulin related determinants.

A rapid method for obtaining mesenchymal stem cells and platelets from bone marrow aspirate

Mesenchymal stem cells (MSCs) and platelet‐rich plasma (PRP) are currently used alone or in combination for therapeutic applications especially for bone repair. We tested whether MSCs can be isolated from bone marrow (BM) aspirate using a commercially available kit commonly used to obtain PRP from peripheral blood (PB). Results revealed that mononuclear cells and platelets from both PB and BM could be efficiently isolated by obtaining a mononuclear and platelet rich fraction (PB‐MPRF and BM‐MPRF, respectively). Starting with comparable volumes, the number of platelets increased 1.5‐fold in BM‐MPRF compared to PB‐MPRF. The number of clonogenic cells in BM‐MPRF samples was significantly higher than whole BM samples as revealed by CFU‐F assay (54.92 ± 8.55 CFU‐F/1.5 x 105 nucleated cells and 32.50 ± 12.43 CFU‐F/1.5 x 105 nucleated cells, respectively). Cells isolated from BM‐MPRF after in vitro expansion fulfilled the definition of MSCs by phenotypic criteria, and differentiated along osteogenic, adipogenic and chondrogenic lineages following induction. Results showed that the kit isolated MSCs and platelets from BM aspirate. Isolated MSCs were further expanded in a laboratory and BM‐MPRF was used clinically following BM withdrawal for rapid intra‐operative cell therapy for the treatment of bone defects. Copyright

Cell growth inhibition and apoptotic effect of the rexinoid 6-OH-11-O-hydroxyphenantrene on human osteosarcoma and mesenchymal stem cells

Natural derivatives of vitamin A, including all-trans-retinoic acid (ATRA), commonly known as retinoids, currently produce favorable results in the treatment of many types of tumors. The rexinoid 6-OH-11-O-hydroxyphenantrene (IIF) is a synthetic derivative of ATRA. Previous in vitro and in vivo studies demonstrated that IIF is able to induce growth inhibition of various cancer cells and is a potent apoptosis-inducing agent with clinical potential. Osteosarcoma (OS) is the most common type of bone cancer, characterized by a rising aggressiveness. Recent evidences suggest that mesenchymal stem cells (MSC) may favour tumor growth and progression. Thus, it is important to investigate whether a compound with potential anti-tumoral properties such as IIF affects not only tumor cells but also MSC. The current study is an attempt to understand the mode of the potential cytotoxicity of IIF on OS cells and MSC. The response to IIF treatment of osteosarcoma SaOS-2, MG63, and U2OS cells and of bone marrow-derived MSC was the subject of investigation. The results showed that IIF significantly inhibited cell growth in OS cell lines and MSC in both a time- and dose-dependent manner, as evaluated by methylene blue assay. This was also associated with altered cell morphology and an increase in cell death with the involvement of apoptosis as demonstrated by NucleoCounter, Hoechst 33342 staining and FACS analysis. No cell death and apoptosis was found in U2OS cells. Analysis of cells treated with 20 and 40μM IIF for 24h by western blot suggests the activation of initiator caspase 9, indicating the involvement of caspases in inducing apoptosis. Furthermore, IIF upregulated the expression of the pro-apoptotic protein Bax and downregulated the anti-apoptotic protein Bcl2. For the first time, our results collectively provide an evidence for cell growth inhibition and activation of apoptosis in human OS cells and MSC by IIF. These results confirm that IIF may be an effective compound for anticancer treatment, including that of OS.

Semi-quantitative monitoring of confluence of adherent mesenchymal stromal cells on calcium-phosphate granules by using widefield microscopy images.

The analysis of cell confluence and proliferation is essential to design biomaterials and scaffolds to use as bone substitutes in clinical applications. Accordingly, several approaches have been proposed in the literature to estimate the area of the scaffold covered by cells. Nevertheless, most of the approaches rely on sophisticated equipment not employed for routine analyses, while the rest of them usually do not provide significant statistics about the cell distribution. This research aims at studying confluence and proliferation of mesenchymal stromal cells (MSC) adherent on OSPROLIFE®, a commercial biomaterial in the form of granules. In particular, we propose a Computer Vision approach that can routinely be employed to monitor the surface of the single granules covered by cells because only a standard widefield fluorescent microscope is required. In order to acquire significant statistics data, we analyse wide-area images built by using MicroMos v2.0, an updated version of a previously published software specific for stitching brightfield and phase-contrast images manually acquired via a widefield microscope. In particular, MicroMos v2.0 permits to build accurate “mosaics” of fluorescent images, after correcting vignetting and photo-bleaching effects, providing a consistent representation of a sample region containing numerous granules. Then, our method allows to make automatically a statistically significant estimate of the percentage of the area of the single granules covered by cells. Finally, by analysing hundreds of granules at different time intervals we also obtained reliable data regarding cell proliferation, confirming that not only MSC adhere onto the OSPROLIFE® granules, but even proliferate over time.

