Spinal neuron histopathology in the<i>Gaa^-/-</i>rat model of Pompe Disease

Pompe Disease (PD) is a lysosomal storage disorder caused by mutations in the acid α-glucosidase (GAA) gene on chromosome 17. The resulting impairment of lysosomal glycogen breakdown leads to neuromuscular dysfunction. Evidence from animal models and humans with Pompe disease indicates that neuropathology contributes to respiratory dysfunction in Pompe disease. However, the only approved treatment for Pompe disease is human recombinant GAA enzyme replacement therapy (ERT) which has a short half-life and does not cross the blood brain barrier. We recently developed a Gaa -/- rat model of Pompe disease that displays early mortality and cardiorespiratory impairments. Prior studies have provided histological evidence for neurodegeneration in the human Pompe spinal cord (PMID: 34191636) and Gaa -/- mouse model (PMID: 19474295). However, to our knowledge, no prior studies have quantified neurodegeneration through total neuronal counts. Accordingly, we used histological methods to estimate the total number of neurons in the spinal cords of 12 month old male Gaa -/- (n=3) and Sprague-Dawley (S-D, n=3) rats. Cervical, thoracic, and lumbar cord segments were harvested following transcardial perfusion, blocked using OCT and cut at 20 µm. Tissues were incubated with an antibody for neuronal nuclear protein (NeuN) to identify neurons. Tissues were imaged using a Keyence microscope. NeuN-positive staining in spinal gray matter was evaluated using QuPath opensource software. Histological analyses were conducted by a blinded reviewer. Inclusion criteria was a clearly identifiable NeuN-positive soma. Three tissue sections were evaluated from each spinal segment per rat. Neurons in the Gaa -/- spinal cord showed prototypical lysosomal storage disease histopathology including vacuolization and a large “swollen” soma in putative motor neurons. The total number of NeuN-positive cells in the cervical spinal cord was reduced by 8.1% in the cervical spinal cord of Gaa -/- compared to S-D rats (p=0.04). In the thoracic spinal cord neuronal counts were reduced by 9.3% in Gaa -/- rats (p=0.31). Total lumbar neuronal counts were similar between groups (p=0.77). This finding is similar to a PD autopsy case report in which cervical and thoracic neurons appeared atrophied whereas lumbar neurons did not (PMID: 34191636). We conclude that neurodegeneration is occurring in the Gaa -/- rat model ofPompe disease and that neurodegeneration may be proceeding more rapidly in the rostral versus caudal spinal cord. 2R01HD052682-11A1 (BJB, DDF) This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.