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Isoform-specific effects of apoE on neurite outgrowth in olfactory epithelium culture.

Hussain A, Luong M, Pooley A, Nathan BP - J. Biomed. Sci. (2013)

Bottom Line: In contrast, treatment with apoE4 did not have an effect on neurite outgrowth.The differential effects of human apoE isoforms on neurite outgrowth were abolished by blocking the low-density lipoprotein receptor-related protein (LRP) with lactoferrin and receptor-associated protein (RAP).ApoE4, the isoform associated with AD, failed to promote neurite outgrowth, suggesting a potential mechanism whereby apoE4 may lead to olfactory dysfunction in AD patients.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biological Sciences, Eastern Illinois University, 600 Lincoln Avenue, Charleston, IL 61920, USA.

ABSTRACT

Background: The apolipoprotein E4 (apoE4) genotype is a major risk factor for developing late-onset Alzheimer's disease (AD). Inheritance of apoE4 is also associated with impairments in olfactory function in early stages of AD. In this project we examined the effects of the three common isoforms of human apoE (apoE2, apoE3, and apoE4) on neuronal differentiation and neurite outgrowth in explant cultures of mouse olfactory epithelium (OE).

Results: The OE cultures derived from apoE-deficient/knockout (KO) mice have significantly fewer neurons with shorter neurite outgrowth than cultures from wild-type (WT) mice. Treatment of the apoE KO culture with either purified human apoE2 or with human apoE3 significantly increased neurite outgrowth. In contrast, treatment with apoE4 did not have an effect on neurite outgrowth. The differential effects of human apoE isoforms on neurite outgrowth were abolished by blocking the low-density lipoprotein receptor-related protein (LRP) with lactoferrin and receptor-associated protein (RAP).

Conclusion: ApoE2 and apoE3 stimulate neurite outgrowth in OE cultures by interacting with the lipoprotein receptor, LRP. ApoE4, the isoform associated with AD, failed to promote neurite outgrowth, suggesting a potential mechanism whereby apoE4 may lead to olfactory dysfunction in AD patients.

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Characterization of the OE culture. (A) Two contiguous phase contrast pictures of the OE culture at 8 DIV were merged to depict the location of the explant (Ex), and the inner (In) and outer (Ot) halos. Scale bar = 50 μm. Representative morphologies of cells immunostained for GBC1 (B), GAP43 (C) and OMP (D) in the OE culture. (E) Quantification of the cell types in the inner and outer halos in OE cultures.
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Figure 1: Characterization of the OE culture. (A) Two contiguous phase contrast pictures of the OE culture at 8 DIV were merged to depict the location of the explant (Ex), and the inner (In) and outer (Ot) halos. Scale bar = 50 μm. Representative morphologies of cells immunostained for GBC1 (B), GAP43 (C) and OMP (D) in the OE culture. (E) Quantification of the cell types in the inner and outer halos in OE cultures.

Mentions: We used a modified protocol to culture olfactory epithelium (OE) cells derived from post-natal mice [26,27]. At 4 days in vitro (DIV) the neuronal precursors and sensory neurons migrate out of the explant and establish as two large halos (Figure 1). The inner halo, which is closer to the explant, is primarily composed of densely populated, irregular shaped cells. About 80% of the cells in the inner halo were positive for GBC-1, a marker for globose basal cells in the mature OE [28,29]. Most of the cells in the boundary of the inner and the outer halo stained for the growth-associated protein (GAP) 43, a marker for immature olfactory sensory neurons in the OE [30-32]. The cells in the outer halo were bipolar in shape and were sparsely distributed. These cells expressed olfactory marker protein (OMP), a marker for mature sensory neurons in the OE [33,34]. In essence, the OE culture technique described herein provides an in vitro model system to study the various cell types that normally resides in the OE.


Isoform-specific effects of apoE on neurite outgrowth in olfactory epithelium culture.

Hussain A, Luong M, Pooley A, Nathan BP - J. Biomed. Sci. (2013)

Characterization of the OE culture. (A) Two contiguous phase contrast pictures of the OE culture at 8 DIV were merged to depict the location of the explant (Ex), and the inner (In) and outer (Ot) halos. Scale bar = 50 μm. Representative morphologies of cells immunostained for GBC1 (B), GAP43 (C) and OMP (D) in the OE culture. (E) Quantification of the cell types in the inner and outer halos in OE cultures.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3717083&req=5

Figure 1: Characterization of the OE culture. (A) Two contiguous phase contrast pictures of the OE culture at 8 DIV were merged to depict the location of the explant (Ex), and the inner (In) and outer (Ot) halos. Scale bar = 50 μm. Representative morphologies of cells immunostained for GBC1 (B), GAP43 (C) and OMP (D) in the OE culture. (E) Quantification of the cell types in the inner and outer halos in OE cultures.
Mentions: We used a modified protocol to culture olfactory epithelium (OE) cells derived from post-natal mice [26,27]. At 4 days in vitro (DIV) the neuronal precursors and sensory neurons migrate out of the explant and establish as two large halos (Figure 1). The inner halo, which is closer to the explant, is primarily composed of densely populated, irregular shaped cells. About 80% of the cells in the inner halo were positive for GBC-1, a marker for globose basal cells in the mature OE [28,29]. Most of the cells in the boundary of the inner and the outer halo stained for the growth-associated protein (GAP) 43, a marker for immature olfactory sensory neurons in the OE [30-32]. The cells in the outer halo were bipolar in shape and were sparsely distributed. These cells expressed olfactory marker protein (OMP), a marker for mature sensory neurons in the OE [33,34]. In essence, the OE culture technique described herein provides an in vitro model system to study the various cell types that normally resides in the OE.

Bottom Line: In contrast, treatment with apoE4 did not have an effect on neurite outgrowth.The differential effects of human apoE isoforms on neurite outgrowth were abolished by blocking the low-density lipoprotein receptor-related protein (LRP) with lactoferrin and receptor-associated protein (RAP).ApoE4, the isoform associated with AD, failed to promote neurite outgrowth, suggesting a potential mechanism whereby apoE4 may lead to olfactory dysfunction in AD patients.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biological Sciences, Eastern Illinois University, 600 Lincoln Avenue, Charleston, IL 61920, USA.

ABSTRACT

Background: The apolipoprotein E4 (apoE4) genotype is a major risk factor for developing late-onset Alzheimer's disease (AD). Inheritance of apoE4 is also associated with impairments in olfactory function in early stages of AD. In this project we examined the effects of the three common isoforms of human apoE (apoE2, apoE3, and apoE4) on neuronal differentiation and neurite outgrowth in explant cultures of mouse olfactory epithelium (OE).

Results: The OE cultures derived from apoE-deficient/knockout (KO) mice have significantly fewer neurons with shorter neurite outgrowth than cultures from wild-type (WT) mice. Treatment of the apoE KO culture with either purified human apoE2 or with human apoE3 significantly increased neurite outgrowth. In contrast, treatment with apoE4 did not have an effect on neurite outgrowth. The differential effects of human apoE isoforms on neurite outgrowth were abolished by blocking the low-density lipoprotein receptor-related protein (LRP) with lactoferrin and receptor-associated protein (RAP).

Conclusion: ApoE2 and apoE3 stimulate neurite outgrowth in OE cultures by interacting with the lipoprotein receptor, LRP. ApoE4, the isoform associated with AD, failed to promote neurite outgrowth, suggesting a potential mechanism whereby apoE4 may lead to olfactory dysfunction in AD patients.

Show MeSH
Related in: MedlinePlus