Effects of neuregulin GGF2 (cimaglermin alfa) dose and treatment frequency on left ventricular function in rats following myocardial infarction.

Neuregulins are important growth factors involved in cardiac development and response to stress. Certain isoforms and fragments of neuregulin have been found to be cardioprotective. The effects of a full-length neuregulin-1ß isoform, glial growth factor 2 (GGF2; USAN/INN; also called cimaglermin) were investigated in vitro. Various dosing regimens were then evaluated for their effects on left ventricular (LV) function in rats with surgically-induced myocardial infarction. In vitro, GGF2 bound with high affinity to erythroblastic leukemia viral oncogene (ErbB) 4 receptors, potently promoted Akt phosphorylation, as well as reduced cell death following doxorubicin exposure in HL1 cells. Daily GGF2 treatment beginning 7-14 days after left anterior descending coronary artery ligation produced improvements in LV ejection fraction and other measures of LV function and morphology. The improvements in LV function (e.g. 10% point increase in absolute LV ejection fraction) with GGF2 were dose-dependent. LV performance was substantially improved when GGF2 treatment was delivered infrequently, despite a serum half-life of less than 2h and could be maintained for more than 10 months with treatment once weekly or once every 2 weeks. These studies confirm previous findings that GGF2 may improve contractile performance in the failing rat heart and that infrequent exposure to GGF2 may improve LV function and impact remodeling in the failing myocardium. GGF2 is now being developed for the treatment of heart failure in humans.

The Evaluation of Magnesium Chloride within a Polyethylene Glycol Formulation in a Porcine Model of Acute Spinal Cord Injury.

A porcine model of spinal cord injury (SCI) was used to evaluate the neuroprotective effects of magnesium chloride (MgCl2) within a polyethylene glycol (PEG) formulation, called "AC105" (Acorda Therapeutics Inc., Ardsley, NY). Specifically, we tested the hypothesis that AC105 would lead to greater tissue sparing at the injury site and improved behavioral outcome when delivered in a clinically realistic time window post-injury. Four hours after contusion/compression injury, Yucatan minipigs were randomized to receive a 30-min intravenous infusion of AC105, magnesium sulfate (MgSO4), or saline. Animals received 4 additional infusions of the same dose at 6-h intervals. Behavioral recovery was tested for 12 weeks using two-dimensional (2D) kinematics during weight-supported treadmill walking and the Porcine Injury Behavior Scale (PTIBS), a 10-point locomotion scale. Spinal cords were evaluated ex vivo by diffusion-weighted magnetic resonance imaging (MRI) and subjected to histological analysis. Treatment with AC105 or MgSO4 did not result in improvements in locomotor recovery on the PTIBS or in 2D kinematics on weight-supported treadmill walking. Diffusion weighted imaging (DWI) showed severe loss of tissue integrity at the impact site, with decreased fractional anisotropy and increased mean diffusivity; this was not improved with AC105 or MgSO4 treatment. Histological analysis revealed no significant increase in gray or white matter sparing with AC105 or MgSO4 treatment. Finally, AC105 did not result in higher Mg2+ levels in CSF than with the use of standard MgSO4. In summary, when testing AC105 in a porcine model of SCI, we were unable to reproduce the promising therapeutic benefits observed previously in less-severe rodent models of SCI.

Glial growth factor 2 promotes functional recovery with treatment initiated up to 7 days after permanent focal ischemic stroke.

Neuregulins are a family of growth factors essential for normal cardiac and nervous system development. The EGF-like domain of neuregulins contains the active site which binds and activates signaling cascades through ErbB receptors. A neuregulin-1 gene EGF-like fragment demonstrated neuroprotection in the transient middle cerebral artery occlusion (MCAO) stroke model and drastically reduced infarct volume (Xu et al., 2004). Here we use a permanent MCAO rat model to initially compare two products of the neuregulin-1 gene and also assess levels of recovery with acute versus delayed time to treatment. In the initial study full-length glial growth factor 2 (GGF2) and an EGF-like domain fragment were compared with acute intravenous delivery. In a second study GGF2 only was delivered starting at 24h, 3 days or 7 days after permanent ischemia was induced. In both studies daily intravenous administration continued for 10 days. Recovery of neurological function was assessed using limb placing and body swing tests. GGF2 had similar functional improvements compared to the EGF-like domain fragment at equimolar doses, and a higher dose of GGF2 demonstrated more robust functional improvements compared to a lower dose. GGF2 improved sensorimotor recovery with all treatment paradigms, even enhancing recovery of function with a delay of 7 days to treatment. Histological assessments did not show any associated reduction in infarct volume at either 48 h or 21 days post-ischemic event. Neurorestorative effects of this kind are of great potential clinical importance, given the difficulty of delivering neuroprotective therapies within a short time after an ischemic event in human patients. If confirmed by additional work including additional data on mechanism(s) of improved outcome with verification in other stroke models, one can make a compelling case to bring GGF2 to clinical trials as a neurorestorative approach to improving outcome following stroke injury.

Chondroitin sulfate proteoglycans in spinal cord contusion injury and the effects of chondroitinase treatment.

Chondroitinase treatment of experimental spinal cord injury improves recovery of sensory, motor, and autonomic functions. Chondroitinase catalyzes the cleavage of glycosaminoglycans (GAGs) from the core proteins of chondroitin sulfate proteoglycans (CSPGs). Little is known about changes in production of these proteoglycans in the clinically relevant contusion model of spinal cord injury or if CSPG content is altered by chondroitinase treatment. Female Long-Evans rats were injured with a forceps contusion injury and treated on alternate days with chondroitinase ABCI or control enzyme via an intrathecal catheter. Spinal cords were analyzed at specific times after injury. The cord was divided in 4 mm long segments, one containing the lesion, two rostral and two caudal to the lesion. These segments were assessed for CSPG protein and message content (NG2, neurocan and phosphacan) by Western blotting and real-time PCR. CSPG protein content was increased by one day post injury for all CSPGs investigated, and was increased in all segments examined rostral and caudal to the lesion site. Significant increases in CSPG were observed with peak content detected at 7, 7 and 14 days post injury for NG2, neurocan and phosphacan, respectively. Chondroitinase treatment had little impact upon the CPSG protein content. Changes in message levels of these CSPGs are also reported. This demonstrates that expression patterns of CSPGs in contusion injury are similar to those surrounding surgical hemisection lesions and demonstrates that the sensory and motor function enhancing effects of chondroitinase are likely due to removal of GAG chains rather than reduction in CSPG content.