Dual Functions of Pericytes and Perivascular Fibroblasts in Cerebrovascular Regeneration After Stroke

Academic Background

Stroke is one of the leading causes of death and disability worldwide. Current therapeutic interventions are mostly limited to acute thrombolytic treatment or thrombectomy, followed by long-term rehabilitation. However, the long-term recovery from stroke is limited, especially regarding cerebrovascular regeneration and functional restoration, which remains a significant challenge. Revascularization is key to supporting tissue regeneration after stroke, as restored blood flow is necessary to provide oxygen and nutrients needed for the implantation of parenchymal neural cells. This process relies on the regeneration of perivascular stroma. Stromal progenitor cells (SPCs) play a crucial role in tissue regeneration in many organs, but the identity and function of SPCs in the brain remain unclear. This study aims to uncover the identity of SPCs in the brain and their roles in cerebrovascular regeneration after stroke, providing new therapeutic targets for neurological recovery post-stroke.

Source of the Paper

This paper was collaboratively completed by scientists including Louis-Philippe Bernier and Jasmin K. Hefendehl from institutions such as the University of British Columbia and Goethe University Frankfurt. The paper was published online in the journal Nature Neuroscience on December 18, 2024, with the DOI: 10.1038/s41593-025-01872-y.

Research Process

Study Subjects and Methods

This study used adult mice as experimental subjects and simulated stroke using a photothrombotic model. The research was mainly divided into the following steps:

1. Establishment and Observation of Stroke Model
   Researchers induced photothrombotic stroke in the somatosensory cortex of mice and subsequently observed cerebrovascular regeneration over 21 days. Using techniques such as optical coherence tomography (OCT) and two-photon microscopy, researchers tracked the reformation and functional recovery of blood vessels after stroke.

2. Tracking of Hic1+ Cells
   To study the distribution and function of SPCs, researchers used transgenic mice marked with the Hic1 gene (Hic1creERT2; Rosa26lsl-tdtomato). By inducing with tamoxifen, researchers labeled Hic1+ cells and their progeny, observing the distribution and functional changes of these cells at different time points after stroke.

3. Single-cell RNA Sequencing (scRNA-seq)
   Researchers performed single-cell RNA sequencing on Hic1+ cells seven days after stroke, analyzing their transcriptomic characteristics. By comparing with the undamaged contralateral hemisphere, researchers identified the transcriptional features of activated pericytes and perivascular fibroblasts after stroke.

4. Cell Proliferation and Migration Studies
   Through EdU labeling, researchers studied the proliferation of Hic1+ cells after stroke. Additionally, using time-lapse imaging technology, researchers observed the migration behavior of these cells after stroke.

5. Vascular Regeneration and Blood-Brain Barrier (BBB) Recovery
   Researchers evaluated vascular regeneration and BBB recovery 21 days after stroke, detecting BBB integrity by injecting dyes of different sizes (such as Evans Blue and Cadaverine).

Main Results

1. Cerebrovascular Regeneration and Accumulation of Hic1+ Cells After Stroke
   The study found that seven days after stroke, Hic1+ cells significantly accumulated in the ischemic area and were closely associated with endothelial cells. These cells gradually migrated towards the ischemic core within 21 days, accompanied by the reformation of blood vessels.

2. Diversity of Hic1+ Cells
   Single-cell RNA sequencing results showed that Hic1+ cells mainly include pericytes, venular smooth muscle cells (SMCs), and perivascular fibroblasts. These cells exhibited different transcriptional features after stroke, with pericytes tending towards angiogenesis and fibroblasts towards fibrotic scar formation.

3. Cell Proliferation and Migration
   Seven days after stroke, Hic1+ cells showed significant proliferative ability, with approximately 69.9% of new cells being EdU-positive. Additionally, these cells exhibited high migratory ability within the ischemic region, detaching from their original vascular structures.

4. Vascular Regeneration and BBB Recovery
   Twenty-one days after stroke, Hic1+ cells re-associated with functional blood vessels, forming a stable blood-brain barrier. Through dye injection experiments, researchers confirmed the restoration of BBB integrity.

Conclusions and Significance

This study reveals the identity of SPCs in the brain and their dual functions in cerebrovascular regeneration after stroke. Pericytes primarily participate in angiogenesis, while perivascular fibroblasts promote fibrotic scar formation. This discovery provides new therapeutic targets for neurological recovery after stroke, particularly through promoting angiogenesis or modulating fibrotic responses to improve long-term rehabilitation outcomes after stroke.

Research Highlights

1. Diversity of Hic1+ Cells
   The study, for the first time, comprehensively analyzed the diversity of Hic1+ cells in the brain through single-cell RNA sequencing technology, including pericytes, venular smooth muscle cells, and perivascular fibroblasts.

2. Dynamic Changes of Cells After Stroke
   The study detailed the proliferation, migration, and functional changes of Hic1+ cells after stroke, revealing the critical role of these cells in cerebrovascular regeneration.

3. Balance Between Angiogenesis and Fibrosis
   The study highlights the different roles of pericytes and perivascular fibroblasts in tissue repair after stroke, providing an important theoretical basis for future therapeutic strategies.

Other Valuable Information

This study also developed an online searchable database (Integrated Single-cell Navigation Portal, iSNAP), through which researchers can browse all single-cell sequencing data to further explore the functions and regulatory mechanisms of cells after stroke. This resource provides an important tool and reference for future research.

This study not only reveals the identity and functions of SPCs in the brain but also provides new therapeutic insights for cerebrovascular regeneration and functional recovery after stroke.