Tenomodulin inhibits retinal neovascularization in a mouse model of oxygen-induced retinopathy

Inhibitory effect of maspinon neovascularization in diabetic retinopathy

BACKGROUND

Diabetic retinopathy (DR) is a serious and potentially blinding complication of diabetes mellitus. Retinal neovascularization is one of the main pathological features of proliferative DR, and inhibiting retinal neovascularization is a research focus.

AIM

The aim was to evaluate the effect of intravitreal injection of recombinant human maspin on neovascularization in DR.

METHODS

An oxygen-induced retinopathy (OIR) mouse model was used to simulate neovascularization in DR. New born C57BL/6J mice were randomly divided to a normal control group, a maspin injection OIR group, and an OIR group. The mice in the maspin injection OIR group were injected with recombinant human maspin in the bilateral vitreous cavity on postnatal day P12, and those in the OIR group were injected with sterile phosphate buffered saline. The protein expression of vascular endothelial growth factor (VEGF) and hypoxia-inducible factor 1-alpha (HIF-1α) in the retina was measured by western blotting, and the mRNA expression of VEGF and HIF-1α was measured by real-time polymerase chain reaction. The vascular cell nuclei that broke through the inner limiting membrane (ILM) were counted in haematoxylin-eosin stained retinal sections.

RESULTS

It was found that the number of vascular cell nuclei breaking through the ILM was 31.8 ± 8.75 in the OIR group, which was significantly more than that in the normal control group (P < 0.001). The number of vascular cell nuclei breaking through the ILM was 6.19 ± 2.91 in the maspin injection OIR group, which was significantly less than that in OIR group (P < 0.01). The relative protein and mRNA expression of VEGF and HIF-1α was significantly lower in the retinas in the maspin injection OIR group than in those in the OIR group (P < 0.01).

CONCLUSION

Maspin inhibited neovascularization in DR by modulating the HIF-1α/VEGF pathway, which provides a potential and effective strategy for the treatment of DR.

Long-term evaluation of retinal morphology and function in a mouse model of oxygen-induced retinopathy

Purpose

Retinopathy of prematurity (ROP) is a condition of aberrant retinal vascularization in premature infants in response to high levels of oxygen used for critical care that can potentially cause blindness. Although therapies to mitigate vascular abnormalities are being evaluated, functional deficits often remain in patients with treated or regressed ROP. This study investigated long-term outcomes of hyperoxia on retinal morphology and function using a mouse model of oxygen-induced ischemic retinopathy (OIR).

Methods

Twenty-two mice were exposed to 77% oxygen to induce OIR, while 23 age-matched control mice were raised in room air (RA). In vivo fluorescein angiography (FA), spectral-domain optical coherence tomography (SD-OCT), and focal electroretinography (fERG) were performed at P19, P24, P32, and P47, followed by histological assessments of retinal morphology, gliosis, microglia activation, and apoptosis.

Results

FA in OIR mice showed capillary attrition despite peripheral revascularization. Inner retina thinning was detected with SD-OCT; outer and inner retinal dysfunction were demonstrated with fERG. Histology of the OIR mice exhibited a thin, disorganized structure. Immunohistochemistry showed increased gliosis, microglial activation, and apoptosis with increasing age from P19 to P47. The synapses between rod photoreceptor cells and rod bipolar cells were ectopically localized in the OIR mice.

Conclusions

We demonstrated histological evidence of persistent ectopic synapses, prolonged cellular apoptosis, and gliosis in the OIR retina that corresponded with long-term in vivo evidence of capillary attrition, inner retinal thinning, and dysfunction despite full peripheral revascularization. Further studies on the mechanisms underlying these persistent phenotypes could enhance our understanding of ROP pathogenesis and lead to new therapeutic targets to preserve visual function in premature infants.

Limiting angiogenesis to modulate scar formation

Angiogenesis, the process of new blood vessel formation from existing blood vessels, is a key aspect of virtually every repair process. During wound healing an extensive, but immature and leaky vascular plexus forms which is subsequently reduced by regression of non-functional vessels. More recent studies indicate that uncontrolled vessel growth or impaired vessel regression as a consequence of an excessive inflammatory response can impair wound healing, resulting in scarring and dysfunction. However, in order to elucidate targetable factors to promote functional tissue regeneration we need to understand the molecular and cellular underpinnings of physiological angiogenesis, ranging from induction to resolution of blood vessels. Especially for avascular tissues (e.g. cornea, tendon, ligament, cartilage, etc.), limiting rather than boosting vessel growth during wound repair potentially is beneficial to restore full tissue function and may result in favourable long-term healing outcomes.

