Frank J. Frassica

Inhibition of TGF-β signaling in mesenchymal stem cells of subchondral bone attenuates osteoarthritis

Osteoarthritis is a highly prevalent and debilitating joint disorder. There is no effective medical therapy for the condition because of limited understanding of its pathogenesis. We show that transforming growth factor β1 (TGF-β1) is activated in subchondral bone in response to altered mechanical loading in an anterior cruciate ligament transection (ACLT) mouse model of osteoarthritis. TGF-β1 concentrations are also high in subchondral bone from humans with osteoarthritis. High concentrations of TGF-β1 induced formation of nestin-positive mesenchymal stem cell (MSC) clusters, leading to formation of marrow osteoid islets accompanied by high levels of angiogenesis. We found that transgenic expression of active TGF-β1 in osteoblastic cells induced osteoarthritis, whereas inhibition of TGF-β activity in subchondral bone attenuated the degeneration of articular cartilage. In particular, knockout of the TGF-β type II receptor (TβRII) in nestin-positive MSCs led to less development of osteoarthritis relative to wild-type mice after ACLT. Thus, high concentrations of active TGF-β1 in subchondral bone seem to initiate the pathological changes of osteoarthritis, and inhibition of this process could be a potential therapeutic approach to treating this disease.Osteoarthritis is a highly prevalent and debilitating joint disorder. There is no effective medical therapy for osteoarthritis due to limited understanding of osteoarthritis pathogenesis. We show that TGF–β1 is activated in the subchondral bone in response to altered mechanical loading in an anterior cruciate ligament transection (ACLT) osteoarthritis mouse model. TGF–β1 concentrations also increased in human osteoarthritis subchondral bone. High concentrations of TGF–β1 induced formation of nestin+ mesenchymal stem cell (MSC) clusters leading to aberrant bone formation accompanied by increased angiogenesis. Transgenic expression of active TGF–β1 in osteoblastic cells induced osteoarthritis. Inhibition of TGF–β activity in subchondral bone attenuated degeneration of osteoarthritis articular cartilage. Notably, knockout of the TGF–β type II receptor (TβRII) in nestin+ MSCs reduced development of osteoarthritis in ACLT mice. Thus, high concentrations of active TGF–β1 in the subchondral bone initiated the pathological changes of osteoarthritis, inhibition of which could be a potential therapeutic approach.

Matrix IGF-1 maintains bone mass by activation of mTOR in mesenchymal stem cells

Insulin-like growth factor 1 (IGF-1), the most abundant growth factor in the bone matrix, maintains bone mass in adulthood. We now report that IGF-1 released from the bone matrix during bone remodeling stimulates osteoblastic differentiation of recruited mesenchymal stem cells (MSCs) by activation of mammalian target of rapamycin (mTOR), thus maintaining proper bone microarchitecture and mass. Mice with knockout of the IGF-1 receptor (Igf1r) in their pre-osteoblastic cells showed lower bone mass and mineral deposition rates than wild-type mice. Further, MSCs from Igf1rflox/flox mice with Igf1r deleted by a Cre adenovirus in vitro, although recruited to the bone surface after implantation, were unable to differentiate into osteoblasts. We also found that the concentrations of IGF-1 in the bone matrix and marrow of aged rats were lower than in those of young rats and directly correlated with the age-related decrease in bone mass. Likewise, in age-related osteoporosis in humans, we found that bone marrow IGF-1 concentrations were 40% lower in individuals with osteoporosis than in individuals without osteoporosis. Notably, injection of IGF-1 plus IGF binding protein 3 (IGFBP3), but not injection of IGF-1 alone, increased the concentration of IGF-1 in the bone matrix and stimulated new bone formation in aged rats. Together, these results provide mechanistic insight into how IGF-1 maintains adult bone mass, while also providing a further rationale for its therapeutic targeting to treat age-related osteoporosis.

Autologous cultured chondrocytes: adverse events reported to the United States Food and Drug Administration.

