Incidence and characteristics of aspiration pneumonia in the Nagasaki Prefecture from 2005 to 2019

BACKGROUND

Aspiration pneumoniae remains a major health concern, particularly in the older population and has poor prognosis; however, the concept itself remains vague worldwide. This study aimed to determine the actual situation and characteristics of aspiration pneumonia from 2005 to 2019 in Nagasaki Prefecture, Japan.

METHODS

Cases of aspiration pneumonia that occurred in the Nagasaki Prefecture between 2005 and 2019 were analyzed using emergency transportation records. The number of occurrences and incidence were analyzed according to age, sex, month, day of the week, and recognition time to clarify the actual situation of aspiration pneumonia.

RESULTS

The total number of new aspiration pneumonia cases was 8,321, and the mean age of the patients was 83.0 years. Annual incidence per 100,000 population increased from 12.4 in 2005 to 65.1 in 2019, with the most prominent increase in the ≥ 80-year-old stratum. Males (55.1%) were more commonly affected than females (44.9%), and 82.2% of the cases involved patients aged ≥ 70 years. No significant correlations were observed between the incidence of aspiration pneumonia and season, month, or day of the week. Aspiration pneumonia occurred frequently in houses (39.8%) and facilities for elderly individuals (40.8%). At 7 days after admission, 80.9% of patients were still hospitalized and 6.5% had died.

CONCLUSIONS

The incidence of aspiration pneumonia with risks of severity and mortality is increasing among elderly individuals. Valid preventive measures are urgently needed based on the findings that the disease occurs in both household and elderly care facility settings, regardless of the season.

Progression of microstructural deterioration in load-bearing immobilization osteopenia

Purpose

Immobilization osteopenia is a major healthcare problem in clinical and social medicine. However, the mechanisms underlying this bone pathology caused by immobilization under load-bearing conditions are not yet fully understood. This study aimed to evaluate sequential changes to the three-dimensional microstructure of bone in load-bearing immobilization osteopenia using a fixed-limb rat model.

Materials and method

Eight-week-old specific-pathogen-free male Wistar rats were divided into an immobilized group and a control group (n = 60 each). Hind limbs in the immobilized group were fixed using orthopedic casts with fixation periods of 1, 2, 4, 8, and 12 weeks. Feeding and weight-bearing were freely permitted. Length of the right femur was measured after each fixation period and bone microstructure was analyzed by micro-computed tomography. The architectural parameters of cortical and cancellous bone were analyzed statistically.

Results

Femoral length was significantly shorter in the immobilized group than in the control group after 2 weeks. Total area and marrow area were significantly lower in the immobilized group than in the control group from 1 to 12 weeks. Cortical bone area, cortical thickness, and polar moment of inertia decreased significantly after 2 weeks. Some cancellous bone parameters showed osteoporotic changes at 2 weeks after immobilization and the gap with the control group widened as the fixation period extended (P < 0.05).

Conclusion

The present results indicate that load-bearing immobilization triggers early deterioration of microstructure in both cortical and cancellous bone after 2 weeks.

Role of Monocytes/Macrophages in the Etiology of Bullous Keratopathy After Argon Laser Iridotomy

Purpose

The etiologic mechanisms of bullous keratopathy (BK) after argon laser iridotomy (ALI) are still unknown. Therefore, we investigated potential mechanisms on BK after ALI.

Methods

Corneal endothelial surface obtained in penetrating keratoplasty for BK after ALI was observed and analyzed immunohistochemically. We investigated how various leukocytes react to cultured human corneal endothelial cells in an inflamed condition and monocytes/macrophages respond to the iris treated by an argon and YAG laser or pigmented and nonpigmented iris treated by an argon laser.

Results

We detected infiltration of CD68- and CD11b-positive monocytes/macrophages in the posterior surface of trephined corneas obtained during penetrating keratoplasty for BK after ALI in three of the seven eyes with ALI. In vitro, monocytes/macrophages, but not T cells, B cells, neutrophils, or pan-leukocytes, removed many cultured human corneal endothelial cells in the medium stimulated with proinflammatory cytokines. Human pigmented iris tissues treated by the argon laser, but not those treated by the YAG laser, attracted many monocytes/macrophages and formed large, round colonies. Human monocytes/macrophages formed large colonies on the argon laser–treated pigmented iris from C3H mice but not nonpigmented iris from albino BALB/c mice.

Conclusions

Our results suggest that monocytes/macrophages, argon laser, and pigmented iris are all involved in the pathogenesis of BK after LI.

Translational Relevance

Etiology in BK after ALI has not been clear, but our findings based on clinical and experimental findings give a critical clue to explain possible mechanisms on BK after ALI.

Visualization of Airborne Particles as a Risk for Microbial Contamination in Orthopedic Surgery

Background: The operating theater is recognized to involve a high frequency of occupational blood and body fluid contacts. Objectives: This study aimed to visualize the production of blood and body fluid airborne particles by surgical procedures and to investigate risks of microbial contamination of the conjunctival membranes of surgical staff during orthopedic operations. Methods: Two physicians simulated total knee arthroplasty (TKA) and total hip arthroplasty (THA) in a bio-clean theater using model bones. The generation and behaviors of airborne particles were filmed using a fine particle visualization system, and numbers of airborne particles per 2.83 L of air were counted at the height of the operating and instrument tables. Each action was repeated five times, and particle counts were evaluated statistically. Results: Numerous airborne particles were dispersed to higher and wider areas while "cutting bones in TKA" and "striking and driving the cup component on the pelvic bone in THA" compared to other surgical procedures. The highest particle counts were detected while "cutting bones in TKA" under unidirectional laminar air flow. Discussion: These results provide a clearer image of the dispersion and distribution of airborne particles and identified higher-risk surgical procedures for microbial contamination of the conjunctival membranes. Surgical staff including surgeons, nurses, anesthesiologists, and visitors, should pay attention to and take measures against occupational infection particularly in high-risk surgical situations.

