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Tissue Engineering

Therapeutic Benefits of Magnetically-Steered Trabecular Meshwork Cell Therapy for Primary Open Angle Glaucoma

(H-310) Therapeutic Benefits of Magnetically-Steered Trabecular Meshwork Cell Therapy for Primary Open Angle Glaucoma

Thursday, October 12, 2023

2:00 PM – 3:00 PM PDT

Location: Exhibit Hall - Row H - Poster # 310

Presenting Author(s)

MB

M. Reza Bahranifard, MS

PhD Candidate
Georgia Institute of Technology
Atlanta, Georgia, United States

Co-Author(s)

JC

Jessica Chan

Student
Georgia Institute of Technology, United States
SE

Stanislav Y. Emelianov

Professor
Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University School of Medicine, United States
MK

Markus H. Kuehn

Professor
The University of Iowa, United States

Primary Investigator(s)

CE

C Ross Ethier

Professor
Georgia Institute of Technology
Atlanta, Georgia, United States

Introduction:: Glaucoma, which affects almost 80 million people worldwide, is the leading cause of irreversible blindness. The most common type, primary open angle glaucoma (POAG), is associated with elevated intraocular pressure (IOP) and thus all current clinical treatments aim to reduce IOP, albeit often with poor success rates. POAG patients show changes in the trabecular meshwork (TM), a key regulator of IOP, including accelerated loss of native TM cells. There is thus significant and growing interest in refunctionalizing the TM using stem cell therapy to treat POAG. Preclinical studies have been promising, yet there remain challenges, including poor delivery efficiency of injected cells to the TM. Recent approaches have used magnetic nanoparticles and “steering” to improve cell delivery to the TM and reduce off-target delivery, but the efficacy of such approaches has not been comprehensively characterized. Here we show that magnetically-steered TM cell therapy performs significantly better vs. the conventional delivery method, lowering the IOP by more than 25% in a mouse model of POAG persistently over 4 months.

Materials and Methods::

Human adipose-derived mesenchymal stem cells (MSCs, Lonza) were incubated overnight with superparamagnetic iron oxide nanoparticles (SA0150, Ocean NanoTech) at 50 µg/ml. Strongly labeled cells were selected by magnetic separation and resuspended at a final concentration of 1 k cells/µl in PBS. Cell injections were performed in 6-7 month old (baseline) Tg-MYOC^Y437H mice, a model of myocilin-associated glaucoma in humans. The animals remained anesthetized by isoflurane as the anterior chamber was cannulated with a needle connected to a microsyringe pump. 1.5 µl of the cell solution was delivered at 2.4 µl/min giving the experimenter enough time to carefully steer the cells to the TM by moving the tip of a magnetized rod (a thin stainless-steel rod connected to a permanent magnet) over the circumference of the limbus. A control cohort of transgenic animals received a sham injection of saline. IOP was measured by rebound tonometry (TonoLab, iCare) in isoflurane-anesthetized animals at the baseline for all experimental groups including non-injected wildtype (WT) and transgenic (Tg) mice, as well as at short-term (3-4 weeks post-injection) and long-term (14-16 weeks post-injection) time points for all injected eyes. Outflow facility was measured by enucleating the eyes and performing a perfusion experiment (iPerfusion) according to a standard protocol. In brief, the eyes were cannulated and stabilized at 8 mmHg followed by perfusion at eight evenly sized pressure steps starting at 4.5 mmHg and ending at 16.5 mmHg. Outflow facility was calculated as the ratio of the steady-state flow rate over IOP for each step.

Results, Conclusions, and Discussions::

MSC delivery led to a marked decrease in the IOP as compared to sham injections both in the short-term (12.8 [11.86,13.74 ] vs. 17.2 [16.2,18.3] mmHg, mean [95% confidence interval]; p< 10^-7) and long-term (12.4 [11.59,13.21 ] vs. 17.2 [15.8,18.6] mmHg; p < 10^-5; Fig. 1). This therapeutic effect was further confirmed by an approximately 3-fold increase in outflow facility of treated eyes compared to sham at both short-term (9.4 [6.5,13.6] nl/min/mmHg vs. 3.6 [2.5,5.1] nl/min/mmHg; p< 0.001) and long-term (8.7 [6.9,10.9] nl/min/mmHg vs.3 [2.1,4.3] nl/min/mmHg; p< 10^-5; Fig. 2A). No meaningful difference was found between the short- and long-term time points in terms of either IOP or outflow facility, indicating the stability of treatment over time. These findings highlight a significant improvement in therapeutic effectiveness using our magnetic delivery technique over the bolus injection approach used in previous studies in the same animal model. Notably, Zhu et al. injected 50,000 induced pluripotent stem cells differentiated to TM cells (iPSC-TMs) to obtain an ~80% increase in outflow facility, while we injected only 1,500 MSCs and recorded approximately a 3-fold increase in outflow facility (Zhu et al., 2016). Unexpectedly, Tg and WT mice showed no significant difference in IOP (p = 0.99) or outflow facility (p=0.86). While we are not certain of the cause, the close agreement between our experimental IOP and the expected IOP calculated using outflow facility measurements gives us confidence in the validity of our findings (p=0.06, n=5; Fig 2B). Interestingly, the lack of IOP elevation in our transgenic animals suggests that even greater IOP lowering might be attained by this treatment in a truly hypertensive glaucomatous eye. The consistency between IOP and facility measurements also indicates that our treatment is specifically affecting the conventional outflow pathway since a decrease in IOP caused by a lowered rate of aqueous humor production or increased unconventional outflow is unlikely to lead to an increase in outflow facility.

We conclude that this study, upon completion, will provide valuable insight on the efficacy and potential of this stem cell treatment for clinical translation in glaucoma patients.

Acknowledgements (Optional): :

Support: NIH grant R01 EY030071 (CRE, SYE, MHK) and the Georgia Research Alliance (CRE).

References (Optional): :

Zhu, W. Proc. Natl. Acad. Sci. 113, E3492–E3500 (2016).