Abstract
Purpose:
Intranasally delivered ST266, the biological, proteinaceous secretome of amnion-derived multipotent progenitor cells, reduces retinal ganglion cell (RGC) loss, optic nerve inflammation, and demyelination in experimental optic neuritis. This unique therapy and novel administration route delivers numerous cytokines and growth factors to the eye and optic nerve, suggesting a potential to also treat other optic neuropathies. Thus, ST266-mediated neuroprotection was examined following traumatic optic nerve injury.
Methods:
Optic nerve crush injury was surgically induced in C57BL/6J mice. Mice were treated daily with intranasal PBS or ST266. RGC function was assessed by optokinetic responses (OKRs), RGCs were counted, and optic nerve sections were stained with luxol fast blue and anti-neurofilament antibodies to assess myelin and RGC axon damage.
Results:
Intranasal ST266 administered daily for 5 days, beginning at the time that a 1-second optic nerve crush was performed, significantly attenuated OKR decreases. Furthermore, ST266 treatment reduced damage to RGC axons and myelin within optic nerves, and blocked RGC loss. Following a 4-second optic nerve crush, intranasal ST266 increased RGC survival and showed a trend toward reduced RGC axon and myelin damage. Ten days following optic nerve crush, ST266 prevented myelin damage, while also inducing a trend toward increased RGC survival and visual function.
Conclusions:
ST266 significantly attenuates traumatic optic neuropathy. Neuroprotective effects of this unique combination of biologic molecules observed here and previously in optic neuritis suggest potential broad application for preventing neuronal damage in multiple optic nerve disorders. Furthermore, results support intranasal delivery as a novel, noninvasive therapeutic modality for eyes and optic nerves.
Traumatic optic neuropathy
1 can result from direct optic nerve injury in penetrating orbital trauma, but more commonly occurs indirectly due to optic nerve stretching from blunt head trauma. Traumatic optic neuropathy is one of the leading types of ocular injury sustained in military combat,
2,3 as well as noncombat traumatic brain injury, in which 60% of traumatic head injuries result in neuro-ophthalmic abnormalities,
4 with 50% of those involving the optic nerves or visual pathways. Traumatic optic nerve injury can result in retinal ganglion cell (RGC) axonal damage and irreversible RGC loss with permanent visual deficits. Medical and surgical treatments have all failed to improve outcomes, and some treatments carry significant risks.
1,5 Thus, novel neuroprotective therapies are needed to prevent neuronal damage and loss of vision following optic nerve trauma.
ST266 (formerly amnion-derived cellular cytokine solution; ACCS) is the biological proteinaceous, secretome of a novel population of cells called amnion-derived multipotent progenitor (AMP) cells that contains physiologic levels of multiple growth factors and cytokines that can stimulate a variety of anti-inflammatory and neuroprotective responses in human cells.
6,7 Intranasal delivery results in rapid accumulation of high levels of proteins from ST266 in the eye and optic nerve, and prevents visual dysfunction, RGC loss, and inflammation in an animal model of optic neuritis, an inflammatory disorder of the optic nerve.
8 Detection of ST266 proteins in the eye and optic nerve within 30 minutes after intranasal administration suggests that proteins gain direct access into the central nervous system and are transported locally,
8 representing a novel delivery method to target the eye that does not depend on systemic vascular absorption through the nasal mucosa. The combination of cytokines and growth factors present in ST266 suggests that it exerts effects by multiple mechanisms, but it remains unknown whether effects of ST266 in optic neuritis are due mainly to suppression of inflammation, direct neuroprotection of RGCs, or perhaps both. Interestingly, one pathway upregulated by ST266 in experimental optic neuritis involves the SIRT1 deacetylase.
8 When activated, SIRT1 deacetylase has previously been shown to prevent RGC loss and preserve vision in both optic neuritis
9–12 and traumatic optic nerve injury.
13 Common features of RGC neuroprotection mediated by both ST266 and SIRT1 activators in experimental optic neuritis include reduction of oxidative stress,
8–12 a conserved mechanism of neuronal cell loss that also occurs in models of traumatic optic neuropathy.
14–16
We hypothesized that ST266 can provide direct neuroprotective effects on RGCs following traumatic injury due to the multiple growth factors and cytokines present in ST266 and their upregulation of SIRT1 and suppression of oxidative stress. Furthermore, the noninvasive intranasal delivery of ST266 represents a potential novel method to target complex protein therapies to the optic nerve to promote effective treatment of optic nerve injury. Surgical optic nerve crush was performed on one eye of young adult C57BL/6J mice. Mice were treated daily with intranasal ST266 or PBS, and RGC function, RGC damage, and myelin damage were assessed.
Intranasal ST266 Improves Visual Function and Reduces Optic Nerve Damage Induced by ONC
Intranasal ST266 Exerts Partial Neuroprotective Effects Induced by More Severe ONC Injury
Intranasal ST266 Maintains Partial Neuroprotective Effects Up to 10 Days Following ONC Injury
The authors thank Noveome Biotherapeutics, Inc. for providing ST266 for the studies reported in this article.
Supported by National Institutes of Health grant EY019014, Research to Prevent Blindness Physician Scientist Award, and the F.M. Kirby Foundation. Portions of this work were subcontracted from grants to Noveome through US Navy Contract N62645-13-C-4014, Cell-Based Wound Therapeutics for Combat Casualties; and The State of Pennsylvania 2014 Bio-Technology Grant SAP#4100068500.
Disclosure: G.A. Grinblat, None; R.S. Khan, None; K. Dine, None; H. Wessel, Noveome (I, E), P; L. Brown, Noveome (E), P; K.S. Shindler, Noveome (F, C)