Inhibitory effect of tenomodulin versus ranibizumab on in vitro angiogenesis

AIM

To evaluate anti-angiogenic effect of tenomodulin (TNMD) and ranibizumab on cell proliferation and capillary-like morphogenesis of vascular endothelial cells under the stimulation of vascular endothelial growth factor (VEGF) in vitro.

METHODS

The effects of TNMD and ranibizumab on VEGF-induced proliferation of human umbilical vein endothelial cells (HUVECs) were evaluated by MTT assay, and the effects of TNMD and ranibizumab on capillary-like structures formed by HUVECs under the stimulation of VEGF were examined in culture. Capillary-like morphogenesis of HUVECs was quantitatively evaluated, and total lengths of tube-like structures per field were measured in a masked way.

RESULTS

HUVECs with both ranibizumab and TNMD protein showed MTT reduction in VEGF-stimulated cell proliferation as expected, while MTT absorbance in the HUVECs with TNMD was significantly declined than that with ranibizumab (P<0.01). The capillary-like structures formed by HUVECs were markedly impaired by the presence of both TNMD and ranibizumab in the culture medium. The total length of the capillary-like structures per field was significantly shorter in the medium with TNMD than that of ranibizumab (P<0.01). The inhibitory effect of TNMD on tube formation in vitro angiogenesis was significantly stronger than that of ranibizumab.

CONCLUSION

TNMD may have stronger inhibitory effect than ranibizumab on in vitro angiogenesis.

Differentially expressed miRNAs in oxygen‑induced retinopathy newborn mouse models

The present study aimed to identify microRNAs (miRNAs) involved in regulating retinal neovascularization and retinopathy of prematurity (ROP). A total of 80 healthy C57BL/6 neonatal mice were randomly divided into the oxygen-induced retinopathy (OIR) group (n=40), in which 7-day-old mice were maintained in 75% oxygen conditions for 5 days, or the control group (n=40). Following collection of retinal tissue, retinal angiography and hematoxylin and eosin (H&E) staining were performed. Total RNA was also extracted from retinal tissue, and miRNA microarrays and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) were performed to identify differentially expressed miRNAs in the two groups. Retinal angiography and H&E staining revealed damage to retinas in the OIR group. Compared with the control group, 67 miRNAs were differentially expressed in the OIR group, of which 34 were upregulated and 33 were downregulated. Of these differentially expressed miRNAs, 32 exhibited a fold change ≥2, of which 21 were upregulated and 11 were downregulated. The results of RT-qPCR for miR-130a-3p and miR-5107-5p were in accordance with those of the miRNA microarray. The newly identified miRNAs may be important in the development of ROP, and may provide a basis for future research into the mechanisms of ROP.

Cnidium officinale extract and butylidenephthalide inhibits retinal neovascularization in vitro and in vivo

BACKGROUND

Retinal neovascularization, which is the pathological growth of new blood vessels, is associated with retinopathy of prematurity, neovascular age-related macular degeneration, diabetic retinopathy and retinal vein occlusion. In this study, we evaluated the effect of an extract of Cnidium officinale Makino (COE) and its bioactive compound, butylidenephthalide (BP), on the migration and tube formation of human umbilical vein endothelial cells (HUVECs), and on retinal pathogenic neovascularization in the oxygen-induced retinopathy (OIR) mouse model.

METHOD

The HUVECs were incubated with COE and BP (0.1-10 μg/ml). The mice were exposed to 75 % oxygen for 5 days starting on the 7(th) postnatal day (P7-P12). Then, the mice were returned to room air and intraperitoneally injected with COE (100 mg/kg) and BP (5 mg/kg) once per day for 5 days (P12-P16). On P17, we measured retinal neovascularization and analyzed the angiogenesis-related proteins expression using protein arrays.

RESULTS

COE and BP inhibit the HUVECs migration and the tube formation in a dose-dependent manner. In addition, COE significantly decreased retinal neovascularization in the OIR mice. COE reduced the expression levels of AREG, ANG, DLL4, Endostatin, IGFBP-2 and VEGF. Additionally, BP also inhibited the retinal neovascularization and down-regulated the expression of AREG, ANG, DLL4 and VEGF.

CONCLUSION

These results suggest that COE and BP exerts antiangiogenic effects on retinal neovascularization by inhibiting the expression of AREG, ANG, DLL4 and VEGF, indicating that antiangiogenic activities of COE may be in part due to its bioactive compound, BP.

