Frozen Fat Tissue Yields Healthy Stem Cells for Future Use

Researchers test if regenerative cells survive deep freezing

For patients with knee osteoarthritis considering Lipogems® treatment, an important question is whether fat tissue can be safely stored for future use. This Danish study explored whether stem cells remain healthy and functional after freezing micro-fragmented adipose tissue (specially processed fat) for extended periods.

The research team collected abdominal fat tissue from seven patients with knee osteoarthritis. The fat was processed using the Lipogems® system, then frozen at minus 80 degrees Celsius. Samples remained frozen between 46 and 150 days. After thawing, scientists tested two methods for extracting stem cells from the tissue.

All seven patients' samples produced viable stem cells

The most encouraging finding was that every single patient's frozen tissue sample yielded healthy, living stem cells. This 100% success rate suggests that cryopreservation (medical freezing) does not destroy the regenerative potential of micro-fragmented fat tissue.

The extracted cells showed low levels of senescence markers. Senescence means cellular aging or breakdown. Low levels indicate the cells remained "young" and functional despite the freezing process.

Cells multiplied normally and maintained healing abilities

Scientists tracked how well the recovered stem cells could grow and divide. Population doubling time—how long cells take to multiply—remained normal through multiple growth cycles. This matters because treatment often requires expanding cell numbers in the laboratory.

The cells also passed critical function tests:

• They successfully transformed into bone-forming cells

• They successfully transformed into fat cells

• These abilities confirm the cells retained their regenerative "stemness"

Multiple healing cell types survived the freezing process

The research identified four distinct stem cell populations in the thawed tissue:

• Adventitial stem cells (cells surrounding blood vessels)

• Pericytes (helper cells supporting blood vessel healing)

• Transitional pericytes (cells shifting between types)

• CD271+ stem cells (cells with strong bone-building potential)

Finding pericytes is particularly relevant. These cells play key roles in tissue repair and are considered clinically important for treating joint conditions.

One extraction method preserved more pericytes

The study compared two techniques for removing stem cells from thawed tissue. Tissue explant culture (letting cells migrate out naturally) preserved significantly more pericytes than enzymatic digestion (using chemicals to break down tissue). At passage four, tissue explant culture yielded 25% pericytes compared to only 3% with enzymatic digestion.

This eightfold difference could influence future treatment preparation. Higher pericyte numbers may translate to better healing outcomes, though this requires further clinical study.

What this means for your treatment decision

This laboratory study offers promising news for knee osteoarthritis patients. Freezing micro-fragmented fat tissue does not appear to destroy its regenerative cells. All key stem cell types that support joint healing survived the process.

For practical purposes, this research suggests future possibilities:

• Fat tissue harvested during one procedure could potentially supply multiple treatments

• Younger, healthier tissue might be stored for use later in life when osteoarthritis worsens

• Repeated treatments—which some studies link to better long-term results—might not require additional liposuction procedures

However, this was a laboratory study with seven patients. It did not test whether frozen-then-thawed cells work as effectively as fresh cells when injected into arthritic knees. The researchers also note that no randomized controlled trials have yet proven the clinical effectiveness of micro-fragmented fat treatment for knee osteoarthritis.

Patients considering Lipogems® should discuss current evidence with their physician. This study adds valuable knowledge about tissue preservation but does not change existing treatment recommendations.

Source: Bagge et al., Journal of Experimental Orthopaedics, 2023.