Researchers at Birjand University of Medical Sciences and collaborating Iranian institutions set out to solve a problem that is both biological and geopolitical. The most promising biological scaffolds for meniscus replacement have often come from pigs, whose tissue closely resembles our own. But across Iran and much of the Middle East, porcine material is culturally and religiously inaccessible, and human donor menisci are in short supply. The team therefore turned to two regionally abundant species, the sheep and the dromedary camel, and asked a deceptively simple question: if you strip the cells out of their menisci, leaving behind only the collagenous framework, how closely does the resulting scaffold match what human tissue can offer?

The answer required an unusually thorough decellularization protocol. Whole menisci from camels and sheep were collected from a local abattoir, while human specimens came from patients undergoing total knee arthroplasty. Each tissue then endured a punishing chemical gauntlet: repeated freeze-thaw cycles to rupture cell membranes, trypsin digestion, two rounds of the detergent Triton X-100, a 72-hour bath in sodium lauryl ether sulfate with EDTA, and a final treatment with peracetic acid to open pores and purge lingering cellular debris. The goal is a paradox familiar to tissue engineers: kill and remove every cell while leaving the intricate extracellular matrix, the collagen fibers and proteoglycans that give the meniscus its strength, essentially untouched.

By the standard benchmarks, the protocol succeeded. Residual DNA fell to 29.67 nanograms per milligram of dry weight in camel scaffolds, 22.33 in human, and 19.67 in sheep, all comfortably below the internationally accepted threshold of 50 nanograms per milligram that signals successful decellularization. Histological staining confirmed that cell nuclei had vanished from both the peripheral and central zones. Yet the process was not without cost. Glycosaminoglycans, the water-loving sugar chains that help the meniscus resist compression, dropped significantly in every species, a well-known vulnerability of these highly soluble molecules to detergent-based processing.

What survived, remarkably, was the architecture. Scanning electron microscopy showed that the highly aligned circumferential collagen network, the load-bearing skeleton of the meniscus, remained intact in all three species, with directionality goodness-of-fit values above 0.8. Decellularized fibers were actually thicker than native ones, swelling from roughly 1.7 to 2.4 micrometers in camel tissue, likely because removing proteoglycans released the compacted fibrils from their molecular tethers. Porosity also rose substantially, from about 20 percent to nearly 32 percent in camel scaffolds, with mean pore sizes expanding to over 129 square micrometers, changes that should ease cell migration and nutrient diffusion once the scaffold is implanted.

Mechanical testing delivered the study’s most encouraging numbers. Although decellularization softened all three tissues, the camel scaffold’s compressive modulus of 1.12 megapascals remained statistically indistinguishable from that of decellularized human meniscus at 0.86 megapascals, despite the camel’s roughly 20 percent numerical advantage. Ultimate tensile strength showed no significant decline in any species after processing, evidence that the circumferential collagen architecture retained its ability to carry tension along the meniscus’s primary load-bearing axis. The researchers attribute this resilience to two factors: the preserved network of circumferential and radial fibers that confines the tissue laterally under compression, and the camel meniscus’s inherently dense native collagen, which the protocol preserved across all groups.

The decisive test came in living tissue. The team implanted small squares of each scaffold under the skin of rats and tracked the immune response over four weeks. In the first week, all three xenogeneic materials provoked comparable acute inflammation, an expected reaction to foreign tissue. By week four, however, the paths diverged sharply. Camel scaffolds showed attenuated inflammation, vigorous migration of fibroblasts deep into the scaffold interior, and signs of active remodeling. Human scaffolds, paradoxically, retained persistent inflammatory infiltrates at their periphery with little fibroblast penetration, while sheep scaffolds showed reduced inflammation but less cellular integration than camel tissue. Quantitative histomorphometry confirmed that camel scaffolds also retained significantly more of their original area, indicating slower degradation and superior structural stability during the critical early remodeling window.

Laboratory assays reinforced the in vivo picture. NIH 3T3 fibroblasts adhered and spread on all three scaffolds, and MTT viability tests showed no cytotoxicity and no meaningful differences among the materials. Co-culture with Jurkat T-lymphocytes revealed that all xenogeneic scaffolds stimulated more T-cell proliferation than flat 2D culture, an honest reminder that animal-derived matrices are not immunologically invisible; camel scaffolds trended toward the lowest proliferation, but the differences did not reach statistical significance. Raman spectroscopy added a molecular fingerprint, detecting preserved collagen-associated peaks including amide I at 1658 and amide III at 1237 inverse centimeters, which could serve as batch-verification markers in future manufacturing. Enzymatic degradation assays told the same durability story: after 14 days in trypsin, camel scaffolds retained 84.31 percent of their mass versus 64.88 percent for human and just 45.23 percent for sheep.

