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Tissue-Engineered Grafts & Bioscaffolds

Tissue-engineered grafts and bioscaffolds for urethral reconstruction represent an emerging but largely preclinical and early-clinical field. The published evidence is heavily male-dominant — only one female-specific clinical report (Ansari & Karram 2017; n = 2 with acellular porcine UBM) has been published — but the underlying biology, scaffold materials, cell sources, and named technologies are not sex-specific.[1] This article consolidates the male and female literature into a single graft-material foundations reference.

For native graft sources, see Buccal Mucosa Graft, Labial Mucosa Graft, and Lingual Mucosa Graft.

The field organizes into three major categories: acellular (non-seeded) bioscaffolds, cell-seeded scaffolds, and tissue-engineered autologous oral mucosa grafts (TEOMG).

Acellular (Non-Seeded) Bioscaffolds​

Decellularized biological matrices that serve as a scaffold for host tissue ingrowth without pre-seeded cells. The scaffold provides structural support and bioactive ECM proteins that promote cell attachment, migration, and tissue regeneration.[2][3]

Small Intestinal Submucosa (SIS)​

SIS (porcine small intestine) is the most extensively studied acellular bioscaffold in clinical urethral reconstruction (exclusively in males to date).

SeriesnFollow-upSuccessNotes
Palminteri 2007[4]20 (M)21 mo85%Failures all in penile / penobulbar with long grafts
Fiala 2007[5]50 (M)31 mo80% (bulbar 80%; penile 56%)Penile location adverse
Palminteri 2012[6]25 (M)71 mo76% (long-term)14% failure for strictures > 4 cm
Palminteri 2024[7]25 SIS vs 25 BMG (propensity matched)13 yrSIS 68% vs BMG 83.4%SIS comparable to BMG only for strictures < 4 cm

The consistent finding across SIS studies is that acellular scaffolds perform well as onlay grafts for short strictures but fail when used for longer defects or tubularized configurations.[2][3][8]

Acellular Bladder Matrix (ABM)​

El-Kassaby / Atala 2008 — the only RCT comparing acellular bladder matrix to BMG in 30 men with complex anterior strictures. In patients with a healthy urethral bed (≤ 2 prior operations) ABM and BMG performed similarly; with > 2 prior operations, ABM success dropped to 2/6 (33%) vs 5/5 (100%) for BMG.[9]

This established the critical principle that acellular scaffolds require a healthy, well-vascularized recipient bed to support tissue regeneration — in scarred or previously operated tissue, they are unreliable.

Acellular Porcine Urinary Bladder Matrix (UBM) — The Only Female-Specific Report​

Ansari & Karram 2017 — the sole published female-specific experience with bioscaffolds. Two women with complete loss of the posterior urethra underwent reconstruction using acellular porcine UBM, combined with Martius flap transposition and biologic pubovaginal sling. In both cases the UBM graft showed successful conversion to what appeared to be normal urethral mucosa on cystoscopy. One patient achieved complete continence; the other showed significant improvement.[1] Encouraging but extremely preliminary.

Cell-Seeded Scaffolds​

The key insight from tissue engineering research is that acellular scaffolds are adequate for onlay repairs but insufficient for tubularized reconstructions — when a complete urethral tube must be created, cell seeding is essential.[3][8][10][11]

Atala Group — Preclinical Tubularized Cell-Seeded Constructs​

Orabi 2013 is the landmark preclinical study from the Atala laboratory: 15 dogs underwent urethroplasty with 6-cm tubularized collagen scaffolds seeded with autologous bladder epithelial and smooth-muscle cells; 6 dogs received unseeded scaffolds. Cell-seeded constructs showed wide-caliber urethras without strictures with histologically normal epithelium and smooth muscle. Unseeded tubularized scaffolds collapsed and strictured in all cases.[10] Cell seeding is mandatory for tubularized urethral substitution — a finding consistently replicated across animal models.[3][8]

Cell Sources Under Investigation​

Cell SourceAdvantagesLimitationsClinical Use
Autologous urothelial cells (bladder biopsy)Native urethral phenotype; proven differentiationInvasive biopsy; limited expansionLimited clinical trials
Autologous oral mucosal cells (buccal biopsy)Minimally invasive; proven in TEOMG3-week culture periodYes (MukoCell)
Urine-derived stem cells (USCs)Non-invasive harvest from voided urine; multipotentEarly-stagePreclinical only[14]
Adipose-derived stem cells (ADSCs)Abundant; paracrine effects; anti-fibroticNo clinical urethral trialsPreclinical only[13]
Bone-marrow MSCsWell-characterized; immunomodulatoryInvasive harvestPreclinical only[17]
Autologous fibroblasts / keratinocytesSkin-derived; easy harvestLimited urethral-specific dataLimited

