In vitro expansion of human cardiac progenitor cells: exploring 'omics tools for characterization of cell-based allogeneic products.

Human cardiac stem/progenitor cells (hCPCs) have been shown to be capable to regenerate contractile myocardium. However, because of their relative low abundance in the heart, in vitro expansion of hCPC is mandatory to achieve necessary quantities for allogeneic or autologous cardiac regeneration therapy applications (10(6)-10(9) cells/patient). Up to now, cell number requirements of ongoing phase I/IIa trials have been fulfilled with production in static monolayer cultures. However, this manufacturing process poses critical limitations when moving to the following clinical phases where hundreds of patients will be enrolled. For this, increased process yield is required, while guaranteeing the quality of the cell-based products. In this work, we developed and validated a robust, scalable, and good manufacturing practice (GMP)-compatible bioprocess for the expansion of high-quality hCPC. We applied platforms extensively used by the biopharmaceutical industry, such as microcarrier technology and stirred systems, and assessed culture conditions' impact on hCPC's quality and potency, as required by regulatory agencies. Complementary analytical assays including gene expression microarrays and mass spectrometry-based approaches were explored to compare transcriptome, proteome, surface markers, and secretion profiles of hCPC cultured in static monolayers and in stirred microcarrier-based systems. Our results show that stirred microcarrier-based culture systems enabled achieving more than 3-fold increase in hCPC expansion, when compared with traditional static monolayers, while retaining cell's phenotype and similar "omics" profiles. These findings demonstrate that this change in the production process does not affect cell's identity and quality, with potential to be translated into a transversal production platform for clinical development of stem-cell therapies.

Tetraspanins displayed in retrovirus-derived virus-like particles and their immunogenicity.

Virus-like particles (VLPs) are a particular subset of subunit vaccines which are currently explored as safer alternatives to live attenuated or inactivated vaccines. VLPs derived from retrovirus (retroVLPs) are commonly used as scaffolds for vaccine candidates due to their ability to incorporate heterologous envelope proteins. Pseudotyping retroVLPs is however not a selective process therefore, host cellular proteins such as tetraspanins are also included in the membrane. The contribution of these host-proteins to retrovirus immunogenicity remains unclear. In this work, human cells silenced and not silenced for tetraspanin CD81 were used to produce CD81(-) or CD81(+) retroVLPs. We first analyzed mice immune response against human CD81. Despite effective silencing of CD81 in retroVLP producing cells, both humoral and cellular immune responses showed persistent anti-CD81 immunogenicity, suggesting cross reactivity to related antigens. We thus compared the incorporation of related tetraspanins in retroVLPs and showed that decreased CD81 incorporation in CD81(-) retro-VLPs is compensated by an increased incorporation of CD9 and CD63 tetraspanins. These results highlight the dynamic nature of host-derived proteins incorporation in retroVLPs membrane, which should be considered when retrovirus-based biopharmaceuticals are produced in xenogeneic cells.

First insights into the biochemistry of tube foot adhesive from the sea urchin Paracentrotus lividus (Echinoidea, Echinodermata).

Sea urchins are common inhabitants of wave-swept shores. To withstand the action of waves, they rely on highly specialized independent adhesive organs, the adoral tube feet. The latter are extremely well-designed for temporary adhesion being composed by two functional subunits: (1) an apical disc that produces an adhesive secretion to fasten the sea urchin to the substratum, as well as a deadhesive secretion to allow the animal to move and (2) a stem that bears the tensions placed on the animal by hydrodynamism. Despite their technological potential for the development of new biomimetic underwater adhesives, very little is known about the biochemical composition of sea urchin adhesives. A characterization of sea urchin adhesives is presented using footprints. The latter contain inorganic residues (45.5%), proteins (6.4%), neutral sugars (1.2%), and lipids (2.5%). Moreover, the amino acid composition of the soluble protein fraction revealed a bias toward six amino acids: glycine, alanine, valine, serine, threonine, and asparagine/aspartic acid, which comprise 56.8% of the total residues. In addition, it also presents higher levels of proline (6.8%) and half-cystine (2.6%) than average eukaryotic proteins. Footprint insolubility was partially overcome using strong denaturing and reducing buffers, enabling the visualization of 13 proteins by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The conjugation of mass spectrometry with homology-database search allowed the identification of six proteins: alpha and beta tubulin, actin, and histones H2B, H3, H2A, and H4, whose location and function in the adhesive are discussed but require further investigation. For the remaining unidentified proteins, five de novo-generated peptide sequences were found that were not present in the available protein databases, suggesting that they might be novel or modified proteins.