A novel postbiotic from Lacticaseibacillus rhamnosus CRL1505 able to enhance the steady-state myelopoiesis

The myelopotentiating effect of postbiotics derived from the probiotic Lacticaseibacillus rhamnosus CRL1505, including the peptidoglycan (PG1505), and the cell wall (CW1505), was evaluated in cyclophosphamide (Cy)-immunosuppressed mice. Adult Swiss mice were orally treated with the CRL1505 strain, the PG1505, or the CW1505 for 15 consecutive days. On day 6, both treated groups and untreated control mice received a single intraperitoneal dose of Cy. Cy administration impaired steady-state myelopoiesis. However, the CW1505 and the CRL1505 strain promoted a significant increase in bone marrow (BM) LSK cells (Lin^-Sca1⁺c-kit⁺), myeloid multipotent precursors (MPP: Lin^-Sca-1⁺c-Kit⁺CD34⁺) and mitotic pool cells. Moreover, both the CW1505 and the CRL1505 strain were the only treatments able to reduce the BM cells undergoing apoptosis at five days post-Cy administration. Consequently, CW1505 minimized leukopenia and promoted a faster recovery of BM mature myeloid cells (Ly6G⁺Gr-1⁺Ly6C^-), as well as blood leukocytes and neutrophils. Additionally, a comparative study with other postbiotics demonstrated that the myelopotentiating properties of the CW1505 are strain-specific.