hiPSC-Derived Cerebral Small Vessel Disease Models
Cerebral small vessel disease (cSVD) is an umbrella term of disorders that affect the small perforating arteries of the brain and is a major cause of stroke and dementia worldwide, but its pathology is yet to be known. We hypothesise that the integrity of the blood brain barrier (BBB) is disrupted and could contribute to increased BBB permeability. Evidence also shows a role of the extracellular matrix (ECM) in the progression of cSVD pathology. We generated *in-vitro* co-culture models using human induced pluripotent stem cells (hiPSCs) with COL4A1, COL4A2, and HTRA1 cSVD-related mutations to assess the shared role ECM plays in cSVD. These mutations induced tight junction abnormalities with Occludin discontinuity and Claudin-5 accumulation in hiPSCs-derived Brain Microvascular Endothelial Cells (iBMECs), which resulted in decreased TEER levels and increased permeability. They also induced apoptosis, migration defects, and transcriptome changes in hiPSCs-derived Mural Cells (iMCs). A co-culture system made of iBMECs and iMCs revealed that iMCs exert a detrimental paracrine effect on iBMECs barrier integrity. These models also expressed high levels of MMP- 14 and show an increase in MMP-2 and MMP-9 activity; inhibiting MMP activity with either doxycycline or shMMP-14 rescued both iBMECs and iMCs phenotypical changes. Our models revealed that iMCs secretome influences barrier integrity, and the shared ECM phenotype include increased MMP-14 levels and tight junction abnormalities, which confirm our hypothesis of barrier disruption leading to BBB leakage. Our rescue models also provide basis for MMP targeting as a therapeutic approach in cSVD.
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