<table class="infobox infobox-therapeutic">
<tr>
<th class="infobox-header" colspan="2">Growth Factor Therapies</th>
</tr>
<tr>
<td class="label">Name</td>
<td><strong>Growth Factor Therapies</strong></td>
</tr>
<tr>
<td class="label">Type</td>
<td>Therapeutic</td>
</tr>
</table>
Growth factor therapies represent a promising neuroprotective and disease-modifying approach to treating neurodegenerative diseases. Growth factors are endogenous proteins that support neuronal survival, promote synaptic plasticity, stimulate neurogenesis, and protect against various pathological insults characteristic of Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and other disorders. This page provides a comprehensive overview of growth factor biology, therapeutic strategies, delivery challenges, and clinical evidence for growth factor-based interventions in neurodegeneration. [@kalia2020]
<table class="infobox infobox-therapeutic">
<tr>
<th class="infobox-header" colspan="2">Growth Factor Therapies</th>
</tr>
<tr>
<td class="label">Name</td>
<td><strong>Growth Factor Therapies</strong></td>
</tr>
<tr>
<td class="label">Type</td>
<td>Therapeutic</td>
</tr>
</table>
Growth factor therapies represent a promising neuroprotective and disease-modifying approach to treating neurodegenerative diseases. Growth factors are endogenous proteins that support neuronal survival, promote synaptic plasticity, stimulate neurogenesis, and protect against various pathological insults characteristic of Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and other disorders. This page provides a comprehensive overview of growth factor biology, therapeutic strategies, delivery challenges, and clinical evidence for growth factor-based interventions in neurodegeneration. [@kalia2020]
Growth factors exert their neuroprotective effects through multiple signaling pathways that promote neuronal survival and function. Upon binding to their respective receptor tyrosine kinases on neuronal membranes, growth factors trigger downstream cascades including the phosphatidylinositol 3-kinase (PI3K)/Akt pathway, mitogen-activated protein kinase (MAPK)/ERK pathway, and phospholipase C-gamma (PLC-γ) pathway. These cascades converge on key survival proteins including [mTOR](/mechanisms/mtor-signaling-pathway), CREB, and FoxO transcription factors, which regulate gene expression programs essential for neuronal viability, synaptic plasticity, and resistance to stress [1]. [@tuszynski2019]
The neuroprotective mechanisms of growth factors include: (1) anti-apoptotic signaling through upregulation of Bcl-2 family proteins and inhibition of caspase activation; (2) antioxidant enzyme induction including superoxide dismutase, catalase, and glutathione peroxidase; (3) mitochondrial dysfunction correction through enhanced mitochondrial biogenesis and quality control; (4) neuroinflammation modulation through reduced microglial activation and pro-inflammatory cytokine production; (5) synaptic plasticity enhancement through increased dendritic spine density and neurotransmitter receptor expression; and (6) adult neurogenesis stimulation in the subventricular zone and hippocampal subgranular zone [2]. [@allen2021]
BDNF is the most extensively studied neurotrophin in neurodegeneration research. Through TrkB receptor activation, BDNF promotes survival of cortical and hippocampal [neurons](/entities/neurons), enhances synaptic plasticity, and plays critical roles in learning and memory. BDNF levels are significantly reduced in AD and PD brains, making replacement therapy a logical therapeutic strategy. Multiple delivery approaches have been explored including recombinant protein infusion, gene therapy with AAV vectors, and small molecule TrkB agonists [3]. [@huang2020]
GDNF family ligands (GFLs) including GDNF, neurturin, artemin, and persephin exert potent protective effects on dopaminergic neurons through GFRα1-4 receptor complexes and RET tyrosine kinase signaling. GDNF has demonstrated robust neuroprotective effects in preclinical PD models and showed promising results in early clinical trials. However, subsequent trials produced mixed results, likely due to delivery challenges and biomarker selection issues [4]. [@rangasamy2022]
The FGF family comprises 22 members that signal through four FGFR isoforms. FGF-2 (bFGF) and FGF-21 have shown neuroprotective properties in AD and PD models. FGF-2 promotes neural stem cell proliferation and neuronal differentiation, while FGF-21 improves glucose metabolism and reduces neuroinflammation. FGF18 has demonstrated efficacy in ALS models through supporting motor neuron survival [5]. [@tuszynski2019a]