Urine-derived stem cells (USCs) are particularly noteworthy as a non-invasive cell source. Wu 2011 demonstrated USCs can differentiate into both urothelial and smooth-muscle cells and form multilayer mucosal structures on SIS scaffolds.[14] Liu 2017 showed autologous USC-seeded SIS significantly improved urethral caliber, epithelialization, smooth-muscle content, and vessel density vs SIS alone in a rabbit model, with reduced inflammation and fibrosis.[18]

Tissue-Engineered Autologous Oral Mucosa Grafts (TEOMG / MukoCell)​

The most clinically advanced tissue-engineered approach is MukoCell — an autologous tissue-engineered oral mucosa graft manufactured from a small (0.5 cm²) buccal biopsy, expanded ex vivo over 3 weeks, and returned as a full-sized graft for urethroplasty. This eliminates the need for large oral mucosa harvest, dramatically reducing donor-site morbidity. CE-marked in the EU; not FDA-approved in the US.[15][16][19]

Clinical Results (All Male Series)​

StudynDesignFollow-upSuccessKey Findings
Ram-Liebig 2017[19]99Prospective multicenter24 mo58.2% (Kaplan-Meier)77% had ≥ 2 prior surgeries; success highly dependent on surgeon experience (0–85.7%)
Barbagli 2018[15]38Retrospective multicenter55 mo (median)84.2%Recurrent strictures only; comparable to native BMG; no adverse reactions to engineered material
Karapanos 2023[16]77 TEOMG vs 76 NOMGSingle-institution comparative52 mo (TEOMG)TEOMG 68.8% vs NOMG 78.9% (p = 0.155)Comparable overall; TEOMG inferior after repeated dilations (31.3% vs 81.3%); significantly less oral morbidity and shorter operative time (median 104 vs 182 min)

The Karapanos comparison is particularly informative: while overall success was statistically comparable, TEOMG showed a significantly lower success rate in patients with prior repeated dilations — paralleling the findings with acellular scaffolds. TEOMG offers significantly shorter operative time and virtually no oral morbidity beyond 3 weeks.[16]

No TEOMG studies have been performed in women, though the technique is theoretically applicable to female BMG urethroplasty.

Next-Generation Technologies​

Several emerging approaches are in preclinical development.[20][21][22]

  • 3D bioprinting — precise fabrication of tubular scaffolds with controlled porosity, mechanical properties, and cell distribution. Multilayered constructs mimicking native urethral architecture (urothelium + smooth muscle + connective tissue) can be printed.[21]
  • Exosome / extracellular-vesicle therapy — ADSC-derived exosomes loaded onto nanoyarn scaffolds have shown anti-inflammatory, anti-fibrotic, and pro-angiogenic effects in rabbit urethral defect models, with no stricture or scar formation at 4 weeks. Sterling 2026 highlighted extracellular vesicles as a promising future direction for BMG-based reconstruction.[22][23]
  • Smart scaffolds — modified SIS patches incorporating bioactive molecules (e.g., protocatechualdehyde / SIS) demonstrated enhanced scarless repair in rabbit models through anti-inflammatory, antioxidant, and pro-regenerative mechanisms.[24]
  • Multilayered hydrogel scaffolds — PVA hydrogels with native-tissue-matched elastic modulus and self-healing inner layers have achieved scar-free urethral healing in rabbits by resisting urine erosion and modulating macrophage polarization.[25]
  • Off-the-shelf acellular collagen mesh (TissueSpan) — Vythilingam 2025 reported an 8-year bench-to-bedside journey developing a liquid collagen-based acellular mesh achieving patent urethras in rabbit (2 cm) and dog (4 cm) models with spontaneous urothelial coverage and smooth-muscle migration. A first-in-man clinical trial has been initiated.[26]
  • Decellularized human urethra — Kuniakova 2023 developed a protocol for decellularizing cadaveric human urethras while preserving ECM architecture, collagen IV, and fibronectin — providing a scaffold that closely mimics native urethral tissue for potential recellularization.[27]

Critical Principles for Clinical Application​

  1. Onlay vs tubularized. Acellular (non-seeded) scaffolds are adequate for onlay repairs where the scaffold is supported by native urethral wall on one side. For tubularized reconstructions (complete circumferential replacement), cell seeding is essential — unseeded tubes consistently collapse and stricture.[3][10][11]
  2. Recipient bed quality. Acellular scaffolds require a healthy, well-vascularized urethral bed for tissue regeneration. In scarred or previously operated tissue (> 2 prior operations), success drops dramatically (33% vs 89% in healthy beds).[9]
  3. Stricture length. SIS and other acellular scaffolds perform best for short strictures (< 4 cm) and underperform for longer defects.[6][7]
  4. Biological vs synthetic scaffolds. Biological scaffolds (SIS, bladder matrix, decellularized tissue) have the advantage of bioactive ECM proteins that promote cell attachment and differentiation. Synthetic scaffolds (PLGA, PCL, PVA) offer unlimited availability and tunable mechanical properties but lack inherent bioactivity.[3][8]

Sex-Specific Considerations​

The application to female urethral reconstruction remains almost entirely theoretical, with only the Ansari & Karram 2-patient UBM report providing female-specific clinical data.[1]

Favorable for female reconstruction:

  • Short female urethra (3–5 cm) means even "long" strictures require relatively small grafts.
  • The vaginal wall provides an excellent vascular bed for scaffold support.
  • Most female strictures are managed with onlay techniques — the configuration most amenable to acellular scaffolds.