Goblet Cell Differentiation Potential in Human Corneal Limbal Epithelial Progenitor Cells In Vitro

Purpose

The existence of goblet cells has been regarded as a critical differential point to distinguish conjunctival epithelium from corneal epithelium in vivo. We tested differentiation potential of single progenitor cells from corneal limbal epithelium with growth factors in vitro.

Methods

Dissociated single cells from corneal limbal epithelium were cultured in the serum- and feeder cell–free medium containing B27 and various growth factors using nontissue culture dishes. Specific marker expression was examined in the colonies stimulated with growth factors. Differentiation of some mucosal epithelia was tested.

Results

Adherent single cells from dissociated single cells in corneal limbal epithelium did not proliferate in the serum- and feeder cell–free medium containing B27 only and formed corneal epithelium with B27 plus epidermal growth factor, while they gave rise to goblet cell with periodic acid Schiff–positive mucin and cytokeratin-3 and-12 expressing corneal epithelium with fibroblast growth factor (FGF)2 stimulation. Colonies stimulated with FGF2 expressed goblet cell specific MUC5AC and cytokeratin-7 mRNA and protein. FGF receptor 1 was a functional receptor for the differentiation to goblet cells and corneal epithelium.

Conclusions

Single corneal limbal progenitor cells give rise to goblet cells and corneal epithelium by FGF2 stimulation via FGF receptor 1 in vitro.

Impact of muscle volume loss on acute oral mucositis in patients undergoing concurrent chemoradiotherapy after oral cancer resection

This study evaluated the association between skeletal muscle mass depletion and severe oral mucositis in patients undergoing concurrent chemoradiotherapy after oral cancer resection. Skeletal muscle mass was evaluated in 60 patients using the skeletal muscle index, which was based on skeletal muscle cross-sectional area (on computed tomography) at the level of the third lumbar vertebra. In accordance with the grading criteria of the Radiation Therapy Oncology Group, patients with a grade ≥3 were defined as having severe oral mucositis. Multivariate logistic regression analysis was used to evaluate independent risk factors for severe oral mucositis. Eleven patients (18.3%) were diagnosed with low skeletal muscle mass. Severe oral mucositis occurred in 17 (28.3%) patients, and the mean skeletal muscle index was 42.8 cm²/m². A low skeletal muscle mass (hazard ratio 18.1; P=0.001) and a chemotherapy regimen consisting of 5-fluorouracil and cisplatin (versus cisplatin only) (hazard ratio 5.5; P=0.015) were independent risk factors for severe oral mucositis. Future prospective studies are warranted to identify effective pre- and perioperative exercises and nutrition programmes to increase low skeletal muscle mass and reduce the incidence of severe oral mucositis in patients undergoing concurrent chemoradiotherapy after oral cancer resection.

Tongue surface model can predict radiation tongue mucositis due to intensity-modulated radiation therapy for head and neck cancer

Acute radiation tongue mucositis has a profound effect on talking and eating. We examined whether the dose-volume histogram obtained from the tongue surface model correlates with mucositis severity, and whether it is useful for predicting acute radiation tongue mucositis in patients with head and neck cancer treated with intensity-modulated radiation therapy. Thirty-six patients who received intensity-modulated radiation therapy for head and neck cancer were analysed for acute radiation tongue mucositis according to the Common Terminology Criteria for Adverse Events, version 4.0, as well as the Radiation Therapy Oncology Group scoring systems. The corresponding high-dose locations in anatomical sub-regions in the tongue surface model and the development of high-grade acute radiation tongue mucositis were compared. The mucositis sites coincided with the high-dose anatomical sub-regions in the tongue surface model. There was a clear dose-response relationship between the mean dose to the tongue and the acute radiation tongue mucositis Radiation Therapy Oncology Group grade. According to the dose-volume histogram, patients receiving 16.0-73.0 Gy to the tongue were susceptible to grade 2-3 toxicity. The tongue surface model can predict the site and severity of acute radiation tongue mucositis. In future, radiation treatment plans ccould be optimized using this model.

Clinicopathological investigation of odontogenic fibroma in tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is an autosomal dominant inherited disease characterized by systemic hamartoma and diverse systemic features. TSC1 and TSC2 are the causative genes, and mental retardation, epileptic seizures, and facial angiofibroma develop in many patients with the disease. The case of a patient with TSC who developed a central odontogenic fibroma of the mandible is reported here. The patient was a 21-year-old woman who was referred with a swelling of the labial gingiva in the region of the right lower lateral incisor and canine. Dental radiography revealed a multilocular radiolucent region with a clear boundary. The right lower lateral incisor and canine were continuous with the lesion and thus were excised en bloc. The lesion was encapsulated and easily dissected. The diagnosis on immunohistological staining was odontogenic fibroma without an epithelial component. TSC1/2 gene mutation causes abnormal activation of mammalian target of rapamycin (mTOR) downstream of the PI3K-AKT pathway. The odontogenic fibroma in this patient was positive for mTOR, suggesting that the development of the odontogenic fibroma was the result of abnormal activation of mTOR, as in angiofibroma. The clinical course of this patient is presented and the developmental mechanism of central odontogenic fibroma is discussed.

