Brain PDGFRβ⁺ Cells Exhibit Diverse Reactive Phenotypes After Stroke Without Requiring KLF4

The pathobiology of ischemic stroke is associated with the activation of brain platelet-derived growth factor receptor (PDGFR)β⁺ perivascular cells. While Krüppel-like factor (KLF)4 is a well-established mediator of peripheral PDGFRβ⁺ cell activation, its role in brain PDGFRβ⁺ cells remains elusive. Herein, we aimed to characterize the spatiotemporal reactivity of brain PDGFRβ⁺ cells, while assessing KLF4 contribution upon experimental ischemic stroke using transgenic mice that enable tracking PDGFRβ⁺ cells or conditionally depleting KLF4 in PDGFRβ⁺ cells. Moving beyond the qualitative descriptors, we sought to develop point pattern analysis (PPA) and topological data analysis (TDA) workflows to generate robust and reusable mathematical models to assess spatial cell responses and tissue scar topological changes. First, we report the emergence of phenotypically distinct reactive parenchymal PDGFRβ⁺ cells, which cannot be causally and exclusively linked, as it is currently proposed, to local cell proliferation or adjacent vascular detachment. Furthermore, we show that KLF4 is barely expressed in brain PDGFRβ⁺ cells under normal conditions and that it is only marginally induced in reactive PDGFRβ⁺ cells at the injured brain. Notably, the conditional attenuation of KLF4 expression specifically in reactive PDGFRβ⁺ cells does not alter spatial cellular distribution nor scar organization. This suggests that, in contrast to peripheral PDGFRβ⁺ cells upon ischemic insults, KLF4 is not a main regulator of the reactivity of brain cells in response to ischemic stroke. Ultimately, our findings supported by open-source spatiotemporal models indicate that the reactivity of brain PDGFRβ⁺ perivascular cells is highly heterogeneous and fundamentally distinct from peripheral PDGFRβ⁺ cells.