OBJECTIVEThe aim of this review is to comprehensively and unbiasedly summarize the improvements in the techniques for classical corneal collagen cross-linking (CXL) by covering the reasons for this improvement, measure, and effect to approach the future direction of the CXL.

DATA SOURCESAll articles used in this review were mainly retrieved from the PubMed database.

STUDY SELECTIONOriginal articles and reviews were selected if they were related to the improvement in the technique of classical CXL. Data were mainly extracted from 94 articles, which are listed in the reference section of this review.

RESULTSThis innovative research involves every step such as instrument preparation, epithelial management, riboflavin instillation, and UVA irradiation. These clinical and experimental results seem promising.

CONCLUSIONSCXL treatment is the only recent promising method for preventing the progress of keratoconus. The limitations and potential complications that accompany classical CXL such as corneal thickness limitations, ultraviolet-A (UVA) light injury, and the impact of de-epithelialization encourage people to research new improvements in techniques. While this research needs to be further investigated, we hope our review can help related researchers and patients.

Collagen ; metabolism ; Cornea ; metabolism ; radiation effects ; Humans ; Ultraviolet Rays

A porcine heart valve was irradiated by Ultraviolet (UV) rays (10 W, 254 nm) for 2, 4, 8 and 24 hours at 4 degrees C to cross-link the structural collagen matrix. The degree of cross-linking was evaluated by assaying the released amount of hydroxyproline (Hyp) from the matrix, and comparing it with the positive controls of valves treated by glutaraldehyde (GA) solution (0.625 wt%) and the negative controls of non-treated fresh valves. The undigested weight ratio of the specimens increased by increasing the UV irradiation time. The undigested weight of the leaflets, tunica interna and tunica externa of the fresh, GA-treated and UV-irradiated specimens after collagenase digestion was compared. As UV irradiation increased, the amount of released hydroxyproline was gradually decreased until 8 hours of irradiation, after which the released hydroxyproline-reduction occurred slightly until 24 hours of irradiation time in this system. A total 47.68% of the hydroxyproline in the valve was cross-linked by UV irradiation after 24 hours, while 73.74% of the hydroxyproline in the positive control was crossed-linked. Light microscopic observation revealed that the typical crimp pattern of collagen fibers decreased and was rearranged into a dense flattened pattern as the UV irradiation induced interfibrilar cross-linking. GA-treated valves demonstrated a denser matrix pattern than the UV-irradiated specimens. Cross-linked collagenous tissue prepared by UV irradiation would be useful for improving durability and reducing the disadvantages related to using a chemical cross-linking agent.
Animal ; Aortic Valve/radiation effects* ; Aortic Valve/metabolism* ; Collagen/radiation effects* ; Collagen/chemistry* ; Hydroxyproline/metabolism ; Swine ; Ultraviolet Rays*

Collagen-based membranous materials of various shapes (gel, film, sponge) are known to be the most promising materials in terms of facilitating the regeneration of dermal defects. In this study, dense and porous collagen membranes were fabricated using air-drying and freeze-drying processes, respectively, and the effect of ultraviolet (UV) radiation on the degree of membrane crosslinking was evaluated by in vitro biodegradation and mechanical testing. A non-irradiated membrane group was used as the negative control and a glutaraldehyde (GA) treated group as the positive control. Scanning electron microscopy showed that, as the freezing temperature decreased to -196 degrees C, the resultant mean pore sizes also decreased; optimal pore size was obtained at a freezing temperature of -70 degrees C. In vitro biodegradation and mechanical testing demonstrated that GA treatment or 4 hours of exposure to UV radiation significantly increased both resistance to collagenase and mechanical strength versus the untreated controls, regardless of the collagen membrane type (dense or porous). Our results suggest that UV treatment is a useful tool for the fabrication of collagen membranes designed to be used as dermal dressings.
Animal ; Cattle ; Collagen/ultrastructure ; Collagen/radiation effects* ; Collagen/metabolism ; Elasticity ; Membranes, Artificial* ; Microscopy, Electron, Scanning ; Porosity ; Tensile Strength ; Ultraviolet Rays*

