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HB-GAM (pleiotrophin) reverses inhibition of neural regeneration by the CNS extracellular matrix

View Article: PubMed Central - PubMed

ABSTRACT

Chondroitin sulfate (CS) glycosaminoglycans inhibit regeneration in the adult central nervous system (CNS). We report here that HB-GAM (heparin-binding growth-associated molecule; also known as pleiotrophin), a CS-binding protein expressed at high levels in the developing CNS, reverses the role of the CS chains in neurite growth of CNS neurons in vitro from inhibition to activation. The CS-bound HB-GAM promotes neurite growth through binding to the cell surface proteoglycan glypican-2; furthermore, HB-GAM abrogates the CS ligand binding to the inhibitory receptor PTPσ (protein tyrosine phosphatase sigma). Our in vivo studies using two-photon imaging of CNS injuries support the in vitro studies and show that HB-GAM increases dendrite regeneration in the adult cerebral cortex and axonal regeneration in the adult spinal cord. Our findings may enable the development of novel therapies for CNS injuries.

No MeSH data available.


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HB-GAM improves axon regeneration through transection injury sites in spinal cord in vivo.(a) Experimental set-up. (b,c) Average number of axon shafts at the caudal edge of the lesion site in (b) and average number of axons that had crossed the entire rostrocaudal extent of the injury site in c over the time following IgG and HB-GAM treatment (*p < 0.05; Mann-Whitney-U test). Error bars, SEM (n = 6, controls; n = 7, HB-GAM-treated mice). (d–i) Through-depth image stacks showing sprouting of cut dorsal column axons into and across spinal cord injury sites following IgG treatment in (d–f) or HB-GAM treatment in (g–i). Caudal is up, Rostral is down. Green lines show the outlines of the injury sites as defined at 0 days. Each image is the through-depth average of multiple optical-slice images ranging from 22–35 (44–70 μm) optical slices for main images, and from 6–9 (12–18 μm) optical slices for insets. (e,f,h,i) show the same regions as shown in (d,g) respectively, at 14 and 28 days after injury. Notice the limited number of axons crossing the rostrocaudal extent of the injury site in response to IgG treatment in (e,f) compared to HB-GAM treatment in (h,i). The stars in (e,f) show region containing spared axons. Insets in (e,f,h,i) show examples of individual axons that were identified at multiple post-injury times. The arrowhead in (e,f) indicates an axon that had crossed the spinal cord injury site at 14 and 28 days. The arrow in (e,f) indicates the distal tip of the same axon within the lesion site. The arrowheads in (h,i) point to an axon that had crossed the injury site at 14 and 28 days. The arrow in (h,i) points to an axon branch located within the injury site at 14 days, but was no longer detected at 28 days. Scale bars are 100 μm for main images and in 50 μm for insets.
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f7: HB-GAM improves axon regeneration through transection injury sites in spinal cord in vivo.(a) Experimental set-up. (b,c) Average number of axon shafts at the caudal edge of the lesion site in (b) and average number of axons that had crossed the entire rostrocaudal extent of the injury site in c over the time following IgG and HB-GAM treatment (*p < 0.05; Mann-Whitney-U test). Error bars, SEM (n = 6, controls; n = 7, HB-GAM-treated mice). (d–i) Through-depth image stacks showing sprouting of cut dorsal column axons into and across spinal cord injury sites following IgG treatment in (d–f) or HB-GAM treatment in (g–i). Caudal is up, Rostral is down. Green lines show the outlines of the injury sites as defined at 0 days. Each image is the through-depth average of multiple optical-slice images ranging from 22–35 (44–70 μm) optical slices for main images, and from 6–9 (12–18 μm) optical slices for insets. (e,f,h,i) show the same regions as shown in (d,g) respectively, at 14 and 28 days after injury. Notice the limited number of axons crossing the rostrocaudal extent of the injury site in response to IgG treatment in (e,f) compared to HB-GAM treatment in (h,i). The stars in (e,f) show region containing spared axons. Insets in (e,f,h,i) show examples of individual axons that were identified at multiple post-injury times. The arrowhead in (e,f) indicates an axon that had crossed the spinal cord injury site at 14 and 28 days. The arrow in (e,f) indicates the distal tip of the same axon within the lesion site. The arrowheads in (h,i) point to an axon that had crossed the injury site at 14 and 28 days. The arrow in (h,i) points to an axon branch located within the injury site at 14 days, but was no longer detected at 28 days. Scale bars are 100 μm for main images and in 50 μm for insets.

Mentions: CSPGs are also potent inhibitors of axonal regeneration and plasticity in the injured spinal cord13467. To test whether HB-GAM could promote axon regeneration across spinal cord injury sites, adult Thy1-CFP mice (blue fluorescent axons in dorsal columns) were subjected to dorso-lateral spinal transection injuries (the experimental protocol summarized in Fig. 7a), immediately followed by injection of HB-GAM or IgG/vehicle (control experiments) at the injury site (5 μl at 1 mg/ml). Glass windows were implanted over the exposed spinal cords for repeated in vivo two-photon imaging of the injury sites262728 from 0 to 4 weeks.


