The cell and gene therapy industry is advancing rapidly, and for clinical-grade cytokines — the critical raw materials behind ex vivo cell expansion and differentiation — batch-to-batch consistency, safety, and a complete documentation chain directly determine the process reproducibility and regulatory timelines of clinical programs.
For hematopoietic stem cell (HSC) expansion, megakaryocyte-directed differentiation, and iPSC-derived hematopoiesis, we are pleased to introduce GMP-grade Recombinant Human TPO (Thrombopoietin) — a compliant, audit-ready cytokine raw material solution for preclinical research and IND filing.
TPO (thrombopoietin) is a key hematopoietic growth factor that regulates megakaryocyte proliferation and maturation and platelet production. It also plays a vital role in ex vivo culture of hematopoietic stem and progenitor cells (HSPCs). Commonly used with SCF, Flt3L and IL-family cytokines, it supports ex vivo HSC expansion and directed differentiation. Applications include HSC research, iPSC-derived hematopoietic differentiation, ex vivo platelet generation and cell therapy manufacturing. Standard research-grade TPO is suitable only for basic laboratory research. Limitations in endotoxin levels, host-cell residues, batch-to-batch consistency and supporting documentation can make it unsuitable for the raw-material release and regulatory filing requirements of clinical programs, creating a bottleneck in the transition from research to clinical development.
1. Biological functions of TPO
TPO is synthesized and secreted primarily by the liver and is the hematopoietic cytokine at the heart of the megakaryocyte-platelet axis. Its receptor, c-Mpl, is expressed on hematopoietic stem and progenitor cells, on cells at every stage of the megakaryocytic lineage, and on platelets.
Megakaryocyte development and platelet production (core function)
• Megakaryocyte Maturation: Acts directly on bone marrow megakaryocytic progenitors to promote proliferation, differentiation, and maturation, fueling dramatic cell enlargement and polyploidization.
• Platelet Biogenesis: Triggers mature megakaryocytes to shed their cytoplasm, generating functional circulating platelets and directly maintaining systemic platelet homeostasis.
• Compensatory Feedback: Sustains baseline peripheral platelet counts. When platelet levels drop, TPO expression rises compensatorily to accelerate platelet recovery.
Supporting Hematopoietic Stem and Progenitor Cells (HSPCs)
• Stemness Maintenance: Supports the quiescence, survival, and self-renewal of hematopoietic stem cells, safeguarding their long-term stemness.
• Synergistic Expansion: In ex vivo cultures, TPO teams up with factors like SCF and Flt-3L to significantly boost the expansion of CD34⁺ hematopoietic stem and progenitor cells.
• Multi-Lineage Support: Beyond the megakaryocytic lineage, TPO participates in broader hematopoietic regulation, promoting the survival of various myeloid progenitors.
Regulating Platelet Survival and Function
• Lifespan Control: Binds to c-Mpl on the platelet surface to help modulate and maintain platelet survival time.
• Activation Tuning: Modestly enhances platelet activation sensitivity, fine-tuning downstream hemostatic signaling pathways.
Other biological effects
• Participates in bone-marrow reconstitution after hematopoietic injury, mediating recovery following radiation- or chemotherapy-induced myelosuppression.
• An essential factor for directing iPSC differentiation toward the megakaryocyte/platelet lineage in ex vivo hematopoietic differentiation systems.
• Expressed at low levels in non-hematopoietic tissues, where it contributes to tissue repair, though this is not its principal function.
2. TPO signaling pathway
Overall activation cascade
TPO binds c-MPL on the cell membrane, inducing receptor homodimerization and a conformational change. The intracellular Box1/Box2 motifs bind and activate pre-associated JAK2 as the primary kinase, with TYK2 playing a secondary role. JAK2 autophosphorylates and phosphorylates tyrosine residues on the c-MPL intracellular domain, creating docking sites for SH2-domain proteins and activating three major downstream pathways: JAK2-STAT5/STAT3, RAS-MAPK-ERK and PI3K-AKT.
JAK2-STAT (core pathway)
• JAK2 phosphorylates receptor tyrosines and recruits STAT5 (dominant) and STAT3;
• STATs undergo tyrosine phosphorylation, dimerize, and translocate to the nucleus;
• Target genes: Cyclin D1, Bcl-xL, c-Myc, P27.
• Function: STAT5 drives megakaryocyte progenitor proliferation, anti-apoptotic signaling, and megakaryocyte maturation, and sustains HSC self-renewal; STAT3 is more engaged in stress, inflammatory, and liver-regeneration responses. Phospho-readouts: p-JAK2, p-STAT5 (Y694), and p-STAT3 (Y705).
RAS-MAPK-ERK pathway (differentiation)
• Upon receptor phosphorylation, the Grb2-SOS complex is recruited, activating the Ras-Raf-MEK-ERK1/2 cascade.
• Function: promotes megakaryocyte differentiation, maturation, and proplatelet formation; prolonged stimulation skews cells toward a differentiated phenotype and upregulates c-Myc to advance the cell cycle.
PI3K-AKT pathway (survival and metabolism)
• After JAK2 phosphorylates the receptor, PI3K is recruited, generating PIP3 and activating AKT.
• Function: suppresses apoptosis, supports cell survival and metabolic reprogramming, and protects progenitor viability.
Negative-feedback regulation (pathway termination)
• SOCS1/SOCS3 (primary): STAT-driven transcription upregulates SOCS, which binds JAK2 and the receptor to inhibit kinase activity and mediate ubiquitin-proteasomal degradation.