Membranes prepared from bovine skin collagen were exposed to 15, 25, 35 KGy gamma-radiation respectively at low temperature. Radiation dose rate of about 22 KGy/h was used. The stability of the membranes was evaluated by measuring resistance of collagen membranes to collagenase digestion. Infrared spectra analyses of collagen films were performed in order to explore possible mechanisms of irradiation modification of collagen membranes. The results revealed that the degree of cross-linking and stability of collagen membranes after gamma-irradiation were improved. The MTT assay and SEM observation of the morphology of L929 mouse fibroblast cells which directly cultured on the collagen membranes were employed to evaluate the cytocompatibility of collagen membranes treated by gamma-ray radiation. In the range of 0 to approximately 25 KGy irradiation dose, no significant difference in cytocompatibility of collagen membranes irradiated by gamma-ray was observed. However, when the irradiation dose was over 25 KGy, the cytocompatibility of collagen membranes was influenced by gamma-radiation to some degree.
Animals ; Cattle ; Collagen ; radiation effects ; Dose-Response Relationship, Radiation ; Gamma Rays ; In Vitro Techniques ; Materials Testing ; Membranes, Artificial ; Mice

Infrared radiation is increasingly and uncritically used for cosmetic and wellness purposes, despite the poorly understood biologic effects of such treatments on humans. In the present study, we investigated the effects of infrared radiation on collagen and elastin production in dermal fibroblasts, as well as the clinical and histopathologic effects of infrared radiation on photo-aged facial skin lesions. In order to determine the effects of infrared radiation on collagen and elastin production, dermal fibroblasts were exposed to infrared radiation for varying lengths of time and collagen and elastin contents were subsequently determined. Additionally, 20 patients with mild to moderate facial wrinkles and hyperpigmented lesions received daily treatments of far infrared radiation (900 to 1000micronm) for six-months. During the treatment, patients and a medical observer conducted independent photographic and clinical evaluations every 4 weeks, and skin biopsies were obtained for histological analysis at baseline and one month post-treatment. We found that the content of collagen and elastin produced by the fibroblasts increased after infrared radiation, and that this increase was proportional to the duration of irradiation exposure. Following 6 months of treatment, all patients reported good (51-75%) improvements in skin texture and roughness. Additionally, patients noted fair (25-50%) improvement in color tone of the skin; however, improvements in hyperpigmented lesions were not observed. Objective medical evaluation of the patients indicated that roughness and laxity were fairly improved, but there was no significant improvement in hyperpigmented lesions. Histological examination failed to reveal any differences as well. These results suggest that infrared radiation may have beneficial effects on skin texture and wrinkles by increasing collagen and elastin contents from the stimulated fibroblasts. Therefore, skin treatment with infrared radiation may be an effective and safe non-ablative remodeling method, and may also be useful in the treatment of photo-aged skin.
Time Factors ; Skin Pigmentation/*radiation effects ; *Skin Aging ; Skin/*radiation effects ; Middle Aged ; *Light ; *Infrared Rays ; Humans ; Fibroblasts/metabolism ; Female ; Elastin/metabolism ; Collagen/metabolism ; Biopsy ; Adult

To determine whether platelet-rich fibrin lysate (PRF-L) could restore the function of chronically ultraviolet-A (UVA)-irradiated human dermal fibroblasts (HDFs), we isolated and sub-cultured HDFs from six different human foreskins. HDFs were divided into two groups: those that received chronic UVA irradiation (total dosages of 10 J cm-2) and those that were not irradiated. We compared the proliferation rates, collagen deposition, and migration rates between the groups and between chronically UVA-irradiated HDFs in control and PRF-L-treated media. Our experiment showed that chronic UVA irradiation significantly decreased (p<0.05) the proliferation rates, migration rates, and collagen deposition of HDFs, compared to controls. Compared to control media, chronically UVA-irradiated HDFs in 50% PRF-L had significantly increased proliferation rates, migration rates, and collagen deposition (p<0.05), and the migration rates and collagen deposition of chronically UVA-irradiated HDFs in 50% PRF-L were equal to those of normal fibroblasts. Based on this experiment, we concluded that PRF-L is a good candidate material for treating UVA-induced photoaging of skin, although the best method for its clinical application remains to be determined.
Blood Platelets/*cytology/*metabolism ; Cell Movement/radiation effects ; Cell Proliferation/radiation effects ; Cells, Cultured ; Collagen/metabolism ; Fibrin/*metabolism ; Fibroblasts/*cytology/metabolism/*radiation effects ; Humans ; Skin/*cytology ; Time Factors ; Ultraviolet Rays/*adverse effects

OBJECTIVETo analyze the potential mechanism of preventive and therapeutic effects of (90)Sr on hypertrophic scar, and to observe its clinical effect.

