Tissue-Engineered Grafts & Bioscaffolds
Tissue engineering has reached small human urethral reconstruction studies, including cell-seeded tubular constructs. Distinguish a cell-free matrix, a matrix seeded with living cells, and an autologous cultured oral graft: their evidence and regulatory status are different.[1][3][27] Most published clinical data concern men; the two-woman urinary bladder matrix report is preliminary evidence.[1][3][27]
The EAU recommends restricting autologous tissue-engineered oral mucosa to clinical trials . It advises against cell-free engineered grafts in extensive spongiofibrosis, after failed urethroplasty, or for strictures longer than 4 cm .[28]
For native donors, see Buccal Mucosa Graft, Oral-Lip Mucosa Graft, and Lingual Mucosa Graft.
Acellular (Non-Seeded) Bioscaffolds
Decellularized biological matrices provide a framework for host tissue ingrowth. Preserved extracellular matrix proteins may support attachment and remodeling. Results depend on the specific scaffold, geometry and recipient bed.[2][3]
Small Intestinal Submucosa (SIS)
Porcine SIS has been studied mainly as an onlay/inlay patch. The following are distinct series or follow-up reports.
| Study | Patients and follow-up | Reported result | Interpretation |
|---|---|---|---|
| Palminteri 2007[4] | 20 men; mean 21 months | 17/20 successful | Three failures involved penile or penile-bulbar repairs; small uncontrolled series. |
| Fiala 2007[5] | 50 men; mean 31.2 months | 40/50 without urethrogram-confirmed restricture; bulbar 9/10, bulbopenile 26/31, penile 5/9 | Radiographic failure definition differs from the reintervention endpoints in the Palminteri series; overall 80% is not the bulbar-specific result. |
| Palminteri 2012[6] | 25 men; mean 71 months | 19/25 successful; reported failure 14% for strictures under 4 cm, 100% for those over 4 cm | — |
| Palminteri 2024[7] | 25 SIS versus 25 buccal grafts after propensity matching | Estimated success at 156 months: 68% versus 83.4% | SIS had poorer outcomes; the authors favored selection below 3 cm, preferably without previous urethrotomy. |
These studies support caution with longer or poorly vascularized repairs.[2][8]
Acellular Bladder Matrix (ABM)
The 2008 El-Kassaby study enrolled 30 men, alternately assigned to buccal mucosa or acellular bladder matrix onlay. In the reported healthy-bed subgroup, patency was 8/9 with matrix versus 10/10 with buccal mucosa; in the unhealthy-bed subgroup, 2/6 versus 5/5. The abstract states that two patients were lost to follow-up, although its four subgroup denominators sum to all 30 enrollees. These unreconciled counts, small subgroups and prior-treatment burden preclude a precise bedside rule based solely on the number of previous operations. The material is a decellularized matrix, not a free living bladder mucosal graft.[9]
Acellular Porcine Urinary Bladder Matrix (UBM) in Women
Ansari and Karram reported two women with loss of the posterior urethral wall. UBM reconstruction was combined with a labial fat-pad flap and biologic pubovaginal sling. One woman became continent and the other improved.[1]
Cell-Seeded Scaffolds
Cell seeding has improved results in several experimental tubular constructs. Cell-seeding requirements vary with scaffold design, defect geometry and host environment; supporting animal results are model-specific.[3][8][11]
Human Tubularized Constructs: Raya-Rivera 2011
Five boys aged 10–14 years with complex posterior urethral defects received tubular scaffolds seeded with autologous bladder-derived epithelial and smooth-muscle cells. At median 71 months of follow-up (range 36–76), all had patent reconstructions. However, one required an early transurethral incision of an anastomotic narrowing, and another required a pubovesical sling for stress incontinence after pelvic/sphincter injury.[27]
Atala Group — Preclinical Tubularized Cell-Seeded Constructs
Orabi's canine study compared 15 cell-seeded and six unseeded 6-cm tubular collagen constructs. Seeded constructs maintained patency while unseeded constructs collapsed in that model. Orabi's canine results support cell seeding in that model; clinical use and newer acellular designs were not tested.[10]
Cell Sources Under Investigation
| Source | Potential advantage | Evidence boundary |
|---|---|---|
| Bladder epithelial and smooth-muscle cells | Patient-derived urinary tissue | Requires biopsy and manufacturing; small human feasibility experience. |
| Oral mucosal cells | Small biopsy rather than a large native graft | Clinical observational series exist for cultured oral mucosa. |
| Urine-derived cells | Collection without tissue biopsy | Wu's human-cell work included laboratory culture and mouse implantation; Liu's urethral repair study used rabbits.[13][17] |
| Adipose-derived cells | Investigated paracrine and vascular effects | Hypoxia-conditioned constructs were studied in vitro and in rabbits.[12] |
| Other mesenchymal cells | Experimental scaffold integration | Bilayer scaffold comparisons with buccal grafts remain animal evidence.[16] |
Tissue-Engineered Autologous Oral Mucosa Grafts (TEOMG / MukoCell)
MukoCell is manufactured from a small oral biopsy, with approximately three weeks of laboratory expansion. In the Karapanos series, its predetermined 3.8 × 2.8 cm size limited combined onlay-and-inlay grafting when the residual urethral plate was narrow.[15] It reduces the amount of native oral tissue harvested but requires coordinated manufacture, delivery and implantation.[14][18]
