So, I thought I'd start out with some general points here to kind of set the stage and frame the rest of the morning here. The disclosures, I believe, none are directly relevant here. Some research support here. So, you know, look at the slides over here, easy to see. My goals here are to go over some brief thoughts on the potentials and current limitations of orthobiologics. Sort of just kind of set the stage, kind of some definitions here. And one important thing I'd like to bring out is some important concepts on cell therapy and how, frankly, we shouldn't even use the word stem cells, quite honestly, in a lot of this. I'll talk a little bit about PRP and cell therapy. I'm going to focus in particular on tendinopathy. You hear probably some other tissues from the other speakers here. So just, again, to set the stage, kind of frame this. Well, you know, what is regenerative medicine? Well, obviously, there's a number of different products out there, autologous blood products, PRP, and other similar type of things that are being developed. So, again, on PRP, there's other autologous formulations now being developed, obviously, cell therapy. And again, I wouldn't even use the term stem cells. We'll kind of talk a little bit about that as we kind of go through here. Obviously, we can use cells from bone marrow, from adipose, and even from these perinatal tissues, umbilical cord bloods, and placenta, and Wharton's jelly, and things like that. Some are using now gene-modified cells. But I would submit to you regenerative medicine is a very broad field, and beyond just cells and PRP, we can think about various cytokines and purified small peptides. But even these matrix scaffolds, and even the potential for systemic modulation, I think it all fits within this whole area of sort of orthobiologic. So it's a big and, frankly, kind of confusing and fast-moving area here. So I'll start with the overall message here. I think, clearly, the techniques and methods to positively affect the biologic events in tissue repair have great potential, but I would submit to you a lot of this is really not yet ready for prime time. Preclinical studies certainly demonstrate promise, but at the same time, we've all seen how indiscriminate use of these sometimes unproven therapies may, in fact, hinder progress in this field for us. So just thinking about cell therapy, just, again, to set the stage again, obviously bone marrow. You know, the majority of cells in bone marrow are hematopoietic stem cells, the cells that are, in fact, you may not even call them stem cells, because they are still limited. They can just form the blood elements. But that's hematopoietic. What we're looking at is mesenchymal cells, the mesenchymal stromal cells, which is the small, small minority of cells in bone marrow. Pictures below show we can obviously get bone marrow from various sources, iliac crest most commonly, but you can aspirate marrow from the paroxysmal humerus, from the interconvular notch during knee surgery, so you can obtain marrow from other areas. Adipose tissue. So three different areas here are kind of types of fat preparations just to kind of, again, provide some basic definitions. So-called microfragmented fat. This is the lipogems. It'll mention more in a moment. I have no relationship, again, with any of these companies. This is the simple mechanical emulsification using different filters and things of a lipo-aspirate. And then you have your stromal vascular fraction, which is basically further processing. Typically, this is enzymatic digestion, which is not allowed in the United States. But the stromal vascular fraction still is a very heterogeneous population of various cell types that you see listed here. So it's still not, by any means, any purified population. Then you can culture the stromal vascular fraction, come up with this, your adipose-derived stromal cells. And then you can produce your cells that are culture-expanded. Again, we can't do that with our current regulatory environment. This lipogem, this is, again, this microfragmented adipose tissue. It's just a single cell or a single-use device that is available. Mechanical emulsification of fat, it kind of breaks up into small particles, removes some of the lipids and oils. May maintain these intact stromal vascular niche, these little globs or clumps of cells, if you will. But again, an area that needs further characterization, because there's such heterogeneity in these materials. Not much clinical data out there. It's just one example of a small little case series, 17 patients, patient in EOA. It just demonstrates there's improvements in symptoms. So a lot of these materials have anti-inflammatory activities, and so they can be symptom-modifying, but rarely are they structure-modifying in any way. And then, as I mentioned, perinatal materials, amniotic membrane, amniotic fluids, cell-derived from umbilical cord blood, Wharton's jelly, this whole area, again, also very much an evolving area. Clearly, these materials have various anti-fibrotic and anti-inflammatory cytokines and a number of immunomodulatory proteins. But whether they have any viable cells is a question, and many of these, frankly, do not. Very little data out there. In fact, right now, and maybe Dr. Werbel talked more to this, a lot of these have been or will be removed from the market with the current end of FDA enforcement discretion. They're starting to enforce some of these rules now such that these are being removed