Genome sequences of actinobacteriophages JorRay, Blocker23, Nibbles, and OlgasClover.

JorRay, Blocker23, Nibbles, and OlgasClover are actinobacteriophages belonging to clusters G1, B2, CT, and DJ, respectively. JorRay and Blocker23 were identified in host bacterium Mycobacterium smegmatis mc2155. Nibbles and OlgasClover were identified in host bacterium Gordonia rubripertincta NRRL B-16540.

Fly-CURE, a multi-institutional CURE using Drosophila, increases students' confidence, sense of belonging, and persistence in research.

The Fly-CURE is a genetics-focused multi-institutional Course-Based Undergraduate Research Experience (CURE) that provides undergraduate students with hands-on research experiences within a course. Through the Fly-CURE, undergraduate students at diverse types of higher education institutions across the United States map and characterize novel mutants isolated from a genetic screen in Drosophila melanogaster. To date, more than 20 mutants have been studied across 20 institutions, and our scientific data have led to eleven publications with more than 500 students as authors. To evaluate the impact of the Fly-CURE experience on students, we developed and validated assessment tools to identify students' perceived research self-efficacy, sense of belonging in science, and intent to pursue additional research opportunities. Our data, collected over three academic years and involving 14 institutions and 480 students, show gains in these metrics after completion of the Fly-CURE across all student subgroups analyzed, including comparisons of gender, academic status, racial and ethnic groups, and parents' educational background. Importantly, our data also show differential gains in the areas of self-efficacy and interest in seeking additional research opportunities between Fly-CURE students with and without prior research experience, illustrating the positive impact of research exposure (dosage) on student outcomes. Altogether, our data indicate that the Fly-CURE experience has a significant impact on students' efficacy with research methods, sense of belonging to the scientific research community, and interest in pursuing additional research experiences.

Genome Sequences of Four Subcluster L2 Mycobacterium Phages, Finemlucis, Miley16, Wilder, and Zakai.

Four subcluster L2 mycobacteriophages, Finemlucis, Miley16, Wilder, and Zakai, that infect Mycobacterium smegmatis mc2155 were isolated. The four phages are closely related to each other and code for 12 to 14 tRNAs and 130 to 132 putative protein-coding genes, including tyrosine integrases, cro, immunity repressors, and excise genes involved in the establishment of lysogeny.

Expansion and angiogenic potential of mesenchymal stem cells from patients with critical limb ischemia.

BACKGROUND: Critical limb ischemia (CLI) is a life- and limb-threatening condition affecting 1% to 10% of the population with peripheral arterial disease. Traditional revascularization options are not possible for up to 50% of CLI patients, in which case, the use of cellular therapies, such as bone marrow-derived mesenchymal stem cells (MSCs), hold great promise as an alternative revascularization therapy. However, no randomized, controlled phase 3 trials to date have demonstrated an improvement in limb salvage with cellular therapies. This may be due to poor cell quality (ie, inability to generate a sufficient number of angiogenic MSCs) or to the inadequate retention and viability of MSCs after delivery, or both. Because concerns remain about the expansion and angiogenic potential of autologous MSCs in the CLI population, the objective of this study was to examine the effect of our novel culture media supplement, pooled human platelet lysate (PL), in lieu of the standard fetal bovine serum (FBS), to improve the expansion potential of MSCs from CLI patients. We also characterized the in vitro angiogenic activity of MSCs from the tibia of amputated CLI limbs compared with MSCs from healthy donors. METHODS: MSCs were obtained from the tibia of four CLI patients (ISC) and four ISC patients with diabetes mellitus (ISC+DM) undergoing major amputation. Healthy MSCs were aspirated from the iliac crest of four young and healthy donors. MSCs were isolated and expanded in culture with PL or FBS. MSCs from passage 3 to 6 were used for phenotypic marker expression and for adipogenic and osteogenic differentiation and were tested for their in vitro angiogenic activity on human microdermal endothelial cells. In parallel MSCs were cultured to passage 11 for population-doubling calculations. RESULTS: MSCs from ISC and ISC+DM patients and from healthy patients exhibited appropriate expression of cell surface markers and differentiation capacity. Population doublings were significantly greater for PL-stimulated compared with FBS-stimulated MSCs in all groups. Biologically active amounts of angiogens were identified in the secretome of all MSCs without consistent trends among groups. PL expansion did not adversely affect the angiogenic activity of MSCs compared with FBS. The ISC and ISC+DM MSCs demonstrated angiogenic effects on endothelial cells similar to those of healthy and ISC MSCs. CONCLUSIONS: PL promotes the rapid expansion of MSCs from CLI and healthy persons. Importantly, MSCs expanded from CLI patients demonstrate the desired angiogenic activity compared with their healthy counterparts. We conclude that autologous MSCs from CLI patients can be sufficiently expanded with PL and be expected to deliver requisite angiogenic effects in vivo. We expect the improved expansion of ISC and ISC+DM with PL to be helpful in improving the successful delivery of autologous MSCs to patients with CLI.

