In recent years, growth factor therapy has emerged as a potential treatment for ischemic brain injury. The efficacy of therapies that either directly introduce or stimulate local production of growth factors and their receptors in damaged brain tissue has been tested in a multitude of models for different Central Nervous System (CNS) diseases. These growth factors include erythropoietin (EPO), vascular endothelial growth factor (VEGF), brain-derived neurotrophic factor (BDNF), and insulin-like growth factor (IGF-1), among others. Despite the promise shown in animal models, the particular growth factors that should be used to maximize both brain protection and repair, and the therapeutic critical period, are not well defined. We will review current pre-clinical and clinical evidence for growth factor therapies in treating different causes of brain injury, as well as issues to be addressed prior to application in humans.

Background and Objectives: Predicting neurodevelopmental outcome for neonates with hypoxic-ischemic encephalopathy (HIE) is important for clinical decision-making, care planning, and parent communication. We examined the relationship between EEG background and neurodevelopmental outcome among children enrolled in a trial of erythropoietin (Epo) or placebo for neonates with HIE treated with therapeutic hypothermia. Methods: Participants had EEG recorded throughout hypothermia. EEG background was classified as normal, discontinuous, or severely abnormal (defined as burst suppression, low voltage suppressed, or status epilepticus) at five one-hour epochs: onset of recording, 24, 36, 48, and 72 hours after birth. The predominant background pattern during the entire cEEG recording was calculated using the arithmetic mean of the five EEG background ratings (normal=0; discontinuous=1; severely abnormal=2) as follows: “predominantly normal” (mean=0), “normal/discontinuous” (0<mean<1), “predominantly discontinuous” (mean=1), “discontinuous/severely abnormal” (1<mean<2), or “predominantly severely abnormal” (mean=2). Primary outcome was death or neurodevelopmental impairment (NDI) defined as cerebral palsy, Gross Motor Function Classification Score ≥1 or cognitive score <90 on Bayley Scales of Infant Toddler Development, 3rd edition at age two years. Neurodevelopment was also categorized into a 5-level ordinal measure: no, mild, moderate, or severe NDI, or death for secondary analysis. We used generalized linear regression models with robust standard errors to assess the relative risk of death or NDI by EEG background in both unadjusted and adjusted analyses controlling for effects of treatment group, sex, HIE severity, and study recruitment site. Results: Among 142 neonates, predominant background EEG pattern was predominantly normal in 35 (25%), normal/discontinuous in 68 (48%), predominantly discontinuous in 11 (7.7%), discontinuous/severely abnormal in 16 (11%), and predominantly severely abnormal in 12 (8.5%). Increasing severity of background across monitoring epochs was associated with increasingly worse clinical outcomes. Children with severe EEG background abnormality at any time point (n=36, 25%) were significantly more likely to die or have severe neurodevelopmental impairment at two years (adjusted relative risk: 7.95, 95% confidence interval 3.49–18.12). Discussion: EEG background is strongly associated with NDI at age two years. These results can be used to assist health care providers to plan follow-up care and counsel families for decision making related to goals of care. NCT02811263.

Background and Purpose: Perinatal stroke is a common cause of life-long neurobehavioral compromise. Mesenchymal stromal cells (MSCs) and EPO (erythropoietin) have each demonstrated short-term benefit with delayed administration after stroke, and combination therapy may provide the most benefit. The purpose of this study is to determine the long-term histological and functional efficacy of enhanced, intranasal stem cell therapy (MSC preexposed to EPO) compared with standard MSC or multidose systemic EPO. Methods: Transient middle cerebral artery occlusion or sham surgery was performed in postnatal day (P) 10 Sprague-Dawley rats, who were treated with single-dose intranasal MSC, MSC preexposed to EPO (MSC/EPO), multidose systemic EPO (EPO3; 1000 u/kg per dose×3 every 72 hours), or cell-conditioned media on P13 (day 3 [P13–P19] for EPO), or on P17 (day 7 [P17–P23] for EPO). At 2 months of age, animals underwent novel object recognition, cylinder rearing, and open field testing to assess recognition memory, sensorimotor function, and anxiety in adulthood. Results: MSC, MSC/EPO, and EPO3 improved brain volume when administered at 3 or 7 days after middle cerebral artery occlusion. MSC/EPO also enhanced long-term recognition memory with either day 3 or day 7 treatment, but EPO3 had the most long-term benefit, improving recognition memory and exploratory behavior and reducing anxiety. Conclusions: These data suggest that single-dose MSC/EPO and multidose systemic EPO improve long-term neurobehavioral outcomes even when administration is delayed, although EPO was the most effective treatment overall. It is possible that EPO represents a final common pathway for improved long-term repair, although the specific mechanisms remain to be determined.

Background: Neonatal stroke affects 1 in 2800 live births and is a major cause of neurological injury. The Sonic hedgehog (Shh) signaling pathway is critical for central nervous system (CNS) development and has neuroprotective and reparative effects in different CNS injury models. Previous studies have demonstrated beneficial effects of small molecule Shh-Smoothened agonist (SAG) against neonatal cerebellar injury and it improves Down syndrome-related brain structural deficits in mice. Here we investigated SAG neuroprotection in rat models of neonatal ischemia–reperfusion (stroke) and adult focal white matter injury. Methods: We used transient middle cerebral artery occlusion at P10 and ethidium bromide (EB) injection in adult rats to induce damage. Following surgery and SAG or vehicle treatment, we analyzed tissue loss, cell proliferation and fate, and behavioral outcome. Results: We report that a single dose of SAG administered following neonatal stroke preserved brain volume, reduced gliosis, enhanced oligodendrocyte progenitor cell (OPC) and EC proliferation, and resulted in long-term cognitive improvement. Single-dose SAG also promoted proliferation of OPCs following focal demyelination in the adult rat. Conclusions: These findings indicate benefit of one-time SAG treatment post insult in reducing brain injury and improving behavioral outcome after experimental neonatal stroke. Impact: A one-time dose of small molecule Sonic hedgehog agonist protected against neonatal stroke and improved long-term behavioral outcomes in a rat model. This study extends the use of Sonic hedgehog in treating developing brain injury, previously shown in animal models of Down syndrome and cerebellar injury. Sonic hedgehog agonist is one of the most promising therapies in treating neonatal stroke thanks to its safety profile and low dosage.