from the market based on both the homologous use criteria as well as reliance on viable cells. So a lot of these amniotic fluid materials will be taken off the market or need to go through a formal IND to get a biologic license application. Some data out there. There's one interesting study I kind of put in here. This author looked at amniotic fluid from three different companies. MSCs could not be identified in any of these materials. There are some cells. Many of these cells are dead. Certainly none of these cells met any criteria for a mesenchymal stromal cell. So now clearly there are various cytokines and factors in these materials, but as far as a source of cells, we should not make any conclusion that these are considered any type of stem cell therapy, and again, don't even use the word stem cell, but clearly these materials may have some bioactive cytokines, but not a source of active cells. I think I would submit to you we currently have very limited ability to use stem cells at all. The basic definition that everybody goes back to is based on culture-expanded, purified cell populations. Stem cells, you know, it's a very, the cellular and molecular criteria are very strict. A stem cell is a cell that has the ability to undergo asymmetric cell division, self-renewal, obviously multi-differentiation potential. That should be differentiated and distinguished from the formulation that we can use in our patients right now. So the International Society for Cell Therapy has set forth these basic criteria that have been used. I won't get into all the details, but essentially the point here, this is for cultured cells, culture-expanded cells, and you can go through all the different cell surface markers and basic criteria that define an MSC, an MSC being a mesenchymal stromal cell. This is not what we currently use. Based on the current regulations under the CFR 361, we can not carry out manipulation of these materials. You can't take these out of the operating room or clinic and do any kind of cell sorting or culture expansion. The number of true stromal cells in these materials, even if you could do that, is vanishingly small, probably less than one in 10,000. Clearly we need more refined criteria for defining all of these cell populations, whether they're cells from adipose, marrow, or something else. But I would submit to you that the term MSC should only be used to refer to a culture-expanded population of cells that meet the formal International Society for Cell Therapy criteria and should not be used to describe these heterogeneous populations of native cells with really undefined properties. So, minimally manipulated cell preparations that are currently used in the U.S. need to be distinguished from sorted, culture-expanded cells produced in the laboratory, and again, this term stem cell should not even be used here because very few of these cells meet any of the cellular or molecular criteria for a stem cell. A better term would probably be a connective tissue degenerate cell. There is a population of cells in many tissues that can, in fact, proliferate and generate progeny with some capacity to differentiate into connective tissue. So, these cells are present tissue. They have a much more limited differentiation repertoire than true stem cells, certainly, and then these cells can be defined by their ability to form colony-forming units in culture. So, the term CTP, connective tissue degenerate, is probably a more accurate term to use. We're talking about cells here. Clearly a big limitation is the heterogeneity in cell therapy. We have, frankly, a rudimentary understanding of currently used therapies, and we need better methods to measure and classify all of these different products here. At the end of the day, as we start moving forward now, we'll start to use these high-dimensional analyses, multi-parameter flow cytometry, or single-cell analysis, things like that that can really help us to define these things. The tremendous heterogeneity makes clear the need to identify some type of sentinel markers of biologic activity, of purity, of potency, of these various formulations that are used. We need to define and understand the critical quality attributes of these different preparations for different conditions. It'll be different for meniscus versus bone versus cartilage versus tendon. And this type of characterization could eventually allow us the ability to remove competing or inhibiting cells or proteins, allowing much more targeted therapies, which may improve our outcomes, ultimately. A real limitation, again, is the heterogeneity in these different preparations. We need to measure and classify what we put in patients. Some nice work from Ian Murray three or four years ago, this minimal information that should be reported for both PRP as well as cells, patient characteristics, all the characteristics of the materials that you put in the patient, how it was aspirated, how it was prepared, all this important detail that should be in our papers. I tried to stress this in editorial several years ago in the American Journal of Sports Medicine, where I concluded kind of the same. The adoption of minimum reporting standards that facilitate the characterization of these biologic therapies will bring us closer to, ultimately, maybe a personalized medicine approach to our patients, where we can use this in a much more refined fashion. I'd submit to you, we should ask ourselves, when we're using anything, what are we trying