Challenging:

  • Rarity of female urethral stricture limits the patient population for clinical trials.
  • Existing techniques (BMG, vaginal flap) already achieve 86–98% success, creating a high bar for new technology to surpass.
  • Proximity to vaginal flora creates a potentially hostile environment for scaffold integration.
  • No female-specific cell-seeded scaffold or TEOMG studies exist.

Summary​

Tissue-engineered grafts and bioscaffolds have progressed from preclinical proof-of-concept to early clinical application but remain far from standard of care. The most clinically mature technology is MukoCell (TEOMG), which achieves 58.2–84.2% success in male strictures with dramatically reduced oral morbidity.[15][16][19] Acellular scaffolds (SIS, bladder matrix) are viable for short onlay repairs in healthy urethral beds but fail in scarred tissue and tubularized configurations.[7][9] Cell-seeded tubularized scaffolds show excellent preclinical results but have not reached clinical trials.[10] For female urethral reconstruction specifically, only 2 patients have been reported using any bioscaffold.[1] Given the high success rates of conventional BMG and vaginal-flap techniques, tissue-engineered approaches are most likely to find their niche in salvage scenarios where autologous tissue is unavailable or has failed.

See Also​

References​

1. Ansari S, Karram M. "Two Cases of Female Urethral Reconstruction With Acellular Porcine Urinary Bladder Matrix." Int Urogynecol J. 2017;28(8):1257–60. doi:10.1007/s00192-016-3262-7

2. Ribeiro-Filho LA, Sievert KD. "Acellular Matrix in Urethral Reconstruction." Adv Drug Deliv Rev. 2015;82–83:38–46. doi:10.1016/j.addr.2014.11.019

3. de Kemp V, de Graaf P, Fledderus JO, Ruud Bosch JL, de Kort LM. "Tissue Engineering for Human Urethral Reconstruction: Systematic Review of Recent Literature." PLoS One. 2015;10(2):e0118653. doi:10.1371/journal.pone.0118653

4. Palminteri E, Berdondini E, Colombo F, Austoni E. "Small Intestinal Submucosa (SIS) Graft Urethroplasty: Short-Term Results." Eur Urol. 2007;51(6):1695–701. doi:10.1016/j.eururo.2006.12.016

5. Fiala R, Vidlar A, Vrtal R, Belej K, Student V. "Porcine Small Intestinal Submucosa Graft for Repair of Anterior Urethral Strictures." Eur Urol. 2007;51(6):1702–8. doi:10.1016/j.eururo.2007.01.099

6. Palminteri E, Berdondini E, Fusco F, De Nunzio C, Salonia A. "Long-Term Results of Small Intestinal Submucosa Graft in Bulbar Urethral Reconstruction." Urology. 2012;79(3):695–701. doi:10.1016/j.urology.2011.09.055

7. Palminteri E, Toso S, Preto M, et al. "Small Intestinal Submucosa Graft Bulbar Urethroplasty Is a Viable Technique: Results Compared to Buccal Mucosa Graft Urethroplasty After Propensity Score Matching." World J Urol. 2024;42(1):123. doi:10.1007/s00345-024-04795-8

8. Žiaran S, Galambošová M, Danišovič L. "Tissue Engineering of Urethra: Systematic Review of Recent Literature." Exp Biol Med. 2017;242(18):1772–85. doi:10.1177/1535370217731289

9. el-Kassaby A, AbouShwareb T, Atala A. "Randomized Comparative Study Between Buccal Mucosal and Acellular Bladder Matrix Grafts in Complex Anterior Urethral Strictures." J Urol. 2008;179(4):1432–6. doi:10.1016/j.juro.2007.11.101

10. Orabi H, AbouShwareb T, Zhang Y, Yoo JJ, Atala A. "Cell-Seeded Tubularized Scaffolds for Reconstruction of Long Urethral Defects: A Preclinical Study." Eur Urol. 2013;63(3):531–8. doi:10.1016/j.eururo.2012.07.041

11. Atala A. "Experimental and Clinical Experience With Tissue Engineering Techniques for Urethral Reconstruction." Urol Clin North Am. 2002;29(2):485–92. doi:10.1016/s0094-0143(02)00033-2

