Vitreous humor and albumin augment the proliferation of cultured retinal precursor cells

Investigation the effects of vitreous humor on proliferation and dedifferentiation of differentiated NTERA2 cells

Mammals have a limited capacity to regenerate their tissues and organs. One of the mechanisms associated with natural regeneration is dedifferentiation. Several small molecules such as vitamin C and growth factors could improve reprogramming efficiency. In this study, the NTERA2-D1 (NT2) cells were induced towards differentiation (NT2-RA) with 10-5 M retinoic acid (RA) for three days and then subjected to various amounts of vitreous humor (VH). Results show that the growth rate of these cells was reduced, while this rate was partly restored upon treatment with VH (NT2-RA-VH). Cell cycle analysis with PI method also showed that the numbers of cells at the S phase of the cell cycle in these cells were increased. The levels of SSEA3 and TRA-1-81 antigens in NT2-RA were dropped but they increased in NT2- RA-VH to a level similar to the NT2 cells. The level of SSEA1 had an opposite pattern. Expression of OCT4 gene dropped after RA treatment, but it was recovered in NT2-RA-VH cells. In conclusion, we suggest VH as a potent mixture for improving the cellular reprogramming leading to dedifferentiation.

Rejuvenation of three germ layers tissues by exchanging old blood plasma with saline-albumin

Heterochronic blood sharing rejuvenates old tissues, and most of the studies on how this works focus on young plasma, its fractions, and a few youthful systemic candidates. However, it was not formally established that young blood is necessary for this multi-tissue rejuvenation. Here, using our recently developed small animal blood exchange process, we replaced half of the plasma in mice with saline containing 5% albumin (terming it a "neutral" age blood exchange, NBE) thus diluting the plasma factors and replenishing the albumin that would be diminished if only saline was used. Our data demonstrate that a single NBE suffices to meet or exceed the rejuvenative effects of enhancing muscle repair, reducing liver adiposity and fibrosis, and increasing hippocampal neurogenesis in old mice, all the key outcomes seen after blood heterochronicity. Comparative proteomic analysis on serum from NBE, and from a similar human clinical procedure of therapeutic plasma exchange (TPE), revealed a molecular re-setting of the systemic signaling milieu, interestingly, elevating the levels of some proteins, which broadly coordinate tissue maintenance and repair and promote immune responses. Moreover, a single TPE yielded functional blood rejuvenation, abrogating the typical old serum inhibition of progenitor cell proliferation. Ectopically added albumin does not seem to be the sole determinant of such rejuvenation, and levels of albumin do not decrease with age nor are increased by NBE/TPE. A model of action (supported by a large body of published data) is that significant dilution of autoregulatory proteins that crosstalk to multiple signaling pathways (with their own feedback loops) would, through changes in gene expression, have long-lasting molecular and functional effects that are consistent with our observations. This work improves our understanding of the systemic paradigms of multi-tissue rejuvenation and suggest a novel and immediate use of the FDA approved TPE for improving the health and resilience of older people.

Intact vitreous humor as a potential extracellular matrix hydrogel for cartilage tissue engineering applications

Decellularisation of tissues, utilising their biochemical cues, poses exciting tissue engineering (TE) opportunities. However, removing DNA from cartilage (dCart) requires harsh treatments due to its dense structure, causing loss of bioactivity and limiting its application as a cartilaginous extra cellular matrix (ECM). In this study, we demonstrate for the first time the successful application of vitreous humor (VH), a highly hydrated tissue closely resembling the glycosaminoglycan (GAG) and collagen composition of cartilage, as an ECM hydrogel to support chondrogenic differentiation. Equine VH was extracted followed by biochemical quantifications, histological examinations, cytotoxicity (human mesenchymal stromal cells, hMSCs and human articular chondrocytes, hACs) and U937 cell proliferation studies. VH was further seeded with hACs or hMSCs and cultured for 3-weeks to study chondrogenesis compared to scaffold-free micro-tissue pellet cultures and collagen-I hydrogels. Viability, metabolic activity, GAG and DNA content, chondrogenic gene expression (aggrecan, collagen I/II mRNA) and mechanical properties were quantified and matrix deposition was visualised using immunohistochemistry (Safranin-O, collagen I/II). VH was successfully extracted, exhibiting negligible amounts of DNA (0.4 ± 0.4 µg/mg dry-weight) and notable preservation of ECM components. VH displayed neither cytotoxic responses nor proliferation of macrophage-like U937 cells, instead enhancing both hMSC and hAC proliferation. Interestingly, encapsulated cells self-assembled the VH-hydrogel into spheroids, resulting in uniform distribution of both GAGs and collagen type II with increased compressive mechanical properties, rendering VH a permissive native ECM source to fabricate cartilaginous hydrogels for potential TE applications. STATEMENT OF SIGNIFICANCE: Fabricating bioactive and cell-instructive cartilage extracellular matrix (ECM) derived biomaterials and hydrogels has over recent years proven to be a challenging task, often limited by poor retention of inherent environmental cues post decellularisation due to the dense and avascular nature of native cartilage. In this study, we present an alternative route to fabricate highly permissive and bioactive ECM hydrogels from vitreous humor (VH) tissue. This paper specifically reports the discovery of optimal VH extraction protocols and cell seeding strategy enabling fabrication of cartilaginous matrix components into a hydrogel support material for promoting chondrogenic differentiation. The work showcases a naturally intact and unmodified hydrogel design that improves cellular responses and may help guide the development of cell instructive and stimuli responsive hybrid biomaterials in a number of TERM applications.