to treat? What is the biologic target? We put these materials in and sort of hope something happens. Do we want to improve vascularity, stimulate cell migration, decrease inflammation, accelerate tissue and matrix remodeling? Do we want to attract various cells? Do we want to affect the matrix breakdown? Maybe we want to do all of these. But it's an important thing to think about and define what we're trying to treat, so we can use this in a much more refined fashion. Identification of these targets may ultimately allow us to match a specific either PRP or cell formulation to a specific tissue. And this obviously requires identification of the underlying cellular and molecular mechanisms of tissue degeneration. You know, chronic tendinosis is probably different than an acutely injured tendon. Arthritis, highly variable, right? It's so heterogeneous. Some patients have a real synovitic joint. Others don't. At the same time, we need to rigorously define both the composition and the biologic activity of these various formulations. And only then can we ultimately match the specific agent with the desired biologic target. Clearly one size does not fit all. We need to tailor our therapy to the pathology. Different sites, acute versus chronic disease, the impact of systemic underlying metabolic abnormalities may play a critically important role when we're obtaining cells from that very patient. The local mechanical environment may affect the biologic response to these various implants. The same PRP or, again, even cell therapy formulation would not be expected to have the same effect on different types of tissues, acute versus chronic, male versus female. You know, older patients, younger patients, you can go on and on. It just points out the heterogeneity in both our patients plus our treatments. These materials can be symptom-modifying but are not likely to be structure-modifying. So we know that these various products can improve symptoms. Cell therapies generally are felt to work via paracrine signaling. There's very little evidence that these cells actually engraft or go on and differentiate once they're implanted in the body. They may have a very transient residence time. They may work, in fact, by producing various signaling molecules as listed here. These cells and different materials can produce a number of different cytokines, chemokines, and various anti-inflammatory and immunomodulatory factors. That's probably more likely how implanted cells work rather than these cells engrafting into the healing tissue and differentiating into newly formed tissue. The biologic effects of cells, again, appears to be due to these various mediators that modify the local environment. So Arnold Kaplan, who first coined the term MSC for mesenchymal stem cell back in 1991, has renamed this, you know, MSCs. You've probably seen this. We're making the distinction that these are signaling cells, that these cells are little pharmacies and produce these various cytokines and various mediators. So when you implant cells, they probably modify the local injury environment rather than, again, directly contributing to healing. So again, in this way, they can modify symptoms, but very little evidence to support that they really regenerate tissue. At the end of the day, cells and other factors, PRP and other blood factors, may, in fact, stimulate the intrinsic stem cell niche that exists in many tissues. Many tissues have a niche, a population of progenitor cells, these connective tissue progenitors. Many of these reside in the walls of blood vessels, probably parasites, these CD146 positive cells. Those cells are there. How do we stimulate those cells? Well, these implanted cells that produce these various factors may work by stimulating the local intrinsic stem cell or progenitor cell niche that is resident in many tissues. Some of my own views on the future of the cell therapy, I think the heterogeneity and the starting material for a cell culture suggest to us that some elements of the available population may be desirable for the tissue, while others may not, in fact, have the potential for generation of the desired tissue. These cells may, in fact, compete with or inhibit the desirable clones in a given population. So, ultimately, if we can develop methods to reproducibly characterize a population of cells, this will allow us the ability to potentially remove these competing or inhibiting cells. We could use cell sorting techniques, ultimately, to select a desired subset of cells based on these specific criteria, eventually allowing us a much more precise match of the cultured cell population to the tissue being treated, so I think it's just a much more refined and precise way to use these therapies. The ability to match the various biologic formulation to the desired biologic target would eventually allow much more sort of precision medicine approach. So, with that, some background, PRP, just very basics here. Two basic kind of formulations, the plasma base, which just typically excludes red cells and white cells, lower platelet concentration, some examples here, whereas your Buffy coat typically includes both plasma and the cellular layer, typically has higher cell or platelet concentrations, but also typically includes white cells, so higher leukocyte concentrations. And so this is kind of just a broad, very simple classification to start with. Just to kind of finish up a little bit here on tendon, what does the clinical data tell us as far as