Effects of mesenchymal stem cells and their exosomes on the healing of large and refractory macular holes

Multipotent mesenchymal stromal cells (MSCs) have potential therapeutic benefit for the treatment of neurological diseases and injury. MSCs interact with and alter brain parenchymal cells by direct cell-cell communication and/or by indirect secretion of factors and thereby promote functional recovery. In this study, we found that MSC treatment of rats subjected to middle cerebral artery occlusion (MCAo) significantly increased microRNA 133b (miR-133b) level in the ipsilateral hemisphere. In vitro, miR-133b levels in MSCs and in their exosomes increased after MSCs were exposed to ipsilateral ischemic tissue extracts from rats subjected to MCAo. miR-133b levels were also increased in primary cultured neurons and astrocytes treated with the exosome-enriched fractions released from these MSCs. Knockdown of miR-133b in MSCs confirmed that the increased miR-133b level in astrocytes is attributed to their transfer from MSCs. Further verification of this exosome-mediated intercellular communication was performed using a cel-miR-67 luciferase reporter system and an MSC-astrocyte coculture model. Cel-miR-67 in MSCs was transferred to astrocytes via exosomes between 50 and 100 nm in diameter. Our data suggest that the cel-miR-67 released from MSCs was primarily contained in exosomes. A gap junction intercellular communication inhibitor arrested the exosomal microRNA communication by inhibiting exosome release. Cultured neurons treated with exosome-enriched fractions from MSCs exposed to 72 hours post-MCAo brain extracts significantly increased the neurite branch number and total neurite length. This study provides the first demonstration that MSCs communicate with brain parenchymal cells and may regulate neurite outgrowth by transfer of miR-133b to neural cells via exosomes. Copyright © 2012 AlphaMed Press.

Large macular holes usually have an increased risk of surgical failure. Up to 44% of large macular holes remain open after 1 surgery. Another 19% to 39% of macular holes are flat-open after surgery. Flat-open macular holes are associated with limited visual acuity. This article presents a modification of the standard macular hole surgery to improve functional and anatomic outcomes in patients with large macular holes. A prospective, randomized clinical trial. Patients with macular holes larger than 400 μm were included. In group 1, 51 eyes of 40 patients underwent standard 3-port pars plana vitrectomy with air. In group 2, 50 eyes of 46 patients underwent a modification of the standard technique, called the inverted internal limiting membrane (ILM) flap technique. In the inverted ILM flap technique, instead of completely removing the ILM after trypan blue staining, a remnant attached to the margins of the macular hole was left in place. This ILM remnant was then inverted upside-down to cover the macular hole. Fluid-air exchange was then performed. Spectral optical coherence tomography and clinical examination were performed before surgery and postoperatively at 1 week and 1, 3, 6, and 12 months. Visual acuity and postoperative macular hole closure. Preoperative mean visual acuity was 0.12 in group 1 and 0.078 in group 2. Macular hole closure was observed in 88% of patients in group 1 and in 98% of patients in group 2. A flat-hole roof with bare retinal pigment epithelium (flat-open) was observed in 19% of patients in group 1 and 2% of patients in group 2. Mean (or median) postoperative visual acuity 12 months after surgery was 0.17 (range, 0.1-0.6) in group 1 and 0.28 (range, 0.02-0.8) in group 2 (P = 0.001). The inverted ILM flap technique prevents the postoperative flat-open appearance of a macular hole and improves both the functional and anatomic outcomes of vitrectomy for macular holes with a diameter greater than 400 μm. Spectral optical coherence tomography after vitrectomy with the inverted ILM flap technique suggests improved foveal anatomy compared with the standard surgery. Copyright © 2010 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

Advances in biomedical research have generated an unprecedented number of potential targets for therapeutic intervention to treat disease or delay disease progression. Unfortunately, many of these targets are not druggable as they are intracellular, present in many cell types, poorly soluble or rapidly inactivated. Although synthetic drug vehicles have successfully circumvented many of these problems, natural particulates such as exosomes that intrinsically possess many attributes of a drug delivery vehicle are highly attractive as potentially better alternatives. Of the cell types known to produce exosomes, the readily available proliferative, immunosuppressive and clinically tested human mesenchymal stem cell (MSC) is the most prolific producer. Its exosomes are therapeutic in animal model of disease and exhibit immunosuppressive activity. The quality and quantity of exosome production is not compromised by immortalization to create a permanent MSC cell line. Therefore, MSC is well suited for mass production of exosomes that are ideal for drug delivery. Copyright © 2012 Elsevier B.V. All rights reserved.