Selection of multipotent cells and enhanced muscle reconstruction by myogenic macrophage-secreted factors

Skeletal muscle regeneration relies on satellite cells, a population of myogenic precursors. Inflammation also plays a determinant role in the process, as upon injury, macrophages are attracted by the damaged myofibers and the activated satellite cells and act as key elements of dynamic muscle supportive stroma. Yet, it is not known how macrophages interact with the more profound stem cells of the satellite cell niche. Here we show that in the presence of a murine macrophage conditioned medium (mMCM) a subpopulation of multipotent cells could be selected and expanded from adult rat muscle. These cells were small, round, poorly adhesive, slow-growing and showed mesenchymal differentiation plasticity. At the same time, mMCM showed clear myogenic capabilities, as experiments with satellite cells mechanically isolated from suspensions of single myofibers showed that the macrophagic factors inhibited their tendency to shift towards adipogenesis. In vivo, intramuscular administrations of concentrated mMCM in a rat model of extensive surgical ablation dramatically improved muscle regeneration. Altogether, these findings suggest that macrophagic factors could be of great help in developing therapeutic protocols with myogenic stem cells.     

Expression of matrilin-1, -2 and -3 in developing mouse limbs and heart.

The expression of matrilin-1, -2 and -3 was studied in the heart and limb during mouse development. Matrilin-1 is transiently expressed in the heart between days 9.5 and 14.5 p.c. Matrilin-2 expression was detected in the heart from day 10.5 p.c. onwards. In the developing limb bud, both matrilin-1 and -3 were observed first at day 12.5 p.c. Throughout development matrilin-3 expression was strictly limited to cartilage, while matrilin-1 was also found in some other forms of connective tissue. Matrilin-2, albeit present around hypertrophic chondrocytes in the growth plate, was mainly expressed in non-skeletal structures. The complementary, but in part overlapping, expression of matrilins indicates the possibility for both redundant and unique functions among the members of this novel family of extracellular matrix proteins.     

Relationships between EGFR signaling-competent and endocytosis-competent membrane microdomains

Membrane microdomains, the so-called lipid rafts, function as platforms to concentrate receptors and assemble the signal transduction machinery. Internalization, in most cases, is carried out by different specialized structures, the clathrin-coated pits. Here, we show that several endocytic proteins are efficiently recruited to morphologically identified plasma membrane lipid rafts, upon activation of the epidermal growth factor (EGF) receptor (EGFR), a receptor tyrosine kinase. Analysis of detergent-resistant membrane fractions revealed that the EGF-dependent association of endocytic proteins with rafts is as efficient as that of signaling effector molecules, such as Grb2 or Shc. Finally, the EGFR, but not the nonsignaling transferrin receptor, could be localized in nascent coated pits that almost invariably contained raft membranes. Thus, specialized membrane microdomains have the ability to assemble both the molecular machineries necessary for intracellular propagation of EGFR effector signals and for receptor internalization.     

Polymorphisms in STK17A gene are associated with systemic lupus erythematosus and its clinical manifestations

Systemic lupus erythematosus (SLE) is an autoimmune disorder with several clinical manifestations. SLE etiology has a strong genetic component, which plays a key role in disease's predisposition, as well as participation of environmental factors, such and UV light exposure. In this regard, we investigated whether polymorphisms in STK17A, a DNA repair related gene, encoding for serine/threonine-protein kinase 17A, are associated with SLE susceptibility. A total of 143 SLE patients and 177 healthy controls from Southern Brazil were genotyped for five STK17A TagSNPs. Our results indicated association of rs7805969 SNP (A and G/A genotype, OR = 1.40 and OR = 1.73, respectively) with SLE predisposition and the following clinical manifestations: arthritis, cutaneous and immunological alterations. When analyzing haplotypes distribution, we found association between TGGTC, TAGTC and AAGAT haplotypes and risk to develop SLE. When considering clinical manifestations, the haplotypes TGGTT and TAGTC were associated with protection against cutaneous alterations and the haplotype TAGTC to hematological alterations. We also observed association between SLE clinical manifestations and ethnicity, with the European-derived patients being more susceptible to cutaneous and hematological alterations.     