Cell sourcing for bone tissue engineering: amniotic fluid stem cells have a delayed, robust differentiation compared to mesenchymal stem cells.

Cell based therapies for bone regeneration are an exciting emerging technology, but the availability of osteogenic cells is limited and an ideal cell source has not been identified. Amniotic fluid-derived stem cells (AFS) and bone-marrow derived mesenchymal stem cells (MSCs) were compared to determine their osteogenic differentiation capacity in both 2D and 3D environments. In 2D culture, the AFS cells produced more mineralized matrix but delayed peaks in osteogenic markers. Cells were also cultured on 3D scaffolds constructed of poly-ε-caprolactone for 15 weeks. MSCs differentiated more quickly than AFS cells on 3D scaffolds, but mineralized matrix production slowed considerably after 5 weeks. In contrast, the rate of AFS cell mineralization continued to increase out to 15 weeks, at which time AFS constructs contained 5-fold more mineralized matrix than MSC constructs. Therefore, cell source should be taken into consideration when used for cell therapy, as the MSCs would be a good choice for immediate matrix production, but the AFS cells would continue robust mineralization for an extended period of time. This study demonstrates that stem cell source can dramatically influence the magnitude and rate of osteogenic differentiation in vitro.

Colonization and osteogenic differentiation of different stem cell sources on electrospun nanofiber meshes.

Numerous challenges remain in the successful clinical translation of cell-based therapies for musculoskeletal tissue repair, including the identification of an appropriate cell source and a viable cell delivery system. The aim of this study was to investigate the attachment, colonization, and osteogenic differentiation of two stem cell types, human mesenchymal stem cells (hMSCs) and human amniotic fluid stem (hAFS) cells, on electrospun nanofiber meshes. We demonstrate that nanofiber meshes are able to support these cell functions robustly, with both cell types demonstrating strong osteogenic potential. Differences in the kinetics of osteogenic differentiation were observed between hMSCs and hAFS cells, with the hAFS cells displaying a delayed alkaline phosphatase peak, but elevated mineral deposition, compared to hMSCs. We also compared the cell behavior on nanofiber meshes to that on tissue culture plastic, and observed that there is delayed initial attachment and proliferation on meshes, but enhanced mineralization at a later time point. Finally, cell-seeded nanofiber meshes were found to be effective in colonizing three-dimensional scaffolds in an in vitro system. This study provides support for the use of the nanofiber mesh as a model surface for cell culture in vitro, and a cell delivery vehicle for the repair of bone defects in vivo.

Amniotic fluid stem cells produce robust mineral deposits on biodegradable scaffolds.

Insufficient availability of osteogenic cells limits bone regeneration through cell-based therapies. This study investigated the potential of amniotic fluid-derived stem (AFS) cells to synthesize mineralized extracellular matrix within porous medical-grade poly-epsilon-caprolactone (mPCL) scaffolds. The AFS cells were initially differentiated in two-dimensional (2D) culture to determine appropriate osteogenic culture conditions and verify physiologic mineral production by the AFS cells. The AFS cells were then cultured on 3D mPCL scaffolds (6-mm diameter x 9-mm height) and analyzed for their ability to differentiate to osteoblastic cells in this environment. The amount and distribution of mineralized matrix production was quantified throughout the mPCL scaffold using nondestructive micro computed tomography (microCT) analysis and confirmed through biochemical assays. Sterile microCT scanning provided longitudinal analysis of long-term cultured mPCL constructs to determine the rate and distribution of mineral matrix within the scaffolds. The AFS cells deposited mineralized matrix throughout the mPCL scaffolds and remained viable after 15 weeks of 3D culture. The effect of pre-differentiation of the AFS cells on the subsequent bone formation in vivo was determined in a rat subcutaneous model. Cells that were pre-differentiated for 28 days in vitro produced seven times more mineralized matrix when implanted subcutaneously in vivo. This study demonstrated the potential of AFS cells to produce 3D mineralized bioengineered constructs in vitro and in vivo and suggests that AFS cells may be an effective cell source for functional repair of large bone defects.