12. Culenova M, Ziaran S, Danisovic L. "Cells Involved in Urethral Tissue Engineering: Systematic Review." Cell Transplant. 2019;28(9–10):1106–15. doi:10.1177/0963689719854363

13. Wan X, Xie MK, Xu H, et al. "Hypoxia-Preconditioned Adipose-Derived Stem Cells Combined With Scaffold Promote Urethral Reconstruction by Upregulation of Angiogenesis and Glycolysis." Stem Cell Res Ther. 2020;11(1):535. doi:10.1186/s13287-020-02052-4

14. Wu S, Liu Y, Bharadwaj S, Atala A, Zhang Y. "Human Urine-Derived Stem Cells Seeded in a Modified 3D Porous Small Intestinal Submucosa Scaffold for Urethral Tissue Engineering." Biomaterials. 2011;32(5):1317–26. doi:10.1016/j.biomaterials.2010.10.006

15. Barbagli G, Akbarov I, Heidenreich A, et al. "Anterior Urethroplasty Using a New Tissue Engineered Oral Mucosa Graft: Surgical Techniques and Outcomes." J Urol. 2018;200(2):448–56. doi:10.1016/j.juro.2018.02.3102

16. Karapanos L, Knorr V, Halbe L, et al. "Comparison of Oral Morbidity and Mid-Term Efficacy of Anterior Urethroplasty Using an Autologous Tissue-Engineered Graft (MukoCell) Versus Native Oral Mucosa Graft." Int J Urol. 2023;30(11):1000–7. doi:10.1111/iju.15247

17. Yudintceva NM, Nashchekina YA, Mikhailova NA, et al. "Urethroplasty With a Bilayered Poly-D,l-Lactide-Co-Ε-Caprolactone Scaffold Seeded With Allogenic Mesenchymal Stem Cells." J Biomed Mater Res B Appl Biomater. 2020;108(3):1010–21. doi:10.1002/jbm.b.34453

18. Liu Y, Ma W, Liu B, et al. "Urethral Reconstruction With Autologous Urine-Derived Stem Cells Seeded in Three-Dimensional Porous Small Intestinal Submucosa in a Rabbit Model." Stem Cell Res Ther. 2017;8(1):63. doi:10.1186/s13287-017-0500-y

19. Ram-Liebig G, Barbagli G, Heidenreich A, et al. "Results of Use of Tissue-Engineered Autologous Oral Mucosa Graft for Urethral Reconstruction: A Multicenter, Prospective, Observational Trial." EBioMedicine. 2017;23:185–92. doi:10.1016/j.ebiom.2017.08.014

20. Habibizadeh M, Mohammadi P, Amirian R, Moradi M, Moradi M. "Engineered Tissues: A Bright Perspective in Urethral Obstruction Regeneration." Tissue Eng Part B Rev. 2025;31(3):209–20. doi:10.1089/ten.TEB.2024.0124

21. Duan L, Wang Z, Fan S, Wang C, Zhang Y. "Research Progress of Biomaterials and Innovative Technologies in Urinary Tissue Engineering." Front Bioeng Biotechnol. 2023;11:1258666. doi:10.3389/fbioe.2023.1258666

22. Sterling J, Hecksher D, Hayden C, et al. "Buccal Mucosa: A Narrative Review — How Does It Work, How Is It Used, What Is Coming Next." Urology. 2026. doi:10.1016/j.urology.2026.03.015

23. Wang L, Cheng W, Zhu J, et al. "Electrospun Nanoyarn and Exosomes of Adipose-Derived Stem Cells for Urethral Regeneration: Evaluations in Vitro and in Vivo." Colloids Surf B Biointerfaces. 2022;209(Pt 2):112218. doi:10.1016/j.colsurfb.2021.112218

24. Huang LP, Liu Y, Li QJ, et al. "A Modified Small Intestinal Submucosa Patch With Multifunction to Promote Scarless Repair and Reinvigoration of Urethra." Adv Healthc Mater. 2023;12(23):e2300519. doi:10.1002/adhm.202300519

25. Jin Y, Wang Y, Yang R, et al. "Multilayered Hydrogel Scaffold Construct With Native Tissue Matched Elastic Modulus: A Regenerative Microenvironment for Urethral Scar-Free Healing." Biomaterials. 2025;312:122711. doi:10.1016/j.biomaterials.2024.122711

26. Vythilingam G, Larsson HM, Yeoh WS, et al. "Off-the-Shelf Implant to Bridge a Urethral Defect: Multicenter 8-Year Journey From Bench to Bed." Urology. 2025;196:294–9. doi:10.1016/j.urology.2024.12.016

27. Kuniakova M, Klein M, Galfiova P, et al. "Decellularization of the Human Urethra for Tissue Engineering Applications." Exp Biol Med. 2023;248(12):1034–42. doi:10.1177/15353702231162092