David J. Zaleske’s research while affiliated with Harvard Medical School and other places

This study examines the use of a devitalized biological knee as a scaffold for repopulation with chondrocytes and tests the hypothesis that the devitalized scaffold would become repopulated with the foreign chondrocytes when placed in a suitable environment. Chimeric knee constructs were engineered in vitro and their ectopic in vivo fate was examined in SCID mice. The constructs were made by applying porous collagen sponges that contained viable bovine articular chondrocytes to shaved articular surfaces of devitalized embryonic chick knees. The chimeric joints were cultured for 1 week and were subsequently transplanted into dorsal subcutaneous pouches of 5-week-old mice. Specimens were prepared for histological analysis at 1, 3, 6, or 8 weeks after transplantation. Controls included empty collagen sponges, collagen sponges seeded with viable bovine chondrocytes, and devitalized chick knees without collagen sponge inserts. One week after in vitro incubation of the constructs, the porous collagen sponges with viable bovine chondrocytes were adherent to the shaved articular surfaces of the devitalized chick joints. There was abundant metachromatic neomatrix around the chondrocytes in the collagen sponges. During maintenance of the constructs in vivo, the chimeric joints exhibited dramatic changes. Bovine chondrocytes proliferated in the collagen sponges and formed abundant new matrix. Bovine chondrocytes migrated into preexisting chick cartilage canals at 1 week. Subsequently, bovine chondrocytes invaded the matrix of the devitalized chick knees. Bovine neocartilage obliterated the interface between the collagen sponge and the devitalized chick cartilage. With time in vivo, the bovine neocartilage expanded and replaced the chick matrix. The devitalized cartilage appears to provide a framework for supporting chondrogenesis in a chimeric joint.

The avascular portion of the meniscus cartilage in the knee does not have the ability to repair spontaneously. Cell-based therapy is able to repair a lesion in the swine meniscus. Controlled laboratory study. Sixteen Yorkshire pigs were divided into four groups. A longitudinal tear was produced in the avascular portion of the left medial meniscus of 4 pigs. Autologous chondrocytes were seeded onto devitalized allogenic meniscal slices and were secured inside the lesion with two sutures. Identical incisions were created in 12 other pigs, which were used as three separate control groups: 4 animals treated with an unseeded scaffold, 4 were simply sutured, and 4 were left untreated. Meniscal samples were collected after 9 weeks, and the samples were analyzed grossly, histologically, and histomorphometrically. Gross results showed bonding of the lesion margins in the specimens of the experimental group, whereas no repair was noted in any of the control group specimens. Histological and histomorphometrical analysis showed multiple areas of healing in the specimens of the experimental group. This study demonstrated the ability of seeded chondrocytes to heal a meniscal tear. Clinical Relevance: Cell-based therapy could be a potential tool for avascular meniscus repair.

Chondroblastomas are benign cartilaginous lesions; however, intervention is necessary to stop progression and alleviate pain. The authors evaluated three patients in whom minimally invasive percutaneous radio-frequency heat ablation was used to treat pathologically proven chondroblastoma to determine whether this treatment demonstrated long-term success. The authors found that this approach may be an effective alternative to surgical intervention in some cases.

Hyaluronan (HA) is a component of cartilage matrix with known effects on chondrocytes. We tested the effects of adding HA to 3-dimensional (3-D) collagen sponges on chondrocyte function in vitro. Bovine articular chondrocytes isolated by collagenase digestion were injected into either collagen or HA/collagen scaffolds comprising different amounts of HA (2, 5, 10, and 14% w/w). Expression of aggrecan and type II collagen genes was measured by gene-specific quantitative competitive reverse transcriptase-polymerase chain reactions, and the extracellular matrix was estimated by histomorphometrical analyses. After 7-day culture, the chondrocytes in 2% (w/w) HA sponges expressed fourfold more mRNA transcripts for type II collagen (p = 0.002) and twofold more mRNA transcripts for aggrecan (p = 0.022) than in control collagen sponges. Furthermore, there was 45% more extracellular matrix in 2% (w/w) HA sponges and 43% less matrix in the 10% (w/w) HA sponges compared with plain collagen sponges (p > 0.05). In sum, a small amount of HA in 3-D collagen scaffolds enhanced chondrogenesis, but a greater amount was inhibitory. This 3-D system represents a novel tool to identify mechanisms by which extracellular matrix molecules influence chondrocyte function. Further, these results show the potential for modifying scaffolds to improve production of engineered cartilage for in vivo applications. © 2000 John Wiley & Sons, Inc. J Biomed Mater Res 55: 13–19, 2001

