PDGFRβ Cells Research Articles

PDGFRβ Cells Rapidly Relay Inflammatory Signal from the Circulatory System to Neurons via Chemokine CCL2

Acute infection, if not kept in check, can lead to systemic inflammatory responses in the brain. Here, weshow that within 2hr of systemic inflammation, PDGFRβ mural cells of blood vessels rapidly secrete chemokine CCL2, which in turn increases total neuronal excitability by promoting excitatory synaptic transmission in glutamatergic neurons of multiple brain regions. By single-cell RNA sequencing, we identified Col1a1 and Rgs5 subgroups of PDGFRβ cells as the main source of CCL2. Lipopolysaccharide (LPS)- or Poly(I:C)-treated pericyte culture medium induced similar effects in a CCL2-dependent manner. Importantly, in Pdgfrb-Cre;Ccl2fl/fl mice, LPS-induced increase in excitatory synaptic transmission was significantly attenuated. These results demonstrate invivo that PDGFRβ cells function as initial sensors of external insults by secreting CCL2, which relays the signal to the central nervous system. Through their gateway position in the brain, PDGFRβ cells are ideally positioned to respond rapidly to environmental changes and to coordinate responses.

Single-Cell RNA Sequencing Identifies Functionally Distinct Fibro-inflammatory and Adipogenic Pdgfrr Progenitor Subpopulations in Visceral Adipose Tissue

White adipose tissue (WAT) remodeling is dictated by coordinated interactions between adipocytes and resident stromal-vascular cells; however, the functional heterogeneity of adipose stromal cells has remained unresolved. We combined single-cell RNA-sequencing and FACS to identify and isolate functionally distinct subpopulations of Pdgfrβ stromal cells within visceral WAT of adult mice. Ly6c- Cd9- Pdgfrβ cells represent highly adipogenic visceral adipocyte precursor cells (“APCs”), whereas Ly6c Pdgfrβ cells represent fibro-inflammatory progenitors (“FIPs”). FIPs lack adipogenic capacity, display pro-fibrogenic/proinflammatory phenotypes, and can exert an anti-adipogenic effect on APCs. The pro-inflammatory and adipogenic phenotypes of Pdgfrβ cells are regulated, at least in part, by Nr4a nuclear receptors. These data highlight the functional heterogeneity of visceral WAT perivascular cells, and provide insight into potential cell-cell interactions impacting adipogenesis and inflammation. These improved strategies to isolate FIPs and APCs from visceral WAT will facilitate the study of physiological WAT remodeling and mechanisms leading to metabolic dysfunction.

PDGFRα+ Progenitor Cells Contribute to Muscle Fibroadipogensis Following Massive Rotator Cuff Tears in a Mouse Model

