PMID- 23724091 OWN - NLM STAT- MEDLINE DCOM- 20140110 LR - 20211021 IS - 1932-6203 (Electronic) IS - 1932-6203 (Linking) VI - 8 IP - 5 DP - 2013 TI - Targeted delivery of TrkB receptor to phrenic motoneurons enhances functional recovery of rhythmic phrenic activity after cervical spinal hemisection. PG - e64755 LID - 10.1371/journal.pone.0064755 [doi] LID - e64755 AB - Progressive recovery of rhythmic phrenic activity occurs over time after a spinal cord hemisection involving unilateral transection of anterolateral funiculi at C2 (SH). Brain-derived neurotrophic factor (BDNF) acting through its full-length tropomyosin related kinase receptor subtype B (TrkB.FL) contributes to neuroplasticity after spinal cord injury, but the specific cellular substrates remain unclear. We hypothesized that selectively targeting increased TrkB.FL expression to phrenic motoneurons would be sufficient to enhance recovery of rhythmic phrenic activity after SH. Several adeno-associated virus (AAV) serotypes expressing GFP were screened to determine specificity for phrenic motoneuron transduction via intrapleural injection in adult rats. GFP expression was present in the cervical spinal cord 3 weeks after treatment with AAV serotypes 7, 8, and 9, but not with AAV2, 6, or rhesus-10. Overall, AAV7 produced the most consistent GFP expression in phrenic motoneurons. SH was performed 3 weeks after intrapleural injection of AAV7 expressing human TrkB.FL-FLAG or saline. Delivery of TrkB.FL-FLAG to phrenic motoneurons was confirmed by FLAG protein expression in the phrenic motor nucleus and human TrkB.FL mRNA expression in microdissected phrenic motoneurons. In all SH rats, absence of ipsilateral diaphragm EMG activity was confirmed at 3 days post-SH, verifying complete interruption of ipsilateral descending drive to phrenic motoneurons. At 14 days post-SH, all AAV7-TrkB.FL treated rats (n = 11) displayed recovery of ipsilateral diaphragm EMG activity compared to 3 out of 8 untreated SH rats (p<0.01). During eupnea, AAV7-TrkB.FL treated rats exhibited 73+/-7% of pre-SH root mean squared EMG vs. only 31+/-11% in untreated SH rats displaying recovery (p<0.01). This study provides direct evidence that increased TrkB.FL expression in phrenic motoneurons is sufficient to enhance recovery of ipsilateral rhythmic phrenic activity after SH, indicating that selectively targeting gene expression in spared motoneurons below the level of spinal cord injury may promote functional recovery. FAU - Gransee, Heather M AU - Gransee HM AD - Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States of America. FAU - Zhan, Wen-Zhi AU - Zhan WZ FAU - Sieck, Gary C AU - Sieck GC FAU - Mantilla, Carlos B AU - Mantilla CB LA - eng GR - R01 HL096750/HL/NHLBI NIH HHS/United States GR - T32 HL105355/HL/NHLBI NIH HHS/United States GR - R01-HL096750/HL/NHLBI NIH HHS/United States GR - T32-HL105355/HL/NHLBI NIH HHS/United States PT - Journal Article PT - Research Support, N.I.H., Extramural PT - Research Support, Non-U.S. Gov't DEP - 20130528 PL - United States TA - PLoS One JT - PloS one JID - 101285081 RN - 147336-22-9 (Green Fluorescent Proteins) RN - EC 2.7.10.1 (Receptor, trkB) SB - IM MH - Animals MH - Anterior Horn Cells/metabolism/pathology MH - Biological Transport MH - Cervical Vertebrae/pathology/*physiopathology/*surgery MH - Dependovirus/metabolism MH - Diaphragm/pathology/physiopathology MH - Electromyography MH - *Gene Transfer Techniques MH - Green Fluorescent Proteins/metabolism MH - Humans MH - Male MH - Motor Neurons/*metabolism MH - Phrenic Nerve/*pathology/physiopathology MH - Rats MH - Rats, Sprague-Dawley MH - Receptor, trkB/*metabolism MH - *Recovery of Function PMC - PMC3665838 COIS- Competing Interests: The authors have declared that no competing interests exist. EDAT- 2013/06/01 06:00 MHDA- 2014/01/11 06:00 PMCR- 2013/05/28 CRDT- 2013/06/01 06:00 PHST- 2013/01/14 00:00 [received] PHST- 2013/04/17 00:00 [accepted] PHST- 2013/06/01 06:00 [entrez] PHST- 2013/06/01 06:00 [pubmed] PHST- 2014/01/11 06:00 [medline] PHST- 2013/05/28 00:00 [pmc-release] AID - PONE-D-13-02397 [pii] AID - 10.1371/journal.pone.0064755 [doi] PST - epublish SO - PLoS One. 2013 May 28;8(5):e64755. doi: 10.1371/journal.pone.0064755. Print 2013.