BACKGROUND Carticel is an autologous cultured chondrocyte product that has been approved by the United States Food and Drug Administration for the repair of symptomatic cartilaginous defects of the femoral condyle that are caused by acute or repetitive trauma in patients who have been previously managed with arthroscopy or other surgical procedures. The present report describes the adverse events following Carticel implantation as reported to the Food and Drug Administration from 1996 to 2003. METHODS We reviewed adverse event reports that had been submitted to the Food and Drug Administrations MedWatch system for information on demographic characteristics, adverse events, and surgical revisions. Adverse events were categorized into sixteen non-mutually exclusive groups. Five categories were used to classify reoperations. Food and Drug Administration regulations require manufacturers to report adverse events; however, reporting by clinicians and others is voluntary. Therefore, adverse event reporting is likely to underestimate the number of event occurrences. Adverse events may be either causally or coincidentally related to the product. RESULTS A total of 497 adverse events among 294 patients receiving Carticel were reported. The median interval from Carticel implantation to the diagnosis of an adverse event was 240 days (range, one to 2105 days). The median age of the patients was thirty-eight years, and 63% of the patients were male. Of the 270 events for which the anatomic site was noted, 258 (96%) involved the femoral condyles. More than one adverse event was reported for 135 patients (46%). The most commonly reported events were graft failure (seventy-three patients; 25%), delamination (sixty-five patients; 22%), and tissue hypertrophy (fifty-two patients; 18%). In addition, eighteen surgical site infections were reported, including eleven joint and seven soft-tissue infections. Surgical revision subsequent to Carticel implantation was mentioned in the records for 273 patients (93%). The reasons for the 389 revision procedures included graft-related problems (187 procedures; 48.1%), periarticular soft-tissue problems (ninety-seven procedures; 24.9%), and intra-articular problems (sixty-three procedures; 16.2%). Eight patients had a total knee replacement. Based on the manufacturers reported distribution of 7500 Carticel lots between 1995 and 2002, 285 patients (3.8%) had an adverse event that was reported to the Food and Drug Administration. CONCLUSIONS The most common adverse events reported in association with the Carticel technique involved graft failure, delamination, and tissue hypertrophy.

Solitary plasmacytoma of bone: mayo clinic experience

A review of 46 cases of solitary plasmacytoma of bone was undertaken in an attempt to better define the clinical features and prognostic indicators associated with this disease. Criteria for inclusion in the study included the following: (a) solitary lytic bone lesion on skeletal survey; (b) histologic confirmation of the lesion; and (c) bone marrow plasmacytosis of less than 10 percent. Patients with extramedullary plasmacytomas and osteosclerotic lesions were excluded. All patients were evaluated with serum and urine protein studies at the time of diagnosis. The median follow-up was 90 months with a minimum of 30 months. Fifty-four percent of the lesions involved the vertebral column. The thoracic spine was the single most commonly involved site (13/46 patients). The initial lesion was treated with radiotherapy in all but three patients in whom complete surgical resection was achieved. Total doses ranged from less than 20 Gy to 70 Gy with a median of 39.75 Gy. Overall, 54% developed multiple myeloma, 2% failed with new bone lesions without multiple myeloma, and 11% developed local recurrences. No patient receiving 45 Gy or more to the solitary lesion had a local failure. While the median time to progression was 18 months, 23% of the failures occurred after 60 months. The five local failures occurred at 7, 12, 18, 40, and 114 months. The overall survival was 74% at 5 years and 45% at 10 years. The 5- and 10-year disease-free survivals, however, were 43 and 25%, respectively. Evidence of abnormal serum and/or urine protein was found in 25 of 46 patients. Neither survival nor disease-free survival was significantly influenced by the presence of abnormal proteins even if they persisted after irradiation.

Parosteal osteosarcoma. A clinicopathological study.

The records of 226 patients (sixty-seven who were managed at our institution and 159 who were identified from the consultation files) who had had a parosteal osteosarcoma were reviewed. The criteria for diagnosis were that, roentgenographically, the lesion had arisen from the surface of the bone and that, histologically, the tumor was well differentiated (Grade 1 or 2); it was characterized by well formed osteoid within a spindle-cell stroma; and, when there was medullary involvement, less than 25 per cent of the medullary cavity was affected. Dedifferentiation was more common (16 per cent of the patients) than previously reported and was associated with a poor prognosis. Cross-sectional imaging studies demonstrated medullary involvement in 22 per cent of the patients, an unmineralized soft-tissue mass peripheral to the mineral component in 51 per cent, and adjacent soft-tissue invasion in 46 per cent. In contrast to the findings in our previous studies, medullary involvement was not a poor prognostic factor. At an average of thirteen years (range, two to forty-one years), eleven of the sixty-seven patients who were managed at our institution died of the tumor; ten of these patients had a dedifferentiated tumor. Statistical analysis of the thirty-nine patients who had had the primary treatment at our institution revealed that incomplete resection was associated with an increased risk of local recurrence and that dedifferentiation markedly increased the risk of metastasis.

