Skip to main page content
U.S. flag

An official website of the United States government

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2004 Jan 14;24(2):356-69.
doi: 10.1523/JNEUROSCI.1219-03.2004.

Odorant receptor expression patterns are restored in lesion-recovered rat olfactory epithelium

Carrie L Iwema  1 , Hengsheng Fang, Daniel B Kurtz, Steven L Youngentob, James E Schwob
Affiliations

Odorant receptor expression patterns are restored in lesion-recovered rat olfactory epithelium

Carrie L Iwema et al. J Neurosci. .

Abstract

Lesions of the olfactory periphery provide a means for examining the reconstitution of a diverse and highly regulated population of sensory neurons and the growth, en masse, of nascent axons to the bulb. The olfactory epithelium and its projection onto the bulb are reconstituted after ablation by methyl bromide gas, and some measure of olfactory function is restored. The extent to which the system regenerates the full repertoire of odorant receptor-expressing neurons, particularly their spatially restricted distribution across the epithelial sheet, is unknown, however, and altered odorant receptor expression might contribute to the persistent distortion of odorant quality that is observed in the lesioned-recovered animals. To address the question of receptor expression in the recovered epithelium, we performed in situ hybridization with digoxigenin-labeled riboprobes for eight odorant receptors on the olfactory epithelium from unilaterally methyl bromide-lesioned and control rats. The data demonstrate that the distribution of sensory neuron types, as identified and defined by odorant receptor expression, is restored to normal or nearly so by 3 months after lesion. Likewise, the numbers of probe-labeled neurons in the lesioned-recovered epithelium are nearly equivalent to the unlesioned side at this time. Finally, our evidence suggests that odorant receptors are distributed in multiple overlapping bands in the normal, unlesioned, and lesioned-recovered epithelium rather than in the conventionally accepted three or four zones. Thus, the primary sensory elements required for functional recovery of the olfactory system after damage are restored, and altered function implies the persistence of a more central failure in regeneration.

