ABSTRACT
Title
Stem cells: a new pharmacological approach to treat neuropathic pain symptoms
Authors
S.Franchi
Department of Pharmacology, University of Milan, Milano
Department of Pharmacology, University of Milan, Milano
Abstract
A non-physiological repair of the lesioned nerve has been advocated as the main cause of the events underlying neuropathic pain. On these premises, we believe that in case of a peripheral nerve lesion, the peripheral administration of stem cells would have been a winning approach in order to avoid this type of disease, prompting a physiological repair of the lesion. In the first part of our studies we used mouse adult neural stem cell (NSC), and then we compared their effects with human mesenchymal stem cells from adipose tissue (hASC), considering their better availability and the faster proliferation rate.
We chose the sciatic nerve chronic constriction injury model in the mouse (CCI) because it produces a robust Wallerian degeneration with additional inflammation. Moreover, since some nerve fibers survive the injury, behavioural testing to assess pain is possible. We investigated the effect of NSC systemic administration on neuropathic pain symptoms, allodynia (Dynamic Plantar Aesthesiomether) and hyperalgesia (Plantar test). The effect on pain was correlated to the biochemical and morphological changes induced by cells. NSC from mice subventricular region, expressing the GFP protein [1], were injected into caudal vein at a dose ranging from 1 to 3 million. The cell injections started at day 7 since CCI. At different times since NSC administration we evaluated their presence at the lesion site and their effect on: painful symptoms; sciatic nerve pro and anti-inflammatory cytokines (Real time PCR, ELISA); spinal cord cFos, SP and CGRP levels and nerve repair. In the second part of the study we used hASC, obtained from human adipose tissue [2]. Twenty four hours after administration, NSC were selectively localized in the injured nerve where they remained up to 7 days. NSC dose-dependently decreased painful behaviour starting 3 days after injection and with an effect still present after 21 days. When the relief decreased a new NSC administration could re-establish it. NSC decreased the pro-inflammatory cytokines IL-1 and IL-6, increased by the pathology, and modulated IL-10 levels. NSC were also able to restore the alterations in cFos and SP induced by CCI in the spinal cord. The biochemical changes induced by NSC and their effect on pain remission seem to be independent from their reparative effect and possibly due to a bidirectional interaction between NSC and the lesioned inflamed nerve. Similarly to NSC, also hASC were able to induce a remission of painful symptomatology. A single injection of 1x106 cells was able to abolish thermal hyperalgesia starting 24 hours since injection with an effect still present 21 days later. Also in this case hASC effect could be re-established by a new administration when it began to vanish. HASC treatment was also able to restore a correct pro-anti-inflammatory cytokine balance in the sciatic nerve.
In conclusion peripheral administration of stem cells of different origin and species (murine NSC and hASC) therapeutically reversed neuropathic pain symptoms in the CCI mouse model. For this reason we believe that abidirectional interaction between stem cells and the lesioned-inflammed nerve is at the basis of the positive modulation of pain and inflammation.
[1] Gritti et al. (1999) Epidermal and fibroblast growth factors behave as mitogenic regulators for a single multipotent stem cell-like population from the subventricular region of the adult mouse forebrain. J Neurosci 19,3287-3297
[2] De Girolamo L et al. (2009) Human adipose-derived stem cells isolated from young and elderly women:their differentiation potential and scaffold interaction during in vitro osteoclastic differentiation. Cytotherapy 11:793-803
We chose the sciatic nerve chronic constriction injury model in the mouse (CCI) because it produces a robust Wallerian degeneration with additional inflammation. Moreover, since some nerve fibers survive the injury, behavioural testing to assess pain is possible. We investigated the effect of NSC systemic administration on neuropathic pain symptoms, allodynia (Dynamic Plantar Aesthesiomether) and hyperalgesia (Plantar test). The effect on pain was correlated to the biochemical and morphological changes induced by cells. NSC from mice subventricular region, expressing the GFP protein [1], were injected into caudal vein at a dose ranging from 1 to 3 million. The cell injections started at day 7 since CCI. At different times since NSC administration we evaluated their presence at the lesion site and their effect on: painful symptoms; sciatic nerve pro and anti-inflammatory cytokines (Real time PCR, ELISA); spinal cord cFos, SP and CGRP levels and nerve repair. In the second part of the study we used hASC, obtained from human adipose tissue [2]. Twenty four hours after administration, NSC were selectively localized in the injured nerve where they remained up to 7 days. NSC dose-dependently decreased painful behaviour starting 3 days after injection and with an effect still present after 21 days. When the relief decreased a new NSC administration could re-establish it. NSC decreased the pro-inflammatory cytokines IL-1 and IL-6, increased by the pathology, and modulated IL-10 levels. NSC were also able to restore the alterations in cFos and SP induced by CCI in the spinal cord. The biochemical changes induced by NSC and their effect on pain remission seem to be independent from their reparative effect and possibly due to a bidirectional interaction between NSC and the lesioned inflamed nerve. Similarly to NSC, also hASC were able to induce a remission of painful symptomatology. A single injection of 1x106 cells was able to abolish thermal hyperalgesia starting 24 hours since injection with an effect still present 21 days later. Also in this case hASC effect could be re-established by a new administration when it began to vanish. HASC treatment was also able to restore a correct pro-anti-inflammatory cytokine balance in the sciatic nerve.
In conclusion peripheral administration of stem cells of different origin and species (murine NSC and hASC) therapeutically reversed neuropathic pain symptoms in the CCI mouse model. For this reason we believe that abidirectional interaction between stem cells and the lesioned-inflammed nerve is at the basis of the positive modulation of pain and inflammation.
[1] Gritti et al. (1999) Epidermal and fibroblast growth factors behave as mitogenic regulators for a single multipotent stem cell-like population from the subventricular region of the adult mouse forebrain. J Neurosci 19,3287-3297
[2] De Girolamo L et al. (2009) Human adipose-derived stem cells isolated from young and elderly women:their differentiation potential and scaffold interaction during in vitro osteoclastic differentiation. Cytotherapy 11:793-803