Standard morphology of the oral commissure and changes resulting from reconstruction for defects involving the commissure

The aim of this study was to characterize the standard morphology of the oral commissure and to describe the changes after reconstruction in patients with through-and-through cheek defects involving the oral commissure. Indices for the morphological analyses of the commissure were derived from examinations of 50 normal Japanese volunteers. Ten patients with full-thickness cheek defects involving the commissure were then evaluated. All of these patients underwent free flap reconstruction with vermilion advancement flaps from the remaining vermilion. The morphology of the commissure with the mouth closed was classified based on the point of entrance of the vermilion into the oral cavity. In normal volunteers, the commissure pattern consisting of the entrance of the upper vermilion into the oral cavity before the lower vermilion and just prior to forming the oral commissure was considered to be the standard. However, in the reconstructed cases, there was an increase in the pattern in which the lower vermilion enters the oral cavity before the upper vermilion for the remaining commissure postoperatively, especially when the lower lip defects were greater than those of the upper lip. It is important to refer not only to the standard morphology of the commissure, but also to the changes according to the extent of resection and the method of reconstruction.

Toxicity of topical antifungal agents to stratified human cultivated corneal epithelial sheets

PURPOSE

Prolonged use of topical antifungal agents may compromise corneal epithelial integrity. Here, we used an in vitro model of human stratified corneal epithelium to compare the ocular toxicity profiles of 4 different antifungal eye drops.

METHODS

Human corneal epithelial cell sheets were cultured in a serum-free medium containing 0.1% micafungin, 1% voriconazole, 5% pimaricin, 0.1% amphotericin B, or controls (saline or 5% glucose). Cell viability and barrier function were measured by WST-1 assay and carboxyfluorescein permeability assay, respectively. Cell migration was measured on a wound healing assay.

RESULTS

WST-1 assay and carboxyfluorescein permeability assay revealed that amphotericin B was the most toxic drug, followed by pimaricin, micafungin, and voriconazole. Cell migration on a wound healing assay was decreased in the following order, amphotericin B, pimaricin, micafungin, and voriconazole.

CONCLUSIONS

Topical micafungin and voriconazole appeared to be the least toxic to the corneal epithelium. Drug prescription should consider not only fungal species and susceptibility but also ocular toxicity and stage of treatment.

Lower lip repair using double opposing rectangular rotation flaps with reconstruction of the mentolabial groove and mental protuberance

The use of a rectangular flap is a well known technique for upper lip repair in cleft lip, but is less common for lower lip repair after tumour resection. We have found this type of flap to be favourable for lower lip reconstruction, especially for the lip to mental region. We describe herein an improvement to the technique in which two opposing rectangular flaps, with the length of one side equal to the vertical distance from the mentolabial groove to the vermilion border, were raised on the lateral sides of a U-shaped defect. Reconstruction was performed by interdigitation of the two flaps and a bilateral vermilion advancement flap. This new approach allows a distinct mentolabial groove and mental protuberance to be created by utilizing two opposing rectangular flaps and redundant tissue, without sacrificing sensation and muscle function. Our results suggest that the technique provides excellent functional and cosmetic outcomes in restoration of the lower lip in properly selected patients.

Effects of postoperative chemotherapy and radiotherapy on patients with squamous cell carcinoma of the oral cavity and multiple regional lymph node metastases

Nodal metastasis in oral squamous cell carcinoma (OSCC) is considered to be a predictor of a poor prognosis. The aim of this study was to investigate the relationship between the number of positive lymph nodes and the prognosis in OSCC patients with nodal metastases and to assess the effects of postoperative radiotherapy (RT) or concurrent chemoradiotherapy (CCRT) on this patient group. A retrospective investigation of 98 patients with OSCC who underwent radical neck dissection and had at least three pathologically positive lymph nodes was performed. The 5-year disease-specific survival rate was 66.7% for patients with 3 positive nodes, while it was significantly lower for those with 4 positive nodes and those with ≥ 5 positive nodes (21.5% and 46.1%, respectively; P < 0.01). The loco-regional control and disease-specific survival rates for the surgery alone, surgery plus RT, and surgery plus CCRT groups were 46.2% and 40.5%, 66.3% and 54.4%, and 81.7% and 52.4%, respectively. For patients with ≥ 4 positive nodes, the loco-regional control rate after surgery plus CCRT was better than that observed after surgery alone (77.5% vs. 32.6%, P = 0.01). Postoperative RT and CCRT have positive impacts on the prognosis of OSCC patients with advanced stage neck disease.

Stromal bed quality and endothelial damage after femtosecond laser cuts into the deep corneal stroma

AIM

To evaluate the stromal bed quality and endothelial damage after femtosecond laser (FSL) cuts into the deep corneal stroma.

