Liver PDM and CM Isolation Using Sucrose Density Gradients

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Solution Overview

Problem

Existing methods for isolating mitochondria from liver tissue are inefficient and struggle with separating lipid droplet-bound mitochondria (PDM) due to the formation of a thin floating fat layer, making separation difficult.

Innovation Solution

A novel method using sucrose gradients and differential centrifugation techniques to isolate PDM and cytosolic mitochondria (CM) by first separating a floating fat layer with low sucrose buffer and then performing high-speed centrifugation to pellet down these mitochondria populations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If differential centrifugation is used to isolate mitochondria, then mitochondria can be concentrated and separated from other organelles, but lipid droplet-bound mitochondria form a thin floating fat layer that is difficult to separate

Engineering Contradiction:

Improvemitochondria separation purityVSAvoidfat layer collection difficulty

Core Design Contradiction:

Manufacturing precisionVSEase of operation

Solution Approach 1:

The patent changes the density parameter of the homogenate by adding sucrose to create a density gradient. This causes the floating fat layer to sink and form a distinct pellet at the bottom of the tube, making it easily collectable while maintaining separation purity of mitochondria from other organelles

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Instead of trying to collect the floating fat layer from the top of the homogenate (which is difficult), the patent inverts the approach by using sucrose to make the fat layer sink to the bottom, transforming it into an easily collectable pellet form

Inventive Principle:

Principle #13The other way round (Inversion)

2Manufacturing precision

If high speed centrifugation is performed to pellet mitochondria, then cytosolic mitochondria can be isolated, but peri-droplet mitochondria remain contaminated with lipid droplets

Engineering Contradiction:

Improvemitochondria isolation purityVSAvoidisolation efficiency

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent segments the mitochondria population into two distinct groups: peri-droplet mitochondria (PDM) that pellet with lipid droplets at low speed, and cytosolic mitochondria (CM) that remain in the supernatant. This segmentation allows separate collection and purification of each mitochondrial subtype without contamination

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses sucrose as an intermediary substance to mediate the separation process. The sucrose creates a density environment where lipid droplets and bound mitochondria can be selectively pelleted, facilitating clean separation from cytosolic mitochondria

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables efficient isolation and characterization of PDM and CM, revealing their distinct roles in healthy and diseased liver conditions, particularly in steatohepatitis progression, with PDM showing higher bioenergetic activity and fatty acid oxidation capacity.

Implementation Method 1

Most methods to isolate mitochondria rely on differential centrifugation, a two-step centrifugation carried out at low speed to remove intact cells, cell debris, tissue debris, and nuclei from whole cell extracts

Methodology Applied

Scientific EffectDifferential centrifugation: Centrifugal Separation

Implementation Method 2

adding cold layering buffer to the centrifuged homogenized liver, resulting in a floating fat layer and a remaining homogenate layer

Methodology Applied

Scientific EffectDensity gradient separation: Density Gradient

Implementation Method 3

centrifuging the floating fat layer at a low speed; removing any pellet formed after centrifugation

Methodology Applied

Scientific EffectCentrifugal separation: Centrifugal Separation

Implementation Method 4

performing centrifugation of the floating fat layer at a high speed to produce a peri-droplet mitochondria (PDM) pellet

Methodology Applied

Scientific EffectHigh-speed centrifugation: Centrifugal Separation

Implementation Method 5

performing centrifugation of the centrifuged homogenate layer sample at a high speed to produce a cytosolic mitochondria (CM) pellet

Methodology Applied

Scientific EffectHigh-speed centrifugation: Centrifugal Separation

Data Source

PatentUS20250305915A1Method to Isolate Lipid Droplet Bound and Unbound Mitochondria from Liver

Publication Date: 2025.10.02 UNIVERSITY OF CINCINNATI

AI summary

A method of isolating multiple mitochondria samples from liver is provided. The separation method isolates PDM from healthy, steatotic or fibrotic livers and enables the characterization of their importance in healthy vs. disease progression. Briefly, after low-speed centrifugation, the fat layer is first separated by overlaying with low sucrose buffer (MSHE) to bring the floating fat layer to the top. Next, the fat layer is collected to isolate PDM, while the supernatant is used to isolate CM.