tendon? So think about PRP, if we just go to a meta-analysis here to kind of jump right in and summarize, because there's so much data out there, much of it conflicting. This particular meta-analysis, they looked at patients treated with PRP for various types of tendinopathies, essentially found a positive effect for a leukocyte-rich PRP, rather than leukocyte-poor in this particular meta-analysis. No real difference between control injections of saline or local anesthetic, and essentially there, based on this, pretty well-done meta-analysis, the recommendations were, use a single injection of a leukocyte-rich formulation, you may use some anesthetic just in the skin, I would not combine any local anesthetics with your cell population or your PRP, you may use an intratendinous injection using the pepperine techniques, and of course that brings in a whole nother area of variability as far as just the mechanical stimulation from needling. Some clinical data, there's other meta-analyses, another systematic review, I just kind of picked a couple of these, they seem to be well-done, they kind of summarize some of this area for us. Here they looked at eccentric exercise therapy versus PRP, and in fact, eccentric exercise was effective in the short-term, single PRP injection provided good results in the short-term, but in fact, multiple PRP injections obtained the best results, so they concluded that either two or three PRP injections for tendinopathy was effective and was recommended, and so there's some clinical data out there to support, again, symptom modification with PRP for tendons. So the bottom line here, if you look at kind of the universe of our accumulating clinical data, which is mixed at best, it would suggest a positive effect for leukocyte-rich PRP systems. Now, there's a disconnect, if you look at the laboratory data, just for interest and not to get into too much, I kind of summarized a couple of points here, a lot has been done by Lisa Fortier and others in the past, in fact, high white cell concentrations lead to increased inflammatory cytokines, as you might expect, and in fact, the laboratory data demonstrates minimizing leukocytes in PRP would be more important than maximizing platelet numbers, but our clinical data, again, suggests that we should use a leukocyte-rich, so why the disconnect? Although leukocytes lead to more inflammatory mediators in laboratory studies, that's how tendons heal, unfortunately, we need inflammation for tissue to heal, ideally, true tissue regeneration would occur if we block our inflammatory pathways, that doesn't happen, that's in the postnatal organism, healing proceeds by this inflammatory process followed by a production of fibrovascular scar tissue, so inflammation clearly is required to initiate healing, this is certainly consistent with the known adverse effects of non-steroidals and other steroidal medications on tissue healing, so at the end of the day, your leukocyte-rich formulations seem to be the most reasonable for tendon. Which brand to use? Again, no way to make any real conclusion, there's such variability out there in the data, and I would be careful to not be dogmatic in any way in these areas, this is a particular systematic review, tremendous heterogeneity between the different PRP separation systems, I put this up just to, not to get into details, but to just demonstrate this heterogeneity in the types of devices used, the cost, the different PRP volumes that are produced, the differences in platelet concentration that come out, again, this just kind of shows, again, the variability in these different types of systems, in platelet concentration, in leukocyte concentration, not to get into all the details, but it just shows you this tremendous heterogeneity, it's very hard to pick which one to use, in fact, I submit to you, it's kind of, we can't until we know what it is we're trying to treat, what is the tissue, what is the biologic target, only then can we start to pick and choose and do this in a much more precise fashion. I'm not gonna go through all the details in the interest of time, but just to make some general points here. Here they looked at the differences in cytokines produced by these different preparations, so there are no real differences in platelet-derived growth factor TGF-beta, but in fact, there's higher PDGF and TGF-beta for those that have higher leukocyte concentrations, which is typically the case, generally with more white cells and the inflammatory mediators that goes with that, you also typically have higher cytokine concentrations, VEGF was noted to be higher in some of these PRP products that have more leukocytes as well, so again, you'll kind of see that the cytokines often kind of trend with your white cell populations here. Another area, should we use local anesthetics when we do PRP? In this study, the tinocytes were cultured with PRP alone or with various local anesthetics, so essentially, what they find here is tinocyte proliferation is inhibited by combining PRP with either steroid or your local anesthetics. All these agents resulted in less cell proliferation and cell viability compared to just putting PRP itself, so in fact, lidocaine and bupivacaine had a greater inhibitor effect than did steroids, so the bottom line here suggests that these agents should not be combined with the PRP when you're doing these injections. My current recommendation, for what it's worth, and admittedly, this is based on evolving and sometimes incomplete