METHODS

Using a 150-kHz FSL, a lamellar cut was aimed at a depth of 100, 300, or 500 μm in porcine corneas. Stromal bed smoothness was graded from light microscopy and scanning electron microscopy images. Rabbit corneas were cut at remaining thicknesses of 70, 100 and 150 μm using the FSL. The effects of peeling off the corneal flap and the distance between laser spots (2 or 4 μm) were examined.

RESULTS

The ratio of damaged cells in the group with a remaining depth of 70 μm was significantly larger than that in the groups with a remaining depth of 150 μm. The ratio of damaged cells in the group with a 4-μm spot separation and the flap peeled off was significantly larger than that in the group with a 4-μm spot separation and the flap not peeled off.

CONCLUSIONS

Corneal endothelial damage is likely to increase when the remaining depth is less than 70 μm, and peeling off the flap damages corneal endothelial cells when the remaining depth is less than 100 μm.

Long-term maintenance of limbal epithelial progenitor cells using rho kinase inhibitor and keratinocyte growth factor

Corneal epithelial stem cells are located in the limbus, the junction between the cornea and the conjunctiva. A limbal epithelium model in vitro would be useful for the study of epithelial stem cells, as well as improving the quality of cultivated epithelial sheets for the treatment of limbal stem cell deficiency. In this study, we succeeded in constructing a limbal epithelium-like structure that could be maintained for at least 5 months in vitro. We modified conventional medium by replacing epidermal growth factor with keratinocyte growth factor (KGF) and adding Y-27632, a rho kinase inhibitor. Using this medium, epithelial cells freshly isolated from human limbus were cocultured with human mesenchymal stem cell-derived feeder cells. Cells formed a stratified layer without air exposure, and both basal and suprabasal layers maintained their unique morphologies for up to 5 months. Basal layers expressed the progenitor marker p63 uniformly and K15 heterogeneously. Expressions of PAX6, K3, and K12 indicated that cell sheets underwent normal differentiation in the corneal epithelium lineage. Although medium was changed daily after day 7, cell debris was observed every day, suggesting that cell sheets underwent turnover. Furthermore, secondary colonies were observed from cells dissociated from 1-month and 3-month cultured sheets. In conclusion, human limbal epithelial cell sheet cultures with KGF and Y-27632 maintained stratification, high expression of both stem/progenitor markers and differentiation markers, and colony-forming cells long-term. This protocol may be useful as an in vitro limbal epithelial model for basic studies.

Angiopoietin-like protein 2 is a potent hemangiogenic and lymphangiogenic factor in corneal inflammation

PURPOSE

We determined the plausible functional role of angiopoietin-like protein 2 (Angptl2) in inflammatory corneal hemangiogenesis and lymphangiogenesis in vivo.

METHODS

Corneal hemangiogenesis and lymphangiogenesis were induced by suturing 10-0 nylon 1 mm away from the limbal vessel in Angptl2 knockout and K14-Angptl2 transgenic mice. We analyzed Angptl2 and interleukin 1β (IL-1β) expressions in normal and vascularized corneas by real-time RT-PCR and immunohistochemistry. Corneal hemangiogenic and lymphangiogenic responses, and macrophage infiltration were assessed by immunofluorescent microscopic studies using specific antibodies against CD31, LYVE-1, and F4/80, and compared to their corresponding background. Subconjunctival injection of Angptl2 siRNA to the sutured corneas was also performed.

RESULTS

Angptl2 mRNA expression increased markedly in the neovascularized corneas compared to the normal cornea. Angptl2 protein was expressed strongly in the corneal epithelium and stroma of the vascularized cornea. The regions showing hemangiogenesis and lymphangiogenesis were increased significantly in K14-Angptl2 mice and reduced in Angptl2(-/-) mice compared to their corresponding background strains. In contrast to control mice, the number of F4/80-positive cells, as well as the expressions of F4/80 and IL-1β were found to be higher in K14-Angptl2 mice and lower in Angptl2(-/-) mice. Subconjunctival injection of Angptl2 siRNA significantly inhibited hemangiogenesis and lymphangiogenesis in the sutured corneas.

CONCLUSIONS

Our findings demonstrated Angptl2 to be upregulated in corneal inflammation, and highlight that corneal hemangiogenesis and lymphangiogenesis may be driven by Angptk2 overexpression via macrophage infiltration and IL-1β expression. Angptl2 may be a novel therapeutic target for preventing blindness.

Tissue engineering of corneal endothelium

Human corneal endothelial cells (HCECs) do not replicate after wounding. Therefore, corneal endothelial deficiency can result in irreversible corneal edema. Descemet stripping automated endothelial keratoplasty (DSAEK) allows selective replacement of the diseased corneal endothelium. However, DSAEK requires a donor cornea and the worldwide shortage of corneas limits its application. This review presents current knowledge on the tissue engineering of corneal endothelium using cultured HCECs. We also provide our recent work on tissue engineering for DSAEK grafts using cultured HCECs. We reconstructed DSAEK grafts by seeding cultured DiI-labelled HCECs on collagen sheets. Then HCEC sheets were transplanted onto the posterior stroma after descemetorhexis in the DSAEK group. Severe stromal edema was detected in the control group, but not in the DSAEK group throughout the observation period. Fluorescein microscopy one month after surgery showed numerous DiI-labelled cells on the posterior corneal surface in the DSAEK group. Frozen sections showed a monolayer of DiI-labelled cells on Descemet’s membrane. These findings indicate that cultured adult HCECs, transplanted with DSAEK surgery, maintain corneal transparency after transplantation and suggest the feasibility of performing DSAEK with HCECs to treat endothelial dysfunction.