METHODSFibroblasts isolated from human hypertrophic scar were cultured in vitro and radiated by (90)Sr with the dose varying from 0 Gy (control group) to 5 Gy (LD group), 10 Gy (MD group), and 15 Gy (HD group). The cell cycle and apoptosis rate were determined by flow cytometry at post radiation hour (PRH) 24, 48, and 72. The concentration of type I collagen in cell supernatant was detected by enzyme-linked immunosorbent assay (ELISA). Therapeutic effects of (90)Sr radiation were evaluated among 348 patients with hypertrophic scars, 40 patients with keloids, and 114 patients for scar prevention after surgical operation. The number of fibroblasts after HE staining was compared among normal skin tissue, hypertrophic scar, and hypertrophic scar treated with (90)Sr radiation. Data were processed with one-way analysis of variance and q test.

RESULTS(1) Apoptotic rates in MD and HD groups at PRH 48 were higher than those at PRH 24, and the apoptotic rate was similar between MD group and HD group at PRH 72. Apoptotic rate in LD group at PRH 48 was significantly higher than that at PRH 24, but it decreased rapidly at PRH 72, which was significantly lower than those in MD and HD groups (with F values all equal to 916.711, P values all below 0.01). (2) At PRH 24, cell ratios of each phase in LD and HD groups were similar, and cell ratio of S phase in HD group [(48.1 ± 1.0)%] was higher than those in the other three groups (with F values all equal to 200.277, P values all below 0.01). At PRH 72, cell ratio of S phase in MD and HD groups was respectively (85.7 ± 5.2)%, (73.0 ± 8.4)%, implying that cells were blocked in S phase, and the values were all higher than those in control and LD groups (with F values all equal to 111.105, P values all below 0.01). (3) At the same time point, the concentration of type I collagen decreased along with the increase of radiation dose (with F values from 5044.449 to 8234.432, P values all below 0.01). With the same radiation dose, the concentration of type I collagen increased along with prolongation of time (with F values from 333.395 to 2973.730, P values all below 0.01). (4) Clinical observation showed the (obvious) effective rate of radiation for pathological scars and that for scar prevention after surgical operation added up to 88.45%. The number of fibroblasts per 200 times visual field in patients after (90)Sr radiation (86 ± 20) was less than that in patients without treatment [(198 ± 65), F = 208.405, P < 0.05].

CONCLUSIONSThe effect of (90)Sr radiation on fibroblasts and extracellular matrix can contribute to inhibition of scar formation, and the clinical effect is significant.

Adolescent ; Adult ; Apoptosis ; radiation effects ; Cell Cycle ; radiation effects ; Cells, Cultured ; Child ; Child, Preschool ; Cicatrix, Hypertrophic ; metabolism ; pathology ; radiotherapy ; Collagen Type I ; metabolism ; Female ; Fibroblasts ; radiation effects ; Humans ; Male ; Strontium Radioisotopes ; therapeutic use ; Young Adult

OBJECTIVETo investigate the effects of quercetin and X-ray on collagen synthesis of cultured human keloid-derived fibroblast and the mechanism.

METHODSCollagen synthesis of cultured human keloid and normal fibroblasts were detected by hydroxyproline colorimetric analysis. Immunocytochemical staining was used to investigate collagen I and III expression. mRNA expression of collagen I and III, and transforming growth factor (TGF)-beta 1 were assayed by reverse transcription-polymerase chain reaction (RT-PCR) and real-time PCR.

RESULTSQuercetin inhibited the collagen synthesis of both keloid and normal fibroblasts in a dose-dependent manner. Immunocytochemical staining indicated that collagen I and III were down-regulated by quercetin and X-ray (P < 0.05), particularly collagen I (P < 0.05). mRNA expression of both collagen I and III in quercetin groups significantly decreased compared with that in control group (P < 0.05), especially in the group treated with both quercetin and X-ray (P < 0.01). mRNA level of TGF-beta 1 gene was down-regulated by quercertin (P < 0.05).

CONCLUSIONSQuercetin will probably be one of the new medicines which could effectively treat keloid. Quercetin combined with X-ray could reduce the dose of radiation.