Objectives:Rotator cuff tears affect an estimated 10% of patients over the age of 60, leading to significant activity related pain and decreased quality of life. After sustaining a tear, the rotator cuff musculature often undergoes muscle atrophy and fatty degeneration, which have been shown to result in poor clinical outcomes and high failure rates for surgical repairs. The cellular processes underlying these fibroadipogenic changes remain unknown although PDGFRβ+ cells have previously been implicated. Recently, it has been demonstrated in hind limb muscle that following acute, reversible injury via Cardiotoxin injection, PDGFRα-expressing cells are responsible for fibrotic and adipogenic muscle degeneration. Our study aimed to distinguish between the contribution of PDGFRα+ PDGFRβ+ cells and PDGFRα- PDGFRβ+ cells to fibroadipogenesis following massive rotator cuff tears.Methods:We performed supraspinatus tenotomy and denervation (TT+DN) operations on 8-10 week-old PDGFRβ-Cre x mTmG mice. These transgenic mice express GFP in cells co-expressing PDGFRβ, which allows PDGFRβ+ cell populations to be tracked via their GFP expression. At 5 days, 2-, 4- and 6-weeks postop, these mice and sham surgery controls were sacrificed and their supraspinatus muscles were harvested. We stained tissue sections with Oil Red O and Picro Sirius to compare levels of adipogenesis and fibrosis after TT+DN, respectively. In addition, sectioned muscle tissues were immuno-labeled with anti-PDGFRα and anti-PDGFRβ to assess differences in PDGFRα+ PDGFRβ+ cell localization. GFP expression was used to trace PDGFRβ cells and their progenies after TT+DN. Dissociated cells from supraspinatus tissue of TT+DN versus sham mice were either analyzed by flow cytometry for PDGFRα and GFP expression at established postop time points or sorted and cultured for in vitro differentiation experiments to assess the fibroadipogenic potential of these cell populations.Results:Oil Red O and Picro Sirius staining demonstrated that supraspinatus tissue reliably underwent significant fibroadipogenic changes that increased over time and were more pronounced 6 weeks following TT+DN. At 6 weeks following massive rotator cuff tears, PDGFRα+ GFP+ cells, GFP+ fibrotic tissue, and GFP+ adipocytes were detected in interstitial scar tissue (Fig. 1), indicating a contribution of PDGFRα+ PDGFRβ+ cells to fibroadipogenesis. Flow cytometry analyses revealed that the frequency of adipogenic PDGFRα+ sub-population was significantly increased 5 days postop and subsequently decreased to basal levels within 2 weeks. PDGFRα+ GFP+ cell populations were significantly more fibrogenic than other cell populations and increased fibrogenic potential was detected in PDGFRα cells from TT+DN mice in vitro (Table 1).Conclusion:PDGFRα+ fibroadipogenic progenitor cells directly contribute to post-injury rotator cuff fibroadipogenesis in a mouse model of massive rotator cuff tears. This cell population likely contributes to muscle atrophy and fatty degeneration of the rotator cuff in human pathology as well. With further development of clinical protocols, perioperative inhibition of this cell population or depletion of PDGFRα+ cells prior to cell transplantation in a regenerative treatment strategy may diminish fatty degeneration and improve clinical outcomes associated with rotator cuff tears.

Redistribution of PDGFRβ cells and NG2DsRed pericytes at the cerebrovasculature after status epilepticus

PurposeThe role of cerebrovascular dysfunction in seizure disorders is recognized. Blood–brain barrier (BBB) damage in epilepsy has been linked to endothelial and glial pathophysiological changes. Little is known about the involvement of pericytes, a cell type that contributes to BBB function. MethodsNG2DsRed mice were used to visualize cerebrovascular pericytes. The pattern of vascular and parenchymal distributions of platelet-derived growth factor receptor beta (PDGFRβ) cells was evaluated by immunohistochemistry. Status epilepticus was induced in NG2DsRed or C57BL/6J mice by intraperitoneal kainic acid (KA). Animals were perfused intracardially using FITC-Dextran or FITC-Albumin to visualize the cerebrovasculature. Colocalization was performed between NG2DsRed, PDGFRβ and microglia IBA-1. Confocal 3D vessel reconstruction was used to visualize changes in cell morphology and position. PDGFRβ expression was also evaluated in vitro using organotypic hippocampal cultures (OHC) treated with kainic acid to induce seizure-like activity. Co-localization of PDGFRβ with the vascular marker RECA-1 and NG2 was performed. Finally, we assessed the expression of PDGFRβ in brain specimens obtained from a cohort of patients affected by drug resistant epilepsy compared to available autoptic brain. ResultsIn vivo, severe status epilepticus (SE) altered NG2DsRed vascular coverage. We found dishomogenous NG2DsRed perivascular ramifications after SE and compared to control. Concomitantly, PDGFRβ+ cells re-distributed towards the cerebrovasculature after severe SE. Cerebrovascular NG2DsRed partially colocalized with PDGFRβ+ while parenchymal PDGFRβ+ cells did not colocalize with IBA-1+ microglia. Using in vitro OHC we found decreased NG2 vascular staining and increased PDGFRβ+ ramifications associated with RECA-1+ microvessels after seizure-like activity. Cellular PDGFRβ and NG2+ colocalization was observed in the parenchyma. Finally, analysis of human TLE brains revealed perivascular and parenchymal PDGFRβ+ cell distributions resembling the murine in vivo and in vitro results. PDGFRβ+ cells at the cerebrovasculature were more frequent in TLE brain tissues as compared to the autoptic control. ConclusionsThe rearrangement of PDGFRβ+ and vascular NG2DsRed cells after SE suggests a possible involvement of pericytes in the cerebrovascular modifications observed in epilepsy. The functional role of vascular–parenchymal PDGFRβ+ cell redistribution and the relevance of a pericyte response to SE remain to be fully elucidated.