Cytopathic effect of Acanthamoeba on human corneal fibroblasts

PURPOSE

Acanthamoeba keratitis is associated with keratocyte depletion in humans. We investigated how Acanthamoebae isolated from corneas affected by Acanthamoeba keratitis interacted with human corneal stromal cells in vitro.

METHODS

Acanthamoebae were isolated from 6 patients with Acanthamoeba keratitis and genotyping was done. Whether the isolated Acanthamoebae could invade the corneal stroma was assessed with denuded corneal stroma ex vivo. The cytopathic effect of Acanthamoeba on cultured corneal fibroblasts from donor corneas was quantitatively evaluated by the MTT assay after culture under various conditions. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) and Annexin V staining were employed to detect apoptotic cells among the corneal fibroblasts co-cultured with Acanthamoebae.

RESULTS

All 6 Acanthamoebae isolated from the patients with Acanthamoeba keratitis were shown to have the T4 genotype by 18S rDNA sequence analysis. Acanthamoebae invaded the denuded corneal stroma in the ex vivo experiments and had a cytopathic effect on human corneal fibroblasts after direct adhesion, but not via chemical mediators. A cytopathic effect was detected with all 6 Acanthamoebae and corneal fibroblasts mainly died by apoptosis, as evidenced by Annexin V staining.

CONCLUSIONS

Acanthamoebae isolated from patients with Acanthamoeba keratitis had a cytopathic effect on human corneal fibroblasts, mainly via induction of apoptosis after direct adhesion. Our findings may provide some clues to the pathophysiology of corneal keratocyte depletion in patients with Acanthamoeba keratitis.

Ultrasound-guided intralesional laser treatment of venous malformation in the oral cavity

An ultrasound-guided intralesional photocoagulation (ILP) technique using a laser is described for treatment of deep venous malformations in the oral cavity. ILP is basically a blind operation and has a risk of unintended destruction of surrounding normal tissue, therefore the authors now routinely use guidance by ultrasonography using a mini-probe to improve the safety and reliability of ILP. This approach enables safe fibre insertion, appropriate laser irradiation, and intraoperative assessment of coagulation. The use of this technique is described in 8 patients. The authors conclude that ultrasound-guided ILP with a laser is a promising technique for less-invasive treatment of a vascular malformation in the oral cavity.

Adhesion, migration, and proliferation of cultured human corneal endothelial cells by laminin-5

PURPOSE

To investigate the expression of laminin-5 (LM5) and its receptors by human corneal endothelial cells (HCECs) and whether recombinant human LM5 influences adhesion, proliferation, and migration of cultured HCECs.

METHODS

The expression of LM5 and its receptors was examined in human donor corneas by immunohistochemistry, reverse transcription-polymerase chain reaction, and flow cytometry. HCECs cultured under serum-free conditions were used for analysis of the biological effects of LM5. Changes in HCEC adhesion and proliferation due to LM5 were evaluated by counting the number of cells. HCEC migration was assessed by quantifying the percentage of wound closure in the wound-healing assay with an image-processing and -analysis software program.

RESULTS

Adult HCECs expressed the LM5 receptor α3β1 integrin, but not LM5 itself. Significantly more cells became adherent to recombinant LM5 (1.0 μg/mL)-coated dishes than to uncoated dishes in the cell adhesion assay. The proliferation of cultured HCECs was moderately promoted by LM5 (1.0 μg/mL) and soluble LM5 (20 ng/mL and 50 ng/mL) in the cell proliferation assay. A significantly higher percentage of wound closure was obtained with medium containing soluble LM5 than with control medium in the wound-healing assay.

CONCLUSIONS

HCECs express the LM5 receptor α3β1 integrin. Recombinant LM5 promotes adhesion, migration, and moderate proliferation of cultured HCECs. It may be a critical factor in promoting HCEC culture and may contribute to the practical use of tissue-engineered HCECs.

[Regenerative medicine and stem cells of corneal epithelium]

Stem cells supply differentiated cells that compose the body organs. Stem cell research is increasing and their use in regenerative medicine is drawing a lot of attention. In ophthalmology, regenerative medicine of the corneal epithelium is already practiced by clinicians, and there is constant improvement in the culture methods. Research leading to the isolation of corneal epithelial stem cells, a kind of adult stem cell whose existence has been suggested, is done using various methods such as flow cytometry and selective culture methods. In this review, regenerative medicine of the corneal epithelium, stem cell isolation and culture methods are explained; and our new discoveries of stem cells' features such as their high adhesive ability is explained.

Isolation of adult progenitor cells with neuronal potential from rabbit corneal epithelial cells in serum- and feeder layer-free culture conditions

PURPOSE

To isolate progenitor cells from rabbit corneal epithelial cells (CEC) in serum- and feeder layer-free culture conditions and to compare the self-renewal capacity of corneal epithelial progenitor cells obtained from the central and limbal regions of the cornea.

METHODS

Tissue samples of New Zealand white rabbit corneas were dissected from the limbal and central regions to obtain CEC for sphere-forming culture, in which the cells formed spheres in serum-free medium containing growth factors. The number of primary and secondary sphere colonies and the size of the primary spheres were compared between the limbal and central regions. To promote differentiation, isolated sphere colonies were plated in dishes coated with poly-L-lysine (PLL)/laminin. The expression of epithelial, neural, and mesenchymal mRNAs was examined in the sphere colonies and their progeny by immunocytochemistry and/or the reverse transcription-polymerase chain reaction (RT-PCR). Adherent differentiated cells from the sphere colonies were also examined morphologically.