Metastatic bone disease: A study of the surgical treatment of 166 pathologic humeral and femoral fractures

A retrospective study of the surgical treatment of 166 metastatic lesions of the humerus and femur in 147 patients was performed. There were 106 women and 41 men whose average age was 62 years. Two-thirds of the patients were treated for complete fractures, while one-third were treated for impending fractures. Breast, lung, and kidney carcinoma accounted for the majority of the primary lesions. One-half of the patients died within nine months of surgery, while one-quarter were alive 19.1 months after surgery. The patients with breast cancer had the best prognosis, while the patients with lung cancer had the worst. The probability of implant failure increased linearly with time to 33% at 60 months. The probability of failure for the femoral lesions was greater, with 44% at 60 months. The average survival in the patients with failed fixation in the femoral lesions was 34.5 months with a mean interval to failure at 17.7 months. The failure rate was high (23%) in proximal femoral lesions treated with a compression screw or nail plate. Common reasons for failure included poor initial fixation, improper implant selection, and progression of disease within the operative field. Bone cement augmentation should be used with the fixation device when possible. Complications due to hip-screw cut-out from the head may also be reduced by applying bone cement around the screw threads.

Dislocation of the knee

The results of treatment for vascular and ligamentous injuries in 17 patients who suffered complete dislocation of the knee were reviewed. Eight patients had 23 associated injuries. All nine patients who had injuries of the popliteal artery had arterial reconstruction with saphenous vein bypass grafts, which were successful in eight (89%). Intraoperative arteriography after vascular repair showed a narrowed anastomosis requiring revision in two (22%) of the nine patients and distal thrombi requiring removal in five (55%) patients. Delay in arterial repair was responsible for the one failure. Eleven patients had satisfactory results after early open ligament repair. The results were less favorable in the patients not treated with early ligament repair.

Extraosseous Ewing's sarcoma. A study of 42 cases

Fifty patients at the Mayo Clinic (Rochester, MN) from 1935 to 1985 met the histologic criteria for extraosseous Ewings sarcoma. Forty‐two had soft tissue primaries without bony involvement and formed the basis for this retrospective study of the clinical behavior and management of extraosseous Ewings sarcoma. There were 19 male and 23 female patients (mean age, 22 years). Metastases were documented in 30 of the patients, six at the time of presentation and 24 occurring up to 11 years later, most commonly to lungs or bone. Three patients were lost to follow‐up. Sixteen of 35 patients (46%) had local recurrence. Overall survival was 15 of 39 (38.5%) at 5 years. Decreased survival was noted with pelvic tumors, incomplete resections, and presence of metastatic disease, whereas increased survival was associated with wide surgical resection with negative microscopic margins, adjuvant local radiation therapy, and presentation since 1970 (48% 5‐year survival compared with 28% before 1970).

Irradiation induces bone injury by damaging bone marrow microenvironment for stem cells

Radiation therapy can result in bone injury with the development of fractures and often can lead to delayed and nonunion of bone. There is no prevention or treatment for irradiation-induced bone injury. We irradiated the distal half of the mouse left femur to study the mechanism of irradiation-induced bone injury and found that no mesenchymal stem cells (MSCs) were detected in irradiated distal femora or nonirradiated proximal femora. The MSCs in the circulation doubled at 1 week and increased fourfold after 4 wk of irradiation. The number of MSCs in the proximal femur quickly recovered, but no recovery was observed in the distal femur. The levels of free radicals were increased threefold at 1 wk and remained at this high level for 4 wk in distal femora, whereas the levels were increased at 1 wk and returned to the basal level at 4 wk in nonirradiated proximal femur. Free radicals diffuse ipsilaterally to the proximal femur through bone medullary canal. The blood vessels in the distal femora were destroyed in angiographic images, but not in the proximal femora. The osteoclasts and osteoblasts were decreased in the distal femora after irradiation, but no changes were observed in the proximal femora. The total bone volumes were not affected in proximal and distal femora. Our data indicate that irradiation produces free radicals that adversely affect the survival of MSCs in both distal and proximal femora. Irradiation injury to the vasculatures and the microenvironment affect the niches for stem cells during the recovery period.

Secondary malignant giant-cell tumor of bone. Clinicopathological assessment of nineteen patients.

Twenty-six patients who had a malignant giant-cell tumor of bone--a sarcoma either juxtaposed to a zone of typical benign giant-cell tumor or occurring at the site of a previously documented benign giant-cell tumor--have been seen at the Mayo Clinic. Of the twenty-six tumors, nineteen were secondary to a previous attempt at local control of a benign giant-cell tumor. All but one of these nineteen patients with a secondary tumor had received therapeutic irradiation four to thirty-nine years earlier. The nature and duration of the symptoms and the sites of predilection of the malignant giant-cell tumors were the same as for benign giant-cell tumor. Fibrosarcoma occurred three times as frequently as osteosarcoma. The best results of treatment of the secondary sarcoma were obtained with early ablation.