title: Overexpression of GRF encapsulated in PLGA microspheres in animal skeletal muscle induces body weight gain.
abstract: Biodegradable nanospheres or microspheres have been widely used as a sustained release system for the delivery of bioagents. In the present study, injectable sustained-release growth hormone-releasing factor (GRF) (1-32) microspheres were prepared by a double emulsion-in liquid evaporation process using biodegradable polylactic-co-glycolic acid (PLGA) as the carrier. The entrapment efficiency was 89.79% and the mean particle size was 4.41 mum. The microspheres were injected into mouse tibialis muscle. After 30 days, mice injected with GRF (1-32) microspheres (group I) gained significantly more weight than any other treatment group, including mice injected with the naked plasmid (group II) (10.26 +/- 0.13 vs. 9.09 +/- 0.56; P < 0.05), a mixture of microspheres and plasmid (group III) (10.26 +/- 0.13 vs. 8.57 +/- 0.02; P < 0.05), or saline (IV) (10.26 +/- 0.13 vs. 6.47 +/- 0.26; P < 0.05). In addition, mice treated with the GRF (1-32) microspheres exhibited the highest expression levels of GRF as detected by PCR, RT-PCR, and ELISA (mean 2.56 +/- 0.40, P < 0.05, overall comparison of treatment with groups II, III, and IV). Additionally, rabbits were injected in the tibialis muscle with the same treatments described above. After 30 days, the group treated with GRF (1-32) microspheres gained the most weight. At day 30 postinjection, weight gain in group I was 63.93% higher than group II (plasmid) (877.10 +/- 24.42 vs. 535.05 +/- 26.38; P < 0.05), 108.59% higher than group III (blank MS) (877.10 +/- 24.42 vs. 420.50 +/- 19.39; P < 0.05), and 93.94% higher than group IV (saline) (877.10 +/- 24.42 vs. 452.25 +/- 27.38; P < 0.05). Furthermore, IGF-1 levels in the serum from GRF microsphere-treated group were elevated relative to all other groups. The present results suggest that encapsulation of GRF with PLGA increases GRF gene expression in muscle after local plasmid delivery, and stimulates significantly more weight gain than delivery of the naked plasmid alone.
authors.affiliation: College of Animal Science, South China Agricultural University, Guangzhou, PR China. zhangyl@scau.edu.cn
authors.forename: Yong-liang
authors.initials: YL
authors.lastname: Zhang
authors.forename: Xiao-hui
authors.initials: XH
authors.lastname: Ren
authors.forename: Song-cai
authors.initials: SC
authors.lastname: Liu
authors.forename: Jian-wei
authors.initials: JW
authors.lastname: Dai
authors.forename: Lin-lin
authors.initials: LL
authors.lastname: Hao
authors.forename: Qing-yan
authors.initials: QY
authors.lastname: Jiang
mesh_terms: D000818:Animals; D001835:Body Weight / Q000187:drug effects / Q000502:physiology; D003692:Delayed-Action Preparations; D004797:Enzyme-Linked Immunosorbent Assay; D013007:Growth Hormone-Releasing Hormone / Q000008:administration & dosage / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D019344:Lactic Acid / Q000008:administration & dosage / Q000737:chemistry*; D008297:Male; D051379:Mice; D008863:Microspheres; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D010957:Plasmids / Q000235:genetics; D011100:Polyglycolic Acid / Q000008:administration & dosage / Q000737:chemistry*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers / Q000008:administration & dosage / Q000737:chemistry*; D011817:Rabbits; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D003692:Delayed-Action Preparations; D011108:Polymers; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D013007:Growth Hormone-Releasing Hormone