Fabrication of Innovative Silk/Alginate Microcarriers for Mesenchymal Stem Cell Delivery and Tissue Regeneration

The aim of this study was to exploit silk fibroin’s properties to develop innovative composite microcarriers for mesenchymal stem cell (MSCs) adhesion and proliferation. Alginate microcarriers were prepared, added to silk fibroin solution, and then treated with ethanol to induce silk conformational transition. Microcarriers were characterized for size distribution, coating stability and homogeneity. Finally, in vitro cytocompatibility and suitability as delivery systems for MSCs were investigated. Results indicated that our manufacturing process is consistent and reproducible: silk/alginate microcarriers were stable, with spherical geometry, about 400 μm in average diameter, and fibroin homogeneously coated the surface. MSCs were able to adhere rapidly onto the microcarrier surface and to cover the surface of the microcarrier within three days of culture; moreover, on this innovative 3D culture system, stem cells preserved their metabolic activity and their multi-lineage differentiation potential. In conclusion, silk/alginate microcarriers represent a suitable support for MSCs culture and expansion. Since it is able to preserve MSCs multipotency, the developed 3D system can be intended for cell delivery, for advanced therapy and regenerative medicine applications.

A new holistic 3D non-invasive analysis of cellular distribution and motility on fibroin-alginate microcarriers using light sheet fluorescent microscopy

Cell interaction with biomaterials is one of the keystones to developing medical devices for tissue engineering applications. Biomaterials are the scaffolds that give three-dimensional support to the cells, and are vectors that deliver the cells to the injured tissue requiring repair. Features of biomaterials can influence the behaviour of the cells and consequently the efficacy of the tissue-engineered product. The adhesion, distribution and motility of the seeded cells onto the scaffold represent key aspects, and must be evaluated in vitro during the product development, especially when the efficacy of a specific tissue-engineered product depends on viable and functional cell loading. In this work, we propose a non-invasive and non-destructive imaging analysis for investigating motility, viability and distribution of Mesenchymal Stem Cells (MSCs) on silk fibroin-based alginate microcarriers, to test the adhesion capacity of the fibroin coating onto alginate which is known to be unsuitable for cell adhesion. However, in depth characterization of the biomaterial is beyond the scope of this paper. Scaffold-loaded MSCs were stained with Calcein-AM and Ethidium homodimer-1 to detect live and dead cells, respectively, and counterstained with Hoechst to label cell nuclei. Time-lapse Light Sheet Fluorescent Microscopy (LSFM) was then used to produce three-dimensional images of the entire cells-loaded fibroin/alginate microcarriers. In order to quantitatively track the cell motility over time, we also developed an open source user friendly software tool called Fluorescent Cell Tracker in Three-Dimensions (F-Tracker3D). Combining LSFM with F-Tracker3D we were able for the first time to assess the distribution and motility of stem cells in a non-invasive, non-destructive, quantitative, and three-dimensional analysis of the entire surface of the cell-loaded scaffold. We therefore propose this imaging technique as an innovative holistic tool for monitoring cell-biomaterial interactions, and as a tool for the design, fabrication and functionalization of a scaffold as a medical device.

Structural characterization of p53 isoforms due to the polymorphism at codon 72 by mass spectrometry and circular dichroism

A common polymorphism at codon 72 of human TP53 gene determines a proline to arginine aminoacidic substitution within the proline-rich domain of p53 protein. The two resulting isoforms (p53P(72) and p53R(72)) are different from a biochemical and biological point of view and many reports suggest that they can modulate individual cancer susceptibility and overall survival. In the attempt to explain the observed biological differences, we characterized the two isoforms by mass spectrometry and circular dichroism (CD) to evaluate the possible alteration in the secondary structure of p53 introduced by this polymorphism. Recombinant human p53R(72) and p53P(72) were produced by using E. coli expression system then purified by chromatography (affinity chromatography and RP-HPLC), and the whole proteins identified by HPLC-ESI-IT and MALDI-TOF analysis. A bottom-up approach, using both MALDI-TOF and HPLC-ESI-QTOF analysis, was then adopted to obtain the sequence information on the two p53 isoforms. To this purpose, peptide maps were obtained by trypsin proteolysis on the two p53 isoforms. The two isoforms proteolytic digests were separated by LC and subsequent mass spectrometry analysis of both entire and fragmented peptides was performed. In particular, precursor peptide ions obtained by ESI were subjected to collision by the triple quadrupole and TOF separation, allowing us to determine the isoforms aminoacidic peptide sequence by peptide ladder sequencing. Because of the presence of arginine, a selective trypsin proteolytic cleavage at R(72), giving rise to two selective shorter peptides, occurred in p53R(72), but was missing in the case of p53P(72) trypsin digest, in which an uncleaved longer peptide was instead identified. Upon primary structure confirmation, the two p53 isoforms were studied by CD in order to investigate the experimental variables, which affect ordered secondary structure adoption. CD analysis indicated that the two isoforms are not structurally different, thus allowing us to exclude that the observed biological differences can be due to a different conformation of the two isoforms introduced by this polymorphism. Furthermore, these studies establish a mass spectrometry method to identify the two isoforms that can be useful for future interactome studies and cancer drug discovery.

Identification of a T cell gene expression clock obtained by exploiting a MZ twin design

Many studies investigated age-related changes in gene expression of different tissues, with scarce agreement due to the high number of affecting factors. Similarly, no consensus has been reached on which genes change expression as a function of age and not because of environment. In this study we analysed gene expression of T lymphocytes from 27 healthy monozygotic twin couples, with ages ranging over whole adult lifespan (22 to 98 years). This unique experimental design allowed us to identify genes involved in normative aging, which expression changes independently from environmental factors. We obtained a transcriptomic signature with 125 genes, from which chronological age can be estimated. This signature has been tested in two datasets of same cell type hybridized over two different platforms, showing a significantly better performance compared to random signatures. Moreover, the same signature was applied on a dataset from a different cell type (human muscle). A lower performance was obtained, indicating the possibility that the signature is T cell-specific. As a whole our results suggest that this approach can be useful to identify age-modulated genes.