3D imaging of tissue integration with porous biomaterials.

Porous biomaterials designed to support cellular infiltration and tissue formation play a critical role in implant fixation and engineered tissue repair. The purpose of this Leading Opinion Paper is to advocate the use of high resolution 3D imaging techniques as a tool to quantify extracellular matrix formation and vascular ingrowth within porous biomaterials and objectively compare different strategies for functional tissue regeneration. An initial over-reliance on qualitative evaluation methods may have contributed to the false perception that developing effective tissue engineering technologies would be relatively straightforward. Moreover, the lack of comparative studies with quantitative metrics in challenging pre-clinical models has made it difficult to determine which of the many available strategies to invest in or use clinically for companies and clinicians, respectively. This paper will specifically illustrate the use of microcomputed tomography (micro-CT) imaging with and without contrast agents to nondestructively quantify the formation of bone, cartilage, and vasculature within porous biomaterials.

Chondrogenic differentiation of amniotic fluid-derived stem cells.

For regenerating damaged articular cartilage, it is necessary to identify an appropriate cell source that is easily accessible, can be expanded to large numbers, and has chondrogenic potential. Amniotic fluid-derived stem (AFS) cells have recently been isolated from human and rodent amniotic fluid and shown to be highly proliferative and broadly pluripotent. The purpose of this study was to investigate the chondrogenic potential of human AFS cells in pellet and alginate hydrogel cultures. Human AFS cells were expanded in various media conditions, and cultured for three weeks with growth factor supplementation. There was increased production of sulfated glycosaminoglycan (sGAG) and type II collagen in response to transforming growth factor-beta (TGF-beta) supplementation, with TGF-beta1 producing greater increases than TGF-beta3. Modification of expansion media supplements and addition of insulin-like growth factor-1 during pellet culture further increased sGAG/DNA over TGF-beta1 supplementation alone. Compared to bone marrow-derived mesenchymal stem cells, the AFS cells produced less cartilaginous matrix after three weeks of TGF-beta1 supplementation in pellet culture. Even so, this study demonstrates that AFS cells have the potential to differentiate along the chondrogenic lineage, thus establishing the feasibility of using these cells for cartilage repair applications.

Noninvasive image analysis of 3D construct mineralization in a perfusion bioreactor.

Although the beneficial effects of perfusion on cell-mediated mineralization have been demonstrated in several studies, the size of the mineralized constructs produced has been limited. The ability to quantify mineralized matrix formation non-invasively within 3D constructs would benefit efforts to optimize bioreactor conditions for scaling-up constructs to clinically relevant dimensions. In this study, we report a micro-CT imaging-based technique to monitor 3D mineralization over time in a perfusion bioreactor and specifically assess mechanisms of construct mineralization by quantifying the number, size, and distribution of mineralized particle formation within constructs varying in thickness from 3 to 9 mm. As expected, mineralized matrix volume and particle number increased with construct thickness. Analyzing multiple concentric volumes inside each construct indicated that a greater proportion of the mineral volume was found within the interior of the perfused constructs. Interestingly, intermediate-sized 6mm thick constructs were found to have the highest core mineral volume fraction and the largest mineralized particles. Two complementary mechanisms of increasing total mineral volume were observed in the 6 and 9 mm constructs: increasing particle size and increasing the number of mineralized particles, respectively. The rate of mineralized matrix formation in the perfused constructs increased from 0.69 mm(3)/week during the first 3 weeks of culture to 1.03 mm(3)/week over the final 2 weeks. In contrast, the rate of mineral deposition in the static controls was 0.01 mm(3)/week during the first 3 weeks of culture and 0.16 mm(3)/week from week 3 to week 5. The ability to monitor overall construct mineralization non-invasively coupled with quantitative analysis of mineralized particle size, number, and distribution offers a powerful tool for elucidating how mineral growth mechanisms are affected by cell type, scaffold material and architecture, or bioreactor flow conditions.

Sarcoma derived from cultured mesenchymal stem cells.

