A highly standardized and characterized human platelet lysate for efficient and reproducible expansion of human bone marrow mesenchymal stromal cells

BackgroundHuman platelet lysate (hPL) represents a powerful alternative to fetal bovine serum (FBS) for human mesenchymal stromal cell (hMSC) expansion. However, the large variability in hPL sources and production protocols gives rise to discrepancies in product quality, characterization and poor batch-to-batch standardization.MethodshPL prepared with more than 200 donors (200+DhPL) or with five donors (5DhPL) were compared in terms of growth factor (GF) contents and biochemical analysis. A multiple protein assay and proteomic analysis were performed to further characterize 200+DhPL batches. We also compared the phenotypic and functional characteristics of bone marrow (BM)-hMSCs grown in 200+DhPL versus FBS+basic fibroblast growth factor (bFGF).ResultsBy contrast to 5DhPL, industrial 200+DhPL displayed a strong standardization of GF contents and biochemical characteristics. We identified specific plasmatic components and platelet-released factors as the most relevant markers for the evaluation of the standardization of hPL batches. We used a multiplex assay and proteomic analysis of 200+DhPL to establish a proteomic signature and demonstrated the robust standardization of batches. 200+DhPL was shown to improve and standardize BM-hMSC expansion compared with FBS+bFGF. The levels of expression of BM-hMSC membrane markers were found to be much more homogeneous between batches when cells were cultured in 200+DhPL. BM-hMSCs cultured in parallel under both conditions displayed similar adipogenic and osteogenic differentiation potential and immunosuppressive properties.ConclusionsWe report a standardization of hPL and the importance of such standardization for the efficient amplification of more homogeneous and reproducible cell therapy products.     

Tumor-Stroma Mechanics Coordinate Amino Acid Availability to Sustain Tumor Growth and Malignancy

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Heme catabolism in the causative agent of anthrax

A challenge common to all bacterial pathogens is to acquire nutrients from hostile host environments. Iron is an important cofactor required for essential cellular processes such as DNA repair, energy production and redox balance. Within a mammalian host, most iron is sequestered within heme, which in turn is predominantly bound by hemoglobin. While little is understood about the mechanisms by which bacterial hemophores attain heme from host‐hemoglobin, even less is known about intracellular heme processing. Bacillus anthracis, the causative agent of anthrax, displays a remarkable ability to grow in mammalian hosts. Hypothesizing this pathogen harbors robust ways to catabolize heme, we characterize two new intracellular heme‐binding proteins that are distinct from the previously described IsdG heme monooxygenase. The first of these, HmoA, binds and degrades heme, is necessary for heme detoxification and facilitates growth on heme iron sources. The second protein, HmoB, binds and degrades heme too, but is not necessary for heme utilization or virulence. The loss of both HmoA and IsdG renders B. anthracis incapable of causing anthrax disease. The additional loss of HmoB in this background increases clearance of bacilli in lungs, which is consistent with this protein being important for survival in alveolar macrophages.     

A sharp incisor tool for predator house mice back to the wild

The house mouse (Mus musculus domesticus), as a successful invasive species worldwide, has to forage a variety of resources. Subantarctic mice display among the most notable diet shift from the usual omnivorous–granivorous diet, relying on a larger proportion of terrestrial animal prey. In agreement, a recent study of their mandible morphology evidenced an evolution of their mandible shape to optimize incisor biting and hence seize preys. Here, the incisors themselves are the focus of a morphometric analysis combined with a 3D study of their internal structure, aiming at a comparison between subantarctic populations (Guillou island, Kerguelen archipelago) with a range of western European continental, commensal mice. The predatory foraging behavior of Guillou mice was indeed associated with a sharper bevel of the lower incisor, which appears as an efficient morphology for piercing prey. The incisor of these mice also displays a reduced pulp cavity, suggesting slower eruption counterbalancing a reduced abrasion on such soft food material. The dynamics of the ever‐growing incisor may thus allow adaptive incisor sculpting and participate to the success of mice in foraging diverse resources.     

Different ways to die in a changing world: Consequences of climate change for tree species performance and survival through an ecophysiological perspective

Anthropogenic activities such as uncontrolled deforestation and increasing greenhouse gas emissions are responsible for triggering a series of environmental imbalances that affect the Earth's complex climate dynamics. As a consequence of these changes, several climate models forecast an intensification of extreme weather events over the upcoming decades, including heat waves and increasingly severe drought and flood episodes. The occurrence of such extreme weather will prompt profound changes in several plant communities, resulting in massive forest dieback events that can trigger a massive loss of biodiversity in several biomes worldwide. Despite the gravity of the situation, our knowledge regarding how extreme weather events can undermine the performance, survival, and distribution of forest species remains very fragmented. Therefore, the present review aimed to provide a broad and integrated perspective of the main biochemical, physiological, and morpho‐anatomical disorders that may compromise the performance and survival of forest species exposed to climate change factors, particularly drought, flooding, and global warming. In addition, we also discuss the controversial effects of high CO₂ concentrations in enhancing plant growth and reducing the deleterious effects of some extreme climatic events. We conclude with a discussion about the possible effects that the factors associated with the climate change might have on species distribution and forest composition.     

Nitrate or ammonium: Influences of nitrogen source on the physiology of a green alga

In freshwaters, algal species are exposed to different inorganic nitrogen (N_i) sources whose incorporation varies in biochemical energy demand. We hypothesized that due to the lesser energy requirement of ammonium ()‐use, in contrast to nitrate ()‐use, more energy remains for other metabolic processes, especially under CO₂‐ and phosphorus (P_i) limiting conditions. Therefore, we tested differences in cell characteristics of the green alga Chlamydomonas acidophila grown on or under covariation of CO₂ and P_i‐supply in order to determine limitations, in a full‐factorial design. As expected, results revealed higher carbon fixation rates for ‐grown cells compared to growth with under low CO₂ conditions. ‐grown cells accumulated more of the nine analyzed amino acids, especially under P_i‐limited conditions, compared to cells provided with . This is probably due to a slower protein synthesis in cells provided with . In contrast to our expectations, compared to ‐grown cells ‐grown cells had higher photosynthetic efficiency under P_i‐limitation. In conclusion, growth on the N_i‐source did not result in a clearly enhanced C_i‐assimilation, as it was highly dependent on P_i and CO₂ conditions (replete or limited). Results are potentially connected to the fact that C. acidophila is able to use only CO₂ as its inorganic carbon (C_i) source.     

Multiple functions of Drosophila BLM helicase in maintenance of genome stability

Bloom Syndrome, a rare human disorder characterized by genomic instability and predisposition to cancer, is caused by mutation of BLM, which encodes a RecQ-family DNA helicase. The Drosophila melanogaster ortholog of BLM, DmBlm, is encoded by mus309. Mutations in mus309 cause hypersensitivity to DNA-damaging agents, female sterility, and defects in repairing double-strand breaks (DSBs). To better understand these phenotypes, we isolated novel mus309 alleles. Mutations that delete the N terminus of DmBlm, but not the helicase domain, have DSB repair defects as severe as those caused by null mutations. We found that female sterility is due to a requirement for DmBlm in early embryonic cell cycles; embryos lacking maternally derived DmBlm have anaphase bridges and other mitotic defects. These defects were less severe for the N-terminal deletion alleles, so we used one of these mutations to assay meiotic recombination. Crossovers were decreased to about half the normal rate, and the remaining crossovers were evenly distributed along the chromosome. We also found that spontaneous mitotic crossovers are increased by several orders of magnitude in mus309 mutants. These results demonstrate that DmBlm functions in multiple cellular contexts to promote genome stability.