NGF was the first discovered neurotrophin and signals through TrkA receptors to support basal forebrain cholinergic neurons that degenerate early in AD. NGF delivery via AAV (CERE-110) has been tested in clinical trials for AD, showing evidence of tolerability and potential biological activity. Challenges include the need for precise targeting to avoid adverse effects and ensuring adequate diffusion through brain tissue [6]. [@tahmasebi2021]
IGF-1 and IGF-2 promote neuronal survival through IGF-1 receptor signaling, which activates PI3K/Akt and MAPK pathways. IGF-1 has shown promise in ALS clinical trials (Talmac et al., 2006) and in PD models. The growth hormone/IGF-1 axis declines with age, potentially contributing to age-related neurodegeneration [7]. [@jin2022]
VEGF supports neurogenesis, angiogenesis, and blood-brain barrier maintenance. Beyond its vascular effects, VEGF directly protects neurons through VEGFR2 signaling. VEGF delivery has shown neuroprotective effects in AD and PD models, though concerns about angiogenic effects in tumors require careful consideration [8]. [@xhima2022]
Clinical trials in AD have tested NGF (CERE-110), BDNF delivery, and FGF family members. The CERE-110 trial showed that AAV-mediated NGF delivery to the basal forebrain was well-tolerated with evidence of target engagement. BDNF gene therapy trials using AAV vectors have completed phase 1 testing showing safety. Phase 2 trials of BDNF mimetics are ongoing [9]. [@whone2019]
GDNF and neurturin trials in PD have produced mixed results. The initial open-label studies showed potential clinical benefit, but double-blind trials failed to meet primary endpoints. Post-hoc analyses suggested benefit in younger patients and those with shorter disease duration. Newer trials using improved delivery methods and combination approaches are underway [10]. [@lundstrom2021]
IGF-1 (Iplex) was approved in Argentina for ALS treatment based on clinical trial data showing slowed disease progression. However, US trials showed conflicting results. Gene therapy approaches using AAV to deliver IGF-1 or other growth factors are being developed [11]. [@sontag2020]
The blood-brain barrier (BBB) presents a major obstacle for growth factor delivery. Most growth factors are large molecules that cannot cross the [BBB](/entities/blood-brain-barrier) efficiently. Strategies to overcome this include: (1) intraparenchymal infusion via convection-enhanced delivery; (2) intrathecal delivery to the cerebrospinal fluid; (3) BBB disruption using focused ultrasound or chemical agents; (4) engineering of BBB-penetrant growth factor variants; and (5) use of viral vectors for gene therapy-mediated brain expression [12]. [@mandel2021]
Precise targeting to specific neuronal populations is challenging. Some growth factors like BDNF signal through multiple receptor types, leading to off-target effects. Engineering of receptor-selective variants and use of targeted delivery vectors can improve specificity. Cell-type specific promoters in gene therapy vectors enable selective expression [13]. [@nagahara2020]
Determining therapeutic dosing windows is complex. Excessive growth factor exposure can cause adverse effects including pain, seizures, and potentially tumorigenesis. Controlled-release formulations and regulated expression systems using regulatable promoters allow for dose optimization [14]. [@kowalski2022]
Combining growth factor therapy with other interventions may enhance efficacy. Notable combinations include: (1) growth factors with exercise, which naturally increases endogenous growth factor expression; (2) growth factors with small molecule neuroprotective agents; (3) growth factors with immunotherapy targeting pathological proteins; and (4) multiple growth factors acting on complementary pathways [15]. [@declercq2023]
Emerging approaches include: (1) engineered neurotrophin variants with improved brain penetration and receptor selectivity; (2) small molecule Trk agonists that can cross the BBB; (3) gene therapy with next-generation vectors achieving broader brain distribution; (4) cell-based therapy using engineered cells secreting growth factors; (5) RFDF (convection-enhanced delivery) techniques improving distribution; and (6) biomarker-driven patient selection for growth factor-responsive subtypes [16].
From the [SciDEX Exchange](/exchange) — scored by multi-agent debate
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