Cartilage Regeneration Without Surgery: How Chondroinductive Therapies Work

Why cartilage is the tissue that does not heal

Articular cartilage is the smooth, glassy layer that covers the ends of bones inside a joint. It lets the knee, hip and shoulder glide with almost no friction and absorbs loads that can reach several times body weight during running or jumping. It is also one of the few tissues in the human body with essentially no capacity to repair itself.

The reason is structural. Hyaline cartilage has no blood vessels, no nerves and no lymphatic drainage. Its cells — chondrocytes — sit isolated inside a dense matrix of type II collagen and proteoglycans, receive nutrients only by diffusion from the synovial fluid, and divide very rarely in adults. When the surface is damaged by trauma, repetitive load or the slow degeneration of osteoarthritis, there is no bleeding, no inflammatory scaffold and no supply of progenitor cells to rebuild the lost tissue. The defect stays, and over time it grows.

Cartilage damage is far from rare. Focal chondral lesions have been reported in as much as 63% of the general population and 36% of athletes undergoing knee arthroscopy, and osteoarthritis is among the leading causes of disability worldwide. For a patient in their forties or fifties with a symptomatic cartilage defect, the current options are a difficult trade-off between symptom control and invasive surgery.

What surgery can and cannot do today

Orthopedic surgeons have a mature toolbox for focal cartilage defects, and the choice of technique depends on the size and location of the lesion and on whether the underlying bone is involved. Small lesions are often treated with marrow stimulation (microfracture), which creates channels to the bone marrow so that blood and marrow cells fill the defect. Medium and large lesions may receive osteochondral autograft or allograft transplantation, or cell-based procedures such as matrix-induced autologous chondrocyte implantation (MACI), in which the patient's own chondrocytes are expanded in a laboratory and implanted in a second operation. A 2021 review published in Cartilage — co-authored by Spero Science founder Prof. Dr. Tiago Lazzaretti Fernandes together with cartilage surgeons from Stanford, Brigham and Women's Hospital, the Hospital for Special Surgery and other centers — organizes these classic and novel procedures into a treatment algorithm based on lesion size, location and subchondral bone involvement.

These techniques work, but they share the same limitations. They require an operation, often two. Marrow stimulation tends to produce fibrocartilage, a scar-like tissue that is mechanically weaker than the original hyaline cartilage and may deteriorate after a few years. Cell-based implants are expensive, logistically complex and depend on cell-manufacturing infrastructure that few countries have. And none of these options address the diffuse, progressive cartilage loss of osteoarthritis, where there is no single defect to fill.

For osteoarthritis itself, treatment remains largely symptomatic: physiotherapy, weight management, analgesics, intra-articular corticosteroids or hyaluronic acid, and eventually joint replacement. There is still no approved therapy that regenerates cartilage or reliably changes the course of the disease.

Chondroinduction: teaching the joint to rebuild cartilage

"Chondroinduction" describes the process of stimulating cells to become cartilage-forming cells — chondrocytes — and to produce cartilage matrix. It is the cartilage counterpart of the osteoinduction that bone biologists have exploited for decades with growth factors such as BMPs.

The joint is not empty of repair potential. The synovial membrane that lines the joint capsule contains mesenchymal stromal cells (MSCs) with a strong intrinsic tendency toward chondrogenic differentiation; so do the bone marrow beneath the cartilage and the fat pad inside the knee. These cells are already there. What they lack is the right signal and the right environment. Left alone, they respond to injury by producing fibrous tissue rather than hyaline cartilage.

A chondroinductive therapy aims to supply that missing signal directly inside the joint. The concept is an injectable formulation that recruits endogenous progenitor cells, drives them toward the chondrocyte lineage and supports the deposition of a type II collagen–rich matrix — without harvesting cells from the patient, without laboratory expansion and without opening the joint. Delivered by a simple intra-articular injection in an outpatient setting, it could be repeated, combined with rehabilitation and used earlier in the disease, when cartilage loss is still limited and the biological cost of regeneration is lowest.

This is the rationale behind the Chondroinductive Molecule, the lead therapeutic platform of Spero Science Innovation: an injectable chondroinductive therapy designed to stimulate cartilage repair and treat osteoarthritis and focal lesions without surgery.

Where the science comes from

Spero Science was founded by orthopedic surgeon-scientists at the University of São Paulo, and the platform builds on more than a decade of published cartilage research by its founders.

