# P-LM421E8, the heparan sulfate chain-conjugated laminin-421-E8 fragment, drives differentiation of human induced pluripotent stem cells into hematopoietic progenitor cells comparable to basic fibroblast growth factor in a chemically defined system

## TL;DR

A new protein, P-LM421E8, helps human stem cells become blood cell precursors as effectively as a common growth factor, possibly by boosting natural signals.

## Contribution

P-LM421E8 supports hematopoietic differentiation without exogenous bFGF, leveraging endogenous FGF signaling.

## Key findings

- P-LM421E8 generates CD34-high/CD117+ hematopoietic progenitor cells comparable to bFGF.
- HPCs from P-LM421E8 show enhanced natural killer cell differentiation potential.
- P-LM421E8 and bFGF do not show additive effects, suggesting similar signaling pathways.

## Abstract

•P-LM421E8 promotes HPC differentiation from hiPSCs comparably to bFGF.•hiPSCs cultured on P-LM421E8 yield HPCs with enhanced NK differentiation capacity.•P-LM421E8 drives HPC differentiation without bFGF, likely via endogenous FGF signals.

P-LM421E8 promotes HPC differentiation from hiPSCs comparably to bFGF.

hiPSCs cultured on P-LM421E8 yield HPCs with enhanced NK differentiation capacity.

P-LM421E8 drives HPC differentiation without bFGF, likely via endogenous FGF signals.

Human induced pluripotent stem cells (hiPSCs) are a promising source for cell-based and regenerative therapies. In this study, we developed and optimized a chemically defined differentiation protocol to generate hematopoietic progenitor cells (HPCs) from hiPSCs. We demonstrated that basic fibroblast growth factor (bFGF) plays a crucial role in enhancing HPC differentiation, particularly when applied during both the mesoderm (ME) and hematopoietic endothelial (HE) induction stages. Additionally, we explored the use of P-LM421E8, a recombinant fusion protein of laminin421-E8 fragment with domain 1 (D1) of perlecan possessing heparan sulfate (HS) chains. Our findings indicate that P-LM421E8 effectively supports HPC differentiation, generating stable CD34-high/CD117+ populations comparable to those produced with bFGF treatment. Furthermore, we observed that HPCs generated on P‑LM421E8‑coated surfaces exhibited superior natural killer (NK) cell differentiation potential. Although both P-LM421E8 and bFGF supported HPC differentiation, no significant additive effects were observed when used together. This suggests that P-LM421E8 can effectively support HPC differentiation without the need for exogenous bFGF, possibly through enhanced interaction with endogenous FGFs. The structural properties of P-LM421E8, which facilitate retention and presentation of FGFs via HS chains on its D1, may contribute to its effectiveness in promoting HPC development. Our findings establish P‑LM421E8 as a potent matrix for HPC differentiation and highlight its promise for refining hematopoietic protocols and advancing cell‑based immunotherapies.