C-Type Natriuretic Peptide Signaling Promotes Bone Marrow Hematopoietic Regeneration and Alleviates Systemic Lymphopenia

Lymphopenia, a condition of lower-than-normal levels of lymphocytes, is associated with compromised immune function, increased susceptibility to infections, and unfavorable outcomes, particularly for cancer patients administered with chemotherapy. Chemotherapy-induced damage to hematopoietic stem cells (HSC) and bone marrow (BM) microenvironment by genotoxic stress leads to impaired HSC regeneration and lymphoid differentiation, which are fundamental mechanisms underlying treatment-related lymphopenia. The intricate interactions between HSC and BM stromal cells regulate stem cell maintenance and lymphocyte production. However, their dynamic underlying molecular mechanisms remain elusive, and treatment strategies for facilitating HSC regeneration and lymphoid differentiation in patients upon chemotherapy remain underdeveloped. To depict the potential hematopoiesis regulators, by analyzing Single-cell RNA sequencing (scRNA-seq) data from eight healthy donors in the human cell atlas, we found that natriuretic peptide receptor C (NPR-C) is predominantly expressed in HSC and megakaryocyte progenitors but negatively in lymphoid progenitors. We generated single-nucleotide knockin mice harboring NPR-C isoleucine 384 to phenylalanine mutant (Nprc^I384F/I384F mice), leading to NPR loss of function. These mice exhibited enhanced BM HSC pluripotency, increased lymphoid differentiation, and elevated peripheral lymphocyte status revealed by scRNA-seq, CyTOF and Complete Blood Test. Mechanistically, enhanced C-type natriuretic peptide (CNP) signaling in Nprc^I384F/I384F mice promotes HSC self-renewal and lymphoid differentiation through stroma cell-mediated HSC maintenance in a cyclic GMP (cGMP)-dependent manner. Importantly, Nprc^I384F/I384F mice maintained higher peripheral lymphocyte levels post-carboplatin challenge, suggesting that activation of CNP signaling resisted chemotherapy-induced lymphopenia. Clinically, the expression of CNP signaling gene signature is significantly associated with increased presence of HSC and lymphoid progenitor, enhanced mesenchyme development, and improved HSC-supporting networks by RNA-seq data analyses of human BM biopsies. Hence, the CNP-triggered signaling cascade in the BM niche promotes HSC regeneration and lymphoid differentiation, antagonizing systemic lymphopenia following genotoxic stress. Our study elucidates the cooperative mechanisms between HSC and stromal cells mediated by CNP-triggered cascades within the BM microenvironment, providing mechanistic insights regarding mitigating stress-induced lymphopenia.