Regulatory distinction: the German Paul-Ehrlich-Institut's official notice records an authorization under §4b(3) of the German Medicines Act, dated April 24, 2024, number PEI.A.12195.01.1. This is not an EU-wide CE mark. The German authorization is national; the EAU's trial-only recommendation still applies.[29][28]
Clinical Results (Male Series)
| Study | Design and follow-up | Result | Limits |
|---|---|---|---|
| Ram-Liebig 2017[18] | Prospective observational, 99 men at eight centers | Kaplan–Meier success 67.3% at 12 months and 58.2% at 24 months | Only 65 and 39 reached those follow-up visits. The recurrence definition was revised post hoc; no control group. |
| Barbagli 2018[14] | Retrospective, 38 men; median 55 months | 32/38 successful | No native-graft comparator; selected recurrent anterior strictures. |
| Karapanos 2023[15] | Retrospective, patient-selected graft choice; 77 TEOMG versus 76 native oral grafts | 53/77 (68.8%) versus 60/76 (78.9%); p=0.155; median follow-up 52 versus 53.5 months. Study-defined failure was Qmax <15 mL/s, inability to pass a 16-Fr cystoscope, or need for further instrumentation. | Different stricture locations and techniques. |
In Karapanos, the subgroup with more than ten prior urethral dilations had success in 5/16 TEOMG versus 10/12 native-graft patients (31.3% versus 83.3%; p=0.006 in the main manuscript). These table-based values differ from the abstract. Oral morbidity was lower with TEOMG, but measurement used a nonvalidated questionnaire without a baseline oral examination. At three weeks, contrast extravasation occurred in 7/77 TEOMG patients versus 5/76 native-graft patients; six TEOMG leaks healed with prolonged catheterization, one persistent TEOMG fistula required surgery, and one native-graft leak required revision.[15] The TEOMG cases overlap the center's earlier report.[15]
Next-Generation Technologies
Bioprinting, extracellular vesicles, modified matrices and mechanically tailored hydrogels remain research platforms. Reviews identify candidate mechanisms.[19][20][21]
- Exosome-loaded nanoyarns, modified SIS and multilayer hydrogels: Laboratory/animal studies reported reduced fibrosis, improved epithelialization or vascularization.[22][23][24]
- TissueSpan acellular collagen mesh: a 2025 study reported one-month patency in rabbit and canine defects.[25] In a 2026 single-arm first-in-human study, five men with short anterior strictures received onlay mesh grafts and completed 24-month follow-up. No device-related adverse events or redo urethroplasties were reported, but three required urethral dilation within 12 months; only two remained free of reintervention. Anatomical success was not systematically assessed, so efficacy relative to autologous grafts remains unproven.[30]
- Decellularized human urethra: the 2023 study used tissue from 12 deceased donors to evaluate processing and matrix preservation.[26]
Critical Principles for Clinical Application
- Identify the actual product and configuration. A living mucosal graft, an acellular patch and a cell-seeded tube are different interventions.
- Assess the recipient bed. Dense scarring can be the very reason it performs poorly.
- Read the endpoint. Primary patency, patency after reintervention and continence are different outcomes.
- Follow the evidence and local authorization.
Sex-Specific Considerations
Female reconstruction requires direct clinical evidence. Prior surgery, irradiation or fistula can compromise adjacent tissue. Established native-tissue options and the specific reconstructive defect remain the clinical comparison.[1]
See Also
- Buccal Mucosa Graft
- Labial Mucosa Graft
- Lingual Mucosa Graft
- Bladder Mucosa Graft
- Liquid / Minced BMG (atlas)
- Female Dorsal Onlay Urethroplasty
- Excision and Primary Anastomosis (male)
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. 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
13. 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
14. 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
15. 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
16. 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
17. 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
18. 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
19. 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
20. 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
21. 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
22. 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
23. 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
24. 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
25. 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
26. 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
27. Raya-Rivera A, Esquiliano DR, Yoo JJ, Lopez-Bayghen E, Soker S, Atala A. Tissue-engineered autologous urethras for patients who need reconstruction: an observational study. Lancet. 2011;377:1175–82. doi:10.1016/S0140-6736(10)62354-9
28. European Association of Urology. Urethral Strictures: Tissue Transfer. 2026. Guideline chapter.
29. Paul-Ehrlich-Institut. Bekanntmachung Nr. 518, May 8, 2024; published June 26, 2024. MukoCell authorization under §4b(3) AMG, p. 2. Official notice.
30. Vythilingam G, Mardiana M, Larsson HM, et al. "First-in-human safety and feasibility study of an acellular collagen mesh for augmentation urethroplasty: an IDEAL stage 1 study." BMC Urol. 2026. doi:10.1186/s12894-026-02323-x