PubMed Disclaimer

Figures

Figure 1.
Figure 1.
Neuronal labeling by ISH with either the OR16 (A) or I7 (E) OR probe in normal rat OE visualized with alkaline phosphatase. Boxed areas are shown at higher power in B and F, respectively. Labeled cells are scattered across a restricted territory of the OE and may be close to each other or more highly separated. C, D, Schematics of the OE illustrating the locations of A and E. Scale bars: (in A) A, E, 200 μm; (in B) B, F, 50 μm.
Figure 2.
Figure 2.
Schematics illustrating OR expression patterns throughout the extent of normal rat OE. Each colored dot designates an OR-positive OSN in a single subject (CI-142) using each of eight OR riboprobes. At each level, the labeling on the eight adjacent sections was compiled onto a single schematic although the OR distributions were separated into three panels for ease of visualization. The boxed area is shown at higher power in Figure 3. The arrows indicate areas where multiple ORs overlap, but only partially.
Figure 3.
Figure 3.
Expanded view of the lateral part of the left OE from the middle level shown in Figure 2, in which the labeling from all eight probes is mapped onto a single copy of the schematic section. Each dot marks the position of an OR-positive OSN, and each color represents an OR subtype as indicated. The arrows designate the progression of OR labeling as one proceeds from central to peripheral along the opposing epithelial surfaces. The progression is also indicated by the order of listing the OR probes across the top from central (at the right) toward peripheral (at the left). Each of the eight ORs in the panel has a unique expression pattern in this and other portions of the adult rat OE.
Figure 4.
Figure 4.
A, B, OSNs labeled by ISH with either OR14 or OR37 riboprobe, respectively, on adjacent sections of control epithelium (CI-127). In this and subsequent figures, the lines drawn in the nasal airspace designate the extent of labeling with the alternate probe on the adjacent section. Note that areas of the epithelium are unique to each probe. C, Double ISH in a single section with both OR14+ OSNs (purple) and OR37+ OSNs (orange). Receptor distribution is stratified, and there is no evidence of colabeling of individual neurons. D, Schematic of a hemisection from the CI-127 showing the location of the photomicrographs. Scale bars: (in B) A, B, 500 μm; C, 100 μm.
Figure 5.
Figure 5.
OSNs labeled by ISH with OR14 (A, E) or OR18 (B, F) riboprobe on adjacent sections of control epithelium (CI-128). The lines drawn in the nasal airspace designate the extent of labeling with the alternate probe on the adjacent section. A, B, High-power photomicrographs of anterior OE. Note the extent of the OE that is devoid of both OR14+ and OR18+ OSNs. C, Schematic of a hemisection of anterior epithelium from CI-128 showing the location of A and B. E, F, High-power photomicrographs of posterior OE. Note that in posterior OE the regions of OR14 and OR18 expression are slightly overlapping at the limits of their respective territories. Asterisks in F highlight OR18+ OSNs that are deep within the OR14 sector. D is a schematic of a hemisection of posterior rat OE showing the location of E and F. Scale bars: (in A) A, B, 200 μm; (in E) E, F, 500 μm.
Figure 6.
Figure 6.
A, B, OSNs labeled by ISH with OR133 or OR107 riboprobe, respectively, in adjacent sections of control epithelium (CI-126) in the region of endoturbinate II and ectoturbinates 2 and 3. The lines drawn in the nasal airspace designate the extent of labeling with the alternate probe on the adjacent section. Note the numerous regions where labeling with OR133 and OR107 overlap despite the concentration of OR133 more medially and OR107 more laterally. C, Schematic of the hemisection from CI-126 showing the location of the photomicrographs. Scale bar: (in B) A, B, 200 μm.
Figure 7.
Figure 7.
Three days after unilateral exposure to MeBr, sensory neurons labeled by OR18 riboprobe are completely eliminated from the epithelium on the side exposed to MeBr (CI-129). A, Photomicrograph showing OR18+ OSNs in the nasal cavity on the side where the naris was closed before MeBr exposure. Boxed area is shown at higher magnification in C. D, Side where the naris was open during the MeBr exposure. B, Schematic of the OE showing the location of the photomicrographs. Scale bars: (in A) A, B, 200 μm; C, 50 μm.
Figure 11.
Figure 11.
A, The average number of probe-positive OSNs in normal rat OE is illustrated for each OR (n = 5). There is no systematic difference in number between the two sides across this set of probes; however, note the variation in total cell number for each OR. B, The average number of probe-positive OSNs in the OE of unilaterally exposed rats is illustrated for each OR (n = 7). Neurons labeled by OR107 and OR124 are fewer in number on the lesioned-recovered side, whereas the rest of the probe-positive populations fall near the line indicating equal numbers on the unlesioned and lesioned-recovered sides.
Figure 8.
Figure 8.
Schematics illustrating OR expression patterns throughout the AP extent of OE from a rat 3 months after unilateral MeBr exposure (CI-133). Lesioned indicates the open-naris side. Unlesioned indicates the closed-naris side. Each colored dot designates an OR-positive OSN. At each level, the labeling on the eight adjacent sections was compiled onto a single schematic, although the OR distributions were separated into three panels for ease of visualization. The absence of OR18 labeling in the epithelium of endoturbinate III of the lesioned side of the middle section of the middle panel (asterisk) is caused by damage to that endoturbinate during ISH processing for OR18. That part of the epithelium is intact on nearby sections and is labeled with OR18 riboprobe in a manner indistinguishable from the unlesioned side.
Figure 9.
Figure 9.
The distribution of OSNs labeled with OR107 riboprobe is restored after recovery from unilateral MeBr lesion. A, OR107 labeling in lateral cul de sac of a control animal (CI-127). B, C, Corresponding areas of the lateral cul de sac from a unilaterally exposed rat at 3 months after lesion (CI-135) on the closed-naris (unlesioned) and the open-naris (lesioned) sides, respectively. The differences in the labeling patterns between the lesioned side and the same region either on the unlesioned side or in the control epithelium are attributable to the patchy replacement of olfactory by respiratory epithelium as shown by the depletion of OMP staining in that area in a nearby section (data not shown). The regions that have undergone respiratory metaplasia are designated by the lines in the nasal cavity. D is a schematic of the OE illustrating the location of A. E, Schematic of the OE illustrating the location of B and C. Scale bar: (in C) A-C, 100 μm.
Figure 10.
Figure 10.
The distribution of OSNs labeled with OR14 riboprobe is restored 3 months after unilateral MeBr lesion (AD-16), as shown by both the full-length OR14 riboprobe (A) and another one derived from the 3′UTR of the OR14 message (B). Both probes produce the same pattern of labeling on both sides. Lesioned indicates the open-naris side. Unlesioned indicates the closed-naris side. Counts indicate that slightly fewer OSNs are labeled by the 3′UTR probe; however, the boundaries of the OR14 territory (arrows) are situated in the same locations on both sides with both probes, suggesting that OSNs labeled by cross-hybridization to a closely related but distinct OR share the same territory, which is restored after the epithelium recovers from injury.
Figure 12.
Figure 12.
Anti-OMP staining of a mid-anteroposterior section through the nasal cavity of a rat exposed unilaterally to MeBr and allowed to recover for 3 months (CI-137). Lesioned indicates the open-naris side. Unlesioned indicates the closed-naris side. Some of the epithelial lining on the lesioned side of the unilaterally exposed rats lacks OMP-positive neurons in contrast to the unlesioned side (lines drawn in the nasal cavity), indicating that it has undergone metaplasia and reconstituted as respiratory epithelium instead of olfactory.
Figure 13.
Figure 13.
A comparison between the conventional four-zone model and the labeling observed with the panel of eight OR probes. The territories for each of the eight probes is shown only along the septal epithelium, except for OR 37, expression of which is limited to the mucosa on the tips of the turbinates (dorsal is to the left). The boundaries for the four zones are transposed from the published patterns of labeling of the mouse epithelium used to develop the four-zone model in relation to the various turbinates (Sullivan et al., 1996). In particular, the ventral boundary for zone 1 is aligned with the boundary between high and low expression levels of the Ig-CAM superfamily member, OCAM/mamFasII, which has been described previously (Yoshihara et al., 1997). OR14 labeling extends into the epithelial region in which OCAM/mamFasII is highly expressed (H. Fang and J. E. Schwob, unpublished observations).
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Belluscio L, Katz LC (2001) Symmetry, stereotypy, and topography of odorant representations in mouse olfactory bulbs. J Neurosci 21: 2113-2122. - PMC - PubMed
    1. Buck L, Axel R (1991) A novel multigene family may encode odorant receptors: a molecular basis for odor recognition. Cell 65: 175-187. - PubMed
    1. Carr V McM, Ring G, Youngentob SL, Schwob JE, Farbman AI (2004) Altered epithelial density and expansion of bulbar projections of a discrete HSP70 immunoreactive subpopulation of rat olfactory receptor neurons in reconstituting olfactory epithelium following exposure to methyl bromide. J Comp Neurol, in press. - PubMed
    1. Chess A, Simon I, Cedar H, Axel R (1994) Allelic inactivation regulates olfactory receptor gene expression. Cell 78: 823-834. - PubMed
    1. Costanzo RM (1991) Regeneration of olfactory receptor cells. Ciba Found Symp 160: 233-242. - PubMed

Publication types