To study the biodistribution of MSCs, we labeled adult murine C57BL/6 MSCs with firefly luciferase and DsRed2 fluorescent protein using nonviral Sleeping Beauty transposons and coinfused labeled MSCs with bone marrow into irradiated allogeneic recipients. Using in vivo whole-body imaging, luciferase signals were shown to be increased between weeks 3 and 12. Unexpectedly, some mice with the highest luciferase signals died and all surviving mice developed foci of sarcoma in their lungs. Two mice also developed sarcomas in their extremities. Common cytogenetic abnormalities were identified in tumor cells isolated from different animals. Original MSC cultures not labeled with transposons, as well as independently isolated cultured MSCs, were found to be cytogenetically abnormal. Moreover, primary MSCs derived from the bone marrow of both BALB/c and C57BL/6 mice showed cytogenetic aberrations after several passages in vitro, showing that transformation was not a strain-specific nor rare event. Clonal evolution was observed in vivo, suggesting that the critical transformation event(s) occurred before infusion. Mapping of the transposition insertion sites did not identify an obvious transposon-related genetic abnormality, and p53 was not overexpressed. Infusion of MSC-derived sarcoma cells resulted in malignant lesions in secondary recipients. This new sarcoma cell line, S1, is unique in having a cytogenetic profile similar to human sarcoma and contains bioluminescent and fluorescent genes, making it useful for investigations of cellular biodistribution and tumor response to therapy in vivo. More importantly, our study indicates that sarcoma can evolve from MSC cultures.

Transplantation of murine bone marrow stromal cells under the kidney capsule to secrete coagulation factor VIII.

Ectopic cell transplantation has been studied as an alternative to whole organ transplantation or as a method to produce secretable proteins for genetic disorders. In this study, bone marrow stromal cells isolated from C57Bl/6 mice were genetically modified to express either lacZ- or B-domain-deleted human factor VIII. In vitro modification of the isolated bone marrow stromal cells was initially performed by transducing increased doses of VSV-G pseudotyped lentiviral vectors expressing lacZ. At a MOI of 25, all of the bone marrow stromal cells were X-gal positive, which maintained their ability to expand and differentiate prior to transplantation into mice. Extremely poor engraftment was observed in the liver, but transplantation of the bone marrow stromal cells expressing lacZ under the kidney capsule resulted in long-term viable X-gal-positive cells for at least 8 weeks (length of study). In vitro expression of human factor VIII was detected in a dose-dependent manner following bone marrow stromal cell with a factor VIII-expressing lentiviral vector. Transplantation of the factor VIII-expressing bone marrow stromal cells under the kidney capsule led to long-term therapeutic expression in the mouse plasma (1-3 ng/ml; n = 4-5 mice/group) for 8 weeks. This study demonstrated that ectopic transplantation of bone marrow stromal cells under the kidney capsule can be effective as a method to express secretable proteins in vivo.

Novel object recognition in Apoe(-/-) mice improved by neonatal implantation of wild-type multipotential stromal cells.

Multipotential bone marrow stromal cells (MSCs) from wild-type (Wt) or apolipoprotein E deficient (Apoe(-/-)) mice were implanted into the cerebral ventricles of Apoe(-/-) mice. MSCs from Wt mice continued expressing apoE up to 6 months after implantation and were associated with enhanced novel object recognition and increased microtubule-associated protein 2 (MAP2) immunoreactivity in the dentate gyrus. These data show that MSCs can be used to distinguish developmental from post-developmental effects of a gene knockout and support their therapeutic potential for neurodegenerative diseases.

Adult stem cells from bone marrow stroma differentiate into airway epithelial cells: potential therapy for cystic fibrosis.

Cystic fibrosis (CF), the most prevalent, fatal genetic disorder in the Caucasian population, is caused by mutations of CF transmembrane conductance regulator (CFTR). The mutations of this chloride channel alter the transport of chloride and associated liquid and thereby impair lung defenses. Patients typically succumb to chronic bacterial infections and respiratory failure. Restoration of the abnormal CFTR function to CF airway epithelium is considered the most direct way to treat the disease. In this report, we explore the potential of adult stem cells from bone marrow, referred to as mesenchymal or marrow stromal stem cells (MSCs), to provide a therapy for CF. We found that MSCs possess the capacity of differentiating into airway epithelia. MSCs from CF patients are amenable to CFTR gene correction, and expression of CFTR does not influence the pluripotency of MSCs. Moreover, the CFTR-corrected MSCs from CF patients are able to contribute to apical Cl(-) secretion in response to cAMP agonist stimulation, suggesting the possibility of developing cell-based therapy for CF. The ex vivo coculture system established in this report offers an invaluable approach for selection of stem-cell populations that may have greater potency in lung differentiation.

Internalized antigens must be removed to prepare hypoimmunogenic mesenchymal stem cells for cell and gene therapy.