The authors are careful about what these results do and do not mean. In the rat model, all three scaffolds were xenografts; in a human patient, human tissue would behave as an allograft with matched immune recognition, so camel material should be seen as a pragmatic regional alternative rather than an immunological upgrade over human transplants. The subcutaneous implantation site also cannot reproduce the biomechanical complexity of the knee, and the study lacked cyclic fatigue testing under physiological loading. Still, the work establishes the first quantitative anatomical dataset for dromedary camel menisci, showing outer circumferences of 105 to 115 millimeters that even exceed human dimensions, and demonstrates for the first time that camel, human, and sheep scaffolds can be systematically benchmarked against one another. The next milestone will be orthotopic implantation in large-animal knees under dynamic load, the true proving ground for any scaffold that hopes to keep people moving after meniscus loss.

Subject of Research: Decellularized xenogeneic meniscus scaffolds from camel and sheep as alternatives to human meniscus grafts

Article Title: Efficacy of decellularized meniscus xenogeneic substitutes from sheep and camels compared to human menisci

Article References: Khakzad, M. R., Vafaei‐Nezhad, S., Talaei‐Khozani, T., Hassanzadeh‐Taheri, M. M., Rezaeipour, M., Hashemi, H., Shadi, M., & Afshar, M. (2026). Efficacy of decellularized meniscus xenogeneic substitutes from sheep and camels compared to human menisci. Bioengineering & Translational Medicine, Article e70161. https://doi.org/10.1002/btm2.70161

Image Credits: AI Generated

DOI: 10.1002/btm2.70161

Keywords: meniscus, decellularization, tissue engineering, extracellular matrix, xenograft, camel, sheep, biocompatibility, collagen scaffold, knee injury, regenerative medicine, biomechanics

The distinction is more than taxonomic housekeeping. Liquid-phase vesicles, which have fuelled a decade of biomarker discovery and therapeutic development, are subject to dilution, clearance and non-specific biodistribution the moment they enter circulation. Matrix-bound vesicles, by contrast, never leave home. They stay tethered to the fibrous network of collagen, glycoproteins and other macromolecules that gives tissue its structure, delivering their cargo of proteins, lipids and microRNAs to neighbouring cells in a strictly local, context-dependent manner. In doing so, they function not merely as passengers within the matrix but as functional components of it, shaping tissue development, regeneration and day-to-day homeostasis.

The technical case for treating matrix-bound vesicles as a separate population rests on molecular evidence. Lipidomic and RNA sequencing studies of vesicles extracted from decellularized extracellular matrix bioscaffolds have revealed cargo profiles that differ measurably from those of vesicles harvested from the surrounding fluid. Proteomic comparisons of liquid-phase and matrix-bound vesicles grown in both two-dimensional and three-dimensional cell cultures reinforce the picture of two biochemically distinct populations. Matrix-bound vesicles carry tissue-specific protein and microRNA signatures, suggesting that they act as regulatory components of the matrix rather than as incidental debris trapped in its fibres.

That tissue specificity is one of the most striking features of the new framework. Vesicles isolated from decellularized cardiac, skeletal muscle, bone and other tissues recapitulate the angiogenic and immunomodulatory properties of their parent matrices, and their microRNA profiles differ from tissue to tissue. In bone, matrix vesicle cargo such as the microRNA miR-125b accumulates within the mineralized matrix and inhibits bone resorption in mouse models. In skeletal muscle, vesicle-associated interleukin-33 has been shown to initiate a pro-regenerative shift in macrophage phenotype after injury, supporting functional recovery. The vesicles, in effect, carry a molecular record of the tissue they came from—and a set of instructions appropriate to that tissue.

