GDNF‐enhanced axonal regeneration and myelination following spinal cord injury is mediated by primary effects on neurons

We previously demonstrated that coadministration of glial cell line‐derived neurotrophic factor (GDNF) with grafts of Schwann cells (SCs) enhanced axonal regeneration and remyelination following spinal cord injury (SCI). However, the cellular target through which GDNF mediates such actions was unclear. Here, we report that GDNF enhanced both the number and caliber of regenerated axons in vivo and increased neurite outgrowth of dorsal root ganglion neurons (DRGN) in vitro, suggesting that GDNF has a direct effect on neurons. In SC‐DRGN coculture, GDNF significantly increased the number of myelin sheaths produced by SCs. GDNF treatment had no effect on the proliferation of isolated SCs but enhanced the proliferation of SCs already in contact with axons. GDNF increased the expression of the 140 kDa neural cell adhesion molecule (NCAM) in isolated SCs but not their expression of the adhesion molecule L1 or the secretion of the neurotrophins NGF, NT3, or BDNF. Overall, these results support the hypothesis that GDNF‐enhanced axonal regeneration and SC myelination is mediated mainly through a direct effect of GDNF on neurons. They also suggest that the combination of GDNF administration and SC transplantation may represent an effective strategy to promote axonal regeneration and myelin formation after injury in the spinal cord. © 2009 Wiley‐Liss, Inc.     

Ras inhibition attenuates myocardial ischemia-reperfusion injury

Myocardial injury, developed after a period of ischemia/reperfusion (I/R) results in the destruction of functional heart tissue, this being replaced by scar tissue. Intracellular signaling pathways mediating cardiomyocyte death are partially understood and involve the activation of Ras. p38-MAPK, JNK and Mst-1 are downstream effectors of Ras protein. We hypothesized that S-farnesylthiosalicylic acid (FTS), a synthetic small molecule that detaches Ras from the inner cell membrane, consequently inhibiting Ras activity, reduces I/R myocardial injury in vitro and in vivo.Wistar rat hearts were isolated, mounted on the Langendorff apparatus and subjected to ischemia (30 min, 37 °C) and reperfusion. During the reperfusion period, the hearts were perfused with FTS (1 μM) solution or control buffer. Left anterior descending (LAD) ligation and subsequent reperfusion was performed in two groups of Wistar rats. Rats received 5 mg/kg FTS or PBS according to two protocols: (A) FTS or PBS were administered daily 7 days prior, immediately before and 14 days (every other day) after LAD occlusion or (B) every other day for 14 days post-I/R. Hearts from FTS-treated rats (Langendorff) and FTS-treated rats (protocol A) showed a significant improvement in myocardial performance and smaller scar tissue compared with the PBS group. Infarct size in the FTS-treated group was 12.7 ± 2% vs. 23.7 ± 4% in the PBS-treated (in vitro) group and 17.3 ± 2.5% vs. 36 ± 7% compared with control I/R rats (in vivo) p < 0.05. These effects may be associated with the down regulation of JNK as a short-term effector and with Mst-1 in the long-term remodeling process.     

Endogenous adipose tissue as a hemostatic: use in microsurgery

Bleeding is a frequent complication of microsurgical repair of small blood vessels and time is spent while hemostasis is accomplished. We studied the hemostatic effect of endogenous adipose tissue on bleeding from rat femoral arterial anastomoses. We measured bleeding time (time from removal of clamps to cessation of active bleeding) and mean arterial blood velocity (using a micro-Doppler system), the latter immediately after anastomosis, and again 7 days post-anastomosis. Bleeding time for vessels with fat applied to the artery was 50% less than when no fat was applied. Blood velocity by day 7 post-anastomosis returned to values equivalent to those for intact arteries. Histological evaluation of the anastomotic site demonstrated no significant differences in inflammatory response between fat-treated and untreated arteries. These data suggest that endogenous adipose tissue may be a useful hemostatic agent devoid of significant effects on small artery blood velocity or histology.     

Cell killing by antibody-drug conjugates

Antibody-drug conjugates (ADCs) are designed to specifically bind to and kill cells expressing their target antigens. In addition to the obvious requirement of the presence of the target antigen on the cell surface, several other factors contribute to the sensitivity of target cells to the action of ADCs. These include (i) the rate of internalization of the ADC, (ii) its proteolytic degradation in late endosomes and lysosomes and the subsequent release of cytotoxic drug, and (iii) the intracellular concentration of the released drug. In addition to killing antigen-expressing cells, some ADCs were found to kill bystander cells irrespective of their antigen expression. This review summarizes the current knowledge of the mechanisms of killing of antigen-expressing and bystander cells by antibody-drug conjugates.     

Single-cell profiling of ineffective erythropoiesis in a mouse model of β-thalassaemia intermedia

Beta-thalassaemia is an inherited haemoglobin disorder characterised by ineffective erythropoiesis (IE). The detailed pathogenesis of IE remains unclear. In this study, we used single-cell RNA sequencing (scRNA-seq) to examine IE in Th3/+ β-thalassaemic mice. The results showed that the erythroid group was remarkably expanded, and genes involved in biological processes such as iron metabolism, haeme synthesis, protein folding, and response to heat were significantly upregulated from erythroid progenitors to reticulocytes in β-thalassaemic mice. In particular, we identified a unique cell population close to reticulocytes, named ThReticulocytes, characterised by a high level of heat shock protein 70 (Hsp70) expression and dysregulation of iron metabolism and haeme synthesis signalling. Treatment of β-thalassaemic mice with the haeme oxygenase inhibitor tin-mesoporphyrin effectively improved the iron disorder and IE, and the ThReticulocyte population and Hsp70 expression were significantly suppressed. This study revealed in detail the progression of IE at the single-cell level and possibly provided clues to find therapeutic targets in thalassaemia.