Adult stem cells from human bone marrow stroma, referred to as mesenchymal stem cells or marrow stromal cells (hMSCs), are attractive candidates for clinical use. The optimal conditions for hMSC expansion require medium supplemented with fetal calf serum (FCS). Some forms of cell therapy will involve multiple doses, raising a concern over immunological reactions caused by medium-derived FCS proteins. By a sensitive fluorescence-based assay we determined that 7 to 30 mg of FCS proteins are associated with a standard preparation of 100 million hMSCs, a dosage that probably will be needed for clinical therapies. Here we present ex vivo growth conditions for hMSCs that reduce the FCS proteins to less than 100 ng per 100 million hMSCs, approximately a 100,000-fold reduction. The cells maintain their proliferative capacity and sustain their ability for multilineage differentiation. Experiments in rats demonstrate that rat MSCs grown in 20% FCS induce a substantial humoral response after repeated administrations, whereas cells grown under the conditions described in this study reduce the immunogenicity in terms of IgG response over 1000-fold to barely detectable levels. Our results have the potential to dramatically improve cellular and genetic therapies using hMSCs and perhaps other cells.

An Alizarin red-based assay of mineralization by adherent cells in culture: comparison with cetylpyridinium chloride extraction.

Alizarin red S (ARS) staining has been used for decades to evaluate calcium-rich deposits by cells in culture. It is particularly versatile in that the dye can be extracted from the stained monolayer and assayed. This study describes a sensitive method for the recovery and semiquantification of ARS in a stained monolayer by acetic acid extraction and neutralization with ammonium hydroxide followed by colorimetric detection at 405 nm. This method was three times more sensitive than an older method involving cetylpyridinium chloride (CPC) extraction and resulted in a better signal to noise ratio, especially for weakly stained monolayers. The assay facilitates detailed inspection of mineralization by phase microscopy and semiquantification of the entire monolayer by extraction and quantification. The sensitivity of the assay is improved by the extraction of the calcified mineral at low pH and, since the mineral is already stained in a quantitative manner, there is no requirement for an additional colorimetric quantification step. Furthermore, the linear range is much wider than those of conventional assays for calcium, making dilutions of mineral extracts prior to measurement unnecessary. It has a wide range of potential uses including tumor characterization, mesenchymal stem cell evaluation, and osteogenic compound screening. Although more labor intensive than CPC extraction, the protocol is more sensitive and yields more reliable results for weakly mineralizing samples.

Adult stem cells from bone marrow (MSCs) isolated from different strains of inbred mice vary in surface epitopes, rates of proliferation, and differentiation potential.

For reasons that are not apparent, it has been difficult to isolate and expand the adult stem cells referred to as mesenchymal stem cells or marrow stromal cells (MSCs) from murine bone marrow. We developed a protocol that provides rapidly expanding MSCs from 5 strains of inbred mice. The MSCs obtained from 5 different strains of mice were similar to human and rat MSCs in that they expanded more rapidly if plated at very low density, formed single-cell-derived colonies, and readily differentiated into either adipocytes, chondrocytes, or mineralizing cells. However, the cells from the 5 strains differed in their media requirements for optimal growth, rates of propagation, and presence of the surface epitopes CD34, stem cell antigen-1 (Sca-1), and vascular cell adhesion molecule 1 (VCAM-1). The protocol should make it possible to undertake a large number of experiments with MSCs in transgenic mice that have previously not been possible. The differences among MSCs from different strains may explain some of the conflicting data recently published on the engraftment of mouse MSCs or other bone marrow cells into nonhematopoietic tissues.

Differentiation, cell fusion, and nuclear fusion during ex vivo repair of epithelium by human adult stem cells from bone marrow stroma.

To investigate stem cell differentiation in response to tissue injury, human mesenchymal stem cells (hMSCs) were cocultured with heat-shocked small airway epithelial cells. A subset of the hMSCs rapidly differentiated into epithelium-like cells, and they restored the epithelial monolayer. Immunocytochemistry and microarray analyses demonstrated that the cells expressed many genes characteristic of normal small airway epithelial cells. Some hMSCs differentiated directly after incorporation into the epithelial monolayer but other hMSCs fused with epithelial cells. Surprisingly, cell fusion was a frequent rather than rare event, in that up to 1% of the hMSCs added to the coculture system were recovered as binucleated cells expressing an epithelial surface epitope. Some of the fused cells also underwent nuclear fusion.