RESULTS

Primary spheres were isolated from both the limbal and central regions of the cornea. The rate of primary sphere formation by CEC from the limbal region (55.6+/-10.6/10,000 cells) was significantly higher than that by cells from the central cornea (43.1+/-7.2/10,000 cells, p=0.0028), but there was no significant difference in the size of primary spheres derived from both regions. The self-renewal capacity of cells from the limbal region was higher than that of cells from the central region, as evidenced by the significantly higher secondary sphere formation rate of limbal cells (38.7+/-8.5/10,000 cells) in comparison with that for central cells (31.3+/-5.7/10,000 cells, p=0.013). The primary sphere colonies expressed bromodeoxyuridine (BrdU), a 63-kDa protein (p63), p75 neurotrophin receptor (p75(NTR)), and nestin, whereas their progeny expressed cytokeratin 3, cytokeratin 12, vimentin, alpha-smooth muscle actin, microtubule-associated protein 2, and neuron-specific enolase on immunocytochemical analysis. These markers were confirmed by RT-PCR.

CONCLUSIONS

Our findings indicate that limbal CEC contain more progenitor cells with a stronger self-renewal capacity than cells from the central region. These progenitor cells differentiate into the epithelial lineage, and can also produce neuronal protein.

Preoperative Evaluation of Cultured Human Corneal Limbal Epithelium on Amniotic Membrane by Confocal Microscopy

PURPOSE

Although sheet transplantation with cultured corneal limbal epithelium has been widely performed as a strategy for ocular surface reconstruction, there has been no optimal method for evaluating the morphology of these sheets prior to transplantation. We propose the use of in vivo confocal microscopy as a novel method for the evaluation of limbal corneal epithelium cultured on amniotic membrane.

METHODS

Human limbal epithelial sheets were grown on amniotic membranes by following a standard protocol and were stained with hematoxylin and eosin. Morphology was studied using in vivo confocal microscopy for cultured corneal epithelium on amniotic membrane, human intact amniotic membranes, and epithelium-denuded human amniotic membranes.

RESULTS

Histologic examination showed a stratified corneal epithelium sheet by the fourth week of culture. The surface and basal layers of the cultured limbal epithelium and amniotic membrane were clearly distinguished by in vivo confocal microscopy. A monolayer of amniotic epithelial cells was observed on the intact amniotic membrane, but not on the epithelium-denuded human amniotic membrane.

CONCLUSIONS

Our findings support the use of in vivo confocal microscopy as a valid technique for the preoperative evaluation of cultured corneal limbal epithelial cell sheets on amniotic membrane.

Ultraviolet Transmittance of Human Limbal Epithelial Cells Cultured on Human Amniotic Membranes

PURPOSE

To evaluate ultraviolet (UV) A and B transmittance by human limbal epithelial cells cultured on human amniotic membranes.

METHODS

Human limbal epithelial cells were taken from the limbus of donor corneas and were cultured on human amniotic membranes with inactivated 3T3 fibroblasts for 2 to 4 weeks. Then, the cultured cells were examined histologically. Next, cells from different culture periods were irradiated with UV-A (365 nm) or UV-B (302 nm) at energy levels ranging from 50 to 800 microW/cm2, and UV transmittance was measured with a UV light meter.

RESULTS

Histological examination revealed a monolayer of corneal epithelial cells on the amniotic membrane after 2 weeks of culture, and a layer of 3-4 cells was formed after 4 weeks. Transmittance of UV-A and UV-B was highest by the amniotic membrane alone, followed in decreasing order by limbal epithelial cells cultured on amniotic membranes for 2 weeks, 3 weeks, and 4 weeks.

CONCLUSIONS

These results indicate that UV absorbance increases in proportion to the number of limbal epithelial cell layers in cultures on amniotic membranes. Limbal epithelial cells may need to be cultured until 3-4 layers are formed in order to prevent ocular damage by UV light after transplantation.

Immunologic mechanisms of corneal allografts reconstituted from cultured allogeneic endothelial cells in an immune-privileged site

PURPOSE

To analyze outcomes and immunologic features after cultured corneal endothelial cell (CEC) transplantation in a murine model.

METHODS

CEC-deprived BALB/c corneas were reconstituted in vitro with an immortalized C3H-CEC cell line and then transplanted orthotopically into recipient BALB/c mice with experimental bullous keratopathy. Graft survival rates, donor-specific delayed hypersensitivity (DTH), and mixed lymphocyte reactions were evaluated in recipient mice after grafting. Fates of CEC transplantation were assessed after adoptive transfer, regrafting, and immunization with C3H splenocytes.

RESULTS

Chimeric CEC allografts composed of cultured allogeneic CECs did not provoke rejection reaction, DTH, or mixed-lymphocyte reactions, unlike the high rejection rate that occurred in full-thickness corneal allografts. Adoptive transfer of splenocytes from mice that had accepted chimeric CEC allografts did not increase the graft survival rate after full-thickness corneal transplantation, and the rejection rate of a second full-thickness graft was not improved in these mice, suggestive of no active immunosuppression. Pre-sensitization by subcutaneous injection of splenocytes with the same haplotype as cultured CECs induced systemic DTH to the same allogeneic antigens but did not promote the rejection of chimeric CEC allografts, suggesting that chimeric CEC allografts are ignored by the host immune system.