HB-GAM (pleiotrophin) reverses inhibition of neural regeneration by the CNS extracellular matrix
HB-GAM improves axon regeneration through transection injury sites in spinal cord in vivo.(a) Experimental set-up. (b,c) Average number of axon shafts at the caudal edge of the lesion site in (b) and average number of axons that had crossed the entire rostrocaudal extent of the injury site in c over the time following IgG and HB-GAM treatment (*p < 0.05; Mann-Whitney-U test). Error bars, SEM (n = 6, controls; n = 7, HB-GAM-treated mice). (d–i) Through-depth image stacks showing sprouting of cut dorsal column axons into and across spinal cord injury sites following IgG treatment in (d–f) or HB-GAM treatment in (g–i). Caudal is up, Rostral is down. Green lines show the outlines of the injury sites as defined at 0 days. Each image is the through-depth average of multiple optical-slice images ranging from 22–35 (44–70 μm) optical slices for main images, and from 6–9 (12–18 μm) optical slices for insets. (e,f,h,i) show the same regions as shown in (d,g) respectively, at 14 and 28 days after injury. Notice the limited number of axons crossing the rostrocaudal extent of the injury site in response to IgG treatment in (e,f) compared to HB-GAM treatment in (h,i). The stars in (e,f) show region containing spared axons. Insets in (e,f,h,i) show examples of individual axons that were identified at multiple post-injury times. The arrowhead in (e,f) indicates an axon that had crossed the spinal cord injury site at 14 and 28 days. The arrow in (e,f) indicates the distal tip of the same axon within the lesion site. The arrowheads in (h,i) point to an axon that had crossed the injury site at 14 and 28 days. The arrow in (h,i) points to an axon branch located within the injury site at 14 days, but was no longer detected at 28 days. Scale bars are 100 μm for main images and in 50 μm for insets.
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f7: HB-GAM improves axon regeneration through transection injury sites in spinal cord in vivo.(a) Experimental set-up. (b,c) Average number of axon shafts at the caudal edge of the lesion site in (b) and average number of axons that had crossed the entire rostrocaudal extent of the injury site in c over the time following IgG and HB-GAM treatment (*p < 0.05; Mann-Whitney-U test). Error bars, SEM (n = 6, controls; n = 7, HB-GAM-treated mice). (d–i) Through-depth image stacks showing sprouting of cut dorsal column axons into and across spinal cord injury sites following IgG treatment in (d–f) or HB-GAM treatment in (g–i). Caudal is up, Rostral is down. Green lines show the outlines of the injury sites as defined at 0 days. Each image is the through-depth average of multiple optical-slice images ranging from 22–35 (44–70 μm) optical slices for main images, and from 6–9 (12–18 μm) optical slices for insets. (e,f,h,i) show the same regions as shown in (d,g) respectively, at 14 and 28 days after injury. Notice the limited number of axons crossing the rostrocaudal extent of the injury site in response to IgG treatment in (e,f) compared to HB-GAM treatment in (h,i). The stars in (e,f) show region containing spared axons. Insets in (e,f,h,i) show examples of individual axons that were identified at multiple post-injury times. The arrowhead in (e,f) indicates an axon that had crossed the spinal cord injury site at 14 and 28 days. The arrow in (e,f) indicates the distal tip of the same axon within the lesion site. The arrowheads in (h,i) point to an axon that had crossed the injury site at 14 and 28 days. The arrow in (h,i) points to an axon branch located within the injury site at 14 days, but was no longer detected at 28 days. Scale bars are 100 μm for main images and in 50 μm for insets.
Mentions: CSPGs are also potent inhibitors of axonal regeneration and plasticity in the injured spinal cord13467. To test whether HB-GAM could promote axon regeneration across spinal cord injury sites, adult Thy1-CFP mice (blue fluorescent axons in dorsal columns) were subjected to dorso-lateral spinal transection injuries (the experimental protocol summarized in Fig. 7a), immediately followed by injection of HB-GAM or IgG/vehicle (control experiments) at the injury site (5 μl at 1 mg/ml). Glass windows were implanted over the exposed spinal cords for repeated in vivo two-photon imaging of the injury sites262728 from 0 to 4 weeks.

View Article: PubMed Central - PubMed

ABSTRACT

Chondroitin sulfate (CS) glycosaminoglycans inhibit regeneration in the adult central nervous system (CNS). We report here that HB-GAM (heparin-binding growth-associated molecule; also known as pleiotrophin), a CS-binding protein expressed at high levels in the developing CNS, reverses the role of the CS chains in neurite growth of CNS neurons in vitro from inhibition to activation. The CS-bound HB-GAM promotes neurite growth through binding to the cell surface proteoglycan glypican-2; furthermore, HB-GAM abrogates the CS ligand binding to the inhibitory receptor PTP&sigma; (protein tyrosine phosphatase sigma). Our in vivo studies using two-photon imaging of CNS injuries support the in vitro studies and show that HB-GAM increases dendrite regeneration in the adult cerebral cortex and axonal regeneration in the adult spinal cord. Our findings may enable the development of novel therapies for CNS injuries.

No MeSH data available.


Related in: MedlinePlus