Autologous Transplantation of Human Cryopreserved Testis Tissue (ReSTORE)

Restoration of Spermatogenesis by Autologous Grafting of Cryopreserved Testis Tissue From Men With Non-Obstructive Azoospermia and Healthy Men With Proven Fertility

For pre-pubertal boys undergoing gonadotoxic therapies, freezing immature testicular tissue (ITT) containing spermatogonial stem cells (SSCs) is currently the only option to potentially preserve future fertility. This experimental clinical study aims to provide proof-of-concept that frozen-thawed, ectopically autotransplanted adult human testicular tissue can support spermatogenesis in healthy adult men.

Study Overview

• Status: Active, not recruiting
• Conditions: Hematologic Diseases; Cancer; Infertility, Male; Azoospermia, Nonobstructive
• Intervention / Treatment: Procedure: Autologous Transplantation of Testis Tissue

Detailed Description

As of 2025, more than 3,000 pre-pubertal boys worldwide have cryopreserved immature testicular tissue, and the number of centers offering this fertility preservation option prior to gonadotoxic therapies continues to grow. The most advanced strategy for future fertility restoration is the ectopic autologous transplantation of frozen-thawed ITT, allowing the tissue to mature, initiate spermatogenesis, and ultimately provide sperm for assisted fertility treatments.

However, the absence of human data and the preservation of ITT samples for later clinical trials have so far hindered clinical translation. To address this knowledge gap, the investigators will conduct a proof-of-concept study involving five healthy adult participants with normal spermatogenesis who have naturally conceived children and do not desire additional biological offspring.

Participants will be recruited from the Department of Urology, Copenhagen University Hospital, Herlev and Gentofte Hospital. During elective hydrocele or spermatocele surgery, testicular biopsies will be collected and cryopreserved. At a later stage, the frozen-thawed tissue fragments will be autotransplanted ectopically beneath the scrotal skin. Over a six-month period, participants will undergo regular follow-up. At the end of this period, the transplanted tissue will be retrieved and evaluated for the presence of sperm. If spermatozoa are identified, their genetic stability will also be assessed. This study will generate essential data on the safety, feasibility, and functional potential of using cryopreserved human testicular tissue for fertility restoration, thereby supporting the advancement of this approach toward clinical implementation.

• Study Type: Interventional
• Enrollment (Actual): 5
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Denmark
  • Capital Region
    • Herlev, Capital Region, Denmark, 2730
      • Copenhagen University Hospital - Herlev and Gentofte

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Men referred to the Department of Urology at Herlev and Gentofte Hospital for the treatment of hydrocele or spermatocele were provided with detailed information about the study and invited to participate. Written study information was distributed, and a mandatory reflection period of at least 24 hours was observed prior to obtaining consent.

Inclusion Criteria:

• Age ≥ 40 years
• Scheduled for an elective hydrocele or spermatocele surgery
• Willing to have a testis biopsy taken during the planned surgery
• At least one biological child, unassisted spontaneous conception
• No current or future fertility wishes
• Written informed consent for the participation in this study

Exclusion Criteria:

• Treatment with testosterone substitution
• Bleeding disorders that render surgery too high a risk
• Other contraindications to surgery
• Unable to give informed consent
• Language difficulties that could compromise the informed consent or quality of examination

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• 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: Autologous Transplantation of Testis Tissue; Autologous transplantation of testis tissue under the scrotal skin	Procedure: Autologous Transplantation of Testis Tissue; Autologous transplantation of testis tissue under the scrotal skin

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Sperm retrieval	The primary outcome of interest is the retrieval of viable sperm by testicular sperm extraction (TESE) from the transplanted testicular tissue	Sperm retrieved yes/no at 6 months post transplantation

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Genetic Stability of retrieved Spermatozoa	If spermatozoa are retrieved, the genome will be sequenced to assess gentic stability of sperm retrieved after autotransplantation of frozen-thawed testicular tissue	Assessed in sperm retrieved 6 months after transplantation
Histology of engrafted testicular Tissue	The autotransplanted and retrieved testicular tissue and potentially sperm will be assessed and characterized histopathologically	Tissue retrieved 6 months after transplantation
Safety of subcutaneous Transplantation	Complications at any point during the study period will be recorded and classified according to Clavien-Dindo	From obtaining the testicular biopsy until full healing from the procedure for retrieving the transplanted tissue, up to 3 months after tissue retrieval

Collaborators and Investigators

• Sponsor: Herlev and Gentofte Hospital
• Collaborators: Rigshospitalet, Denmark; University of Copenhagen
• Investigators: Principal Investigator: Elena von Rohden, MD, Department of Urology, Copenhagen University Hospital - Herlev and Gentofte

Study record dates

Study Major Dates

• Study Start (Actual): November 4, 2024
• Primary Completion (Actual): December 17, 2025
• Study Completion (Estimated): March 1, 2027

Study Registration Dates

• First Submitted: December 13, 2025
• First Submitted That Met QC Criteria: January 21, 2026
• First Posted (Actual): January 23, 2026

Study Record Updates

• Last Update Posted (Actual): January 23, 2026
• Last Update Submitted That Met QC Criteria: January 21, 2026
• Last Verified: October 1, 2025

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Urogenital Diseases; Genital Diseases; Genital Diseases, Male; Male Urogenital Diseases; Infertility; Hemic and Lymphatic Diseases; Neoplasms; Hematologic Diseases; Infertility, Male; Azoospermia, Nonobstructive
• Other Study ID Numbers: H-24039098; 2096-00027B (Other Grant/Funding Number: Independent Research Fund Denmark (DFF)); P-2024-17175 (Registry Identifier: Privacy (Capital Region of Denmark's research registry))

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Risk of re-identification of individual participants due to small sample size

Drug and device information, study documents

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