Silencing SERCA1b in a few fibers stimulates growth in the entire regenerating soleus muscle
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The neonatal isoform of the sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 1 (SERCA1b) is a dominant Ca2+ pump in the young fibers of regenerating muscle. In vivo transfection of about 1% of the fibers with SERCA1b RNAi plasmid resulted in no apparent change in the transfected fibers, but enhanced the increase of fresh weight and fiber size in the whole regenerating rat soleus muscle, until the normal size was reached. Co-transfection of calcineurin inhibitor cain/cabin-1 with SERCA1b RNAi was sufficient to cut down the widespread growth stimulation, but the subsequent transfection of cain into the SERCA1b RNAi transfected muscle did not inhibit muscle growth. The SERCA1b RNAi preferably upregulated the expression of the NFAT reporter lacZ compared to controls when co-transfected into the fibers. Notably, perimuscular injection of interleukin-4 (IL-4) antibody but not that of an unrelevant antibody completely abolished the growth-promoting effect of SERCA1b RNAi. This indicates that silencing SERCA1b in a few fibers stimulates the calcineurin-NFAT-IL-4 pathway and fiber growth in the whole regenerating soleus. These results suggest the presence of an autocrine–paracrine coordination of growing muscle fibers, and put forward a new method to stimulate skeletal muscle regeneration.
KeywordsSERCA1b Muscle regeneration Calcineurin Interleukin-4 Fiber growth
Eukaryotic green fluorescent protein
Slow type myosin heavy chain
Nuclear factor of activated T-cells
- RT PCR
Reverse transcriptase polymerase chain reaction
Adult fast type sarcoplasmic/endoplasmic reticulum Ca2+ ATPase
Neonatal sarcoplasmic/endoplasmic reticulum Ca2+ ATPase
Thank you to Dr. Paul Rosenberg for the NRElacZ plasmid, to Dr. Peter Vangheluwe and Dr. Magdolna Kósa for technical help. This work was supported by the TéT B-3/99, B-9/02, B-20/04 and the ETT 168/2003 grants in Hungary and the BIL 99/19 and BIL 02/18 from the Ministerie Vlaamse Gemeenschap, Belgium.
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