Adult ; Cells, Cultured ; Collagen Type I ; biosynthesis ; genetics ; radiation effects ; Collagen Type III ; biosynthesis ; genetics ; radiation effects ; Dose-Response Relationship, Drug ; Female ; Fibroblasts ; metabolism ; pathology ; radiation effects ; Humans ; Keloid ; metabolism ; pathology ; Male ; Quercetin ; administration & dosage ; pharmacology ; RNA, Messenger ; biosynthesis ; Skin ; cytology ; Transforming Growth Factor beta1 ; biosynthesis ; genetics ; radiation effects

PURPOSE: To evaluate cultured human artificial skin as an experimental model for studying radiation effects in vitro. MATERIALS AND METHODS: The skin was constructed by culturing keratinocytes over collagen lattice which made by culturing fibroblasts. Two groups were irradiated to gamma rays at single dose of 25 Gy with or without 3.5% of DMSO. Ultrastructures were investigated by electron microscopy after irradiation. The number of epidermal layers and expression of cytokeratin (CK) 14 and 10 were also seem by light microscopy. RESULTS: At 2 days after irradiation in experimental group without DMSO, necrotic cells were rarely found in the spinosal layer and undercornified cells were visible in the horney layer. Similar findings were also found in experimental group with DMSO but in mild form. The number of epidermal layers in experimental group without DMSO were significantly fewer than other group. CK 14 expressed in all the layer excluding horney layer but CK 10 expressed over 3~4 basal layers. Such patterns of CK expression were similar to all groups. It is suggested that structures of the keratinocytes and epidermal formation could be disturbed by irradiation in artificial skin and that DMSO can protect these damages. CONCLUSION: Therefore this work could be used as an organotypic experimental model in vitro using human cells for studying radiation effect in skin. Furthermore structural findings provided in this study could be used as useful basic data in further study using this model.
Collagen ; Dimethyl Sulfoxide* ; Fibroblasts ; Gamma Rays ; Humans* ; Keratinocytes ; Keratins ; Microscopy ; Microscopy, Electron ; Models, Theoretical ; Radiation Effects ; Skin ; Skin, Artificial*

BACKGROUNDConnective tissue growth factor (CTGF) is a potent fibrogenic cytokine which has been associated with progressive glomerulosclerosis and tubulointerstitial fibrosis. We investigated the role of CTGF on the progression of a rat model of radiation nephropathy.

METHODSThe model of radiation nephropathy in rats was established as follows: control group (n = 12), underwent only laparotomy; irradiated group (n = 20), underwent a laparotomy, then the rats were subjected to a single dose 25 Gy X-ray to the kidneys. The rats were followed up one, three, six and nine months after renal exposure to radiation.

RESULTSRenal dysfunction was noted early in irradiated rats. Histological analysis showed focal glomerular sclerotic lesions at an early stage after irradiation. Radiation-induced glomerular and tubulointerstitial injuries were particularly severe the sixth month after irradiation as compared to the control group (P < 0.01). By immunohistochemistry, increased expression of CTGF was noted in the irradiated kidneys, which began to increase from the first month after irradiation, and remained significantly higher at the sixth and ninth month after irradiation (P < 0.01). Upon Western blot analysis CTGF protein expression showed an increase in the radiation treated kidneys compared with the control rats. The expression of CTGF closely correlated with the progression of radiation nephropathy. The expression of alpha-smooth muscle actin, vimentin, type III collagen and type IV collagen was also high in the irradiated kidney as compared to control rat kidneys (P < 0.05), and was most severe at the sixth and ninth month after irradiation (P < 0.01). By double immunostaining, CTGF expressing cells were found to be alpha-SMA-positive myofibroblasts and vimentin-positive tubular epithelial cells. Glomerular expression of CTGF closely correlated with the glomerular expression of alpha-SMA (r = 0.628, P < 0.01), vimentin (r = 0.462, P < 0.05) and accumulation of type IV collagen (r = 0.584, P < 0.01) in the irradiated kidney. Similarly, the expression of CTGF was positively correlated with the expression of alpha-SMA (r = 0.613, P < 0.01), vimentin (r = 0.629, P < 0.01), deposition of type III collagen (r = 0.741, P < 0.001) and type IV collagen (r = 0.799, P < 0.0001) in the tubulointerstitium of the irradiated kidney. Finally the expression of CTGF after the irradiation of the kidney positively correlated with the levels of blood urea nitrogen and serum creatinine.

CONCLUSIONOverexpression of CTGF may play an important role in the development and progression of glomerulosclerosis and tubulointerstitial fibrosis in radiation nephropathy.

Actins ; analysis ; Animals ; Collagen Type III ; analysis ; Collagen Type IV ; analysis ; Connective Tissue Growth Factor ; analysis ; physiology ; Kidney ; radiation effects ; Kidney Diseases ; etiology ; Male ; Radiation Injuries, Experimental ; etiology ; Rats ; Rats, Wistar ; Vimentin ; analysis