data, I typically would use, as we've suggested here, a leukocyte-rich PRP formulation for tendon. OA would be different. I put that in to make the distinction. If you're treating arthritis, it's often leukocyte-poor. I'm not going to get into cartilage. I think maybe Jason will do more on that. Consider ultrasound-guided injection. Local anesthetic may just in the skin, but again, don't combine that with your materials here. I usually start with one single injection, and if symptoms don't improve over, you know, one to two weeks, you may consider extending to a series of three injections. Some data does demonstrate better results with a series of injections. Then you get into cost and logistics, and these are not covered by insurance, and patients pay out of pocket, and the results are variable, so I don't routinely start with the three-series injection series when I do this here. The post-injection protocol, the recommendations for rehab and activity following PRP are largely empirical and are based really on very little robust clinical data. Some have recommended avoidance of NSAIDs, but really there's very little basic science or even clinical data to support this recommendation. Current recommendation, but you have to tell your patients something, and they want something, so this is kind of just where you're marrying research with kind of clinical medicine. General recommendation is light activity for three days or so, followed by a gradual progression. Generally an eccentric exercise regimen is standard for treatment of tendinopathy, but clearly further data is required to understand how mechanical load on the tendon will affect the biologic response to PRP. We put a little, get a little summary here in the recent, in the Orthopedic Journal of Sports Medicine, where we looked at the literature as far as our antiploidal therapies contraindicated, and most of these studies, we just evaluate the use of NSAIDs as an antiploidal therapy. Most of these are in vitro analyses. Essentially what we concluded here, I'll put at the bottom here, there really is very little support for the common clinical practice of withholding antiploidal therapies in patients being treated with PRP. This is just in the OGSM recently, and we, a lot of this is based on a vitro work, very little in vivo clinical data. But at the end of the day, certainly it's hard to be dogmatic about these recommendations for patients. What is the data of PRP for cuff? Well, for tendinopathy, a couple studies here just to kind of highlight, it's a particular study from, actually from Serbia. They use autologous condition serum, so this Orthokine or Regenikine in this country, not FDA approved. They found a positive effect in symptoms. This other study from Turkey, placebo-controlled, double-blind, randomized, so a well-done trial, found no difference in their patient-reported outcome measures. Another study, Andy Carr in the UK. This is patients undergoing surgery, a chromoplasty randomized to concomitant PRP or no treatment. They found no differences in their outcome scores, and in fact, the tendon biopsy at 12 weeks demonstrated more apoptosis in those treated with PRP than ultrasound-guided biopsy of the tendon 12 weeks after the chromoplasty. So PRP seemed to have a negative effect there. And the study from Switzerland, randomized, again, double-blind trial, no real differences in outcomes at 12 months. In fact, they found the incidence of adverse effects seems to be greater. So in summary here, not recommended at this time for tendinopathy, so your impingement syndrome type of patient. What about rotator cuff repair? Chris Jo from Korea, randomized controlled trial, PRP gels at the repair site, no differences in your outcome measures, but the retear rate was lower in the PRP-treated group. So structural improvements. This group from Alan Wang in Australia, randomized controlled trial, delayed injections of PRP at post-op day seven and 14, no real differences. And this group from Brazil, another randomized controlled trial, PRP applied at the time of surgery, no real differences. I put these in to kind of highlight the variability in our literature, and these are some of the better studies. Meta-analyses do, in fact, suggest improved structural healing. Chan, this group, this is with Tom Vangs-Ness, a nicely done meta-analysis, demonstrates that the retear rate was lower in patients treated with PRP at the time of cuff repair. So that seemed to be positive. This group from Harvard in Switzerland, another meta-analysis, the risk ratio for retear seemed to be lower in those patients treated with PRP for small or medium tears. They felt it probably was not cost-effective, though, based on the incremental cost-effectiveness ratio, but clearly some data to support structural improvements. From Ireland, Ian Hurley from Dublin, another meta-analysis, they compared PRP and a platelet-rich fibrin. Essentially, they find that PRP did have the ability to improve healing rates intended, but this platelet-rich fibrin matrix, a different material, did not. So again, shows just kind of the variability that's out there. So bottom line here seems to be, I think you can conclude that PRP does appear to have some beneficial effect for improvement in structural healing. Again, I think we clearly need further data in this area. We looked at this platelet-rich fibrin matrix material. This is basically taking PRP, add calcium chloride back in the prep, and do a second spin where you kind of clot it. It makes it almost like chewing gum. You can put a suture in it and put this in the repair site. We found no real differences in outcomes, in healing rates, and in fact, based on a logistic regression, those patients receiving the PRFM seem to have a higher rate of tendon defects. So nothing much there. Back to the Hurley study again, where the platelet-rich fibrin matrix also had a negative effect. So bottom line right now, these platelet-rich fibrin matrices are not recommended for cuff repair. Cell therapy, not much data out there. Philippe Pernod, the best study out there. It's not really been reproduced, interestingly. Concentrated mirror-derived cells in patients undergoing cuff repair. 