3D endothelial cell spheroid/human vitreous humor assay for the characterization of anti-angiogenic inhibitors for the treatment of proliferative diabetic retinopathy

Proliferative diabetic retinopathy (PDR) represents a main cause of acquired blindness. Despite the recognition of the key role exerted by vascular endothelial growth factor (VEGF) in the pathogenesis of PDR, limitations to anti-VEGF therapies do exist. Thus, rapid and cost-effective angiogenesis assays are crucial for the screening of anti-angiogenic drug candidates for PDR therapy. In this context, evaluation of the angiogenic potential of PDR vitreous fluid may represent a valuable tool for preclinical assessment of angiostatic molecules. Here, vitreous fluid obtained from PDR patients after pars plana vitrectomy was used as a pro-angiogenic stimulus in a 3D endothelial cell spheroid/human vitreous assay. The results show that PDR vitreous is able to stimulate the sprouting of fibrin-embedded HUVEC spheroids in a time- and dose-dependent manner. A remarkable variability was observed among 40 individual vitreous fluid samples in terms of sprouting-inducing activity that was related, at least in part, to defined clinical features of the PDR patient. This activity was hampered by various extracellular and intracellular signaling pathway inhibitors, including the VEGF antagonist ranibizumab. When tested on 20 individual vitreous fluid samples, the inhibitory activity of ranibizumab ranged between 0 and 100% of the activity measured in the absence of the drug, reflecting a variable contribution of angiogenic mediators distinct from VEGF. In conclusion, the 3D endothelial cell spheroid/human vitreous assay represents a rapid and cost-effective experimental procedure suitable for the evaluation of the anti-angiogenic activity of novel extracellular and intracellular drug candidates, with possible implications for the therapy of PDR.

Therapeutic Potential of Anti-Angiogenic Multitarget N,O-Sulfated E. Coli K5 Polysaccharide in Diabetic Retinopathy

Vascular endothelial growth factor (VEGF) blockers have been developed for the treatment of proliferative diabetic retinopathy (PDR), the leading cause of visual impairments in the working-age population in the Western world. However, limitations to anti-VEGF therapies may exist because of the local production of other proangiogenic factors that may cause resistance to anti-VEGF interventions. Thus, novel therapeutic approaches targeting additional pathways are required. Here, we identified a sulfated derivative of the Escherichia coli polysaccharide K5 [K5-N,OS(H)] as a multitarget molecule highly effective in inhibiting VEGF-driven angiogenic responses in different in vitro, ex vivo, and in vivo assays, including a murine model of oxygen-induced retinopathy. Furthermore, K5-N,OS(H) binds a variety of heparin-binding angiogenic factors upregulated in PDR vitreous humor besides VEGF, thus inhibiting their biological activity. Finally, K5-N,OS(H) hampers the angiogenic activity exerted in vitro and in vivo by human vitreous fluid samples collected from patients with PDR. Together, the data provide compelling experimental evidence that K5-N,OS(H) represents an antiangiogenic multitarget molecule with potential implications for the therapy of pathologic neovessel formation in the retina of patients with PDR.

Albumin and mammalian cell culture: implications for biotechnology applications

Albumin has a long historical involvement in design of media for the successful culture of mammalian cells, in both the research and commercial fields. The potential application of albumins, bovine or human serum albumin, for cell culture is a by-product of the physico-chemical, biochemical and cell-specific properties of the molecule. In this review an analysis of these features of albumin leads to a consideration of the extracellular and intracellular actions of the molecule, and importantly the role of its interactions with numerous ligands or bioactive factors that influence the growth of cells in culture: these include hormones, growth factors, lipids, amino acids, metal ions, reactive oxygen and nitrogen species to name a few. The interaction of albumin with the cell in relation to these co-factors has a potential impact on metabolic and biosynthetic activity, cell proliferation and survival. Application of this knowledge to improve the performance in manufacturing biotechnology and in the emerging uses of cell culture for tissue engineering and stem cell derived therapies is an important prospect.