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Bacterial conjunctivitis in Muc1 null mice
R Kardon1, R E Price, J Julian
1Department of Biochemistry and Molecular Biology, University of Texas M.D. Anderson Cancer Center, Houston, USA.
Purpose:
In contrast to wild-type mice, genetically engineered Mucin1 (Muc1) null animals display a marked propensity for development of blepharitis and conjunctivitis. Molecular approaches confirmed the presence of Muc1 mRNA and protein in the conjunctival tissue of wild-type mice and identified the bacterial species in Muc1 null symptomatic mice.
Methods:
Muc1 null animals housed in a conventional facility were examined for visually apparent inflammation of the eye and surrounding tissue. Blood taken from overtly affected animals was assayed for antibodies to common murine viral agents. Swabs of infected eyes and whole eye preparations were used to detect and speciate bacterial pathogens. Frozen sections of whole eye, lid margin, and Harderian gland were immunostained with antibodies to Muc1 and cytokeratin 14, both epithelial cell markers. Northern blot analysis and reverse transcription-polymerase chain reaction (RT-PCR) were performed on RNA isolated from conjunctiva and Harderian gland of wild-type mice to compare relative levels of transcript.
Results:
Student's unpaired t-test performed on the eye inflammation frequency of Muc1 null mice confirmed a statistical significance (P < 0.01) when compared to wild-type background animals housed in the same room. Analysis of blood samples from affected Muc1 null animals detected no common murine viral pathogens. Bacterial analysis of conjunctival swabs and whole eye preparations demonstrated the presence of coagulase-negative Staphylococcus, Streptococcus type alpha, and Corynebacterium group G2. Muc1 antibody staining of wild-type sections revealed the presence of Muc1 on conjunctival goblet and non-goblet cells and on the epithelium of the Harderian gland. Serial sections stained with cytokeratin 14 antibody confirmed the epithelial nature of cells expressing the Muc1 protein. RNA from conjunctiva and Harderian gland subjected to RT-PCR and northern blot analysis showed an abundance of Muc1 transcript in these tissues.
Conclusions:
Muc1 mRNA and protein are present in murine conjunctival and Harderian gland epithelia. Animals lacking Muc1 mRNA and protein are predisposed to developing eye inflammation when compared to wild-type animals with an intact Muc1 gene. Muc1 appears to play a critical protective role at the ocular surface, presumably by acting as a barrier to infection by certain bacterial strains.
Insights
Mice lacking Mucin1 (Muc1) protein develop eye inflammation, indicating Muc1 plays a protective role at the ocular surface. This protein acts as a barrier against bacterial infections, preventing conditions like blepharitis and conjunctivitis.
Area of Science:
- Ophthalmology
- Immunology
- Microbiology
Background:
- Mucin1 (Muc1) is a glycoprotein found on epithelial surfaces.
- Muc1's role in ocular surface protection is not fully understood.
- Muc1 null mice exhibit increased susceptibility to certain conditions.
Purpose of the Study:
- To investigate the role of Mucin1 (Muc1) in the development of eye inflammation.
- To identify the molecular and microbial factors associated with eye inflammation in Muc1 null mice.
- To determine if Muc1 acts as a protective barrier against ocular pathogens.
Main Methods:
- Comparison of eye inflammation frequency between Muc1 null and wild-type mice.
- Bacterial culture and identification from infected ocular tissues.
- Immunohistochemical analysis of Muc1 expression in ocular tissues.
- Molecular analysis (RT-PCR, Northern blot) of Muc1 mRNA levels.
Main Results:
- Muc1 null mice showed a significantly higher incidence of eye inflammation (blepharitis, conjunctivitis) compared to wild-type mice.
- Bacterial pathogens, including Staphylococcus, Streptococcus, and Corynebacterium, were identified in symptomatic Muc1 null mice.
- Muc1 protein and mRNA were detected in the conjunctiva and Harderian gland epithelia of wild-type mice.
Conclusions:
- Mucin1 (Muc1) is expressed in murine ocular surface epithelia and the Harderian gland.
- Absence of Muc1 predisposes mice to bacterial-induced eye inflammation.
- Muc1 plays a crucial protective role at the ocular surface, likely by forming a barrier against bacterial infection.