Catalina Guerra

Early versus late treatment of spinal cord compression with long-term intrathecal enzyme replacement therapy in canine mucopolysaccharidosis type I

Enzyme replacement therapy (ERT) with intravenous recombinant human alpha-l-iduronidase (IV rhIDU) is a treatment for patients with mucopolysaccharidosis I (MPS I). Spinal cord compression develops in MPS I patients due in part to dural and leptomeningeal thickening from accumulated glycosaminoglycans (GAG). We tested long-term and every 3-month intrathecal (IT) and weekly IV rhIDU in MPS I dogs age 12-15months (Adult) and MPS I pups age 2-23days (Early) to determine whether spinal cord compression could be reversed, stabilized, or prevented. Five treatment groups of MPS I dogs were evaluated (n=4 per group): IT+IV Adult, IV Adult, IT + IV Early, 0.58mg/kg IV Early and 1.57mg/kg IV Early. IT + IV rhIDU (Adult and Early) led to very high iduronidase levels in cervical, thoracic, and lumber spinal meninges (3600-29,000% of normal), while IV rhIDU alone (Adult and Early) led to levels that were 8.2-176% of normal. GAG storage was significantly reduced from untreated levels in spinal meninges of IT + IV Early (p<.001), IT+IV Adult (p=.001), 0.58mg/kg IV Early (p=.002) and 1.57mg/kg IV Early (p<.001) treatment groups. Treatment of dogs shortly after birth with IT+IV rhIDU (IT + IV Early) led to normal to near-normal GAG levels in the meninges and histologic absence of storage vacuoles. Lysosomal storage was reduced in spinal anterior horn cells in 1.57mg/kg IV Early and IT + IV Early animals. All dogs in IT + IV Adult and IV Adult groups had compression of their spinal cord at 12-15months of age determined by magnetic resonance imaging and was due to protrusion of spinal disks into the canal. Cord compression developed in 3 of 4 dogs in the 0.58mg/kg IV Early group; 2 of 3 dogs in the IT + IV Early group; and 0 of 4 dogs in the 1.57mg/kg IV Early group by 12-18months of age. IT + IV rhIDU was more effective than IV rhIDU alone for treatment of meningeal storage, and it prevented meningeal GAG accumulation when begun early. High-dose IV rhIDU from birth (1.57mg/kg weekly) appeared to prevent cord compression due to protrusion of spinal disks.

Glycosaminoglycan storage in neuroanatomical regions of mucopolysaccharidosis I dogs following intrathecal recombinant human iduronidase

Chen A, Vogler C, McEntee M, Hanson S, Ellinwood MN, Jens J, Snella E, Passage M, Le S, Guerra C, Dickson P. Glycosaminoglycan storage in neuroanatomical regions of mucopolysaccharidosis I dogs following intrathecal recombinant human iduronidase. APMIS 2011; 119: 513–21.

Preclinical Testing and Optimization of a Novel Fetal Micropacemaker

Yaniv Bar-Cohen, MD, FHRS, Gerald E. Loeb, MD, Jay D. Pruetz, MD, Michael J. Silka, MD, Catalina Guerra, DVM, Adriana N. Vest, BE, Li Zhou, MS, Ramen H. Chmait, MD From the Division of Cardiology, Children’s Hospital Los Angeles; and Keck School of Medicine, University of Southern California, Los Angeles, CA, Department of Biomedical Engineering, University of Southern California, Los Angeles, California, C.W. Steers Biological Resources Center, Los Angeles Biomedical Research Institute, Harbor–University of California, Los Angeles, Torrance, California, and Department of Obstetrics and Gynecology, Keck School of Medicine, University of Southern California, Los Angeles, California.

Intra-articular enzyme replacement therapy with rhIDUA is safe, well-tolerated, and reduces articular GAG storage in the canine model of mucopolysaccharidosis type I.

BACKGROUND Treatment with intravenous enzyme replacement therapy and hematopoietic stem cell transplantation for mucopolysaccharidosis (MPS) type I does not address joint disease, resulting in persistent orthopedic complications and impaired quality of life. A proof-of-concept study was conducted to determine the safety, tolerability, and efficacy of intra-articular recombinant human iduronidase (IA-rhIDUA) enzyme replacement therapy in the canine MPS I model. METHODS Four MPS I dogs underwent monthly rhIDUA injections (0.58 mg/joint) into the right elbow and knee for 6 months. Contralateral elbows and knees concurrently received normal saline. No intravenous rhIDUA therapy was administered. Monthly blood counts, chemistries, anti-rhIDUA antibody titers, and synovial fluid cell counts were measured. Lysosomal storage of synoviocytes and chondrocytes, synovial macrophages and plasma cells were scored at baseline and 1 month following the final injection. RESULTS All injections were well-tolerated without adverse reactions. One animal required prednisone for spinal cord compression. There were no clinically significant abnormalities in blood counts or chemistries. Circulating anti-rhIDUA antibody titers gradually increased in all dogs except the prednisone-treated dog; plasma cells, which were absent in all baseline synovial specimens, were predominantly found in synovium of rhIDUA-treated joints at study-end. Lysosomal storage in synoviocytes and chondrocytes following 6 months of IA-rhIDUA demonstrated significant reduction compared to tissues at baseline, and saline-treated tissues at study-end. Mean joint synovial GAG levels in IA-rhIDUA joints were 8.62 ± 5.86 μg/mg dry weight and 21.6 ± 10.4 μg/mg dry weight in control joints (60% reduction). Cartilage heparan sulfate was also reduced in the IA-rhIDUA joints (113 ± 39.5 ng/g wet weight) compared to saline-treated joints (142 ± 56.4 ng/g wet weight). Synovial macrophage infiltration, which was present in all joints at baseline, was abolished in rhIDUA-treated joints only. CONCLUSIONS Intra-articular rhIDUA is well-tolerated and safe in the canine MPS I animal model. Qualitative and quantitative assessments indicate that IA-rhIDUA successfully reduces tissue and cellular GAG storage in synovium and articular cartilage, including cartilage deep to the articular surface, and eliminates inflammatory macrophages from synovial tissue. CLINICAL RELEVANCE The MPS I canine IA-rhIDUA results suggest that clinical studies should be performed to determine if IA-rhIDUA is a viable approach to ameliorating refractory orthopedic disease in human MPS I.

Thalamic mediation of hypoxic respiratory depression in lambs.

Immaturity of respiratory controllers in preterm infants dispose to recurrent apnea and oxygen deprivation. Accompanying reductions in brain oxygen tensions evoke respiratory depression, potentially exacerbating hypoxemia. Central respiratory depression during moderate hypoxia is revealed in the ventilatory decline following initial augmentation. This study determined whether the thalamic parafascicular nuclear (Pf) complex involved in adult nociception and sensorimotor regulation (Bentivoglio M, Balerecia G, Kruger L. Prog Brain Res 87: 53-80, 1991) also becomes a postnatal controller of hypoxic ventilatory decline. Respiratory responses to moderate isocapnic hypoxia were studied in conscious lambs. Hypoxic ventilatory decline was compared with peak augmentation. Pf and/or adjacent thalamic structures were destroyed by the neuron-specific toxin ibotenic acid (IB). IB lesions involving the thalamic Pf abolished hypoxic ventilatory decline. Lesions of adjacent thalamic nuclei that spared Pf and control injections of vehicle failed to blunt hypoxic respiratory depression. Our findings reveal that the thalamic Pf region is a critical controller of hypoxic ventilatory depression and thus a key target for exploring molecular concomitants of forebrain pathways regulating hypoxic ventilatory depression in early development.