Laboratory Study
Intracerebral transplantation of human adipose tissue stromal cells after middle cerebral artery occlusion in rats

https://doi.org/10.1016/j.jocn.2007.03.016Get rights and content

Abstract

The transplantation of cells capable of neuronal differentiation has great potential for the treatment of neurological conditions. I examined whether human adipose tissue stromal cells (hATSCs) can be induced to undergo neuronal differentiation. I isolated hATSCs from human liposuction tissue and induced neuronal differentiation using azacytidine. After neuronal induction, the hATSCs adopted a more neuronal morphology. These hATSCs were injected into the lateral ventricle of the rat brain, after which they migrated to various parts of the brain. After ischemic brain injury induced by middle cerebral artery occlusion (MCAO), a large number of cells migrated to the injured cortex. Intracerebral grafting of hATSCs significantly enhanced the recovery of functional motor deficits in MCAO rats. These data indicate that transplanted hATSCs survive, migrate and differentiate in the ischemic microenvironment and improve neurological recovery after stroke in rats.

Introduction

Neurotransplantation has been to investigate development, plasticity and regeneration of the central nervous system.1 Transplanted adipose tissue stromal cells may aid in the restoration of lost function by contributing trophic support or integrating into functional synaptic networks with host tissues. Experiments involving animal models and humans have produced promising results in this regard.[2], [3], [4]

Stem cells have the capacity for self-renewal and differentiation into diverse cell types. During embryogenesis, totipotent stem cells give rise to ectoderm, mesoderm, and endoderm.5 Transplantation of embryonic stem cells into the brain ameliorates neurological deficits in animal models of Parkinson’s disease6 and spinal cord injury.7 Transplanted embryonic stem cells have been shown to survive and differentiate into oligodendrocytes, astrocytes and dopaminergic neurons.[6], [7] However, immune rejection needs to be overcome to allow the clinical use of embryonic stem cell transplantation. Recent research has suggested that mesenchymal stem cells (MSCs) from bone marrow are capable of differentiating into various brain cells. Bone marrow stromal cells (BMSCs) have also been reported to differentiate into neural cells in vitro.[8], [9], [10] When BMSCs are transplanted into the lateral ventricles of neonatal mice, they migrate to various brain regions and differentiate into cells with astrocytic and neuronal phenotypes.11 Similarly, when human MSCs are directly infused into rat striatum, engraftment and differentiation into astrocytes occurs.12 Transplanted BMSCs have also been shown to migrate extensively throughout adult animals. Following intravenous bone marrow transplantation in rodents, BMSCs have been detected in many non-hematopoietic tissues,[13], [14] including the brain.[15], [16], [17] Interestingly, bone marrow transplantation has been shown to effectively prevent the progression of neurological signs and symptoms in some clinical trials, if performed at a sufficiently early stage of Parkinson’s disease. Recently, rodent bone marrow cells grafted into the ischemic rat brain were found to yield a functional improvement.18 BMSCs have also been used as vehicles for gene delivery to various tissues, including the brain.[19], [20], [21], [22] These findings suggest that BMSCs are a potential source of brain progenitor cells. However, they can only be obtained by bone marrow biopsy, a potentially painful procedure. Thus, it would be advantageous to identify similar multipotent stromal cells in tissue sites outside the bone marrow microenvironment.

Adipose tissue, like bone marrow, is derived from the embryonic mesoderm and contains a heterogenous stromal cell population.[23], [24] These similarities between adipose and bone marrow tissue, together with the fact that MSCs have been identified in several tissues, make it seem likely that a stem cell population could be isolated from human adipose tissue. In fact, MSCs isolated from adipose tissue have been shown to differentiate into multiple mesodermal tissues, including bone, fat and muscle.[25], [26], [27] Differentiation into neuron-like cells expressing neuronal markers has been reported.28

Therefore, adipose tissue has been identified as an alternative source of pluripotent stromal cells.[25], [26], [29] These cells have been termed adipose tissue stromal cells (ATSCs), as they are self-renewing and can be induced to differentiate into various mesenchymal tissues, including chondrocytes, adipocytes, osteoblasts and myocytes.[25], [26], [27] ATSCs have been shown to display both epithelial cell and hepatocytic morphological features, neither of which is a mesenchymal lineage.28 However, the fate of human ATSCs (hATSCs) and the functional outcome after in vivo transplantation has not been determined. In the present study, I investigated whether hATSCs could integrate into various parts of the brain, and ameliorate neurological deficits in rats with ischemic brain injury.

Section snippets

Adipose tissue preparation

The subcutaneous adipose tissue was acquired from patients undergoing elective surgery. Patients consented to the procedure, which was approved by the institution review board. The adipose tissue was transported to the laboratory in saline solution within 2 h of removal. The tissue was washed at least three times with two volumes of Hank’s balanced salt solution (HBSS) buffer to remove any blood. The tissue was then digested with one volume of type I collagenase (1 g/L in HBSS buffer with 1%

ATSC characterization

Within 2–3 passages after the initial plating of the primary culture, the hATSCs appeared as a monolayer of large, flat cells. As the cells approached confluence, they showed a more spindle-shaped, fibroblastic morphology (Fig. 1). The hATSCs became relatively homogeneous in appearance as the cells were passaged. However, two distinct populations were seen, large flattened cells and relatively elongated or spindle-shaped cells (Fig. 1).

Detection of ischemic brain region

To demonstrate the extent of infarction, 2-mm coronal brain

Discussion

The main findings of the present study are that the transplanted hATSCs survived and migrated in the rodent brain, with no evidence of immune destruction, and that the rats showed improved neurological function after transplantation following ischemia. Similar effects of bone marrow stem cells on the functional deficits induced by ischemic brain injury have been reported elsewhere.[18], [34] The surface phenotype of ATSCs is similar to that of bone marrow-derived stromal cells.[35], [36], [37]

Acknowledgement

This paper was supported by Namseoul University funding.

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