Phase 1 clinical study of an embryonic stem cell-derived retinal pigment epithelium patch in age-related macular degeneration

Age-related macular degeneration (AMD) remains a major cause of blindness, with dysfunction and loss of retinal pigment epithelium (RPE) central to disease progression. We engineered an RPE patch comprising a fully differentiated, human embryonic stem cell (hESC)-derived RPE monolayer on a coated, synthetic basement membrane. We delivered the patch, using a purpose-designed microsurgical tool, into the subretinal space of one eye in each of two patients with severe exudative AMD. Primary endpoints were incidence and severity of adverse events and proportion of subjects with improved best-corrected visual acuity of 15 letters or more. We report successful delivery and survival of the RPE patch by biomicroscopy and optical coherence tomography, and a visual acuity gain of 29 and 21 letters in the two patients, respectively, over 12 months. Only local immunosuppression was used long-term. We also present the preclinical surgical, cell safety and tumorigenicity studies leading to trial approval. This work supports the feasibility and safety of hESC-RPE patch transplantation as a regenerative strategy for AMD

Adaxial/abaxial specification in the regulation of photosynthesis and stomatal opening with respect to light orentation and growth with CO2 enrichment in the C4 species Paspalum dilatatum

Whole-plant morphology, leaf structure and composition were studied together with the effects of light orientation on the dorso-ventral regulation of photosynthesis and stomatal conductance in Paspalum dilatatum cv. Raki plants grown for 6 wk at either 350 or 700 µl l¿1 CO2. Plant biomass was doubled as a result of growth at high CO2 and the shoot:root ratio was decreased. Stomatal density was increased in the leaves of the high CO2-grown plants, which had greater numbers of smaller stomata and more epidermal cells on the abaxial surface. An asymmetric surface-specific regulation of photosynthesis and stomatal conductance was observed with respect to light orientation. This was not caused by dorso-ventral variations in leaf structure, the distribution of phosphoenolpyruvate carboxylase (PEPC) and ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) proteins or light absorptance, transmittance or reflectance. Adaxial/abaxial specification in the regulation of photosynthesis results from differential sensitivity of stomatal opening to light orientation and fixed gradients of enzyme activation across the leaf

A Model of the Generalized Stoichiometry of Electron Transport Limited C3 Photosynthesis: Development and Applications

We describe an extended Farquhar, Von Caemmerer and Berry (FvCB) model for the RuBP regeneration-limited or electron transport-limited steady-state C3 photosynthesis. Analytical algorithms are presented to account for (i) the effects of Photosystem (PS) I and II photochemical efficiencies and of cyclic electron transport around PS I (CET) on the photosynthetic quantum yields and related interphotosys-tem excitation partitioning, and (ii) CET and pseudocyclic electron transport (PET) that may act in concert with linear electron transport (LET, with or without the Q-cycle) to permit flexibility in the ratio of NADPH and ATP synthesis to meet the variable demands of the carbon reduction cycle and photorespiration. The two widely used forms of the original FvCB model represent the most and least efficient electron transport stoichiometry, respectively, of special cases covered by the extended model. The generalized model integrates most basic elements of C3 photosynthesis. The model implies that even within the electron transport-limited range the relationship between quantum yields of CO2 assimilation and PS II photochemical efficiency is linear only if the latter varies in proportion with PS I photochemical efficiency. The model can be used (i) to assess any occurrence of alternative electron transport and to answer ‘what-if’ questions with respect to uncertain or unmeasured parameters, and (ii) to estimate photosynthetic parameters by curve-fitting to combined gas exchange and biophysical measurements (e.g. chlorophyll fluorescence) under various irradiance and CO2 levels. As long as current biophysical measurements were accurate, our analyses support (i) the possible in vivo occurrence of CET and basal PET even under limiting irradiance, (ii) CET as a ‘brake’ for LET to accommodate the balance between quantum yields of electron transport and CO2 assimilation, and (iii) the mode of a variable Q-cycle to obtain a correct NADPH/ATP ratio with varying light and CO2 levels if no ATP from chloroplast is used for processes other than carbon reduction and photorespiration. Our model provides a tool to facilitate understanding the stoichiometries, bioenergetics and regulation of photosynthesis under different environmental conditions

Survey of tools for measuring in vivo photosynthesis

Measurements of in vivo photosynthesis are powerful tools that probe the largest fluxes of carbon and energy in an illuminated leaf, but often the specific techniques used are so varied and specialized that it is difficult for researchers outside the field to select and perform the most useful assays for their research questions. The goal of this chapter is to provide a broad overview of the current tools available for the study of in vivo photosynthesis so as to provide a foundation for selecting appropriate techniques, many of which are presented in detail in subsequent chapters. This chapter also organizes current methods into a comparative framework and provides examples of how they have been applied to research questions of broad agronomical, ecological, or biological importance. The chapter closes with an argument that the future of in vivo measurements of photosynthesis lies in the ability to use multiple methods simultaneously and discusses the benefits of this approach to currently open physiological questions. This chapter, combined with the relevant methods chapters, could serve as a laboratory course in methods in photosynthesis research or as part of a more comprehensive laboratory course in general plant physiology methods