• SHP1 phosphatase: directly dephosphorylates JAK2 and the receptor for rapid signal shutdown.
• LNK and PIAS proteins: suppress STAT transcriptional activity.
• Receptor internalization and degradation: the TPO-MPL complex is internalized and TPO degraded, damping the signal; platelets act as a sponge for circulating TPO via MPL, maintaining systemic homeostasis.
Figure 1. TPO signaling pathway
3. Core application scenarios
Ex vivo expansion of hematopoietic stem cells (HSCs)
• TPO is an indispensable core factor in HSC self-renewal and expansion cultures. It is typically combined with SCF, Flt-3L, and IL-6 to preserve stemness and drive proliferation in the development of ex vivo expansion systems GMP-grade material meets the safety and compliance requirements that cell-therapy raw materials must satisfy for IND/NDA filings.
![Figure 2. Components of ex vivo HSC culture systems [1]](https://cdn.shopify.com/s/files/1/0803/9419/1166/files/37_0d8a60b2-1ff5-49f2-bff5-81897d13c2cc.png?v=1793000101)
Figure 2. Components of ex vivo HSC culture systems [1]
Ex vivo platelet generation
• TPO is the core cytokine for producing functional platelets ex vivo from iPSC- or cord-blood-derived stem cells, supporting platelet-like particle manufacture and the development of blood substitutes.
Megakaryocyte differentiation
• Guides CD34⁺ HSCs and iPSC-derived HSCs toward megakaryocyte differentiation ex vivo; TPO engages the c-Mpl receptor to drive megakaryocyte proliferation, maturation, and polyploidization.
Hematopoietic organoid construction
• Supports bone-marrow organoid and hematopoietic-niche models that recapitulate the in vivo microenvironment for studying hematopoietic development and thrombopoiesis.
Drug discovery and pharmacodynamic evaluation
• TPO receptor agonist screening: serves as the positive control for small-molecule TPO-receptor agonists and antibody therapeutics.
• Thrombocytopenia pharmacology models: evaluates the effects of candidate drugs on megakaryocyte proliferation and platelet production; supports early pharmacodynamic assessment for ITP and chemotherapy-induced thrombocytopenia therapies.
• Neutralizing-antibody detection: serves as a reference standard for detecting anti-TPO neutralizing antibodies during antibody-drug development.
In vivo animal studies
• Dosing studies in thrombocytopenia animal models to evaluate platelet-raising efficacy in vivo, together with pharmacokinetic and toxicological support.
4. YEASEN GMP-grade recombinant human TPO
This recombinant human TPO is produced using a high-efficiency eukaryotic expression system to preserve its native conformation and biological activity. It specifically binds the c-Mpl receptor and activates downstream signaling. Unlike standard research-grade products, it is manufactured, purified, quality-controlled and packaged in accordance with GMP requirements, with traceability throughout the process. This approach helps avoid batch variability, contamination risks and compliance gaps associated with conventional protein raw materials, providing a GMP-grade raw material for preclinical research, regulatory submissions and industrial production.
Product advantages
• High purity: greater than 95%, minimizing immune reactions caused by host-cell protein (HCP) or residual host-cell DNA.
• Batch-to-batch consistency: safeguards the stability and reproducibility of cell culture processes.
• Regulatory compliance: meets the regulatory expectations for cell-therapy products and supports IND filings.
• Animal-origin-free: free of animal viruses, pathogenic substances and adventitious contamination, with a high safety profile.
Adherence to regulatory standards
GMP-grade protein production and quality control conform to the following systems and processes:
• Chinese Pharmacopoeia, 2020 edition, Volume III, general requirements — quality control of raw materials and excipients used in the manufacture of biological products;
• USP General Chapter <92>, Growth Factors and Cytokines Used in Cell Therapy Manufacturing;
• Ph. Eur. General Chapter 5.2.12, Raw Materials of Biological Origin for the Production of Cell-based and Gene Therapy Medicinal Products.
Quality management system
• GMP proteins are manufactured, tested, and released under an ISO 13485:2016-certified quality management system, ensuring batch-to-batch consistency and material traceability;
• Approved certificate of analysis (COA) provided;
• No animal-derived materials and no animal-origin production environment;
• Manufacturing site for pharmaceutical starting materials and excipients;
• On-site and virtual audits supported.
Quality and safety testing
• Residual host-cell DNA: < 20 ng/mg;
• Residual host-cell protein: < 0.5 ng/μg;
• Sterility test: positive;
• Mycoplasma test: negative;
• Adventitious virus test: negative.
5. GMP-grade ultra-clean production base
Manufactured under the GMP framework — from establishment of the seed cell banks (MCB/WCB) through upstream culture, downstream purification, and final fill-finish — with rigorous quality risk management (QRM) applied throughout, ensuring the safety, consistency, and traceability of every batch.
Figure 3. YEASEN GMP-grade cytokine production environment
6. Product data
SDS-PAGE
Figure 4. Purity is greater than 95% as determined by SDS-PAGE under reducing conditions.
Bioactivity
Figure 5. The ED50, determined by a cell proliferation assay using human M-07e cells, is less than 10 ng/mL.
Related products
|
Product Name |
Cat. No. |
Pack Size |
|
92363ES |
10 μg / 50 μg / 1 mg |
|
|
Recombinant Human Thrombopoietin/TPO Protein (Research Grade) |
92360ES |
10 μg / 50 μg / 1 mg |
Reference
Wilkinson, A.C., Igarashi, K.J. & Nakauchi, H. Haematopoietic stem cell self-renewal in vivo and ex vivo. Nat Rev Genet 21, 541-554 (2020).