Mycobacteria mobility shift assay: a method for the rapid identification of Mycobacterium tuberculosis and nontuberculous mycobacteria

The identification of mycobacteria is essential because tuberculosis (TB) and mycobacteriosis are clinically indistinguishable and require different therapeutic regimens. The traditional phenotypic method is time consuming and may last up to 60 days. Indeed, rapid, affordable, specific and easy-to-perform identification methods are needed. We have previously described a polymerase chain reaction-based method called a mycobacteria mobility shift assay (MMSA) that was designed for Mycobacterium tuberculosis complex (MTC) and nontuberculous mycobacteria (NTM) species identification. The aim of this study was to assess the MMSA for the identification of MTC and NTM clinical isolates and to compare its performance with that of the PRA-hsp65 method. A total of 204 clinical isolates (102 NTM and 102 MTC) were identified by the MMSA and PRA-hsp65. For isolates for which these methods gave discordant results, definitive species identification was obtained by sequencing fragments of the 16S rRNA and hsp65 genes. Both methods correctly identified all MTC isolates. Among the NTM isolates, the MMSA alone assigned 94 (92.2%) to a complex or species, whereas the PRA-hsp65 method assigned 100% to a species. A 91.5% agreement was observed for the 94 NTM isolates identified by both methods. The MMSA provided correct identification for 96.8% of the NTM isolates compared with 94.7% for PRA-hsp65. The MMSA is a suitable auxiliary method for routine use for the rapid identification of mycobacteria.     

Association of CD209 and CD209L polymorphisms with tuberculosis infection in a Northeastern Brazilian population

Tuberculosis (TB) caused by Mycobacterium tuberculosis, is major cause of morbidity and mortality worldwide. So far, many candidate genes have been investigated for their possible association with TB. Dendritic cell-specific intercellular adhesion molecule 3 (ICAM-3) grabbing non-integrin (DC-SIGN) and Liver/lymph node-specific intercellular adhesion molecule-grabbing non-integrin (L-SIGN), encoded by CD209 and CD209L genes respectively, are known for binding to M. tuberculosis on human dendritic cells and macrophages. We screened 4 single nucleotide polymorphisms (SNPs) in the promoter region of CD209, namely ?939G>A (rs735240), ?871A>G (rs735239), ?336A>G (rs4804803) and ?139G>A (rs2287886) and tandem repeat polymorphisms in exon 4 of CD209 and CD209L genes looking for association with TB in a Northeastern Brazilian population (295 subjects, 131 TB patients and 164 healthy controls). The ?139G>A and ?939G>A SNPs were associated with susceptibility to TB, and in particular with pulmonary and extra-pulmonary forms respectively. The ?871A>G and ?336A>G SNPs were associated, the first with protection to both pulmonary and extra-pulmonary TB, the latter only with the pulmonary form. An association between GGAG haplotype and protection to TB infection was also found. Also tandem repeat polymorphism in CD209L exon 4 was associated with TB infection. This study provides evidence of an association between CD209 and CD209L polymorphisms and TB development in a Brazilian population, suggesting that variations in these genes may influence the protection and susceptibility to infection caused by M. tuberculosis.     

Helicobacter pylori‐derived neutrophil‐activating protein increases the lifespan of monocytes and neutrophils

An invariable feature of Helicobacter pylori‐infected gastric mucosa is the persistent infiltration of inflammatory cells. The neutrophil‐activating protein (HP‐NAP) has a pivotal role in triggering and orchestrating the phlogistic process associated with H. pylori infection. Aim of this study was to address whether HP‐NAP might further contribute to the inflammation by increasing the lifespan of inflammatory cells. We report that HP‐NAP is able to prolong the lifespan of monocytes, in parallel with the induction of the anti‐apoptotic proteins A1, Mcl‐1, Bcl‐2 and Bcl‐X_L. This effect does not result from a direct action on the apoptotic machinery, but rather it requires the release of endogenous pro‐survival factors, such as interleukin‐1β, which probably acts in synergy with other unidentified mediators. We also report that HP‐NAP promotes the survival of Ficoll‐purified neutrophils in a monocyte‐dependent fashion: indeed, mononuclear cell depletion of Ficoll‐purified neutrophils completely abolished the pro‐survival effect by HP‐NAP. In conclusion, our data reinforce the notion that HP‐NAP has a pivotal role in sustaining a prolonged activation of myeloid cells.