Myoblasts and myoblast‐conditioned medium attract the earliest spinal neurites from frog embryos.

Abstract

SUMMARY1. A study was made of the capacity of newly segmented somites, unsegmented mesoderm and medium conditioned by each of these tissues to attract the growth of the earliest spinal neurites from the neural tube of Xenopus laevis in tissue culture.2. When presented with segmented somitic myoblasts or sheets of skin, spinal neurites grew selectively towards the somitic myoblasts. Neurites were not attracted specifically to somitic myoblasts from their own rostrocaudal level. A variable proportion of myoblasts from unsegmented caudal mesoderm differentiated and elongated in co-culture with neural tube and skin. These myoblasts also attracted neural outgrowths, but only if present in sufficient numbers.3. An agar slab containing medium conditioned by the presence of segmented myoblasts for 1 day attracted neurite outgrowths. A source of medium conditioned by the presence of undifferentiated, unsegmented myotomal mesoderm alone did not attract neurite outgrowths. Nerve growth factor (NGF) at a range of concentrations in the agar source (500-10000 ng/ml) did not attract the earliest neurite outgrowths.4. It is concluded that the earliest skeletal myoblasts from Xenopus laevis embryos may attract neural outgrowths by releasing a soluble factor. Myoblasts may have to develop to the stage of somite segmentation before secretion of such an agent begins. The release of a myoblast-derived factor so early in development may assist directed nerve growth in vivo.

Retained Medullary Cord in Humans: Late Arrest of Secondary Neurulation

“…The distal nerve roots in our cases are presumably equivalent coccygeal roots that are retained together with the medullary (coccygeal) cord segments. The absence of motor response in these roots is not surprising because outgrowth of motor axons from the primitive neural tube requires the attracting signals from emerging myotubes, [44][45][46] and the caudal somites of these patients probably never survived to become tail musculature. These roots therefore likely contain only sensory fibers that may not have corresponding dermatomes in the caudal body.…”

Injection of Autologous Muscle Stem Cells (Myoblasts) for the Treatment of Vocal Fold Paralysis: A Pilot Study

“…Myoblasts may also have an innate role for enhancing neuronal growth and recovery. In embryogenesis, myoblasts have been shown to secrete neurotrophic factors to guide neurons to their appropriate muscle end targets 18 . In adult humans, recovery from denervation injuries is also mediated by neurotrophic factors such as glial cell line‐derived neurotrophic factor (GDNF) and insulin‐like growth factors (IGF‐1 and IGF‐2).…”

“…In embryogenesis, myoblasts have been shown to secrete neurotrophic factors to guide neurons to their appropriate muscle end targets. 18 In adult humans, recovery from denervation injuries is also mediated by neurotrophic factors such as glial cell line-derived neurotrophic factor (GDNF) and insulin-like growth factors (IGF-1 and IGF-2). These key factors demonstrate increased expression in acutely denervated skeletal muscle, possibly representing a myoblastic response.…”

Evidence of innervation following extracellular matrix scaffold-mediated remodelling of muscular tissues

“…Previous developmental studies show that nerves can create a myotrophic environment to promote the recruitment of muscle (Brockes, 1984; Dietz, 1989; Ashby et al, 1993; Suzuki et al, 2005). The reciprocal neurotrophic effect of muscle formation is well known in both developmental and regenerative models (McCaig, 1986; Grinnell, 1995; Carlson, 2005; Kingham and Terenghi, 2006). The dual neurotrophic and angiogenic effects of blood vessels and nerves, respectively, have also been extensively studied (Carmeliet, 2003), and nerve may in fact guide the growth of blood vessels in normal development in vivo (Mukouyama et al, 2002).…”