Peripheral blood-derived monocytes show neuronal properties and integration in immune-deficient rd1 mouse model upon phenotypic differentiation and induction with retinal growth factors

Abstract

Background Cell therapy is one of the most promising therapeutic interventions for retinitis pigmentosa. In the current study, we aimed to assess if peripheral blood-derived monocytes which are highly abundant and accessible could be utilized as a potential candidate for phenotypic differentiation into neuron-like cells. Methods The peripheral blood-derived monocytes were reconditioned phenotypically using extrinsic growth factors to induce pluripotency and proliferation. The reconditioned monocytes (RM) were further incubated with a cocktail of growth factors involved in retinal development and growth to induce retinal neuron-like properties. These cells, termed as retinal neuron-like cells (RNLCs) were characterized for their morphological, molecular and functional behaviour in vitro and in vivo. Results The monocytes de-differentiated in vitro and acquired pluripotency with the expression of prominent stem cell markers. Treatment of RM with retinal growth factors led to an upregulation of neuronal and retinal lineage markers and downregulation of myeloid markers. These cells show morphological alterations resembling retinal neuron-like cells and expressed photoreceptor (PR) markers. The induced RNLCs also exhibited relative membrane potential change upon light exposure suggesting that they have gained some neuronal characteristics. Further studies showed that RNLCs could also integrate in an immune-deficient retinitis pigmentosa mouse model NOD.SCID-rd1 upon sub-retinal transplantation. The RNLCs engrafted in the inner nuclear layer (INL) and ganglion cell layer (GCL) of the RP afflicted retina. Mice transplanted with RNLCs showed improvement in depth perception, exploratory behaviour and the optokinetic response. Conclusions This proof-of-concept study demonstrates that reconditioned monocytes can be induced to acquire retinal neuron-like properties through differentiation using a defined growth media and can be a potential candidate for cell therapy-based interventions and disease modelling for ocular diseases.

Transplantation of retinal pigment epithelium and photoreceptors generated concomitantly via small molecule-mediated differentiation rescues visual function in rodent models of retinal degeneration

“…NOD.SCID-rd1 mouse, developed in NII, New Delhi [ 15 , 22 ], is a double knockout model ( PDE6B−/− PRKDC−/− ) that mimics RP with slow-progressing photoreceptor degeneration. The model is bereft of photoreceptors by P28 and does not have functional adaptive immunity.…”

“…Neuroprotection and photoreceptor rescue through transplanted photoreceptor progenitors/precursors cells have been shown in the rd1 mouse and Gnat −/− mouse model of night blindness [ 34 , 42 ]. Very recently, our collaborators demonstrated that peripheral blood-derived monocytes show neuronal properties and integration in immune-deficient rd1 mouse model upon phenotypic differentiation and induction with retinal growth factors [ 22 ]. Previously, they reported that while BALB/c displayed an intact retina, CBA/J and NOD.SCID-rd1 lost their outer segment (rod cells) of the photoreceptor layer and ONL in 4 weeks.…”

Comparing stem cells, transdifferentiation and brain organoids as tools for psychiatric research

“…While one team did not [ 126 ], several independent laboratories, including ours, encountered that a subpopulation of monocytes can proliferate under certain culture conditions. [ 114 – 116 , 123 , 127 ] We only found a small degree of replication, which in our hands, limits the expandability of pluripotent monocytes [ 114 ]. In contrast, Zhao and colleagues were able to expand and store these cells for future experiments [ 115 ].…”

“…In contrast, Zhao and colleagues were able to expand and store these cells for future experiments [ 115 ]. Results from Mishra et al suggest replication in pluripotent monocytes is only temporary, peaking at day 6 and abating by day 10 [ 127 ]. These discrepancies in replication rates could be explained by methodological differences in generating pluripotent monocytes.…”

iTreg mediated TGF-Β1 therapy improves functional engraftment of cell therapy in rd1 Retinitis Pigmentosa mouse model

“…We transplanted iTregs in the sub-conjunctiva, leading to a sustained release of TGF-Β1 into the retina of 4 weeks old rd1 in-vitro-generated Retinal Neuron Like Cells (RNLCs) as cell therapy in the study [32]. These RNLCs were generated from blood monocytes in a two-step culture procedure and shown to be functionally similar to retinal cells including photoreceptors and can rescue vision perception in the rd1 model [32]. We then evaluated whether the adjunct TGF-Β1 treatment could improve the survival of cell therapy and hence rescue vision in the rd1mouse model.…”