Single Nuclei Sequencing in Human Skeletal Muscle After Unloading (ULLS23)

Injuries often require people to undergo some degree of limb immobilization. This comes at a high cost in terms of muscle mass and function losses. At the molecular level, it is completely unknown how the different cells in the muscle respond to this complete lack of mechanical stimuli.

The investigators will explore cell type specific changes in skeletal muscle after a short period of unloading, and specifically examine the behavior of myogenic stem cells with particular attention to potential unloading-induced maturation into fast- or slow-twitch muscle fibers.

Ten healthy young participants will perform a 5-day Unilateral Lower Limb Suspension (ULLS) intervention, where one leg is continuously subjected to unloading, i.e., lack of mechanical stimuli. Before and after the ULLS period, participants will perform muscle function testing and MRI scans to assess muscle size in the lower limbs. Immediately after the ULLS, two muscle biopsies will be obtained, one from each leg. The tissue will be employed for single-nuclei RNA sequencing analysis and immunohistochemistry experiments.

This project will be the first to analyze cell type specific changes induced by complete, short-term lack of mechanical stimuli in skeletal muscle. This will add a new dimension to the understanding of the processes directing this type of muscle atrophy (i.e., muscle loss in otherwise healthy individuals) and thus help to develop effective countermeasures to offset muscle changes.

Study Overview

• Status: Enrolling by invitation
• Conditions: Unilateral Lower Limb Suspension
• Intervention / Treatment: Other: Unilateral lower limb suspension

• Study Type: Interventional
• Enrollment (Estimated): 10
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Sweden
  • Stockholm
    • Huddinge, Stockholm, Sweden, 14152
      • Karolinska Institutet

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 40 years (Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Healthy young adult men

Exclusion Criteria:

• An age younger than 18 or older than 40 years
• Contraindications to magnetic resonance imaging (MRI)
• Contraindications to maximal intensity resistance exercise
• Contraindications to unloading (i.e., ULLS)
• Very high physical activity levels (determined using a standard Godin Leisure-Time Exercise Questionnaire (GLTEQ))
• Hypertension (>140/90 mm Hg)
• History of malignancy
• History of coagulation dysfunction
• History of musculoskeletal or neurological disorders
• History of cardiovascular disease
• History of cerebrovascular disease
• History of respiratory disease
• History of gastrointestinal disease
• History of renal disease
• History of past or present condition requiring long-term drug prescriptions.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: Unilateral lower limb suspension; Participants will perform a 5-day unloading intervention using the ULLS model. Short-length crutches, aided by handgrip and forearm support distal to the elbow will be used to assist in any upright or ambulatory activity. One foot (randomized in a counterbalance manner) will be equipped with a shoe having a 10-cm thick sole, which permits the unloaded limb to move passively about the hip joint while adopting a near straight position.

Other: Unilateral lower limb suspension; Participants will perform a 5-day unloading intervention using the ULLS model. Short-length crutches, aided by handgrip and forearm support distal to the elbow will be used to assist in any upright or ambulatory activity. One foot (randomized in a counterbalance manner) will be equipped with a shoe having a 10-cm thick sole, which permits the unloaded limb to move passively about the hip joint while adopting a near straight position.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Single nuclei RNA sequencing	Single nuclei RNA sequencing from skeletal muscle (m. vastus lateralis) from both legs	Immediately after the 5-day unilateral unloading intervention

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Muscle mass	Muscle volume of quadriceps muscle group (and individual muscles) assessed by MRI in both legs	Before and immediately after the 5-day unloading intervention
Concentric isokinetic torque of knee extensor muscles	Concentric isokinetic torque of knee extensor muscles at 30°/s, 90°/s, 180°/s and 300°/s, measured with an isokinetic dynamometer unilaterally in both legs	Before and immediately after the 5-day unloading intervention
Isometric torque of knee extensor muscles	Isometric torque of knee extensor muscles at 60° knee flexion, measured with an isokinetic dynamometer unilaterally in both legs	Before and immediately after the 5-day unloading intervention

Collaborators and Investigators

• Sponsor: Karolinska Institutet

Study record dates

Study Major Dates

• Study Start (Actual): March 5, 2023
• Primary Completion (Estimated): December 1, 2024
• Study Completion (Estimated): August 1, 2025

Study Registration Dates

• First Submitted: March 13, 2023
• First Submitted That Met QC Criteria: March 23, 2023
• First Posted (Actual): April 6, 2023

Study Record Updates

• Last Update Posted (Actual): June 21, 2024
• Last Update Submitted That Met QC Criteria: June 19, 2024
• Last Verified: June 1, 2024

More Information

Terms related to this study

• Keywords: Skeletal muscle; ULLS; single nuclei RNA sequencing
• Other Study ID Numbers: Dnr 2022-04662-01

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No