Molecular characterization and function of tenomodulin, a marker of tendons and ligaments that integrate musculoskeletal components

Tendons and ligaments are dense fibrous bands of connective tissue that integrate musculoskeletal components in vertebrates. Tendons connect skeletal muscles to the bone and function as mechanical force transmitters, whereas ligaments bind adjacent bones together to stabilize joints and restrict unwanted joint movement. Fibroblasts residing in tendons and ligaments are called tenocytes and ligamentocytes, respectively. Tenomodulin (Tnmd) is a type II transmembrane glycoprotein that is expressed at high levels in tenocytes and ligamentocytes, and is also present in periodontal ligament cells and tendon stem/progenitor cells. Tnmd is related to chondromodulin-1 (Chm1), a cartilage-derived angiogenesis inhibitor, and both Tnmd and Chm1 are expressed in the CD31⁻ avascular mesenchyme. The conserved C-terminal hydrophobic domain of these proteins, which is characterized by the eight Cys residues to form four disulfide bonds, may have an anti-angiogenic function. This review highlights the molecular characterization and function of Tnmd, a specific marker of tendons and ligaments.

Tenogenic modulating insider factor: Systematic assessment on the functions of tenomodulin gene

Tenomodulin (TNMD, Tnmd) is a gene highly expressed in tendon known to be important for tendon maturation with key implications for the residing tendon stem/progenitor cells as well as for the regulation of endothelial cell migration in chordae tendineae cordis in the heart and in experimental tumour models. This review aims at providing an encompassing overview of this gene and its protein. In addition, its known expression pattern as well as putative signalling pathways will be described. A chronological overview of the discovered functions of this gene in tendon and other tissues and cells is provided as well as its use as a tendon and ligament lineage marker is assessed in detail and discussed. Last, information about the possible connections between TNMD genomic mutations and mRNA expression to various diseases is delivered. Taken together this review offers a solid synopsis on the up-to-date information available about TNMD and aids at directing and focusing the future research to fully uncover the roles and implications of this interesting gene.

A Prospectus of Tenomodulin

Tenomodulin is a type II transmembrane glycoprotein that can regulate growth of tendon. The human tenomodulin encoding gene is mapped to Х chromosome and encodes a polypeptide consisting of 317 alpha amino acids. The protein is located on the cell surface as N-glycosylated or non-N-glycosylated polypeptide with molecular mass of 45 and 40 kDa, respectively. The molecule consists of three domains and a short cytoplasmic tail at N-terminus. Tenomodulin is predominantly expressed in dense connective hypovascularized tissues such as tendons, skeletal muscle epimysium, and ligaments. Furthermore, tenomodulin is an efficient marker of tenocyte differentiation and plays an important role in the regulation of tenocyte proliferation, tendon development, and angiogenesis inhibition. A number of tenomodulin gene polymorphisms have been recently associated with a risk of obesity, diabetes, systemic immune mediators, cholesterol levels, Alzheimer disease, and age-related macular degeneration. Tenomodulin is involved in cell adhesion, determination of cell morphology, cell aging and bone mineral density. It is expected to play an important role in tendon recovery, tendon tissue engineering, anti-tumor therapy, treatment of chordal disruption, and remodeling of extracellular matrix.

Inhibitory effect of Samul-tang on retinal neovascularization in oxygen-induced retinopathy

BACKGROUND

Retinal neovascularization is a common cause of vision loss in proliferative diabetic retinopathy, retinopathy of prematurity and age-related macular degeneration. Samul-tang (SMT) is a widely used traditional herbal medicine in East Asia and is also known as Shimotsu-to in Japanese and Si-Wu decoction in Chinese. This study was designed to evaluate the inhibitory effect of SMT on retinal pathogenic angiogenesis in a mouse model of oxygen-induced retinopathy (OIR).

METHOD

The mice were exposed to a 75% concentration of oxygen for five days, starting on postnatal day 7 (P7-P12). The mice were then exposed to room air and were intraperitoneally injected with SMT (10 mg/kg or 50 mg/kg) once per day for five days (P12-P16). On P17, we measured retinal neovascularization and evaluated both the expression of angiogenesis-related proteins and changes in the gene expression level in the mRNA.

RESULTS

SMT reduced the area of the central retina and reduced retinal neovascularization in OIR mice. The protein array revealed that SMT reduced the level of SDF-1 protein expression. Quantitative real-time PCR revealed that the HIF-1α, SDF-1, CXCR4 and VEGF mRNA levels in the retinas of OIR mice were elevated compared with those of normal control mice. However, SMT decreased the levels of HIF-1α, SDF-1, CXCR4 and VEGF mRNA in OIR mice.

CONCLUSION

We are the first to elucidate that SMT inhibits the retinal pathogenic angiogenesis induced by ischemic retinopathy in OIR mice. SMT significantly inhibited retinal neovascularization by downregulating HIF-1α, SDF-1, CXCR4 and VEGF. Based on the results of our study, SMT could be a useful herbal medicine for treating ischemic retinopathy.