The Effect of Mesenchymal Stem Cell Secretome on Corneal Endothelial Cell Preservation in an Oxidative Injury Model.

PURPOSE: To describe a reproducible oxidative injury model in ex vivo porcine corneas and to investigate the effects of corneal mesenchymal stem cell (Co-MSC) secretome and specific factors on the preservation of corneal endothelium after oxidative injury. METHODS: Porcine corneas underwent vital staining with trypan blue and alizarin red with different concentration and time points. Ex vivo porcine corneas were exposed (endothelial side) to varied concentrations of hydrogen peroxide. After injury, 3 groups of 5 corneas underwent treatment with secretome from either a wild-type (WT) murine Co-MSC, a pigment epithelium derived factor (PEDF) knock out (K/O) murine Co-MSC, or basal media for 4 hours at 37°C. The viability of the endothelium was evaluated using the optimized vital staining protocol. RESULTS: The optimal vital staining was achieved with 0.4% trypan blue for 60 seconds and 0.5% alizarin red for 90 seconds. The optimal oxidative injury (for consistency and level of damage) was obtained with 1% hydrogen peroxide for 15 seconds. Treatment with both WT Co-MSC and PEDF K/O Co-MSC secretome significantly reduced the endothelial damage compared with control (17.2% ± 10.0%, 33.5% ± 11.6%, and 68% ± 17%, respectively, P < 0.01). The WT Co-MSC secretome was significantly more effective compared with PEDF K/O Co-MSC secretome (P < 0.05). CONCLUSIONS: A reproducible model of vital staining and oxidative injury is described for studying porcine corneal endothelial survival. Our results demonstrate a beneficial role of a corneal MSC secretome in reducing oxidative damage to the corneal endothelium. In addition, it suggests a potential role for PEDF in this process.

Correlates of Google Search Rankings for Spine Surgeons: An Analysis of Academic Pedigree, Social Media Presence, and Patient Ratings.

STUDY DESIGN: Prospective observational study. OBJECTIVE: The objective of this study is to identify correlates of search ranking among academic pedigree, online ratings, and social media following. SUMMARY OF BACKGROUND DATA: Patients increasingly rely on online search in selecting healthcare providers. When choosing a spine surgeon, patients typically value surgical skill and experience as well as demeanor/bedside manner. It is unclear whether current search engine ranking algorithms reflect these preferences. METHODS: A Google.com search for the top 25 spine surgeon websites by search ranking was conducted for each of the largest 25 American cities. Resulting websites were then perused for academic pedigree, experience, and practice characteristics. Surgeons' research output and impact were then quantified via number of publications and H-index. Online ratings and followers in various social media outlets were also noted. These variables were assessed as possible correlates of search ranking via linear regression and multivariate analyses of variance. RESULTS: A total of 625 surgeons were included. Three categorical variables were identified as significant correlates of higher mean Google search ranking-orthopedics (vs. neurosurgery) as a surgical specialty (P = 0.023), board certification (P = 0.024), and graduation from a top 40 residency program (P = 0.046). Although the majority of the identified surgeons received an allopathic medical education, there was no significant difference in the mean rank of surgeons who had an MD versus DO medical degree (P = 0.530). Additionally, none of the continuous variables collected, including years in practice (P = 0.947), publications (P = 0.527), H-index (P = 0.278), social media following such as on Facebook (P = 0.105), or online ratings such as on Healthgrades (P = 0.080), were significant correlates of Google search ranking. CONCLUSIONS: Google search rankings do not always align with patient preferences, currently promoting orthopedic over neurosurgical specialists, graduation from top residency programs, and board certification, while largely ignoring academic pedigree, research, social media presence, and online ratings. LEVEL OF EVIDENCE: 3.

Depletion of Caveolin-1 in Type 2 Diabetes Model Induces Alzheimer's Disease Pathology Precursors.

Type 2 diabetes mellitus (T2DM) is a risk factor for the development of late-onset Alzheimer's disease (AD). However, the mechanism underlying the development of late-onset AD is largely unknown. Here we show that levels of the endothelial-enriched protein caveolin-1 (Cav-1) are reduced in the brains of T2DM patients compared with healthy aging, and inversely correlated with levels of ß-amyloid (Aß). Depletion of Cav-1 is recapitulated in the brains of db/db (Leprdb ) diabetic mice and corresponds with recognition memory deficits as well as the upregulation of amyloid precursor protein (APP), BACE-1, a trending increase in ß-amyloid Aß42/40 ratio and hyperphosphorylated tau (p-tau) species. Importantly, we show that restoration of Cav-1 levels in the brains of male db/db mice using adenovirus overexpressing Cav-1 (AAV-Cav-1) rescues learning and memory deficits and reduces pathology (i.e., APP, BACE-1 and p-tau levels). Knocking down Cav-1 using shRNA in HEK cells expressing the familial AD-linked APPswe mutant variant upregulates APP, APP carboxyl terminal fragments, and Aß levels. In turn, rescue of Cav-1 levels restores APP metabolism. Together, these results suggest that Cav-1 regulates APP metabolism, and that depletion of Cav-1 in T2DM promotes the amyloidogenic processing of APP and hyperphosphorylation of tau. This may suggest that depletion of Cav-1 in T2DM underlies, at least in part, the development of AD and imply that restoration of Cav-1 may be a therapeutic target for diabetic-associated sporadic AD.SIGNIFICANCE STATEMENT More than 95% of the Alzheimer's patients have the sporadic late-onset form (LOAD). The cause for late-onset Alzheimer's disease is unknown. Patients with Type 2 diabetes mellitus have considerably higher incidence of cognitive decline and AD compared with the general population, suggesting a common mechanism. Here we show that the expression of caveolin-1 (Cav-1) is reduced in the brain in Type 2 diabetes mellitus. In turn, reduced Cav-1 levels induce AD-associated neuropathology and learning and memory deficits. Restoration of Cav-1 levels rescues these deficits. This study unravels signals underlying LOAD and suggests that restoration of Cav-1 may be an effective therapeutic target.

Human Hippocampal Neurogenesis Persists in Aged Adults and Alzheimer's Disease Patients.

Whether hippocampal neurogenesis persists throughout life in the human brain is not fully resolved. Here, we demonstrate that hippocampal neurogenesis is persistent through the tenth decade of life and is detectable in patients with mild cognitive impairments and Alzheimer's disease. In a cohort of 18 participants with a mean age of 90.6 years, Nestin+Sox2+ neural progenitor cells (NPCs) and DCX+ neuroblasts and immature neurons were detected, but their numbers greatly varied between participants. Nestin+ cells localize in the anterior hippocampus, and NPCs, neuroblasts, and immature neurons are evenly distributed along the anterior to posterior axis. The number of DCX+PCNA+ cells is reduced in mild cognitive impairments, and higher numbers of neuroblasts are associated with better cognitive status. The number of DCX+PCNA+ cells correlates with functional interactions between presynaptic SNARE proteins. Our results suggest that hippocampal neurogenesis persists in the aged and diseased human brain and that it is possibly associated with cognition.