Elsevier

Brain Research

Volume 1030, Issue 1, 24 December 2004, Pages 19-27
Brain Research

Research report
Expression of insulin-like growth factor 1 and receptor in ischemic rats treated with human marrow stromal cells

https://doi.org/10.1016/j.brainres.2004.09.061Get rights and content

Abstract

Human bone marrow stromal cells (hMSCs) enhance neurological recovery after stroke in rodents, possibly via induction of growth factors. We therefore elected to test the effects of hMSC treatment on insulin-like growth factor 1 (IGF-1), which plays an important role in growth, development, neuroprotection and repair in the adult. Rats (n=57) were subjected to permanent middle cerebral artery occlusion (MCAo) and injected intravenously with 3×106 hMSCs or phosphate-buffered saline (PBS) at 1 day after MCAo. Functional outcome was measured after MCAo using a modified Neurological Severity Score (mNSS). Gene expression of IGF-1 and IGF-1 receptor (IGF-1R) in the ischemic brain tissue were measured at 2 and 7 days after MCAo using reverse transcription–polymerase chain reaction (RT-PCR). Immunohistochemistry was performed to measure the expression of bromodeoxyuridine (BrdU), doublecortin (DCX), IGF-1 and IGF-1R at 7, 14 and 30 days after MCAo. Treatment of MCAo with hMSCs significantly improved functional recovery from 14 to 30 days. MAB1281-labeled hMSCs entered the ischemic brain and increased time-dependently. hMSC treatment significantly increased IGF-1 mRNA and BrdU+, DCX+, IGF-1+ and IGF-1R+ cells compared to PBS-treated rats (p<0.05). The percentage of BrdU+ or DCX+ cells colocalized with IGF-1 increased in the hMSC-treated rats compared to the PBS-treated rats (p<0.05). IGF-1 and IGF-1R may contribute to improved functional recovery and increased neurogenesis after treatment of stroke with hMSCs.

Introduction

Neural stem or progenitor cells reside in the subventricular zone (SVZ) throughout the life of mammals [19], [20], and are capable of giving rise to neurons, astrocytes and other cell types [17]. In addition, brain injuries such as focal ischemia have been shown to induce neurogenesis in the SVZ [23], [49]. Previous studies have demonstrated that bone marrow stromal cells (MSCs) administered intravenously after stroke migrate selectively and target damaged brain, increase angiogenesis, enhance neurogenesis, promote neural stem cell proliferation and migration and improve functional recovery [9], [12], [27]. However, the molecular mechanisms underlying these MSC-evoked neurorestorative and brain plasticity processes remain obscure.

The phenotypic state of a cell is influenced by a variety of extracellular signals. Insulin-like growth factor 1 (IGF-1) is a polypeptide growth factor that plays an important role in normal brain growth and development [2], [18], and has been shown to have neurotrophic and neuroprotective effects in vitro and in vivo in different lesion models [7], [16], [21], [28], [40], [42]. Its pleiotropic effects range from classical trophic actions on neurons such as housekeeping or anti-apoptotic/pro-survival effects to modulation of brain-barrier permeability, neuronal excitability, increasing neurogenesis and participating in brain angiogenesis [7], [46]. The binding of IGF-1 to IGF-I receptor (IGF-1R) activates the receptor tyrosine kinase (RTK) activity, which can lead to changes in gene expression, cell phenotype, cell proliferation, differentiation and migration [22].

Therefore, in the present study, we sought to investigate the molecular mechanisms underlying the human bone marrow stromal cell (hMSC) effect on both neural cell proliferation and migration after stroke in rat, by measuring the expression levels of IGF-1, IGF-1R mRNA and proteins in response to hMSC treatment.

Section snippets

Materials and methods

All experimental procedures have been approved by the Institutional Animal Care and Use Committee.

Administration of hMSCs improves neurological function

The severity of MCAo was balanced between the hMSC- and control-treated groups (p=0.97). hMSCs by time interaction was detected (p-value for interaction=0.03). Treatment at 1 day after MCAo with hMSCs marginally improved functional recovery at 7 days (p=0.07), significantly improved functional recovery, as evidence by improved mNSS at 14 (p<0.01), 21 and 30 days (p<0.05) compared with ischemia rats treated with PBS (Table 1).

Administration of hMSCs increases brain expression of IGF-1 mRNA

RT-PCR showed IGF-1 mRNA level was very low in normal rats, but there

Discussion

Neurological recovery after stroke likely involves a cascade of events, including angiogenesis, neurogenesis and synaptogenesis. The results of the present study demonstrate that treatment of stroke with intravenously administered hMSCs after induction of focal cerebral ischemia achieved a significant neurogenic effect. The endogenous factors which promote neurogenesis are not yet identified. Because cell proliferation, differentiation and survival are under the control of growth factors in

Acknowledgements

This work was supported by NIH grants PO1 NS42345 and RO1 NS45041. hMSCs were supplied by Cognate Therapeutics. The authors thank Cynthia Roberts and Lei Wang for their technical assistance and Deborah Jewell for secretarial support.

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