Department of Odontology, Clinical Oral Physiology, Umeå University, 90187 Umeå, Sweden.
Histochem Cell Biol. 2012 Oct;138(4):669-82. doi: 10.1007/s00418-012-0985-5. Epub 2012 Jul 10.
Adult human jaw muscles differ from limb and trunk muscles in enzyme-histochemical fibre type composition. Recently, we showed that the human masseter and biceps differ in fibre type pattern already at childhood. The present study explored the myosin heavy-chain (MyHC) expression in the young masseter and biceps muscles by means of gel electrophoresis (GE) and immuno-histochemical (IHC) techniques. Plasticity in MyHC expression during life was evaluated by comparing the results with the previously reported data for adult muscles. In young masseter, GE identified MyHC-I, MyHC-IIa MyHC-IIx and small proportions of MyHC-fetal and MyHC-α cardiac. Western blots confirmed the presence of MyHC-I, MyHC-IIa and MyHC-IIx. IHC revealed in the masseter six isomyosins, MyHC-I, MyHC-IIa, MyHC-IIx, MyHC-fetal, MyHC α-cardiac and a previously not reported isoform, termed MyHC-IIx'. The majority of the masseter fibres co-expressed two to four isoforms. In the young biceps, both GE and IHC identified MyHC-I, MyHC-IIa and MyHC-IIx. MyHC-I predominated in both muscles. Young masseter showed more slow and less-fast and fetal MyHC than the adult and elderly masseter. These results provide evidence that the young masseter muscle is unique in MyHC composition, expressing MyHC-α cardiac and MyHC-fetal isoforms as well as hitherto unrecognized potential spliced isoforms of MyHC-fetal and MyHC-IIx. Differences in masseter MyHC expression between young adult and elderly suggest a shift from childhood to adulthood towards more fast contractile properties. Differences between masseter and biceps are proposed to reflect diverse evolutionary and developmental origins and confirm that the masseter and biceps present separate allotypes of muscle.
成人的颌骨肌肉在酶组织化学纤维类型组成上与肢体和躯干肌肉不同。最近，我们发现人类的咬肌和肱二头肌在儿童时期就已经存在纤维类型模式的差异。本研究通过凝胶电泳（GE）和免疫组织化学（IHC）技术探索了年轻咬肌和肱二头肌中的肌球蛋白重链（MyHC）表达。通过将结果与以前报道的成人肌肉数据进行比较，评估了生命过程中 MyHC 表达的可塑性。在年轻的咬肌中，GE 鉴定出 MyHC-I、MyHC-IIa、MyHC-IIx 和少量的 MyHC-胎儿和 MyHC-α 心脏。Western blot 证实了 MyHC-I、MyHC-IIa 和 MyHC-IIx 的存在。IHC 在咬肌中显示了六种同工型，即 MyHC-I、MyHC-IIa、MyHC-IIx、MyHC-胎儿、MyHC-α 心脏和以前未报道的同工型 MyHC-IIx'。大多数咬肌纤维共表达两种到四种同工型。在年轻的肱二头肌中，GE 和 IHC 都鉴定出了 MyHC-I、MyHC-IIa 和 MyHC-IIx。两种肌肉中均以 MyHC-I 为主。年轻的咬肌比成人和老年人的咬肌表现出更多的慢肌和更少的快肌和胎儿肌 MyHC。这些结果提供了证据表明，年轻的咬肌在 MyHC 组成上是独特的，表达 MyHC-α 心脏和 MyHC-胎儿同工型以及以前未被识别的 MyHC-胎儿和 MyHC-IIx 的潜在剪接同工型。年轻成人和老年人咬肌 MyHC 表达的差异表明，从儿童期到成年期，肌肉的收缩特性向更快的方向转变。咬肌和肱二头肌之间的差异被认为反映了不同的进化和发育起源，并证实了咬肌和肱二头肌具有不同的肌肉同种型。
