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Ultrastructural Fragility and Type IV Collagen Abnormality of the Anterior Lens Capsules in a Patient with Alport Syndrome
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Ultrastructural Fragility and Type IV Collagen Abnormality of the Anterior Lens Capsules in a Patient with Alport Syndrome Kazuo Takei,* Airi Furuya,† Sachiko Hommura* and Naoto Yamaguchi‡ *Department of Ophthalmology, Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Japan; † Department of Ophthalmology, Tsukuba University Hospital, Tsukuba, Japan; ‡Division of Nephrology, Department of Internal Medicine, Mito Saisei-kai General Hospital, Mito, Japan Purpose: To investigate ultrastructural and immunohistological abnormalities of the lens capsules in a patient with Alport syndrome. Methods: Two anterior lens capsules were obtained at phacoemulsification from a 43-year-old female patient with bilateral lenticonus who was affected by Alport syndrome . The right capsule was examined by transmission electron microscopy and the left capsule was stained with two monoclonal antibodies against the triple-helical domains of type IV collagen ␣2 and ␣5 chains. Results: Numerous vertical dehiscences with many disrupted interdigitations were observed in the right anterior lens capsule. Decreased reactivity of monoclonal antibodies against type IV collagen ␣5 chain and normal reactivity against the ␣2 chain were shown in the left anterior lens capsule. Conclusion: The ultrastructural fragility of the anterior lens capsules in this patient with Alport syndrome appears to be associated with the abnormality of the type IV collagen molecules including the ␣5 chain. Jpn J Ophthalmol 2001;45:103– 104 © 2001 Japanese Ophthalmological Society Key Words: Alport syndrome, lens capsule, type IV collagen.
Introduction Alport syndrome is an inherited renal, ocular, and auditory disorder arising from mutations in the gene COL4A5, which encodes the ␣5 chain of type IV collagen.1 Anterior lenticonus frequently occurs in this syndrome, and ultrastructural abnormalities of the anterior lens capsule in the region of the lenticonus were demonstrated in previous studies.2 Although Jpn J Ophthalmol 45, 103–110 (2001) © 2001 Japanese Ophthalmological Society Published by Elsevier Science Inc.
there have been many reports regarding immunohistological abnormalities of type IV collagen in glomerular basement membranes, type IV collagen abnormality in the anterior lens capsule remains to be elucidated. In 1994, Cheong et al stained the anterior lens capsules of two Alport patients with antibodies against type IV collagen ␣1 to ␣5 chains.3 One capsule showed no reactivity to antibodies against the ␣3, ␣4, and ␣5 chains and in the other, reactivity to these antibodies was preserved. There has been no immunohistological report regarding anterior lenticonus in Alport patients since then.
Materials and Methods At phacoemulsification, we obtained two anterior lens capsules from a 43-year-old Alport female patient with bilateral lenticonus and cataract (Figure 1A). The inheritance of this Alport patient appears to be sporadic. The right capsule was fixed in 2.5% glutaraldehyde for 24 hours, postfixed with 1.0% osmium tetroxide, dehydrated in alcohol and embedded in epoxy resin for transmission electron microscopy. Cryostat sections of the left capsule were stained with two monoclonal antibodies (Shigei Medical Research Institute, Okayama) against the triple-helical domains of the type IV collagen ␣2 and ␣5 chains. The anterior lens capsule from a 69-year-old male patient with senile cataract (grade 2) and no systemic disease was also obtained for the control at the time of cataract surgery. Informed consent to the collection of capsules was obtained from the patients.
Results As shown in previous studies,2 the lens epithelial cells were well-preserved, but there were numerous blebs due to disrupted interdigitation on the basal side of the cells in the capsules from the Alport patient (Figure 1B). Large numbers of partial capsular dehiscences containing fibrillar material were beginning at the inner surface and extending straight out or curving around to join other dehiscences (Figure 1B). In both the Alport and the senile cataract patients, the anterior lens capsules showed reactivity to antibodies against the ␣2 chain (Figure 2). Regarding this reactivity to the antibody against the ␣5 chain, a marked reduction was shown in the Alport patient’s capsules compared to the specimen from the senile cataract patient (Figure 2).
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Jpn J Ophthalmol Vol 45: 103–110, 2001
Figure 1. (left panel) Anterior lenticonus in slit-lamp micrograph of right eye of 43-year-old female Alport syndrome patient. (right panel) Transmission electron micrograph of right lens material from same patient in region of lenticonus. There are many extracellular blebs containing some surgical artifacts and large numbers of partial capsular dehiscences containing fibrillar material beginning at inner surface and extending straight out or curving around to join other dehiscences.
