Prednisolone induces microglial activation in the subnucleus caudalis of the rat trigeminal sensory complex

Soluble CX3CL1-expressing retinal pigment epithelium cells protect rod photoreceptors in a mouse model of retinitis pigmentosa

BACKGROUND

Retinitis pigmentosa (RP) is an inherited retinal disease that results in photoreceptor degeneration, leading to severe vision loss or blindness. Due to its genetic heterogeneity, developing a new gene therapy to correct every genetic mutation contributing to its progression is infeasible. Photoreceptor transplantation can be harnessed to restore vision; however, this approach is limited by poor cell survival and synaptic integration into the neural retina. Thus, we developed a combined cell and gene therapy that is expected to protect photoreceptors in most, if not all, cases of RP.

METHODS

Human embryonic stem cells (hESCs) modified with our FailSafe™ system were genetically engineered to overexpress sCX3CL1, an inhibitor of microglia activation that has been shown to preserve photoreceptor survival and function in mouse models of RP, independent of the genetic cause. These cells were differentiated into human retinal pigment epithelium (hRPE) cells and used as therapeutic cells due to their longevity and safety, both of which have been demonstrated in preclinical and clinical studies. Transgenic hRPE were delivered into the subretinal space of immunodeficient mice and the rd10 mouse model of RP to evaluate donor cell survival and retention of transgene expression. The outer nuclear layer was quantified to assess photoreceptor protection.

RESULTS

Transgenic FailSafe™ hRPE (FS-hRPE) cells can survive for at least four months in the retina of immunodeficient mice and retain transgene expression. However, these cells do not persist beyond two weeks post-injection in the retina of immunocompetent rd10 recipients, despite Cyclosporine A treatment. Nevertheless, sCX3CL1-expressing FailSafe™ hRPE cells prevented photoreceptor degeneration in a local acting manner during the duration of their presence in the subretinal space.

CONCLUSIONS

Transgenic hESCs differentiate into hRPE cells and retain sCX3CL1 transgene expression both in vitro and in vivo. Moreover, hRPE cells delivered to the subretinal space of rd10 mice prevented photoreceptor degeneration in a local-acting manner, suggesting that this approach could have applications for preserving photoreceptors in specific subregions of the retina, such as the macula. Overall, our study not only reveals the potential of a combined cell and gene therapy for the treatment of RP, but also the possibility of using hRPE cells to deliver therapeutic biologics in situ to treat diseases over long-term.

Orofacial skin inflammation increases the number of macrophages in the maxillary subregion of the rat trigeminal ganglion in a corticosteroid-reversible manner

Inflammation of the cutaneous orofacial tissue can lead to a prolonged alteration of neuronal and nonneuronal cellular functions in trigeminal nociceptive pathways. In this study, we investigated the effects of experimentally induced skin inflammation by dithranol (anthralin) on macrophage activation in the rat trigeminal ganglion. Tissue localization and protein expression levels of ionized calcium-binding adaptor molecule 1 (Iba1), a macrophage/microglia-specific marker, and proliferation/mitotic marker antigen identified by the monoclonal antibody Ki67 (Ki67), were quantitatively analyzed using immunohistochemistry and western blots in control, dithranol-treated, dithranol- and corticosteroid-treated, and corticosteroid-treated trigeminal ganglia. Chronic orofacial dithranol treatment elicited a strong pro-inflammatory effect in the ipsilateral trigeminal ganglion. Indeed, daily dithranol treatment of the orofacial skin for 3-5 days increased the number of macrophages and Iba1 protein expression in the maxillary subregion of the ipsilateral ganglion. In the affected ganglia, none of the Iba1-positive cells expressed Ki67. This absence of mitotically active cells suggested that the accumulation of macrophages in the ganglion was not the result of resident microglia proliferation but rather the extravasation of hematogenous monocytes from the periphery. Subsequently, when a 5-day-long anti-inflammatory corticosteroid therapy was employed on the previously dithranol-treated orofacial skin, Iba1 immunoreactivity was substantially reduced in the ipsilateral ganglion. Collectively, our findings indicate that both peripheral inflammation and subsequent anti-inflammatory therapy affect macrophage activity and thus interfere with the functioning of the affected sensory ganglion neurons.

Nerve Injury Increases the Expression of Alpha-2/Delta-1 Subunit of L-Type Calcium Channel in Sensory Neurons of Rat Spinal and Trigeminal Nerves

By immunohistochemistry, an effect of nerve injury on distribution of alpha-2/delta-1 subunit of L-type calcium channel was investigated in rat's 4th and 5th lumbar dorsal root ganglia (DRGs), trigeminal ganglion (TG), and mesencephalic trigeminal nucleus (Mes5). The immunoreactivity was expressed by 52.2% of DRG neurons and 31.4% of TG neurons in intact animals. These neurons mostly had small-to-medium-sized cell bodies. In the DRG and TG, alpha-2/delta-1 subunit-positive neurons were lightly or moderately stained. However, the number of alpha-2/delta-1 subunit-immunoreactive (-IR) neurons dramatically increased in the ipsilateral DRG at 3-28 days after sciatic nerve transection (75.3-79.5%) and in the ipsilateral TG at 7 days after infraorbital nerve transection (66.3%). The IR density of alpha-2/delta-1 subunit in DRG and TG neurons was also elevated by the transection. In the injured DRG and TG, many sensory neurons with small-to-medium-sized cell bodies were strongly stained. Some large DRG and TG neurons showing strong staining intensity also appeared after the treatment. In the intact Mes5, sensory neurons were mostly devoid of alpha-2/delta-1 subunit-immunoreactivity (0.4%). However, alpha-2/delta-1-IR sensory neurons on the ipsilateral side of the Mes5 dramatically increased at 7 days after masseteric nerve transection (31.3%). A double immunofluorescence method also demonstrated that c-Jun activating transcription factor 3 (ATF3)-positive DRG (98.3-99.9%) and Mes5 (81.8%) neurons mostly co-expressed alpha-2/delta-1 subunit after the nerve injuries. However, alpha-2/delta-1 subunit immunoreactivity was relatively infrequent among ATF3-immunonegative DRG neurons (51.6-74.1%) and Mes5 neurons (<1%). The present study indicates that the nerve injury increases the protein level of alpha-2/delta-1 subunit among several types of axotomized sensory neurons in the spinal and trigeminal nervous systems.

Dentin hypersensitivity-like tooth pain seen in patients receiving steroid therapy: An exploratory study

To ascertain whether steroid therapy evokes dentin hypersensitivity (DH)-like tooth pain, we performed a study based on compelling evidence from patients receiving steroid therapy. An exploratory study was conducted using a questionnaire for 220 patients prescribed steroids who attended the Department of Hematology and Rheumatology of Tohoku University Hospital. Group comparisons between patients with and without steroid pulse therapy were analysed by statistical means. In this study, any DH-like tooth pain that commenced subsequent to steroid treatment was defined as steroid-derived (SD) tooth pain. The prevalence of SD tooth pain was 17.7% (39/220 patients). SD tooth pain was triggered in many vital teeth by cold and/or hot water (84.2% and 23.7%, respectively) with the pain characterised as continuous, in contrast to typical DH tooth pain. SD tooth pain was significantly more frequent in pulse therapy patients than in non-pulse therapy patients (p < 0.05). Logistic regression analysis adjusted for age and sex showed similar results (odds ratio = 3.74, p = 0.013). Moreover, a positive correlation was observed between the steroid dose and pain score (ρ = 0.642). Dose reduction or discontinuation of steroid therapy relieved SD tooth pain in all cases. Thus, steroid therapy can evoke DH-like tooth pain during treatment.