title: Supplementary immunocytochemistry of hepatocyte growth factor production in activated macrophages early in muscle regeneration.
abstract: Regenerative intramuscular motor-innervation is thought to reside in the spatiotemporal expression of axon-guidance molecules. Our previous studies showed that resident myogenic stem cells, satellite cells, up-regulate a secreted neural-chemorepellent semaphorin 3A (Sema3A) during the early-differentiation period, in response to hepatocyte growth factor (HGF) elevated in injured muscle. However, a paracrine source of the HGF release is still unknown. Very recently, we proposed a possible contribution of anti-inflammatory macrophages (CD206-positive M2) by showing that M2 cells infiltrate predominantly at the early-differentiation phase (3-5 days post-injury) and produce/secrete large amounts of HGF. However, in understanding this concept there still remains a critical need to examine if phagocytotic pro-inflammatory macrophages (CD86-positive M1), another activated-phenotype still present at the early-differentiation phase concerned, produce HGF upon muscle injury. The current immunocytochemical study demonstrated that the HGF expression is negative for M1 prepared from cardiotoxin-injured Tibialis anterior muscle at day 5, in contrast to the intense fluorescent-signal of M2 served as a positive control. This supplementary result advances our understanding of a spatiotemporal burst of HGF secretion from M2 populations (not M1) to impact Sema3A expression, which ensures a coordinated delay in attachment of motoneuron terminals onto damaged and generating fibers during the early phase of muscle regeneration.
authors.affiliation: Department of Animal and Marine Bioresource Sciences, Graduate School of Agriculture, Kyushu University, Fukuoka, Japan.
authors.forename: Shoko
authors.initials: S
authors.lastname: Sawano
authors.forename: Takahiro
authors.initials: T
authors.lastname: Suzuki
authors.forename: Mai-Khoi Q
authors.initials: MK
authors.lastname: Do
authors.forename: Hideaki
authors.initials: H
authors.lastname: Ohtsubo
authors.forename: Wataru
authors.initials: W
authors.lastname: Mizunoya
authors.forename: Yoshihide
authors.initials: Y
authors.lastname: Ikeuchi
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Tatsumi
mesh_terms: D000818:Animals; D017228:Hepatocyte Growth Factor / Q000032:analysis* / Q000096:biosynthesis*; D007150:Immunohistochemistry / Q000379:methods; D008262:Macrophage Activation / Q000235:genetics*; D008264:Macrophages / Q000378:metabolism*; D008297:Male; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D012038:Regeneration; D040121:Semaphorin-3A / Q000378:metabolism
chemical_list: D040121:Semaphorin-3A; D017228:Hepatocyte Growth Factor
keywords: activated macrophage; hepatocyte growth factor (HGF); immunocytochemistry; moto-neuritogenesis; muscle regeneration; semaphorin 3A