Discussion Immunohistochemical studies, using ␣–chain-specific monoclonal antibodies on tissue specimens from healthy people and patients with Alport syndrome, have shown that there are three forms of type IV collagen molecules in mammalian basement membranes, namely ␣1/␣1/␣2, ␣3/␣4/␣5, ␣5/␣5/␣6.4 The absence of or decrease in the content of ␣3/␣4/ ␣5 molecules in the glomerular basement membrane causes renal disease in both X-linked and autosomal recessive forms of Alport syndrome.4 In the lens capsule, ␣1 and ␣2 chains are major components, although approximately 6% of the collagen is in the
form of ␣3 and ␣4 chains.5 The situation has been less clear for the ␣5 chain. Our immunohistochemical findings indicate that the abnormality of type IV collagen molecules, including the ␣5 chain, might be involved in the ultrastructural fragility of the anterior lens capsules in Alport syndrome patients It would be much more definitive if a larger series of Alport patients could be examined, for evaluation of a number of anterior capsules. The limitation in collecting samples from one laboratory is apparent. Therefore, a number of immunohistological reports regarding Alport lens capsules should be published. Received: May 9, 2000 Correspondence and requests for reprints to: Kazuo TAKEI, MD, PhD, Department of Ophthalmology, Institute of Clinical Medicine, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba-shi, Ibaraki-ken 305-8575, Japan Kazuo Takei and Airi Furuya contributed equally to this report.
References
Figure 2. Anterior lens capsule reactivity to antibody against ␣2 (IV) and ␣5 (IV) chains. Thickness of control capsule from senile cataract patient is about twice that of Alport syndrome patient’s capsule (original magnification ⫻20). In both Alport and senile cataract patients, capsules showed reactivity to antibody against ␣2 chain, but less reactivity to antibody against ␣5 chain was shown in Alport capsule compared to senile cataract capsule.
1. Barker DF, Hostikka SL, Zhou J, et al. Identification of mutations in the COL4A5 collagen gene in Alport syndrome. Science 1990;248:1224–7. 2. Streeten BW, Robinson MR, Wallace R, et al. Lens capsule abnormalities in Alport’s syndrome. Arch Ophthalmol 1987;105:1693–7. 3. Cheong HI, Kashtan CE, Kim Y, et al. Immunohistologic studies of type IV collagen in anterior lens capsules of patients with Alport syndrome. Lab Invest 1994;70:553–7. 4. Sado Y, Kagawa M, Naito I, et al. Organization and expression of basement membrane collagen IV genes and their roles in human disorders. J Biochem Tokyo 1998;123:767–76. 5. Barnard K, Burgess SA, Carter DA, et al. Three-dimensional structure of type IV collagen in the mammalian lens capsule. J Struct Biol 1992;108:6–13. PII S0021-5155(00)00297-5
Ultrastructural Fragility and Type IV Collagen Abnormality of the Anterior Lens Capsules in a Patient with Alport Syndrome Kazuo Takei,* Airi Furuya,† Sachiko Hommura* and Naoto Yamaguchi‡ *Department of Ophthalmology, Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Japan; † Department of Ophthalmology, Tsukuba University Hospital, Tsukuba, Japan; ‡Division of Nephrology, Department of Internal Medicine, Mito Saisei-kai General Hospital, Mito, Japan Purpose: To investigate ultrastructural and immunohistological abnormalities of the lens capsules in a patient with Alport syndrome. Methods: Two anterior lens capsules were obtained at phacoemulsification from a 43-year-old female patient with bilateral lenticonus who was affected by Alport syndrome . The right capsule was examined by transmission electron microscopy and the left capsule was stained with two monoclonal antibodies against the triple-helical domains of type IV collagen ␣2 and ␣5 chains. Results: Numerous vertical dehiscences with many disrupted interdigitations were observed in the right anterior lens capsule. Decreased reactivity of monoclonal antibodies against type IV collagen ␣5 chain and normal reactivity against the ␣2 chain were shown in the left anterior lens capsule. Conclusion: The ultrastructural fragility of the anterior lens capsules in this patient with Alport syndrome appears to be associated with the abnormality of the type IV collagen molecules including the ␣5 chain. Jpn J Ophthalmol 2001;45:103– 104 © 2001 Japanese Ophthalmological Society Key Words: Alport syndrome, lens capsule, type IV collagen.
Introduction Alport syndrome is an inherited renal, ocular, and auditory disorder arising from mutations in the gene COL4A5, which encodes the ␣5 chain of type IV collagen.1 Anterior lenticonus frequently occurs in this syndrome, and ultrastructural abnormalities of the anterior lens capsule in the region of the lenticonus were demonstrated in previous studies.2 Although Jpn J Ophthalmol 45, 103–110 (2001) © 2001 Japanese Ophthalmological Society Published by Elsevier Science Inc.
there have been many reports regarding immunohistological abnormalities of type IV collagen in glomerular basement membranes, type IV collagen abnormality in the anterior lens capsule remains to be elucidated. In 1994, Cheong et al stained the anterior lens capsules of two Alport patients with antibodies against type IV collagen ␣1 to ␣5 chains.3 One capsule showed no reactivity to antibodies against the ␣3, ␣4, and ␣5 chains and in the other, reactivity to these antibodies was preserved. There has been no immunohistological report regarding anterior lenticonus in Alport patients since then.