100% of the repairs with cell augmentation healed by six months versus two-thirds in those patients with no cells. In a 10-year follow-up, you see maintained outcomes with much higher healing rates in the MSC-treated group. Long-term cuff integrity is better in those who received a higher number of cells. So this is probably the longest data out there, and again, really has not really been reproduced, but positive effects there. This is a group from Korea using adipose-derived cells. The one above Hernigou was marrow. This is adipose-derived cells. Patients had no difference in their outcome measures, their PRMs, but the re-tear rate on MR was much higher in the conventional repair group versus the cell group. So again, some evidence of structural improvements in healing here. So bottom line seems to be a cell therapy approach is promising for improvement in structural healing. Clearly, further study is needed. My current approach for cuff repair, I'll consider PRP for cuff repair, and I don't frankly have a strong data to have a preference for the specific formulation. I generally would not use this for tendinopathy, as we've shown here. Adipose-derived cells seem to be promising, but certainly needs further work, and we have some ongoing trials at HSS. One is using just that, using stromal vascular fraction, using enzymes to digest. So this is under an IDE. We have investigational device exemption to use enzymatic digestion. Another trial going on using gene-modified cells, human umbilical vein-derived cells under an IND. So we'll see how this goes over the next year as we complete these trials. Lastly, some systemic factors. Just think about tendon, and I mentioned at the beginning of this area, from regenerative medicine, not just PRP in cells. Vitamin D. Clearly, vitamin D affects osteoblastic activity, affects muscle. There's preclinical studies suggesting vitamin D deficiency may be related to impaired tendon healing. In fact, clinical data shows that lower serum levels of vitamin D are related to higher levels of fatty degeneration in tendon, and some of these large national insurance databases suggest that perioperative vitamin D levels may, in fact, be related to outcomes. So this is a modifiable factor, and you might consider perioperative supplementation. What about PTH, parathyroid hormone? Again, the reason to look at these is rotator cuff tendon healing occurs by bone growing into the tendon, so an osteoinductive agent may have value here. Clearly, PTH can improve osteoblastic activity. There's some preclinical animal studies suggesting that PTH can have a positive effect on tendon-to-bone healing, and it's a clinical study a couple years ago. 31 patients receiving daily injections of Forteo, teriparatide, for three months, and the rate of re-tear was lower in those PTH-treated patients. Maybe something to consider. It's costly, though. Hard to get insurance to cover this. It's costly for the patient, so maybe not so practical. And lastly, statin therapy. There's some evidence that simvastatin reduces the risk of tendinopathy. Statins can affect fibrocartilage and, actually, tendon cells, so statins are an interesting class of drugs. Clearly, it needs further work as well, but these, again, these are available drugs. Certainly, if a patient's on statin therapies, as many are, tell them to continue. Factors with inhibitory effects on cuff healing. Think about this. Hypercholesterol, diabetes. Again, we mentioned vitamin D, so we can think about checking our hemoglobin A1C or vitamin D levels. I try to avoid NSAIDs in the early, post-operative healing period due to the need for inflammation to kind of initiate and regulate the early healing phases. Smoking, obviously, has an adverse effect. There's some data demonstrating that obesity actually can be related to adverse healing as well. I'm gonna skip this. I had put in one slide on meniscus repair, but I'll finish up to stay on time for the rest of the group. I summarized by saying we, all of us, in orthopedics and primary care and physiatry, treating these patients, need exercise leadership in this area. Many practitioners in a number of different specialties advertise cell therapy for numerous conditions, often implausible conditions. Often, you see these exorbitant charges. There's this really indiscriminate use. There's aggressive marketing in this whole area. Patients are told they can avoid surgery. That, in fact, may delay use of proven therapies. I think we need exercise leadership in this area. Take the high road. Continue to study this area that has tremendous potential, but that does need further work. Thank you.

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orthobiologics

cell therapy

platelet-rich plasma

regenerative medicine

stem cells