Myo/Nog cells are present in the ciliary processes, on the zonule of Zinn and posterior capsule of the lens following cataract surgery

Abstract

Myo/Nog cells, named for their expression of MyoD and noggin, enter the eye during early stages of embryonic development. Their release of noggin is critical for normal morphogenesis of the lens and retina. Myo/Nog cells are also present in adult eyes. Single nucleated skeletal muscle cells designated as myofibroblasts arise from Myo/Nog cells in cultures of lens tissue. In this report we document the presence of Myo/Nog cells in the lens, ciliary body and on the zonule of Zinn in mice, rabbits and humans. Myo/Nog cells were rare in all three structures. Their prevalence increased in the lens and ciliary body of rabbits 24 h following cataract surgery. Rabbits developed posterior capsule opacification (PCO) within one month of surgery. The number of Myo/Nog cells continued to be elevated in the lens and ciliary body. Myo/Nog cells containing alpha smooth muscle actin and striated muscle myosin were present on the posterior capsule and overlaid deformations in the capsule. Myo/Nog cells also were present on the zonule fibers and external surface of the posterior capsule. These findings suggest that Myo/Nog contribute to PCO and may use the zonule fibers to migrate between the ciliary processes and lens.

Depletion of Myo/Nog Cells in the Lens Mitigates Posterior Capsule Opacification in Rabbits

“…Fewer than 9% of lenses administered these doses of G8:3DNA:Dox exhibited greater than mild levels of peripheral PCO. Administration of the drug as a sustained delivery formulation may reduce the incidence of PCO even further and protect the lens from Myo/Nog cells that migrate on the zonule fibers from the ciliary processes to the lens 36 (Gerhart JV, et al IOVS 2017;58:ARVO E-Abstract 3635). The modularity of the 3DNA platform, as well as the wide range of available conjugation chemistries, allows for the direct attachment of a variety of small drugs.…”

“…One month after surgery, Myo/Nog cells are present on the internal and external surfaces of the posterior capsule; express a-SMA, MyoD, and striated muscle myosin; and overlay wrinkles in the capsule. 36 In this report, we describe the effect of depleting Myo/Nog cells on the development of PCO following cataract surgery in rabbits.…”

“…24,28,30 Myo/Nog cells also react to wounding in the embryo and adult. [30][31][32][33][34][35][36][37] Within 24 hours of epidermal abrasion, Myo/Nog cells increase in number and populate the wound. 38 In the retina, the Myo/Nog population expands in response to hypoxia and damaging levels of light.…”

“…Within 24 hours of cataract surgery, their number was significantly elevated in the lens, ciliary body, and cornea. 36 Myo/Nog cells also have been found on the zonules of Zinn, apparently migrating between the ciliary processes and lens 36 (Gerhart JV, et al IOVS 2017;58:ARVO E-Abstract 3635). One month after surgery, Myo/Nog cells are present on the internal and external surfaces of the posterior capsule; express a-SMA, MyoD, and striated muscle myosin; and overlay wrinkles in the capsule.…”

Myo/Nog cells are nonprofessional phagocytes

“…The dynamic behavior of Myo/Nog cells also has been observed in the lens. Upon injury to the lens epithelium, they migrate to the wound and differentiate into myofibroblasts that synthesize alpha smooth muscle actin (α-SMA) and striated muscle specific proteins [12][13][14][15][16]. Eliminating Myo/Nog cells in explant cultures of human lens tissue with either the targeting G8 monoclonal antibody (mAb) and complement or a drug consisting of the G8 mAb conjugated to 3DNA nanocarriers for doxorubicin prevents the emergence of myofibroblasts [14].…”