The functionality of stem cells is tightly regulated by cues from the niche, comprising both intrinsic and extrinsic cell signals. Besides chemical and growth factors, biophysical signals are important components of extrinsic signals that dictate the stem cell properties. The materials used in the fabrication of scaffolds provide the chemical cues whereas the shape of the scaffolds provides the biophysical cues. The effect of the chemical composition of the scaffolds on stem cell fate is well researched. Biophysical signals such as nanotopography, mechanical forces, stiffness of the matrix, and roughness of the biomaterial influence the fate of stem cells. However, not much is known about their role in signaling crosstalk, stem cell maintenance, and directed differentiation. Among the various techniques for scaffold design, nanotechnology has special significance. The role of nanoscale topography in scaffold design for the regulation of stem cell behavior has gained importance in regenerative medicine. Nanotechnology allows manipulation of highly advanced surfaces/scaffolds for optimal regulation of cellular behavior. Techniques such as electrospinning, soft lithography, microfluidics, carbon nanotubes, and nanostructured hydrogel are described in this review, along with their potential usage in regenerative medicine. We have also provided a brief insight into the potential signaling crosstalk that is triggered by nanomaterials that dictate a specific outcome of stem cells. This concise review compiles recent developments in nanoscale architecture and its importance in directing stem cell differentiation for prospective therapeutic applications.

Mitochondria are indispensable organelles implicated in multiple aspects of cellular processes, including tumorigenesis. Heat shock proteins play a critical regulatory role in accurately delivering the nucleus-encoded proteins through membrane-bound presequence translocase (Tim23 complex) machinery. Although altered expression of mammalian presequence translocase components had been previously associated with malignant phenotypes, the overall organization of Tim23 complexes is still unsolved. In this report, we show the existence of three distinct Tim23 complexes, namely, B1, B2, and A, involved in the maintenance of normal mitochondrial function. Our data highlight the importance of Magmas as a regulator of translocase function and in dynamically recruiting the J-proteins DnaJC19 and DnaJC15 to individual translocases. The basic housekeeping function involves translocases B1 and B2 composed of Tim17b isoforms along with DnaJC19, whereas translocase A is nonessential and has a central role in oncogenesis. Translocase B, having a normal import rate, is essential for constitutive mitochondrial functions such as maintenance of electron transport chain complex activity, organellar morphology, iron-sulfur cluster protein biogenesis, and mitochondrial DNA. In contrast, translocase A, though dispensable for housekeeping functions with a comparatively lower import rate, plays a specific role in translocating oncoproteins lacking presequence, leading to reprogrammed mitochondrial functions and hence establishing a possible link between the TIM23 complex and tumorigenicity. N ormal cellular function requires homeostatic counterbalance of various metabolic pathways, with mitochondria playing a central role in the complex processes. Proper mitochondrial function requires a plethora of different proteins, which are recruited into the organelle through well-defined inner membrane protein translocation machinery (1-3). The presequence translocase or the TIM23 complex accounts for import of approximately 60% of the total mitochondrial proteome and hence is critical for mitochondria biogenesis (4). In yeast, the subunit organization and functional annotations of the machinery are well established and show the presence of a single translocase performing the matrixdirected protein translocation. The yeast presequence translocase consists of a core channel composed of Tim23 along with Tim17. Both Tim23 and Tim17 are essential and form the channel component for the entry of the polypeptide chain. Nonessential accessory proteins, such as Tim21 and Pam17, are involved in conserved interactions with the core components and are important in the maintenance of the overall organization of the machinery. The TIM23 core channel is involved in a cooperative interaction with the matrix-directed import motor (composed of mtHsp70, Tim44, Mge1, and the Pam18-Pam16 subcomplex) in driving the import process (1, 2, 5-9). Tim23 and Tim17 form the central channel and along with Tim50 are involved in presorting the incoming polypeptide chains (1, 2, 4...

