WISP1 drives a mechanically active immune modulatory and proliferative cardiac myofibroblast state.

Pathological cardiac remodeling is driven by the proliferation and differentiation of resident fibroblasts into active myofibroblasts and results in excessive extracellular matrix (ECM) deposition and tissue stiffening. Expression of the matricellular protein WISP1 has previously been shown to be increased with cardiac fibrosis and promote myofibroblast activity, but the mechanisms by which this occurs remain unknown. Primary cardiac fibroblasts were isolated from adult mouse hearts and treated with recombinant WISP1 or TGFβ1 both alone and in combination to determine the functional role of the matricellular protein WISP1 in driving cardiac myofibroblast activity. WISP1 significantly increased alpha-smooth muscle actin and collagen type I expression, total collagen secretion, collagen gel contractility, and wound healing equally in fibroblasts from both male and female mice. However, WISP1 alone failed to induce expression of periostin, a hallmark myofibroblast marker, suggesting the resulting WISP1-dependent cell phenotype is unique and/or acting through non-canonical pathways. Indeed, inhibition of P38 MAPK completely ablated the WISP1-dependent increase in αSMA and collagen expression, while having little to no impact on TGFβ1-dependent expression of myofibroblast marker genes. We next employed a multi-omics approach to define the functional impact of WISP1 on fibroblast cell-state within the transcriptome, cytosolic, and secreted ECM proteome. RNA-seq results show that WISP1 broadly promotes the expression of proliferative and immune modulatory genes at the transcriptomic level, while having very little impact on traditional myofibroblast and ECM modifying gene expression programs. At the proteome level, WISP1 was again a much weaker mediator of traditional myofibroblast and ECM proteins. However, in agreement with RNA-seq data, we observed a strong WISP1-dependent enrichment for proliferation-associated proteins in the cytosolic proteome and inflammation-associated proteins in the ECM proteome. Interestingly, WISP1 also showed a context-dependent response with TGFβ1, suggesting a more complex and yet to be elucidated signaling interaction between these independent mediators of myofibroblast activity. In conclusion, our data suggests that WISP1 promotes a unique proliferative and immune-modulatory myofibroblast phenotype.