Materials and Methods At phacoemulsification, we obtained two anterior lens capsules from a 43-year-old Alport female patient with bilateral lenticonus and cataract (Figure 1A). The inheritance of this Alport patient appears to be sporadic. The right capsule was fixed in 2.5% glutaraldehyde for 24 hours, postfixed with 1.0% osmium tetroxide, dehydrated in alcohol and embedded in epoxy resin for transmission electron microscopy. Cryostat sections of the left capsule were stained with two monoclonal antibodies (Shigei Medical Research Institute, Okayama) against the triple-helical domains of the type IV collagen ␣2 and ␣5 chains. The anterior lens capsule from a 69-year-old male patient with senile cataract (grade 2) and no systemic disease was also obtained for the control at the time of cataract surgery. Informed consent to the collection of capsules was obtained from the patients.
Results As shown in previous studies,2 the lens epithelial cells were well-preserved, but there were numerous blebs due to disrupted interdigitation on the basal side of the cells in the capsules from the Alport patient (Figure 1B). Large numbers of partial capsular dehiscences containing fibrillar material were beginning at the inner surface and extending straight out or curving around to join other dehiscences (Figure 1B). In both the Alport and the senile cataract patients, the anterior lens capsules showed reactivity to antibodies against the ␣2 chain (Figure 2). Regarding this reactivity to the antibody against the ␣5 chain, a marked reduction was shown in the Alport patient’s capsules compared to the specimen from the senile cataract patient (Figure 2).
0021-5155/01/$–see front matter
104
Jpn J Ophthalmol Vol 45: 103–110, 2001
Figure 1. (left panel) Anterior lenticonus in slit-lamp micrograph of right eye of 43-year-old female Alport syndrome patient. (right panel) Transmission electron micrograph of right lens material from same patient in region of lenticonus. There are many extracellular blebs containing some surgical artifacts and large numbers of partial capsular dehiscences containing fibrillar material beginning at inner surface and extending straight out or curving around to join other dehiscences.
Discussion Immunohistochemical studies, using ␣–chain-specific monoclonal antibodies on tissue specimens from healthy people and patients with Alport syndrome, have shown that there are three forms of type IV collagen molecules in mammalian basement membranes, namely ␣1/␣1/␣2, ␣3/␣4/␣5, ␣5/␣5/␣6.4 The absence of or decrease in the content of ␣3/␣4/ ␣5 molecules in the glomerular basement membrane causes renal disease in both X-linked and autosomal recessive forms of Alport syndrome.4 In the lens capsule, ␣1 and ␣2 chains are major components, although approximately 6% of the collagen is in the
form of ␣3 and ␣4 chains.5 The situation has been less clear for the ␣5 chain. Our immunohistochemical findings indicate that the abnormality of type IV collagen molecules, including the ␣5 chain, might be involved in the ultrastructural fragility of the anterior lens capsules in Alport syndrome patients It would be much more definitive if a larger series of Alport patients could be examined, for evaluation of a number of anterior capsules. The limitation in collecting samples from one laboratory is apparent. Therefore, a number of immunohistological reports regarding Alport lens capsules should be published. Received: May 9, 2000 Correspondence and requests for reprints to: Kazuo TAKEI, MD, PhD, Department of Ophthalmology, Institute of Clinical Medicine, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba-shi, Ibaraki-ken 305-8575, Japan Kazuo Takei and Airi Furuya contributed equally to this report.
References
Figure 2. Anterior lens capsule reactivity to antibody against ␣2 (IV) and ␣5 (IV) chains. Thickness of control capsule from senile cataract patient is about twice that of Alport syndrome patient’s capsule (original magnification ⫻20). In both Alport and senile cataract patients, capsules showed reactivity to antibody against ␣2 chain, but less reactivity to antibody against ␣5 chain was shown in Alport capsule compared to senile cataract capsule.
1. Barker DF, Hostikka SL, Zhou J, et al. Identification of mutations in the COL4A5 collagen gene in Alport syndrome. Science 1990;248:1224–7. 2. Streeten BW, Robinson MR, Wallace R, et al. Lens capsule abnormalities in Alport’s syndrome. Arch Ophthalmol 1987;105:1693–7. 3. Cheong HI, Kashtan CE, Kim Y, et al. Immunohistologic studies of type IV collagen in anterior lens capsules of patients with Alport syndrome. Lab Invest 1994;70:553–7. 4. Sado Y, Kagawa M, Naito I, et al. Organization and expression of basement membrane collagen IV genes and their roles in human disorders. J Biochem Tokyo 1998;123:767–76. 5. Barnard K, Burgess SA, Carter DA, et al. Three-dimensional structure of type IV collagen in the mammalian lens capsule. J Struct Biol 1992;108:6–13. PII S0021-5155(00)00297-5