The review also documents how this record changes with age and disease, and the implications are unsettling. Studies of aged breast tissue show that matrix-bound vesicles from older matrices carry cargo that promotes invasiveness in breast epithelial and cancer cells, suggesting that the aged microenvironment itself can actively contribute to tumour progression. Cardiac tissue-resident vesicles regulate fibroblast activation in an age- and sex-dependent manner, and multi-omics profiling of young and aged plasma and matrix-bound vesicles has identified anti-fibrotic microRNAs enriched in the young versions, with therapeutic activity validated in a heart-on-a-chip model. In colorectal cancer, vesicles trapped in decellularized tumour matrix preserve disease-associated signatures of the tumour microenvironment, while cancer-associated fibroblasts have been shown to produce matrix-bound vesicles that influence endothelial cell function. The matrix, in other words, is not a passive scaffold but an active archive of pathological state.

Therapeutically, the localized nature of matrix-bound vesicles is both their greatest asset and their central challenge. Because they act where they are placed, they are natural candidates for integration into engineered tissues and biomaterial delivery platforms. Matrix-bound vesicles embedded in cartilaginous extracellular matrix have enabled functional reconstruction of tracheal defects, vesicles from decellularized tumours have been used as platforms for targeting parent tumour cells and tumour-associated stromal cells, and injectable microsphere systems are being developed for sustained delivery in adipose tissue engineering. Immunomodulatory matrix-bound vesicles derived from urinary bladder matrix have mitigated influenza-mediated lung inflammation while preserving antiviral responses, eased rheumatoid arthritis in preclinical models, and alleviated particulate-induced periprosthetic osteolysis. Recent work even suggests these vesicles can accumulate in bone marrow and induce durable epigenetic changes in myeloid progenitors and macrophages, hinting at effects that outlast the vesicles themselves.

Compared with their liquid-phase cousins, matrix-bound vesicles may also sidestep some of the biodistribution problems that have plagued systemic vesicle therapies. Circulating vesicles must survive the bloodstream, cross vascular barriers and find the right tissue before releasing their cargo, and much of the dose is lost along the way. A vesicle pre-positioned within an implanted scaffold or hydrogel faces no such gauntlet. The trade-off is that delivery becomes inseparable from the biomaterial itself: the scaffold must retain the vesicles, present them to infiltrating host cells and release them, if release is desired, on a controlled schedule. This couples vesicle therapy directly to the maturing field of engineered extracellular matrices, decellularized scaffolds and bioprinted tissues.

Getting there, the authors caution, requires solving problems that the liquid-phase vesicle field has only partially addressed. Isolation of matrix-bound vesicles depends on decellularization protocols whose harshness can alter yield, purity and function, and different isolation methods produce vesicles with different biological behaviour. Characterization remains hampered by the heterogeneity of vesicle populations and by the lack of standardized reporting, although community frameworks such as the MISEV guidelines are pushing the field toward rigor. Downstream, translating cargo profiles into diagnostics or therapeutics will demand bioinformatics integration across proteomics, lipidomics and transcriptomics, and manufacturing clinical-grade material will require scalable, validated processes. The review singles out innovations in isolation, characterization, bioinformatics and bioengineered delivery as the four pillars on which translational success will rest.

What emerges from the analysis is a reframing of how biologists should think about the space between cells. The extracellular matrix has long been appreciated as a mechanical and structural environment that influences stem cell fate, angiogenesis and fibrosis. The new work positions matrix-bound vesicles as the signalling layer of that environment—a distributed, tissue-encoded communication network that operates alongside, and distinct from, the systemic vesicle traffic carried in blood, urine, saliva and other biofluids. If the framework holds, diagnostics could one day read the vesicular archive embedded in a biopsy or decellularized scaffold to reconstruct a tissue’s recent history, and regenerative therapies could seed engineered implants with vesicles pre-loaded with the molecular instructions a healing tissue needs. The quiet postal service in the matrix, long overlooked, may prove to be one of the most consequential mail routes in the body.

Subject of Research: Matrix-bound extracellular vesicles as tissue-specific, matrix-anchored mediators of local intercellular signalling in health, ageing and disease

Article Title: Matrix-bound extracellular vesicles

Article References: Matrix-bound extracellular vesicles. (n.d.). https://doi.org/10.1038/s44222-026-00477-9

Image Credits: AI Generated

DOI: 10.1038/s44222-026-00477-9

Keywords: extracellular vesicles, matrix-bound vesicles, extracellular matrix, tissue engineering, regenerative medicine, biomarkers, microRNA, decellularization, immunomodulation, tumour microenvironment, drug delivery, Nature Reviews Bioengineering