The group developed and validated a large-animal model for testing cartilage therapies, using a Brazilian miniature pig with full-thickness chondral defects in the knee, published in Stem Cell Reviews and Reports in 2018. That model has since been used to compare tissue-engineering approaches under Good Manufacturing Practice conditions. In a 2024 preclinical study in Pharmaceutics, scaffold-free tissue-engineered constructs made from synovial stromal cells produced significantly better cartilage coverage and quality than untreated defects after six months, with MRI (MOCART) and histological (ICRS-2) scores that approached those of native cartilage on T2 mapping.

The same team led a 2024 systematic review and meta-analysis in the Journal of Orthopaedic Translation of 25 randomized controlled trials (1,048 participants) on advanced mesenchymal stromal cell therapy for knee osteoarthritis. It found lower pain scores at 12 months compared with viscosupplementation and no difference in serious adverse events — while making the honest point that the certainty of evidence is still limited and better-designed trials are needed. That combination of enthusiasm for regenerative biology and rigor about evidence is the culture Spero Science was built on.

The lesson from this body of work is clear: cells that already live in the joint can rebuild cartilage if they are guided properly. The Chondroinductive Molecule is the attempt to turn that guidance into a product that does not require a cell-manufacturing facility or an operating room.

Development status and regulatory pathway

The Chondroinductive Molecule is in preclinical and translational development. The program follows the standard sequence for an injectable regenerative therapeutic: formulation and characterization, in vitro chondrogenic potency assays, large-animal efficacy and safety studies, and preparation of the regulatory dossier. In Brazil, the pathway runs through ANVISA, the national health regulatory agency; the program is designed from the start so that the same data package can support submissions in other jurisdictions.

Spero Science develops this platform within the São Paulo translational ecosystem — the University of São Paulo Medical School (FMUSP), Hospital das Clínicas HC-FMUSP, Hospital Sírio-Libanês — and with institutional partners that include FAPESP, EMBRAPII, InovaHC and Eretz.bio.

What it would mean for patients — and for partners

For patients, a chondroinductive injection would change the moment at which cartilage repair becomes possible: earlier, cheaper and with far less risk than surgery, and applicable to osteoarthritis rather than only to isolated defects. For health systems, it would move cartilage repair from the operating room to the outpatient clinic.

For investors and industry partners, the platform sits at the intersection of two large unmet needs — osteoarthritis and focal cartilage lesions — with a founding team that has already published the preclinical models, the cell-therapy evidence and the surgical algorithms that define the field. Spero Science is open to co-development, licensing and investment conversations around this platform.

Learn more about the Chondroinductive Molecule, explore our cell therapy and tissue engineering platform, or partner with us.

References

• Hinckel BB, Thomas D, Vellios EE, Hancock KJ, Calcei JG, Sherman SL, Eliasberg CD, Fernandes TL, Farr J, Lattermann C, Gomoll AH. Algorithm for Treatment of Focal Cartilage Defects of the Knee: Classic and New Procedures. Cartilage. 2021;13(1_suppl):473S-495S. https://doi.org/10.1177/1947603521993219

• Fernandes TL, Shimomura K, Asperti A, et al. Development of a Novel Large Animal Model to Evaluate Human Dental Pulp Stem Cells for Articular Cartilage Treatment. Stem Cell Rev Rep. 2018;14(5):734-743. https://doi.org/10.1007/s12015-018-9820-2

• Fernandes TL, Santanna JPC, de Faria RR, Pastore ER, Bueno DF, Hernandez AJ. Tissue Engineering Construct for Articular Cartilage Restoration with Stromal Cells from Synovium vs. Dental Pulp — A Pre-Clinical Study. Pharmaceutics. 2024;16(12):1558. https://doi.org/10.3390/pharmaceutics16121558

• Tabet CG, Pacheco RL, Martimbianco ALC, Riera R, Hernandez AJ, Bueno DF, Fernandes TL. Advanced therapy with mesenchymal stromal cells for knee osteoarthritis: Systematic review and meta-analysis of randomized controlled trials. J Orthop Translat. 2024;48:176-189. https://doi.org/10.1016/j.jot.2024.07.012

• Fernandes TL, Bueno DF, Shimomura K, Shao Z, Gomoll AH. Editorial: Tissue Engineering and Cell Therapy for Cartilage Restoration. Front Cell Dev Biol. 2022;10:947588. https://doi.org/10.3389/fcell.2022.947588