In Vitro Rheology Predicts Improved Spreadability of Tazarotene 0.045% Lotion Versus Trifarotene 0.005% Cream.

BACKGROUND: Intrinsic properties of vehicles used to deliver topical therapies can profoundly impact drug penetration, efficacy, patient acceptance, and treatment adherence. Therefore, advancements in vehicle technology demand sophisticated, quantitative approaches to describe and differentiate topical formulations. The objective of these studies was to quantitatively evaluate spreadability of two topical formulations for the treatment of acne via in vitro rheological measurement (how a substance’s flow characteristics change under applied stress or force) and spreadability on living skin. METHODS: Rheological characteristics (shear-thinning, rigidity, yield stress, and yield strain) of tazarotene 0.045% lotion and trifarotene 0.045% cream were measured using 5 samples of each product. In a clinical split-body study, each formulation was applied to one side of the back of healthy volunteers, and the extent to which each formulation could be spread was measured. RESULTS: Compared to trifarotene cream, tazarotene lotion demonstrated lower mean viscosity, rigidity, and yield stress, and higher yield strain, suggesting a superior spreadability profile. This finding was confirmed in the split-body study of 30 healthy White adults, in which the average area of spread was significantly larger for tazarotene lotion than trifarotene cream (167.0 vs 130.3 cm2; P<0.001). CONCLUSIONS: Rheological assessment effectively predicted the superior spreadability of tazarotene 0.045% lotion versus trifarotene 0.005% cream on living skin. Given the importance of aesthetics of topical formulations, techniques to quantify these properties may have broad implications when developing novel vehicle formulations for dermatology. J Drugs Dermatol. 2022;21(3):250-257. doi:10.36849/JDD.6703.

Osteophyte formation after ACL rupture in mice is associated with joint restabilization and loss of range of motion.

Osteophytes are a typical radiographic finding during osteoarthritis (OA). Osteophytes are thought to form in response to joint instability; however, the time course of osteophyte formation and joint stabilization following joint injury is not well understood. In this study, we investigated the time course of osteophyte formation and joint function following non-invasive knee injury in mice. We hypothesized that initial joint instability following knee injury would initiate osteophyte formation, which would in turn restabilize the joint and reduce range of motion (ROM). Mice were subjected to non-invasive anterior cruciate ligament (ACL) rupture. Anterior-posterior (AP) joint laxity, ROM, and chondro/osteophyte formation were measured immediately after injury, and 2, 4, 6, and 8 weeks post-injury. Chondrophyte areas at each time point were measured with histology, while mineralized osteophyte volume was determined using micro-computed tomography. Immediately after ACL rupture, AP joint laxity was increased twofold, while ROM was increased 11.7%. Chondrophytes appeared by 2 weeks post-injury, corresponding with a decrease in AP joint laxity and ROM. By 8 weeks post-injury, considerable osteophyte formation was observed around the joint, AP joint laxity returned to control levels, and joint ROM decreased to 61% of control values. These data support a role for chondro/osteophytes in joint restabilization after injury, and provide crucial insight into the time course and pathology of joint degeneration during OA development in the mouse. Statement of Clinical Significance: Results from this study increase understanding of conditions leading to osteophyte formation.© 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:466-473, 2017.

Rapamycin Reverses Metabolic Deficits in Lamin A/C-Deficient Mice.

The role of the mTOR inhibitor, rapamycin, in regulation of adiposity remains controversial. Here, we evaluate mTOR signaling in lipid metabolism in adipose tissues of Lmna-/- mice, a mouse model for dilated cardiomyopathy and muscular dystrophy. Lifespan extension by rapamycin is associated with increased body weight and fat content, two phenotypes we link to suppression of elevated energy expenditure. In both white and brown adipose tissue of Lmna-/- mice, we find that rapamycin inhibits mTORC1 but not mTORC2, leading to suppression of elevated lipolysis and restoration of thermogenic protein UCP1 levels, respectively. The short lifespan and metabolic phenotypes of Lmna-/- mice can be partially rescued by maintaining mice at thermoneutrality. Together, our findings indicate that altered mTOR signaling in Lmna-/- mice leads to a lipodystrophic phenotype that can be rescued with rapamycin, highlighting the effect of loss of adipose tissue in Lmna-/- mice and the consequences of altered mTOR signaling.