KnockOut™ Serum Replacement (KSR)
Quick Facts
| Feature | Information |
|---|---|
| Supplement Type | Serum replacement |
| Composition | Proprietary defined formulation |
| Typical Working Concentration | 15-20% (v/v) |
| Primary Function | Maintains pluripotency while reducing spontaneous differentiation |
| Primary Application | ESC and iPSC culture |
Overview
KnockOut™ Serum Replacement (KSR) is a chemically defined alternative to fetal bovine serum (FBS) developed specifically for pluripotent stem cell culture. Compared with serum, KSR provides a more controlled culture environment, minimizes batch-to-batch variability, and reduces spontaneous differentiation.
KSR is most commonly used with KnockOut™ DMEM for the maintenance, expansion, reprogramming, and genome editing of embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs).
Composition
Although the complete formulation is proprietary, KSR contains a defined mixture of:
| Component | Function |
|---|---|
| Albumin | Carrier protein and osmotic support |
| Lipids | Membrane synthesis |
| Amino acids | Protein synthesis |
| Vitamins | Cellular metabolism |
| Antioxidants | Protection against oxidative stress |
| Trace elements | Enzyme cofactors |
Biological Role
KSR supports:
- Pluripotent stem cell self-renewal
- Colony formation
- Cell survival
- Controlled proliferation
- Genome stability
- Reduced spontaneous differentiation
Typical Applications
KSR is routinely used for:
- Human embryonic stem cells (hESCs)
- Mouse embryonic stem cells (mESCs)
- Induced pluripotent stem cells (iPSCs)
- Stem cell reprogramming
- CRISPR genome editing
- Clonal expansion
- Developmental biology
- Directed differentiation protocols
Recommended Use
| Parameter | Recommendation |
|---|---|
| Working Concentration | 15-20% (v/v) |
| Mouse ESCs | Typically 15% |
| Human ESCs/iPSCs | Typically 20% |
Always optimize the concentration according to the published protocol or cell line recommendations.
Advantages
- Defined alternative to FBS
- Excellent batch-to-batch consistency
- Supports long-term pluripotency
- Reduces spontaneous differentiation
- Highly reproducible
- Well established in stem cell research
Limitations
- Proprietary formulation
- More expensive than FBS
- Primarily intended for pluripotent stem cells
- Increasingly replaced by fully defined feeder-free media (e.g., Essential 8, StemFlex) for some applications
Comparison with Related Supplements
| Supplement | Primary Function |
|---|---|
| KSR | Defined serum replacement for pluripotent stem cells |
| Fetal Bovine Serum (FBS) | Undefined serum supplement for general cell culture |
| Essential 8 / StemFlex | Fully defined media for feeder-free pluripotent stem cell culture |
References
- Gibco™ KnockOut™ Serum Replacement Product Information.
- Thomson JA et al. Embryonic stem cell lines derived from human blastocysts. Science (1998).
- Takahashi K, Yamanaka S. Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors. Cell (2006).
- Freshney RI. Culture of Animal Cells: A Manual of Basic Technique and Specialized Applications.
- ATCC Animal Cell Culture Guide.