Modeling aging and retinal degeneration with mitochondrial DNA mutation burden.

Somatic mitochondrial DNA (mtDNA) mutation accumulation has been observed in individuals with retinal degenerative disorders. To study the effects of aging and mtDNA mutation accumulation in the retina, a polymerase gamma (POLG) exonuclease-deficient model, the PolgD257A mutator mice (D257A), was used. POLG is an enzyme responsible for regulating mtDNA replication and repair. Retinas of young and older mice with this mutation were analyzed in vivo and ex vivo to provide new insights into the contribution of age-related mitochondrial (mt) dysfunction due to mtDNA damage. Optical coherence tomography (OCT) image analysis revealed a decrease in retinal and photoreceptor thickness starting at 6 months of age in mice with the D257A mutation compared to wild-type (WT) mice. Electroretinography (ERG) testing showed a significant decrease in all recorded responses at 6 months of age. Sections labeled with markers of different types of retinal cells, including cones, rods, and bipolar cells, exhibited decreased labeling starting at 6 months. However, electron microscopy analysis revealed differences in retinal pigment epithelium (RPE) mt morphology beginning at 3 months. Interestingly, there was no increase in oxidative stress and parkin-mediated mitophagy in the ages analyzed in the retina or RPE of D257A mice. Additionally, D257A RPE exhibited an accelerated rate of autofluorescence cytoplasmic granule formation and accumulation. Mt markers displayed different abundance in protein lysates obtained from retina and RPE samples. These findings suggest that the accumulation of mtDNA mutations leads to impaired mt function and accelerated aging, resulting in retinal degeneration.

Modeling aging and retinal degeneration with mitochondrial DNA mutation burden.

Somatic mitochondrial DNA (mtDNA) mutation accumulation has been observed in individuals with retinal degenerative disorders. To study the effects of aging and mtDNA mutation accumulation in the retina, a Polymerase gamma (POLG) deficiency model, the POLGD257A mutator mice (PolgD257A), was used. POLG is an enzyme responsible for regulating mtDNA replication and repair. Retinas of young and older mice with this mutation were analyzed in vivo and ex vivo to provide new insights into the contribution of age-related mitochondrial dysfunction due to mtDNA damage. Optical coherence tomography (OCT) image analysis revealed a decrease in retinal and photoreceptor thickness starting at 6 months of age in mice with the POLGD257A mutation compared to wild-type (WT) mice. Electroretinography (ERG) testing showed a significant decrease in all recorded responses at 6 months of age. Sections labeled with markers of different types of retinal cells, including cones, rods, and bipolar cells, exhibited decreased labeling starting at 6 months. However, electron microscopy analysis revealed differences in retinal pigment epithelium (RPE) mitochondria morphology beginning at 3 months. Interestingly, there was no increase in oxidative stress observed in the retina or RPE of POLGD257A mice. Additionally, POLGD257A RPE exhibited an accelerated rate of autofluorescence cytoplasmic granule formation and accumulation. Mitochondrial markers displayed decreased abundance in protein lysates obtained from retina and RPE samples. These findings suggest that the accumulation of mitochondrial DNA mutations leads to impaired mitochondrial function and accelerated aging, resulting in retinal degeneration.

Assessing the Impact of Punch Geometries on Tablet Capping Using a Newly Proposed Capping Index.

PURPOSE: Increased tablet anisotropy could lead to increased tablet capping propensity. Tooling design variables such as cup depth could serve as a key player for inducing tablet anisotropy. METHODS: A new capping index (CI) consisting of the ratio of compact anisotropic index (CAI) and material anisotropic index (MAI) is proposed to evaluate tablet capping propensity as a function of punch cup depth. CAI is the ratio of axial to radial breaking force. MAI is the ratio of axial to radial Young's modulus. The impact of various punch cup depths [flat face, flat face beveled edge, flat face radius edge, standard concave, shallow concave, compound concave, deep concave, and extra deep concave] on the capping propensity of model acetaminophen tablets was studied. Tablets were manufactured at 50, 100, 200, 250, and 300 MPa compression pressure at 20 RPM on different cup depth tools using Natoli NP-RD30 tablet press. A partial least squares model (PLS) was computed to model the impact of the cup depth and compression parameters on the CI. RESULTS: The PLS model exhibited a positive correlation of increased cup depth to the capping index. The finite elemental analysis confirmed that a high capping tendency with increased cup depth is a direct result of non-uniform stress distribution across powder bed. CONCLUSIONS: Certainly, a proposed new capping index with multivariate statistical analysis gives guidance in selecting tool design and compression parameters for robust tablets.

Compression-decompression modulus (CDM) - an alternative/complementary approach to Heckel's analysis.

The novel modulus-based approach was developed to characterize the compression behavior of the materials and how it results into tablet mechanical strength (TMS) of the final tablet. The force-displacement profile for the model materials (Vivapur® 101, Starch 1500®, Emcompress®, and Tablettose® 100) was generated at different compression pressures (100, 150, and 200 MPa) and speeds (0.35, 0.55, and 0.75 m/s) using compaction emulator (Presster™). A generated continuous compression profile was evaluated with Heckel plot and the proposed material modulus method. The computed compression parameters were qualitatively and quantitatively correlated with TMS by principal component analysis and principal component regression, respectively. Compression modulus has negatively correlated, while decompression modulus is positively correlated to TMS. Proposed modulus descriptors are independent of particle density measurements required for the Heckel method and could overcome the limitations of the Heckel method to evaluate the decompression phase. Based on the outcome of the study, a two-dimensional compression and decompression modulus classification system (CDMCS) was proposed. The proposed CDMCS could be used to define critical material attributes in the early development stage or to understand reasons for tablet failure in the late development stage.

Surface-Modified G4 PAMAM Dendrimers Cross the Blood-Brain Barrier Following Multiple Tail-Vein Injections in C57BL/6J Mice.

Intracranial injections are currently used to deliver drugs into the brain, as most drugs cannot cross the blood-brain barrier (BBB) following systemic injections. Moreover, multiple dosing is difficult with invasive techniques. Therefore, viable systemic techniques are necessary to facilitate treatment paradigms that require multiple dosing of therapeutics across the BBB. In this study, we show that mixed-surface fourth-generation poly(amidoamine) (PAMAM) dendrimers containing predominantly biocompatible hydroxyl groups and a few amine groups are taken up by cultured primary cortical neurons derived from mouse embryo. We also show that these dendrimers cross the BBB following their administration to healthy mice in multiple doses via tail-vein injections and are taken up by neurons and the glial cells as evidenced by appropriate staining methods. Besides the brain, the dendrimers were found mostly in the kidneys compared to other peripheral organs, such as liver, lungs, and spleen, implying that they may be readily excreted, thereby preventing potential toxic accumulation in the body. Our findings provide a proof-of-concept that appropriate surface modifications of dendrimers provide safe, biocompatible nanomaterial with the potential to deliver therapeutic cargo across the BBB into the brain via multiple tail-vein injections.