In this study, devitalized meniscal tissue pre-seeded with viable cultured chondrocytes was used to repair a bucket-handle incision in meniscal tissue transplanted to nude mice. Lamb knee menisci were devitalized by cyclic freezing and thawing. Chips measuring four by two by one-half millimeters were cut from this devitalized tissue to serve as scaffolds. These chips were then cultured either with or without viable allogeneic lamb chondrocytes. From the inner third of the devitalized meniscal tissue, rectangles were also cut approximately 8 x 6 mm. A 4 mm bucket-handle type incision was made in these blocks. The previously prepared chips either with (experimental group) or without viable chondrocytes (control group) were positioned into the incisions and secured with suture. Further control groups included blocks of devitalized menisci with incisions into which no chips were positioned and either closed with suture or left open with no suture. Specimens were transplanted to subcutaneous pouches of nude mice for 14 weeks. After 14 weeks, seven of eight experimental specimens (chips with viable chondrocytes) demonstrated bridging of the incision assessed by gross inspection and manual distraction. All the control groups were markedly different from the experimental group in that the incision remained grossly visible. Histological analysis was consistent with the differences apparent at the gross level. Only the experimental specimens (chips with viable chondrocytes) with gross bridging demonstrated obliteration of the interface between incision and scaffold. None of the control specimens revealed any cells or tissue filling the incision. Tissue engineering using scaffolds and viable cells may have an application in meniscal repair in vivo.

The objective of this study was to evaluate the biomechanical properties of newly formed cartilaginous tissue synthesized from isolated chondrocytes. Cartilage from articular joints of lambs was either digested in collagenase to isolated chondrocytes or cut into discs that were devitalized by multiple freeze-thaw cycles. Isolated cells were incubated in suspension culture in the presence of devitalized cartilage matrix for 3 weeks. Multiple chondrocyte/matrix constructs were assembled with fibrin glue and implanted subcutaneously in nude mice for up to 6 weeks. Testing methods were devised to quantify integration of cartilage pieces and mechanical properties of constructs. These studies showed monotonic increase with time in tensile strength, fracture strain, fracture energy, and tensile modulus to values 5-10% of normal articular cartilage by 6 weeks in vivo. Histological analysis indicated that chondrocytes grown on dead cartilage matrix produced new matrix that integrated individual cartilage pieces with mechanically functional tissue.

More than 50 surgical procedures have been described for treatment of chronic lateral ankle instability. Anatomic repairs have come into favor in the recent literature based on short-term studies, which have used objective measures for outcome. A long-term (range, 7-20 years; average, 12.6) patient-oriented outcome analysis was performed on 20 patients that underwent a modified Evans procedure for chronic lateral ankle instability by the senior author over a 13-year period. There was a 91% follow-up on all located patients (20 of 22). All patients had mechanical and functional instability, and all had failed conservative therapy. A questionnaire, based on the outcomes questionnaire developed by the American Academy of Orthopaedic Surgeons was used to determine functional stability. The patient's ability to perform recreational or competitive sporting activities at specific time intervals were also assessed (preinjury, 1 year postoperatively, present time). Overall result was considered satisfactory if five criteria were met: patents (a) were happy with the outcome of surgery, (b) were able to perform desired level of activities, (c) had functional stability, (d) were pain free performing desired level activities, (e) would undergo procedure again. The entire cohort demonstrated satisfactory results in 19 (95%) of 20 respondents at 1 year and 17 (85%) at present time. Grouping patients into competitive (12 cases) and recreational (eight cases) athletes demonstrated six of 12, and seven of eight reached their preinjury level (p = 0.074). In this study, we showed that surgical reconstruction using a modified Evans procedure is a reliable and effective treatment for chronic lateral instability. This procedure has proved to stand the test of time, as demonstrated by a patient-oriented outcome analysis. The elite athlete may be better served by a procedure using the principles of anatomic rather than augmented repair; however, the long-term data to our knowledge has yet to be published.

The clinical response of growth plate to exogenous forces is well recognized, although the organ-level mechanisms are poorly understood. Physeal cartilage from 5- to 7-day-old bovine distal radii was subjected to 245 N of tension or 245 N of compression (0.012 MPa) in organ culture over a 24-h period. Eleven specimens (six tension, five compression) were assayed for cellular proliferation with tritiated thymidine. Eighteen specimens (12 tension, six compression) were assayed far synthetic activity with radioactive sulfate. Media were assayed for prostaglandin production. Tension increased whereas compression decreased synthetic activity and prostaglandin production by physeal cartilage in explant culture over a 24-h period. There was no significant change in thymidine uptake. Physeal cartilage can respond to both tension and compression and, in the short term, appears to alter synthetic activity without changing the rate of cell proliferation. This study system allows local sampling and manipulation of the physeal organ environment and may lead to ways of approaching growth-plate pathologies in vivo.

The clinical response of growth plate to exogenous forces is well recognized, although the organ-level mechanisms are poorly understood. Physeal cartilage from 5- to 7-day-old bovine distal radii was subjected to 245 N of tension or 245 N of compression (0.012 MPa) in organ culture over a 24-h period. Eleven specimens (six tension, five compression) were assayed for cellular proliferation with tritiated thymidine. Eighteen specimens (12 tension, six compression) were assayed for synthetic activity with radioactive sulfate. Media were assayed for prostaglandin production. Tension increased whereas compression decreased synthetic activity and prostaglandin production by physeal cartilage in explant culture over a 24-h period. There was no significant change in thymidine uptake. Physeal cartilage can respond to both tension and compression and, in the short term, appears to alter synthetic activity without changing the rate of cell proliferation. This study system allows local sampling and manipulation of the physeal organ environment and may lead to ways of approaching growth-plate pathologies in vivo.