Age-related macular degeneration (AMD) and proliferative diabetic retinopathy (PDR) are one of the major causes of blindness caused by neo-vascular changes in the retina. Intravitreal anti-VEGF injections are widely used in the treatment of wet-AMD and PDR. A significant percentage of treated patients have complications of repeated injections. Resveratrol (RES) is a polyphenol phytoalexin with anti-oxidative, anti-inflammatory and anti-proliferative properties. Hence, we hypothesized that if RES is used in combination with bevacizumab (BEV, anti-VEGF), it could reverse the adverse effects that precipitate fibrotic changes, drusen formation, tractional retinal detachment and so on. Human retinal pigment epithelial cells were treated with various combinations of BEV and RES. There was partial reduction in secreted VEGF levels compared to untreated controls. Epithelial-mesenchymal transition was lower in BEV + RES treated cultures compared to BEV treated cultures. The proliferation status was similar in BEV + RES as well as BEV treated cultures both groups. Phagocytosis was enhanced in the presence of BEV + RES compared to BEV. Furthermore, we observed that notch signaling was involved in reversing the adverse effects of BEV. This study paves way for a combinatorial strategy to treat as well as prevent adverse effects of therapy in patients with wet AMD and PDR.

Citation: Murugeswari P, Firoz A, Murali S, et al. Vitamin-D3 (α-1, 25(OH) 2D3) protects retinal pigment epithelium from hyperoxic insults. Invest Ophthalmol Vis Sci. 2020;61(2):4. https://doi.org/10.1167/iovs.61.2.4 PURPOSE.Oxidative stress affects the retinal pigment epithelium (RPE) leading to development of vascular eye diseases. Cholecalciferol (VIT-D) is a known modulator of oxidative stress and angiogenesis. This in vitro study was carried out to evaluate the protective role of VIT-D on RPE cells incubated under hyperoxic conditions. METHODS.Cadaver primary RPE (PRPE) cells were cultured in hyperoxia (40% O 2 ) with or without VIT-D (α-1, 25(OH) 2D3). The functional and physiological effects of PRPE cells with VIT-D treatment were analyzed using molecular and biochemical tools. RESULTS.Vascular signaling modulators, such as vascular endothelial growth factor (VEGF) and Notch, were reduced in hyperoxic conditions but significantly upregulated in the presence of VIT-D. Additionally, PRPE conditioned medium with VIT-D induced the tubulogenesis in primary human umbilical vein endothelial cells (HUVEC) cells. VIT-D supplementation restored phagocytosis and transmembrane potential in PRPE cells cultured under hyperoxia. CONCLUSIONS. VIT-D protects RPE cells and promotes angiogenesis under hyperoxic insult.These findings may give impetus to the potential of VIT-D as a therapeutic agent in hyperoxia induced retinal vascular diseases.Keywords: retinal pigment epithelium, vitamin D, hyperoxia, vascular endothelial growth factor (VEGF), tubulogenesis O xidative stress is the result of an imbalance between the synthesis of reactive oxygen species (ROS) and the levels of antioxidants in the cells. It plays a major role in the pathophysiology of various ocular diseases, such as agerelated cataract, macular degeneration, glaucoma, diabetic retinopathy, and retinitis pigmentosa, by affecting cellular and vascular physiological aspects. 1,2 Antioxidants, such as enzymatic antioxidants, vitamins, minerals, carotenoids, and flavonoids, are the primary scavengers of ROS reducing levels of oxidative stress. 3 Cholecalciferol (vitamin-D3 (VIT-D)) has diverse functions, including modulation of inflammation, angiogenesis, oxidative stress, and fibrosis. 4,5 Recent studies have demonstrated an association between VIT-D and retinal pathophysiological conditions, such as age-related macular degeneration (AMD), diabetic retinopathy, and retinopathy of prematurity (ROP). 6−8 These studies implicated deficiency of VIT-D to higher risk for early/late AMD, whereas a supplementation leads to delay or prevention in the progression of AMD. 6,9 Although VIT-D receptors as well as enzymes for VIT-D metabolism are present in the retina, choroid, and retinal pigment epithelium (RPE) cells, their functions are still not well understood. 6 VIT-D has been studied as a potential inhibitor of angiogenesis in a mouse model of oxygen-induced ischemic retinopathy (OIR). 10 A correlation of VIT-D and vascular endothelial growth factor (VEGF) has been ob...