CONCLUSIONS

These findings indicate that immunologic ignorance rather than active immunosuppression is important for the rejection-free acceptance of chimeric CEC allografts. Transplantation of corneal grafts formed with allogeneic CECs could be an ideal treatment strategy to overcome postoperative rejection.

Tissue engineering of corneal stroma with rabbit fibroblast precursors and gelatin hydrogels

PURPOSE

To isolate fibroblast precursors from rabbit corneal stroma using a sphere-forming assay, to engineer corneal stroma with the precursors and gelatin, and to establish the therapeutic application of precursors in a rabbit corneal stroma.

METHODS

In the in vitro study, a sphere-forming assay was performed to produce precursors from rabbit corneal stroma. Corneal stroma was engineered by cultivating precursors in porous gelatin for one week. In the in vivo study, the engineered corneal stromal sheet with precursors (precursor/gelatin group) or with fibroblasts (fibroblast /gelatin group) or without cells (gelatin group) was transplanted to a pocket of rabbit corneal stroma. Gene expression and extracellular matrix production were examined immunohistochemically in each group one week and four weeks after surgery.

RESULTS

In the in vitro study, cells in the spheres were BrdU-positive, and their progeny were keratocan-positive. The study also showed that the corneas transplanted with a porous gelatin sheet did not show any opacity four weeks after transplantation in any group. In the gelatin sheet of the precursor/gelatin group, a more intense expression of type I collagen was observed relative to the other two groups four weeks after the surgery.

CONCLUSIONS

Our findings demonstrate that the transplantation of fibroblast precursors combined with gelatin hydrogel into the corneal stroma is a possible treatment strategy for corneal stromal regeneration.

A novel isolation technique of progenitor cells in human corneal epithelium using non-tissue culture dishes

The existence of adult stem cells or progenitor cells in the human corneal epithelium (i.e., self-renewing squamous cells) has long been suggested, but these cells have not yet been isolated. Here we describe a novel isolation technique using non-tissue culture dishes to enrich progenitor cells, which are able to reconstitute a three-dimensional human corneal epithelial equivalent from single cells in serum-, feeder-, and bovine pituitary extract-free medium. These cells showed original tissue-committed differentiation, a high proliferative capacity, and limited self-renewal. Laminin-5 was measured by mass spectrometric analysis. Pretreatment of cells with anti-laminin-5 antibody demonstrated that laminin-5 was important in allowing corneal epithelial progenitor cells to adhere to non-tissue culture dishes. Hydrophilic tubes (used for cell collection throughout this study) are essential for efficient isolation of adherent corneal epithelial progenitor cells expressing laminin-5. These findings indicate that our new technique using non-tissue culture dishes allows the isolation of progenitor cells from human corneal limbal epithelium and that laminin-5 has a critical role in the adhesion of these cells.

Decellularizing corneal stroma using N2 gas

PURPOSE

To examine the efficacy of a novel method of decellularizing porcine corneal stroma using N(2) gas from liquid N(2) and the feasibility of using decellularized porcine corneal stroma in a corneal transplantation model in rabbits.

METHODS

Porcine corneas were placed in a tube, and N(2) gas from liquid N(2) was poured into the tube to freeze the corneas and make the inside of the tube hypoxic. After fastening the cap firmly, the tube was kept at room temperature for seven days, and the porcine corneas were examined histologically. A porcine corneal stromal disk treated with the aforementioned method was inserted into a pocket of rabbit corneal stroma and observed for six months.

RESULTS

Hoechst 33342 and hematoxylin and eosin staining both showed few cellular nuclei in the porcine corneal stroma incubated in N(2) gas for one week. A terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay showed many positively stained nuclei in the porcine corneal stroma incubated in N(2) gas for three days. The porcine corneal stroma that was decellularized and transplanted into a rabbit corneal stromal pocket remained clear for six months after transplantation.

CONCLUSIONS

This method using N(2) gas decellularizes corneal stroma without reducing corneal transparency.

Isolation and distribution of rabbit keratocyte precursors

PURPOSE

To isolate multipotent precursors from the rabbit corneal stroma and to compare the distribution and proliferative capacity of keratocyte precursors obtained from the central and peripheral regions of the corneal stroma.

METHODS

The rabbit corneal stroma was divided into a peripheral region (6.0-10.0 mm in diameter) and a central region (6.0 mm in diameter). A sphere-forming assay was then performed to isolate precursors from the stroma of each region. To promote differentiation, isolated sphere colonies were plated in wells with a medium containing fetal bovine serum. Expression of various markers by the sphere colonies and their progeny was examined using immunocytochemistry and/or reverse-transcription polymerase chain reaction (RT-PCR).

RESULTS

The rate of primary sphere formation by cells from the peripheral stroma (51.4+/-10.1/10,000 cells) was significantly higher than by cells from the central stroma (35.9+/-3.0/10,000 cells; p=0.00021). Secondary sphere formation rate was significantly higher in the peripheral stroma (45.6+/-6.4/10,000 cells) than in the central stroma (33.4+/-2.1/10,000 cells; p=0.00002). Cells from the spheres were positive for CD34 and nestin. Their progeny showed a keratocyte-like spindle shape and expressed vimentin, alpha-smooth muscle actin, and two neural differentiation markers (microtubule-associated protein-2 and neuron-specific enolase). Expression of nestin and vimentin was confirmed by RT-PCR.

CONCLUSIONS

Our findings demonstrate that both the peripheral and central regions of the corneal stroma contain a significant number of precursors, but the peripheral stroma has more precursors with a stronger proliferative capacity than that of cells from the central stroma.

Transplantation of a sheet of human corneal endothelial cell in a rabbit model

PURPOSE

To develop a novel method for constructing a sheet of human corneal endothelial cells (HCECs) and examine the properties of the HCEC sheet.

METHODS

HCECs were cultured on a cell culture insert for a week; ethylenediamine tetraacetic acid was applied from the bottom of the cell culture insert to attenuate the attachment of HCECs. The sheet of HCECs was constructed by bluntly detaching the cell sheet with a spatula. HCEC cell sheets were placed on the posterior surface of excised rabbit corneal buttons and transplanted onto the corneal beds of donor rabbits. In two eyes from the HCEC sheet group, cultured HCECs were labeled with PKH26 to observe the localization of HCECs after transplantation.

RESULTS

Cultured HCECs could be bluntly detached en bloc from the bottom of a culture insert. Immunostaining for ZO-1, Na+, K+-ATPase, laminin, fibronectin, and type IV collagen was positive in the cell sheet. The average cell density in a HCEC sheet was 2,425 cells/mm(2). After HCEC sheet transplantation, corneal edema decreased much earlier in the HCEC group than in the control group. In the HCEC sheet group, the monolayer of continuous cells attached to the posterior surface of the transplanted rabbit cornea and the posterior surface of transplanted cornea was covered with PKH26-labeled cells. The average endothelial cell density in the HCEC sheet group seven days postoperatively was 2,244 cells/mm(2).

CONCLUSIONS

This technique for producing an HCEC sheet might be useful in regenerative medicine for the cornea and reconstruction of the corneal endothelium.

Characterization of Bone Marrow–Derived Cells in the Substantia Propria of the Human Conjunctiva

PURPOSE

To characterize the main population of bone marrow-derived cells (BMCs) in human normal subconjunctiva and make a comparison with BMCs in the corneal stroma and epithelium.

METHODS

Normal human donor corneas with attached conjunctiva were examined by fluorescence microscopy after single and double staining for multiple markers. CD68(+) cells were separated from the conjunctival tissues by using magnetic beads, and the expression of toll-like receptor (TLR) 2 and TLR4 was examined. Surface markers of CD68(+) cells were compared with those of BMCs from the corneal stroma and epithelium.

RESULTS

CD45(+) cells were detected in the substantia propria of the conjunctiva, and approximately 60% of these cells were CD68(+). All the CD68(+) cells expressed HLA-DR and CD14. CD68(+) cells isolated from conjunctival tissues expressed TLR2 and TLR4 on flow cytometry. BMCs in both the corneal stroma and the subconjunctiva expressed scavenger receptor CD163. Macrophage mannose receptor CD206 was expressed by BMCs in the substantia propria of the conjunctiva, but not by BMCs in the corneal stroma or epithelium.

CONCLUSIONS

These findings demonstrated that the main population of BMCs in the substantia propria of normal human conjunctiva is CD68(+)CD14(+)HLA-DR(+) cells. These BMCs express scavenger receptor, macrophage mannose receptor, TLR2, and TLR4 and may play a role in adaptive and innate immune responses in the human ocular surface. These cells are phenotypically different from the CD68(-)CD206(-) monocyte- lineage cells found in the corneal stroma and the CD11c(+)CD68(-)CD163(-)CD206(-) dendritic cells residing in the corneal epithelium.

Autologous transplantation of conjunctival epithelial cells cultured on amniotic membrane in a rabbit model

PURPOSE

To evaluate the feasibility of autologous transplantation in a rabbit model of conjunctival epithelial cells cultured on amniotic membrane for ocular surface reconstruction.

METHODS

Limbal stem cell deficiency was induced in the right eyes of 30 rabbits. This was done by performing a lamellar keratectomy of the entire cornea and a complete removal of the limbus and conjunctiva, extending 5 mm outside the limbus. Autologous conjunctival specimens were obtained from the left eyes of ten of those rabbits and cultured for four weeks on denuded amniotic membrane. Cultured epithelium was examined by transmission electron microscopy. Four weeks after lamellar keratectomy, conjunctivalized corneal surfaces were excised and autologous cultured conjunctival epithelial sheets transplanted (Conj-AM group, n=10). The controls were rabbits that underwent corneal surface removal but not transplantation (No Transplantation group, n=10) and those that underwent corneal surface removal but received only amniotic membrane (AM Alone group, n=10). A neovascularization and corneal opacity scoring system was used to evaluate each eye in the two months after surgery.

RESULTS

Cultured conjunctival epithelium formed three to four layers on denuded amniotic membrane. Averaged scores of corneal neovascularization and corneal opacity two months after transplantation were significantly low in the Conj-AM group as compared with those in the AM and no transplantation groups.

CONCLUSIONS

Transplantation of autologous conjunctival epithelial cells cultured on amniotic membrane should prove an effective strategy for treating total limbal stem cell deficiency.